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ACCELERATED DECLINE OF POTTED CHRYSANTHEMUM ASSOCIATED
WITH ELEVATED NITROGEN FERTILIZATION: EVALUATION OF
CARBOHYDRATES AND SOLUBLE PROTEINS AS PREDICTORS AND
MEDIATORS OF DECLINE
DISSERTATION
Presented in Partial Fulfillment of the Requirements for the Degree Doctor of
Philosophy in the Graduate School of The Ohio State University
By
Stephen A. Carver, B.S., M.S.
The Ohio State University
1995
Dissertation Committee: Approved by
Michael Knee, Advisor Morris G. Cline Teny J. Logan Advisor Maurice E. Watson Graduate Program in Horticulture UMI Number: 9533942
UMI Microform 9533942 Copyright 1995, by UMI Company. All rights reserved.
This microform edition 1b protected against unauthorized copying under Title 17, United States Code.
UMI 300 North Zeeb Road Ann Arbor, MI 4B103 To My Wife Sandy, and To Our Two Daughters, Rachel and Stephanie ACKNOWLEDGMENTS
I express my sincere appreciation to Dr. Michael Knee for his guidance, insight and patience during this odyssey. I would also like to thank each of the other members of my advisoiy committee: Drs. Morris G. Cline, Terry J. Logan, and Maurice E. Watson, for their advice, suggestions, and for the encouragement that each of them have given me. I am thankful for the frendship and council of Drs. Allen Hammer, Harold Wilkins, and
Luther Waters, Jr. To Dr. Robert Joly o f Purdue University, who generously allowed me the use of his computerized pressure bomb, thank you. For the opportunity to begin this degree process, I am indebted to Dr. Harry K. Tayama.
I thank Dennis Kirven, Executive Director of the Ohio Florists' Association, for his understanding and for the considerations that he extended to me during the writing of this manuscript. For the financial support and individual and coiporate encouragement of the Ohio Florists' Association and the Ohio Floriculture Foundation throughout this journey, I am deeply obliged.
To my wife Sandy, for your love, support, and sacrifice, I am eternally grateful.
I also thank our daughters Rachel and Stephanie for their sacrifice and understanding.
Finally, I thank the Lord my God for His countless blessings and for the grace and peace that He has given me. VITA
February 18, 1953 Bom - Columbus, Ohio
1975 B.S., The Ohio State University, Department of Plant Pathology
1977 M.S., The Ohio State University
1977-1987 Plant pathologist, ChemLawn Services Corporation Diagnostic Lab Columbus, Ohio
1987-1994 Research Associate I / Graduaate Research Associate, The Ohio State University
1994-Present Membership/Technical Education Coordinator, the Ohio Florists' Association
PUBLICATIONS
Sirag-Ali, Y.S., H.K. Tayama, T.L. Prince, and S.A. Carver. 1990. Identification of developmental phases in poinsettia. J. Amer. Soc. Hort. Sci. 115:729-731.
Tayama, H.K., and S.A. Carver. 1990. Zonal geranium growth and flowering response to six chemical growth regulators. HortScience 25:82-83.
Sirag-Ali, Y.S., H.K. Tayama, T.L. Prince, and S.A. Carver. 1990, The relationship between maturity level and splitting in poinsettia. HortScience 25:1616-1618,
Tayama, H.K., and S.A. Carver. 1992. Comparison of resin-coated and soluble fertilizer formulations in the production o f zonal geranium, potted chrysanthemum, and poinsettia. HortTechnoIogy 2:476-479.
Carver, S.A. and H.K. Tayama. 1992. Stock plant lateral node number influences splitting o f‘Eckespoint Lilo’ poinsettia. HortTechnoIogy 2:206-207 Tayama, H.K., and S.A. Carver. 1992. Concentration response of zonal geranium and potted chrysanthemum to uniconazole. HortScience 27:126-128
Tayama, H.K., and S.A. Carver. 1992. Residual efficacy of uniconazole and daminozide on potted 'Bright Golden Anne’ chrysanthemum. HortScience 27:124-125.
FIELDS OF STUDY
Major Field: Horticulture
Chemical growth regulator efficacy on poinsettia, chrysanthemum, geranium, and bedding plants. Dr. H.K. Tayama, The Ohio State University.
Production of geraniums, poinscttias, and chrysanthemums using controlled release fertilizers, Dr. H.K. Tayama, The Ohio State University.
Analysis of chrysanthemum chlorophyll, carbohydrate, and soluble protein levels at harvest and during postproduction, Dr. M. Knee, The Ohio State University.
v TABLE OF CONTENTS
DEDICATION...... ii
ACKNOWLEDGMENTS...... iii
VITA ...... iv
LIST OF TABLES...... viii
LIST OF FIGURES...... xii
LIST OF ABBREVIATIONS...... xiv
INTRODUCTION...... I
CHAPTER PAGE
I. CONTROLLED-RELEASE FERTILIZERS AND POSTPRODUCTION LONGEVITY IN A FLOOD AND EBB SYSTEM...... 7
Materials and Methods ...... 13 Results...... 16 Discussion ...... 20
II. DECLINE VS. SENSCENCE IN WELL FERTILIZED CHRYSANTHEMUMS...... 33
Materials and Methods ...... 34 Results...... 37 Discussion ...... 44 HI. FOLIAR CARBOHYDRATE LEVELS AS INDICATORS OF POSTPRODICTION LONGEVITY...... 46
Materials and Methods ...... 49 Results...... 52 Discussion ...... 55
IV. EVALUATION OF ROOT CARBOHYDRATE LEVELS AND ROOT FUNCTION AS A MECHANISM OF ACCELERATED DECLINE IN WELL FERTILIZED CHRYSANTHEMUMS .... 61
Materials and Methods ...... 62 Results...... 65 Discussion ...... 79
GENERAL DISCUSSION...... 81
ABSTRACT...... 88
APPENDICES, ADDITIONAL DATA...... 90
LIST OF REFERENCES...... 104
vii LIST OF TABLES PAGE
TABLE
1. Expl. ‘Bright Golden Anne* growth responses to controlled-release fertilizer (CRF). No water soluble fertilizer at beginning of production. 21
2. Expl. ‘Bright Golden Anne' growth responses to controlled-release fertilizer (CRF). Water soluble fertilizer used at beginning of production 22
3. Exp2. ‘Spirit’ growth responses to controlled-release fertilizer (CRF).. 25
4. Exp2. ‘Iridon’ growth responses to controlled-release fertilizer(CRF).. 26
5. Exp3. 'Spirit* growth responses to controlled-release fertilizer (CRF).. 30
6. Exp4. 'Spirit' growth responses to Osmocote 14-14-14 at two rates and to Peter's 20-10-20 Peatlite ...... 38
7. Exp4. Coefficient of Determination (r3) between postproduction flower longevity and ...... 40
8. Exp5. 'Spirit' growth responses at moderate and high levels of nitrogen fertility ...... 43
9. Exp6. Impact of fertilizer regimes on chrysanthemum production and postproduction characteristics ...... 53
10. Exp6. Foliar and growing medium nutrient levels at harvest .... 54
11. Exp6. Influence of fertilizer levels on leaf starch, total soluble carbohydrate, soluble protein, and chlorophyll content measured at the end o f production and again afler two weeks in postproduction ...... 58
12. Exp6. Responses of selected leaf, root and growing medium parameters to different fertilizer regimes ...... 59
viii TABLES (continued)
TABLE PAGE
13. Exp6. Relationships between postproduction longevity and other selected plant mcasurments ...... 60
14. Exp7. Response of *Spirit' at harvest to different nitrogen rates, sources, and termination periods ...... 1...... 71
15. Exp7. Response o f‘In don’ at harvest to different nitrogen rates, sources, and termination periods ...... i...... 72
16. Exp7. Growing medium analysis at harvest ...... 73
17. Exp7. Foliar analysis at harvest ...... 74
18. Exp7. Resonse of ‘Spirit’ and Tridon’roots at harvest and during postproduction at harvest and in postproduction (PP) to different nitrogen rates, sources and termination periods ...... ■...... 75
19. Exp7. ‘Spirit’ root total N, total soluble protein and total soluble carbohydrates at harvest, 1, and 2 weeks postproduction ...... 76
20. Exp7. Relationships between postproduction longevity ahd other selected plant measurements for ‘Spirit’ both trials ...... 78
APPENDIX PAGE
21. Expl. "Bright Golden Anne1 chrysanthemum growth response to four rates of two controlled release fertilizers (CRF), both without 20-10-20 water soluble fertilizer (WSF) @ 400 mg N/L during the first five irrigations.. 90
22. Expl. 'Bright Golden Anne1 chrysanthemum growth respc nse to four rates o f two controlled release fertilizers (CRF), both with 20-10-20 water soluble fertilizer (WSF) @ 400 mg N/L during the first five irrigations.. 91
ix TABLES (continued)
APPENDIX PAGE
23. Expl. ANOVA (and Omega Squared) chart for 'Bright Golden Anne' chrysanthemum parameters measured. CRF - Controlled Release Fertilizers (Osmocote 14-14-14 vs Nutricote 14-14-14 Type 100). WSF = water soluble fertilizer (@ 400 mg N/L) injected or not injected during the first five irrigations. Rate “ amount of CRF incorporated into the growing medium ...... 93
24. Expl. Bright Golden Anne* chrysanthemum postproduction flower life On days) in response to four rates of two controlled release fertilizers (CRF) both cither with or without 20-10-20 water soluble fertilizer (WSF) @ 400 mg N/L during the first five irrigations ...... 94
25. Exp2. Production and postproduction response of'Spirit' to three rates (0.5, 1.0, and 2.0 the recommended rate) of Osmocote 14-14-14 (100 - 120 day release period) and two Osmocotc-like control release fertilizers (CRF) also with ratios of 14-14-14, but with release periods o f40-60 days and 70-90 days ...... 95
26. Exp2. Production and postproduction response of'Iridon* to three rates (0.5, 1.0, and 2.0 the recommended rate) of Osmocote 14-14-14 (100 • 120 day release period) and two Osmocote-like control release fertilizers (CRF) also with ratios of 14-14-14, but with release periods o f40-60 days and 70-90 days ...... 96
27. Exp3. Production and postproduction response of'Spirit' to three rates (0.25,1.0, and 4.0 the recommended rate) of Osmocote 14-14-14 (100 - 120 day release period) and two Osmocote-like control release fertilizers (CRF) also with ratios of 14-14-14, but with release periods o f40-60 days and 70-90 days ...... 97
28. Exp3. Foliar nutrient levels at harvest (plus N at disbud) in response of 'Spirit' to three rates (0.25, 1.0, and 4.0 the recommended rate) of Osmocote 14-14-14 (100 - 120 day release period) and two Osmocote- like control release fertilizers (CRF) also with ratios of 14-14-14, but with release periods o f40-60 days and 70-90 days ...... 98
29. Exp6, Impact of Osmocote 14-14-14, Hyro-Sol at two rates of N, and to Peter's 20-10-20 Peatlite fertilizer regimes on 'Spirit' production and postproduction characteristics and growing medium nutrient levels. . . . 99
x TABLES (continued)
APPENDIX PAGE
30. Exp6, 'Spirit' Foliar nutrient levels at harvest and leaf starch, total soluble carbohydrate, soluble protein, and chlorophyll content at harvest and at two weeks into postproduction (postp) ...... 100
31. Exp 6. Impact of Osmocote 14-14-14, Hyro-Sol at two rates of N, and to Peter's 20-10-20 Pcatlite fertilizer regimes on Iridon1 production and postproduction characteristics and growing medium nutrient levels. . . . 101
32. Exp 6. Iridon* Foliar nutrient levels at harvest and leaf starch, total soluble carbohydrate, soluble protein, and chlorophyll content at harvest and at two weeks into postproduction (postp) ...... 102 LIST OF FIGURES
FIGURES PAGE
1. Expl. Total foliar nitrogen content for ‘Bright Golden Anne’ during production in response to 4 CRF rates, no W SF ...... 23
2. Expl. Total foliar nitrogen content for 'Bright Golden Anne' during production in response to 4 CRF rates,with WSF starter ...... 24
3. Exp2 Nitrate concentration at 3 growing medium sampling depths due to controlled-release fertilizer rates. Repeated Measures revealed that fertilizer rate, medium location, and their interaction were significant, but CRF and interactions involving CRF were not 27
4. Exp2 Soluble salts at 3 growing medium sampling depths due to controled-rclease fertilizer rates. Repeated Measures revealed that fertilizer rate, medium location, and their interaction were significant, but CRF and interactions involving CRF were not ...... 28
5. Exp2 pH at 3 growing medium sampling depths due to controled- release fertilizer rates. Repeated Measures revealed that fertilizer rate, medium location, and their interaction were significant, but CRF and interactions involving CRF were n o t ...... 29
6. Exp4. Chlorophyll content (mg/g leaf fresh weight) of ‘Spirit* during postproduction ...... 41
7. Exp7. Average daily transpiration rates for 'Spirit' (top) and 'Iridon' (bottom) during postproduction. Note: Treatment 100:25-BC = 100 mg/L N — 25 mg/L of it from N H /, fertilized until bud color, -H = fertilized until harvest. Treatments 400:20(100)= 400 mg/L N - 20 (100) mg/L of it from N H / ...... 77
xii 4 «
FIGURES (continued)
APPENDIX PAGE
8. Expl. Total foliar nitrogen content for ‘Bright Golden Anne* produced at several rates of CRF with or without WSF “starter** during first 3 weeks (first five irrigations) ...... 103
XIII LIST OF ABBREVIATIONS USED:
BGA 'Bright Golden Anne* chrysanthemum
CRF Controlled-release fertilizer, e.g. Osmocote 14-14-14 and Nutricotc 14-14-14 Type 100
C V Coefficient of variability = (sample standard deviation / sample mean) • 100
EC Electrical conductivity
LSD Fisher's least significant difference
OSM Osmocote 14-14-14
PPL Postproduction longevity
TSC Total soluble carbohydrates
WSF Water soluble fertilizer, e.g. Peter’s 20-10-20
xiv INTRODUCTION
The research reported in this manuscript began as an effort to provide a practical
solution for a problem that growers using flood and ebb (or ebb and flow) production
systems were experiencing. Once a solution to the problem was achieved, the focus
shifted to determining the physiological basis for the problem.
The problem that growers were experiencing was an accelerated loss of
postproduction quality (often observed as a loss of foliar tuipdity or marginal necrosis and
foliar collapse, and/or a floral discoloration or collapse) and longevity of many potted crops (this study focused on chrysanthemums). This accelerated decline during postproduction occurred despite the fact that the plants appeared to be of excellent quality while still on the flood and ebb benches in the greenhouse. These plants contained high foliar nutrient levels and were aesthetically very pleasing, i.e. large, full, robust and dark green. However, these very same heavily fertilized plants seemed to decline or collapse once they left the ideal environment of the greenhouse sooner than plants fertilized at more modest levels.
A brief description of a typical flood and ebb production system will help explain the interpretation of the problem and the rationale for its solution that was adopted, Flood
1 and ebb is a system in which potted crops are maintained on water-tight floors or bench
tops. Plants are commonly fertilized during irrigation by pumping a solution that contains
water soluble fertilizers (WSF) onto the floors or benches. The irrigation solution is drawn
up through the bottom of the pots and into the growing medium by capillary action. Afler
a sufficient period of time (usually 5 to 20 minutes), the solution is drained from the bench
or floor, filtered to remove growing medium and other particulate matter, and then
returned to the holding tank. Water is added to the tank to replace the solution drawn up
by the growing medium or lost due to evaporation. Electrical conductivity (EC)
measurements are taken, and used in many operations as a rough measure o f total nutrient
levels. Solution pH measurements are also taken and adjustments are made to bring both
pH and nutrient levels to within a predetermined desirable range.
There are many potential benefits to this system which have lead to the installation
of flood and ebb in many newer greenhouses. Some of these benefits include minimization
or elimination of runoff from greenhouses and reduced quantities of water and fertilizer
(and expense). Flood and ebb, when used as described, however, has a major drawback;
it is easy to lose control of the fertilizer program. Every time the growing medium is irrigated, another dose of fertilizer is added to the pots. Since the growing medium is seldom, if ever, leached in this system, high nutrient levels quickly accumulate in the growing medium and then in the plants. For the purposes of this research I postulated that as long as plants remain in the near ideal environment of the greenhouse where neither light or water are limiting (in relative terms), plants continue to thrive. Presumably, photosynthesis is able to maintain the carbohydrate levels sufficient to sustain the elevated
level of cellular activity stimulated by superoptimal nutrient (perhaps nitrogen) levels.
Once these active plants are moved to the more stressful home/retail environment, where
light levels are usually low and irrigation is sporadic at best, carbohydrate levels arc
depicted and the plant seems to run down. This hypothesis suggested that avoiding excess
fertilization during production but ensuring adequate nutrient availability early, during the
active vegetative growth period (about first 7 weeks, Tsujita, 1974; Woodson and Boodlcy
1983,1984), would maintain greenhouse bench quality and minimize the loss of home/retail
keeping quality.
The principal goal of the first three experiments, discussed in Chapter 1, was to
evaluate the effect of several fertilizer programs using controlled-release fertilizers (CRF)
on production quality and postproduction keeping quality of a crop produced in a flood
and ebb system. The next two experiments described in the second chapter, moved from
the flood and ebb system to an open production system in which the growing media were
irrigated from overhead and the leachate allowed to run off. The goal was to recreate the problem in a production system that would allow better control of individual nutrient availability. The last two chapters (3 and 4) discuss three hypotheses that were formulated in an attempt to provide a physiological explanation for the problem of accelerated decline. The three hypotheses tested were: 1) excessive nitrogen depletes carbohydrate reserves in the carbohydrate generating plant organs, the leaves, predisposing plants to postproduction decline; 2) periodic calcium sprays, beginning at disbud, minimize the hastened loss of postproduction quality of heavily fertilized plants; and 3) heavy N H / fertilization depletes carbohydrates in the roots, minimizing the roots ability to incorporate the toxic ammonium into nontoxic organic N compounds, resulting in accelerated root death and decay and loss of hydraulic conductivity.
Chrysanthemums were planted, in all experiments, as rooted cuttings, one per 11.5 cm (0.5 liter) pot, filled with Mctro-Mix 350, and grown as pinched plants. They were placed under intermittent mist for 3 to 4 days and under long-day conditions for the first
2 weeks while the root systems grew to the sides and bottoms of the pot. Plants were then maintained under short-day conditions until bud color. At the beginning of short day conditions, plants were pinched, leaving six to eight nodes on the stems. The chrysanthemums were then pruned to the three most vigorous auxiliary stems once the longest stems had reached 5 to 6.5 cm in length. This usually occurred about two weeks following the pinch. Two to three bi-weekly sprays of the chemical growth regulator, daminozide, beginning at pruning, were used to manage plant growth.
Plants in all experiments were grown on 1.8 by 2.4 meter (6 x 8 ft) Rough Brothers
(Cincinnati, Ohio) flood and ebb benches. To simplify experimental procedures, in none of the experiments was the irrigation solution recycled. This was warranted because the principal problem of the use of flood and ebb, the build up of fertilizer salts in the pots, occurs not because the irrigation solution is recycled, but because pots are subirrigated.
In the first three studies, plants were subirrigated by flooding the bench tops with fresh water or fertilizer solution. No fungicide drench was used during these three studies to minimize the potential confounding effect of leaching. In the remaining four studies, plants
were irrigated from overhead with the excess allowed to leach out the bottom of the pots
and from the benches. Plants in these four studies were drenched with a Benomyl/Truban
combination on a three to four week interval during production. Chrysanthemums in all
the experiments were put on a preventive insecticide program throughout production.
Various insecticides were used in this program, including: a Margosan-O/Avid tank mix,
a Thiodan/Tempo tank mix, and Mavrik Aquaflow. Despite this and other precautions,
thrips populations built rapidly during postproduction in several instances, resulting in lost
floral (but not foliar) longevity.
In most experiments, three plants from each experimental unit were taken at
harvest (when two of the three inflorescences on each plant had approximately 6 to 8 rows
of expanded ray florets) and sleeved, boxed, and moved to the postproduction room.
After three days, plants were removed from the box, unsleeved, set on benches in the
postproduction room, and irrigated as needed with distilled water from a plastic watering
can. The medium (except for some in Experiment 1) was irrigated from overhead with the
leachate allowed to drain off. In Experiment 1 half the plants were irrigated in
postproduction as described above and half were subirrigated. Light levels were
maintained at 4 to 5 pmol/m^s ("SO ft candles) for 12 to 24 hours a day depending on the
experiment as an approximation of home/retail lighting conditions. Temperatures were
maintained at 21 ± 2° C and at approximately 60% relative humidity. Inflorescence decline was noted when ray florets began wilting or when the outer most row or two of florets began to wither and dry. Foliar decline was noted when one quarter to one third of the leaves on any of the three stems on the plants were permanently wilted or showed signs of chlorosis and necrosis. CHAPTER I
Controlled-Release Fertilizers and Postproduction Longevity in a Flood and Ebb
System
A number of studies have examined the pattern of N use during floral crop production, and the relationship between fertilizer rate and time of fertilizer termination as it relates to production/postproduction quality. Lunt and Kofranck (19S9) found that high N levels during early vegetative growth stages of cut chrysanthemum development were essential for quality blooms. Boodley and Meyer (1965) found that 'BonnafTon
Deluxe' chrysanthemum had its highest rate of N and K accumulation during the first 4 weeks of growth.
Woodson and Boodley (1983) measured dry weights and N accumulation and partitioning in the aboveground parts of the chrysanthemum cultivar 'Gt. #4 Indianapolis
White' at 0, 2, 4, 6, 8, and 9 weeks afler planting. They followed standard fertilizer recommendations with N and K supplied in concentrations of200 mg/L each, derived from
Ca(NOj)2 and KN03. The rate of total dry matter accumulation continued to increase during the study, but not uniformly throughout the plant. Between weeks six and nine, accumulation in the vegetative tissues had slowed or ceased while accelerating rapidly in the inflorescences. The pattern of total N accumulation differed somewhat from dry
7 weight accumulation. The rate of total N accumulation began to decrease after week 6; plants continued to take up N, but at a slower rate than before. Total N content of leaves increased at a slow rate between weeks six and eight, then decreased slightly during the last week of monitoring, while N content of the inflorescences increased during the same period. Woodson and Boodley (1983), drew several conclusions. First, early stages of growth are critical for N availability. Second, photosynthetic activity (as determined by continued diy weight gains) was more than sufficient to meet demands of the developing inflorescences. Third, availability of newly absorbed and reduced N was inadequate (as determined by the net loss of N from the vegetative tissues) for the inflorescences' needs.
Finally, since N fertilization was supplied at a consistently high rate throughout crop development, the decrease in N accumulation during the later stages of growth was likely the result of a decrease in the plants' inherent N requirement and/or a decrease in the plants' capacity to absorb available N.
In a subsequent study, Woodson and Boodley (1984) evaluated the effect of 52.5 v.s. 210 mg NOj-N/L (other nutrients held constant in a complete Hoagland solution) on leaves, stems and roots. Measurements of dry weight, N accumulation and partitioning, and nitrate reductase activity (NRA - in the leaves only, where they found over 70% of the
NRA occurs) were taken at three weeks after planting, visible bud (day 46), first visible bud color (day 63), and inflorescence maturity (day 77). Dry matter continued to accumulate in all tissues of plants maintained under both N regimes through the study with one exceptioa Roots of plants receiving the lower N treatment reached the maximum dry 9 weight by day 63. Plants fertilized at the lower N rate also exhibited a remobilization of reduced N from the vegetative tissues to the inflorescence after day 63. Nitrate content of the leaves and stems declined during later stages of growth in plants fertilized at both levels of N, The authors noted that the decrease in N O / uptake during inflorescence development was accompanied by an increase in remobilization of reduced N from the vegetative tissues to the inflorescence. Since N O / content of the above ground tissues declined during the reproductive growth stages, regardless of the rate of application of N, the authors concluded that the plants seemed incapable of drawing or translocating the needed N O / from the medium. Woodson and Boodley concluded both studies by stressing the importance of early N fertilization.
What happens if high nutrient availability is maintained throughout production?
Lunt and Kofranek (1959) stated, "Sustained high N levels in the root zone until blooming consistently led to a condition ofbrittle leaf in the plant which was undesirable from the marketing viewpoint. Thus, low N levels in the root zone in the last three or four weeks before bloom appeared to be desirable."
Joiner (1962) working with the chrysanthemum cultivar 'Blue chip* found that increasing N levels in four geometric steps from 50 to 400 mg N/L in the irrigation water during production incrementally decreased the keeping quality of flowers cut and maintained in refrigeration at 7°C for four days.
Prince et al.(1990, unpublished data) worked with chrysanthemum cultivars Bright
Golden Anne* and Torch', fertilized with a controlled release fertilizer (CRF, Osmocote 10
14-14-14) at 7.1 kg/m3 (the recommended rate), one half the recommended rate plus water soluble fertilizer (WSF, Peter's 20-10-20 Peatlite) injected into the irrigation stream at every irrigation at a rate o f200 mg N/L, and WSF alone injected at 200 mg N/L. Foliage from all treatments contained normal nutritional levels but N, P, K, Mn, Fe, Cu, and B levels were higher in plants fertilized with the water soluble fertilizer (with or without
CRF) than in plants fertilized with CRF alone. Plants produced with WSF were larger
(taller and larger diameter); had greater total dry weight; and produced larger, darker leaves. Total leaf number, however, was not affected. Flower number was also not affected by fertilizer source. These production responses were coupled with accelerated floral and foliar decline in a simulated shipping and retail postproduction environment compared to plants receiving only CRF. This observation held for both cultivars, but especially for Torch'.
Gerberick (1989) evaluated time of WSF termination during production on the postproduction quality of three chiysanthemum cultivars: Torch', 'Iridon', and 'Spirit'. He top dressed a CRF at VS x the recommended rate and supplemented with 200 mg WSF-N/L injected at every irrigation. Treatments were based on termination date o f the supplemental WSF fertilization. He evaluated the effects of supplemental fertilizer termination at disbud, visible bud color, or harvest on the foliar nutrient concentration and the foliar and floral longevity under simulated shipping and retail postproduction environments. The difference in treatment response was cultivar specific. 'Iridon* showed no difference in postproduction life in response to the different treatments, while 'Spirit* revealed a significant difference in foliar longevity between treatments with termination at disbud showing the best response.
In a similar study, Nell et al. (1989) found that Mountain Peak* potted chrysanthemum fertilized with a WSF (20-10-20) at 300 mg N/L injected at every irrigation until three weeks prior to flowering, lasted an average of 6 to 10 days longer in postproduction than similar plants fertilized to flowering. Longevity was partially dependent, however, on the light level under which the plants were grown. Early fertilizer termination did not improve postproduction longevity of plants under the mean maximum photosynthetic photon flux (PPF) level of 500 pmoI/m2»s, while it improved longevity of plants grown under light levels o f300 and 100 pmol/m2*s by approximately a week.
Finally, Roude et. al. (1991a) found that varieties 'Iridon', 'Copper Hostess', and
U p' grown in Metro-Mix 350 fertilized with Peter's 20-10-20 Peatlite at every irrigation exhibited reduced postproduction longevity With increasing N levels from 150 to 450 mg
N/L. This effect, however, was not observed when plants were grown in a peat-perlite- sand mix or in Vergro Klay Mix.
All these studies, just cited, were conducted in open production systems where the presence of excess fertilizer salts in the growing medium was minimized due to leaching.
If high fertilizers levels resulted in a loss of postproduction keeping quality in an open production system, it seemed logical that higher fertilizer salt levels, which would develop in a closed, non-leached, subirrigated system such as flood and ebb could present a problem. Most growers who use a flood and ebb system, now typically use only 33 to 12
50% of the rate of fertilizer that they used in open, top irrigated systems. At the time this research was undated, however, some growers used the same fertilizer rates they had used previously in an open production system, during the first part of flood and ebb production and then switched over to tap water for the rest of the crop cycle. This required a second holding tank to store the pond, well, or city water. Such a two-holding tank remedy worked well in a large greenhouse range where a angle crop of relatively uniform age was grown. It became more cumbersome, however, when different crops and/or different growth stages arc produced within the same flood and ebb bay or range.
The use of CRFs seemed to be a possible alternative solution. Because CRFs can be incorporated into the growing medium prior to planting, the fertilizer program for each pot is self contained. Therefore, growing different crops at different growth stages in the same area should cause little difficulty because no additional WSF is needed. In addition, total nutrient availability during the life of the pot in production is controlled. The question remained, would CRFs, such as Osmocote 14-14-14 or Nutricote 14-14-14 Type
100 provide enough nutrition during the early portion of production to insure production quality without having to apply so much that postproduction keeping quality suffered.
Several papers have looked at the release rate of Osmocote 14-14-14. Harbaugh and Wilfret (1981) reported that 50% of the nutrients became available within 2.5 weeks when the Osmocote was placed in a beaker of water and held at a constant 30°C, 3.5 weeks when the water was at23°C, and 7 weeks at 16°C. Patel and Sharma (1977) placed
Osmocote 14-14-14 in a column filled with sand held at field capacity moisture and 26°C. 13
They found that they were able to recover about 11% of the N placed in the system after
1 week, about 25% after 4.5 weeks, and about 50% after 9 weeks. Meadows and Fuller
(1983), working with Osmocote 19-6-12 (which has the same 3-4 month release period as Osmocote 14-14-14), found that 20% of the N was released within 2.5 weeks, 31% with 4.5 weeks, and 43% with 7 weeks when it was incorporated into a pinebark/sand medium (4:l,v/v). The medium temperature(s) was not stated.
Nutricote 14-14-14 Type-100 releases 80% of its N within 100 days when the soil temperature is 25°C, according the manufacturer's literature. It releases 50% of its N in
7 weeks at a soil temperature of 25*0, in 4.5 weeks at 30°C, and 3 weeks at 35°C. About half the time is needed at each temperature for a release of 25% of the N.
We set up three experiments to evaluate the value of CRFs in providing ample nutrition to support early vegetative growth and produce a quality chrysanthemum crop while minimizing loss of postproduction keeping quality.
Materials and Methods
All three experiments followed the pattern discussed in the introduction. The aspects that were specific to each are discussed below.
Experiment I. This experiment was set up in the greenhouse as a split plot design with 'Bright Golden Anne' grown on eight 1.8 by 2.4 meter (6 x 8 ft) flood and ebb benches. The first main plot factor was CRF. Pots on half of the eight benches received
Osmocote 14-14-14 incorporated into the growing medium, the other half received Nutricotc 14-14-14 Type 100. The second main plot factor was a WSF starter. Half the
Osmocote and Nutricote benches received Peter 20-10*20 Peatlite injected into the irrigation stream at 400 mg N/L during the first five irrigations. This added a total of approximately 250 mg of soluble N to each pot at the beginning of the production cycle.
There were two replications of each of the four main plot factor combinations. Each of the resulting eight main plot/replications was randomly assigned to a bench. The subplot factor within each bench was CRF rate. There were four rates; no CRF, 0.5x the recommended rate (- 3.5 kg CRF/m* or about 250 mg N/pot), lx (- 7.1 kg CRF/mJ or about 500 mg N/pot), or 2x (- 14.2 kg CRF/m1 or about 1.0 g N/pot). There were 30 plants per subplot. In addition, there were two postproduction treatments. Three pots from each WSF x rate split plot were irrigated during postproduction from overhead and three were subirrigated. For purposes of simplifying the postproduction analysis, the two
CRF treatments were analyzed separately. Even with this simplification the experimental design for the postproduction portion of this experiment was a split-split plot.
Foliar samples (youngest fhlly expanded leaves) for nutrient analysis were taken beginning one week after planting and were repeated on a weekly basis throughout production, except during week 10 for the no CRF/no WSF starter treatments. Additional data was collected at harvest, including; plant height (from pot rim to top of plant) and diameter (average of two measurements taken at 90°); leaf area (Li-Cor LI3100 Area meter, Lincoln NB), fresh and dry weights, and number per plant; inflorescence diameter, and days to flower.
Experiment 2, This experiment was begun November 10,1990. Osmocote 14-14- 15
14 again was used, along with two experimental Osmocote-like CRFs. Like Osmocote, both experimental had ratios of 14-14-14. The difference among them was the time period during which nutrients release and become available to the plant. Osmocote 14-14-14
(hereafter referred to as Osmocote) has a release period of 100 to 120 days (at a soil temperature of21°C), while the experimcntals had release periods of 40 to 60 days (CRF-
40) or 70 to 90 days (CRF-70). Each treatment was replicated three times, yielding nine treatment/replications, each assigned to an flood and ebb bench. The treatments were blocked across the greenhouse to take into account a slight temperature gradient. Each bench was divided with 'Spirit* grown on one half and Torch' on the other. Since cultivar assignment was not randomized (by design), no statistical comparisons were made between cultivars. Based on the literature, I felt that there would be differences in cultivar response and I was not interested in exploring this point. The 60 plants of each cultivar on each bench were divided into 3 subplot treatments based on the rate of CRF used. The rates were the same as those used in Experiment 1, except that no control (no CRF) treatments were included. There was no separate postproduction factor in this experiment as all plants (3 samples from each treatment/replication of each cultivar) were watered from overhead with distilled water.
In this second experiment, foliar samples (youngest fully expanded leaves) were taken for analysis, but only at harvest. The other parameters measured were the same as those in Experiment 1, with the addition of growing medium analyses. The growing medium from several pots from each treatment/replication, of'Spirit' only, were divided 16 into the bottom half, middle and top quarters. After the CRF pearls had been removed from each sample, the growing medium samples were submitted to the REAL lab at
OARDC where they were analyzed via saturated paste extract protocol.
Experiment 3. This experiment, started February IS, 1991, was essentially a repeat of Experiment 2, with three changes. First, only the cultivar'Spirit* was used. Second, the rates of each CRF used were changed to 0.25x (1.8 kg CRF/mJ <* 125 mg N/0.5 L pot),
Ix (7.2 kg CRF/m1* 500 mg N/0.5 L pot), and 4x (28.5 kg CRF/m3 « 2 g N/0.5 L pot).
Finally, growing medium analyses were not conducted.
Results:
Experiment I. There was veiy little difference, either observational or statistical, between plants fertilized with Osmocote 14-14-14 or Nutricote 14-14-14 Type 100.
Therefore, information presented in Tables 1 and 2, and Figures 1 and 2 is pooled across
CRF treatments. An expanded table is presented in the Appendix (Tables 21 - 24). 'Bright
Golden Anne* growth, as indicated by plant height and diameter and average leaf area and dry weight, typically increased with increasing rates of either CRF. Number of days to flower, however, decreased with increasing CRF. These responses were expected. Plants that received the early charge of WSF were larger and more robust than plants that received none (Tables 1 and 2). As an example, plants that received the starter WSF but no CRF were about 3 to 4 times the size of plants that received no fertilizer at all and were very similar in size as those that received 3,5 kg/m3 CRF but no WSF. The difference in plant size and leaf characteristics between plants that did and did not receive the WSF 17 starter charge was much smaller in those plants that also received the higher CRF treatments.
There were no statistical differences observed in postproduction flower longevity between plants top or subirrigated during the postproduction period. Therefore, data were pooled. Plants that received no fertilizer were not deemed saleable at the end of production and were omitted from the postproduction study. There were no statistical differences in post production longevity among WSF starter and CRF effects and interaction (Tables 1 and 2).
Foliar N content of plants, both with and without starter WSF, showed several interesting trends over time (Figures 1 and 2). First, N content in the leaves of plants maintained under the two lower CRF rates (no WSF) declined during the vegetative growth period (about the first 7 weeks). Both sets of plants exhibited chlorosis, the control plants throughout production, those receiving O.Sx CRF treatments later in production, especially as the inflorescence began developing. Second, foliar N of plants at the higher CRF rates remained relatively constant until the reproductive period, beginning after week seven, when they dropped significantly. Foliar N appeared to recover somewhat during the last week of production. Third, the pattern of foliar N content in BGA' that received the WSF starter was similar to those that didn't. The only exception was that foliar N content of plants under the two lower CRF treatments began to decline during the vegetative phase at about week five. Finally, the foliar N levels of all BGA' that received the WSF starter dropped significantly after week seven, again just as inflorescenses were developing.
Experiment 2. As in the first experiment, there was very little difference in plant growth in response to the three different nutrient release-rate Osmocote-types. For that reason data presented in Tables 3 and 4 are pooled across CRF type. Expanded tables are presented in the Appendix (Tables 25 and 26). Both cultivars were slightly shorter but fuller (larger leaves) at the 2x CRF rate compared to the lx. Iridon* exhibited a slight reduction in the days to flower as CRF rate increased. This same trend was not observed with 'Spirit*. 'Spirit' appeared to show decreased postproduction floral longevity with increasing CRF rate. This trend, however, was not significant.
Subirrigation of pots with CRF incorporated into the medium resulted in stratification of salts, NOs', and pH. Nitrate and fertilizer salt levels increased from the bottom to the top of the pot (Figures 3 and 4). The increase was most significant for the highest (2x) rate of CRF. Medium pH values varied very little (not significantly) within a pot, but varied significantly among CRF treatments (Figure 5). Pots fertilized at the high
CRF rate had a medium pH of about 4.S, at the recommended CRF rate the pH ranged from 5.5 (in the bottom half of the pot) to 5.2 (in the top layer), and at the low CRF rate the pH was about 6.
Experiment 3. As in the two previous experiments, plants receiving the same amount of fertilizer were very similar regardless of the CRF formulation used. Therefore data were pooled across CRF formulation to highlight differences in plant response produced by different CRF rates. Most plant growth characteristics and leaf nutrient levels 19 improved or increased with CRF rate (Table S, and Table 27 in the Appendix). Plants grown at the 4x rate appeared to have the highest on-the-production-bench quality as they were the fullest, darkest green, and most vigorous. Plants fertilized at the lx rate were acceptable but were not as full as those receiving the 4x rate. Plants fertilized at the 0.25x rate were thin, chlorotic, and at best, marginally acceptable.
Flower longevity in the postproduction room did not follow the pattern of improvement with increasing fertilization rate that was observed with production characteristics. Flower longevity of plants fertilized at the 4x rate was one and two weeks shorter than those fertilized at the 0,2Sx and lx rates, respectively. Symptoms of flower and leaf senescence differed in plants fertilized at the 0.25x and lx rates compared to those at the 4x rate. Ray florets withered and basal leaves turned chlorotic on plants with low to recommended CRF nutrition, while florets and leaves lost turgjdity on plants with high nutritional levels, despite irrigation practices that were sufficient to keep plants of the other treatments in postproduction turgid.
Polynomial regression revealed close associations (significant to the 0.01 level) between decreasing postproduction flower longevity and increasing foliar levels of N (r2
= 0.87), P (r2- 0.79), and K (r2 ° 0.63).
Pisg»55ion
In Experiment 1, the pattern of foliar N content, at least in plants that received at least 7.1 kg Osmocotc/m’, nutrition, remained stable or increased during the vegetative portion of production, but dropped sharply as floral development commenced. This 20 occurred, despite the fact that essentially all the N originally supplied to the plant, except that which had already been absorbed by the plant, was still in the pots. The drop in foliar
N content during floral development is in general agreement with observations made by ,
Woodson and Boodley (1993). One observation that we made in these studies that differs from theirs is that during the last week of production, N content in the leaves increased.
The significance of this observation, especially with regard to postproduction longevity is unknown, because it was observed in all plants of Experiment 1 regardless of CRF rate.
In addition, no significant differences were observed in postproduction longevity in that study. Whether “the decrease in N accumulation during the later stages of growth is likely the result of a decrease in the plants' inherent N requirement and/or a decrease in the plants' capacity to absorb available N" (Woodson and Boodley, 1983) could not be determined from this study. The rise in foliar N content during the last week of production observed in this experiment, however, does not support the idea that the earlier drop in foliar N content that occurred during development of the inflorescence was due to insufficient or unavailable levels of N in the medium.
Nutrient (N) levels, at harvest, in the bottom and middle layers of growing medium of pots fertilized with CRF at the recommended rate, were low to adequate to support chrysanthemum growth. Levels in the top layers approached superoptimal. Nitrate levels in all layers of growing medium of pots fertilized at twice the recommended rate were well above target levels. Soluble salt levels in the medium were stratified in a pattern similar to that found for NO,*. TBbjleJ^j3j£K*BrigbtGoldenAna££uwthres|)o^^ 1 1 1 Plant Flower Days Avg. leaf Avg. leaf Floral Foliar diameter to dry wgL area postprodnctkn N* Fertilizer treatment1 (an) (an) flower (mg) (an1) life (days) (K)
No CRF (Ox) 173 12.1 55 ' 122 40 3.4 — 13
3.61cgCRFAn*(%x) 26.1 222 12.4 91 110 13.9 21 33
7.1 kgCRFAn*(lx) 29.2 25.0 1Z7 85 120 202 23 43
14.2 kg CRF/m* (2x) 31.1 28.1 128 82 130 26.7 23 52
Trend analvaisr LO** LO** LO** LO** LQ** LO** NS z The values presented in this table are a composite (average) of the vahies obtained fnxn plants grown with Osmocote 14-14-14 and Nutricote 14*14-14 Type 100. Values for these two CRFs were combined because they were statistically indistinguishable. Y linear trend (L) and/or quadratic trend (Q) significant at the 0.01 (**) or 0.05 (*) lew!, or not significant (NS) x Youngest expanded letw s sampled at harvest. Optimal range is 4lo 6 percent (Dole and Wilkins, 1989) T able! Expl.‘Bright Golden Anne* grinvth responses to controlled-rdcaae fertilizer (CRF). W ater soluble fertilizer used a t beginning of production.
Plant Plant Flower Days Avg. leaf Avg. leaf Floral Foliar height diameter diameter to diyw gl area postproduction N Fertilizer treatment* (cm) (an) (an) flower (mg) (cm?) life (days) (percent)*
No CRF (Ox) 29.9 22.0 10.4 97 120 17.4 21 3.0
3 .6 kg CRF/m’ (Vix) 32.1 26.8 12.7 93 120 23.6 25 43
7.1 kgCRFAn’ (lx) 32.6 283 123 87 110 25.7 18 4.8
147 kg CRF/m’ (2x) 323 29.7 12.7 84 140 29.8 22 53
Tread analysis* NS ... LQ* LO* L* NS L** NS z The values presented in this table we a composite (avenge) of the values obtained from plints grown with Osmocote 14-14-14 and Nutricote 14-14-14 Type 100. Valuea for thews two CRF« were cnmhtned because thry were statistically mrfwttngitishahlc T Linear trend (L) and/or quadratic trend (Q) significant at the 0.01 (•*) or 0.05 (•) level, or not significant (NS) x Youngest expanded lervci aampled at harvest. Optimal range is 4 to 6 percent (Dole and Wilkins, 1989) I Figure 1. Exp. 1. Tota] foliar N content for 'Bright Golden Anoe’ during production in response to 4 CRF rales, no WSF.no CRF rales, 4 to response in production Golden during Anoe’ 'Bright for content N 1. Tota] foliar Exp. 1. Figure
PERCENT NITROGEN 4 3 5 6 2 0 1 H a - Control 3.6 kg/cu m —4— 7.1 kg/ai m 14.2 kg/a 14.2 m kg/ai —4— 7.1 m kg/cu 3.6 Control - a H WEEK j m I iue . x .Ttlfle otn o Bih odnAn’drn rdcini epnet R tswt S tre. to WSF starter. CRF 4 ntes,with to response in production during Golden Anne’ ‘Bright for N content 1.folier Total Exp 2. Figure
PERCENT NITROGEN 4 6 7 5 2 3 oto 36k/um — m kg/cu 3.6 Control LSD 0.05 = .48 = 0.05 LSD W eeks after planting after eeks W 4 — 7.1 kg/cu m 14.2 kg/cu m kg/cu 14.2 m kg/cu 7.1 — T^|lc3;^}22;JS^if|TOwthri2g™ ^ilo_COT&iolIocUrdeasefatil^ff^CR^
Plant Plant Flower Days Avg. leaf Avg. leaf Floral Foliar height diameter diameter to dtywgL area postproduction N* Fertilizer treatment? (cm) (cm) (on) flower (mg) (cm*) life (days) (percent)
3.6 kg CRF/m* (’/jx) 21.6 20.0 10.2 78 45 93 17 4.9
7.1 kg CRF/m* (lx) 243 21.7 10.8 76 50 11.2 15 5.8
14.2 kg CRF/m3 (2x) 22.2 21.1 11.6 77 60 11.6 12 6.8
Trend analysis* S** Q* NS NS L** NS NS z The vibes presented in this table are i composite (average) of the values obtained from plants grown with Osmocote 14-14-14 and two Osmocotc-like experimental fertilizers. Values for these throe CRFs were combined because they were statistically indistinguishable. Y Linear trend (L)aad/or quadratic trend (Q)sigm5canl at the 0.001 (***), 0.01 (*•) or 0.05 (•) level, or not significant (NS) x Youngest expanded leaves sampled at harvest Optimal range is 4 lo 6 percent (Dole and Wilkins, 1989) T^le^^^itedorf^owthrggonsaloCo^^U^kdttsefa^EonJCRF^
Plant Plant Flower Days Avg. leaf Avg. leaf Floral Foliar height diameter diameter to dry wgL area postproductioa N* Fertilizer treatment (cm) (an) (an) flower (mft) (cm?) life (days) (percent)
3.6 kg CRFArf (Vix) 19.9 19.4 8.6 81 49 115 7 5.6
7.1 leg CRF/m? (lx) 195 20.8 8.9 79 57 145 7 6.0
142 kg CRFAn* (2x) 16.8 205 8.8 77 60 14.8 9 6.7
Trend analysis* L*** 0* Q" L* L** NS L*** 2 The values presented in this table are a composite (avenge) of the values obtained from plants grown with Osmocote 14-14-14 and two Osmocote-like experimental fertilizers. Values for these three CRFswere enmhmed hecsnse theyn m statistically tndistmguishahlc T Linear trend (L) tad/or quadratic trend (Q) significant H the 0.001 (•••), 0.01 (**) or 0.05 (*) level, or not significant (NS) x Youngest expanded ksrwsj sampled at harvest. Optimal range is 4 to 6 parent (D de and Wilkins, 1989)
w Figure 3. Exp. 2 N O / coooentntioo at 3 growing medium sampling depths due to cootrollcd-rdcasc fertilizer rates. Repeated Measures revealed revealed Measures not. Repeated CRF involving were CRF interactions and but rates. significant, were fertilizer interaction and their location, medium rate, cootrollcd-rdcasc to due fertilizer depths growing sampling that medium 3 at / coooentntioo O N 2 Exp. 3. Figure
mg/kg NITRATE 1400 1000 1200 0 0 6 1 600 400 800 200 3.6— BOTTOMHALF LSD .05=419 kg CRF/cu m —!— 7.1 kg CRF/cu m ■ 142 kg CRF/cu kg m 142 ■ —!— CRF/cukg 7.1 m CRF/cukg m GROWING MEDIUM SAMPUNG DEPTH MEDIUM GROWING SAMPUNG MIDDLE QUARTER
TOP QUARTER TOP Figure 4. Exp.2 Soluble salts al 3 growing medium sampling depths due to oootroled-rdcMC fertilizer rales. Repeated Measures revealed revealed Measures Repeated rales. fertilizer oootroled-rdcMC to due depths growing medium sampling 3 al salts Soluble Exp.2 4. Figure that fertilizer rale, medium location, and their interaction were significant, but CRF and interactions involving CRF not. were involving CRF and interactions but significant, were interaction their and medium location, rale, fertilizer that
dS/m 12 10 14 6 1 6 4 8 2 0 ♦ 3.6 kg CRF/cu m —I— 7.1 kg CRF/cu m M 14.2 CRF/cu 14.2 kg m M CRF/cukg —I— 7.1 m kg CRF/cu 3.6 m ♦ BOTTOMHALF LSD .05=2.1 GROWING MEDIUMSAMPLING DEPTH MIDDLEQUARTER
TOP QUARTER TOP 6.5
5 5 -
LSD .05 = 31 ^ ------£ 5 -
4.5 -
4 - l '"" 1 ' 1 111 1 BOTTOM HALF MIDDLE QUARTER TOP QUARTER GROWING MEDIUM SAMPLING DEPTH
M 3.6 kg CRF/cu m 7.1 kg CRF/cu m 14.2 kg CRF/cu m
Figure 5. Exp. 2 pH al 3 growing medium sampling depths due to con£rokd-rele«se fertilizer rates. Repeated Measures revealed that fertilizer rate, mcdhnn location, and thdr interaction were significant, but CRF «nd interactions involving CRF were not to NO Table 5. Exp3, *Spirit‘ growth responses to controlkd-rcleasc fertilizer (CRF).
Plant Plant Flower Days Avg. leaf Avg. leaf Floral Foliar height diamrtrr diameter to dry wgt. area postprod N Frrtilm -r fn**frTV*ntz (cm) (cm) (cm) flower (mg) (cm1) life (days) (percent)
1.8 kg CRF/m1 (‘/oc) 21.4 15.6 9.7 77 48 6.7 30 23
7.1kgCRF/kn’ (Ix) 27.6 20.1 10.8 73 82 11.8 37 3.8
28JkgCRFAn*(4x) 26.0 2 2 J 11.5 70 87 12.4 23 5.9
Trend analysis* LQ*** LO*** L*** LO*** LO*** LO*** LO*** L*** z The values presented in this table arc ■ composite (average) of the values obtained from plants grown with Osmocote 14-14-14 and two Osmocote-like experimental fertilizers. Values for these three CRFs were combined because they were statistically indistinguishable. Y Linear tread (L) and/or quadratic trend (Q) significant it the 0.001 (•*•), 0.01 (**) or 0.05 (*) level, or not significant (NS) Biembaum (1992) stated that the build up of high fertilizer salts in a subirrigated pot is not the problem that it was once thought to be because the salts move to the top of the medium out of range of most of the root system. Experiments 1 and 2 were not designed to evaluate that hypothesis, but the results lend some support. The fertilizer salt level in the top quarter of the growing medium that received 14.2 kg CRF/m1 in
Experiment 2 was almost 16 dS/m but only 5 to 7 dS/m below that point. The pattern of foliar N content in Experiment 1 also indirectly lends some support. Figure 8 in the
Appendix is a partial combination of Figures 1 and 2. It highlights the higher foliar N during the first 5 weeks in plants that received a WSF boost. After the first 5 weeks foliar
N content decreased below levels that received the same amount of total N from CRF alone, suggesting a reduction in the availability of water soluble N. Does the nutrient stratification in the pot effectively make all soluble nutrients unavailable to the plant? On the contrary, the foliar N content of plants receiving WSF (or WSF and CRF) approximated the level found in plants that received equal amount of N from CRF alone
(Fig 8, Appendix). Yelanich and Biembaum (1994) fertilized poinsettias with 100 mg N/L in a trickle irrigation system that allowed no leaching from the pot and that resulted in nutrient stratification in the media. They found that plants were equal in quality to those heavily leached (* 40%) with 400 mg N/L. The results of Experiment 1 suggest that the total amount of fertilizer applied has a bigger impact on nutrient availability (based on plant growth and foliar nutrient responses) than does nutrient stratification. 32
Based on these studies, controlled-release fertilizers (e.g. Osmocote, Nutricote) can be used in an flood and ebb system to produce aesthetically pleasing plants and minimize the loss of postproduction quality and life associated with over fertilization.
However, just as cultivars show differences in sensitivity to chemical growth regulators, they appear to show differences in their tolerance to high fertility as it impacts postproduction keeping quality.
There were no differences observed among plants grown with Osmocote or either of the two experimental Osmocote-like formulations, despite the differences in their nutrient release periods. This suggests that the initial nutrient release rate from the three materials is similar enough, especially during the early vegetative growth period, to allow equivalent growth in an flood and ebb environment. Results of the first experiment with the WSF starter imply that a portion of the CRF might be replaced with less expensive
WSF preplant incorporated into the medium with the CRF. CHAPTER n
Decline vs. Senescence in Well Fertilized Chrysanthemums
Results of Experiment 3 showed that 'Spirit' grown with low to moderate nutritional levels exhibited different symptoms of floral and foliar decline than those that were maintained at high nutritional levels. Plants in the first group exhibited symptoms that seemed to fit the classical description of senescence. The process of senescence in flowers and leaves is marked by a rapid loss of macromolcculcs, i.e. soluble proteins and
RNA, along with an increase in hydrolase activity. In leaves, there is also a rapid decline in the rate of photosynthesis and loss of chlorophyll as the chloroplasts disintegrate.
Finally, tissues collapse and dry (Woolhouse,1978; Thomas and Stoddard, 1980; Stoddard and Thomas, 1982, Mei and Thimann, 1994). Nutrient deficiency, particularly of N, hastens senescence. Symptoms that were observed on 'Spirit' included a chlorosis of foliage, typically beginning with leaves at the base of the plant, followed by necrosis and withering; inflorescences exhibited withering and browning of the ray florets. These symptoms were more pronounced and occurred sooner in chrysanthemums produced with
CRF at 0.25x the recommended rate but also were observed to a more limited degree in those produced at the recommended rate.
33 34
Symptoms of decline in 'Spirit* fertilized at 4x the recommended rate included a
loss of turgor in the leaves (usually first observed in the basal and terminal leaves) and
individual ray florets, despite the presence of ample moisture in the growing medium.
Wilted leaves eventually became necrotic sometimes along the margins, but more often beginning at the petiole and base of the leaf blade. There was very little evidence of chlorosis in the leaves of these plants even as they turned necrotic. The differences in symptoms of decline resulting from different levels of nutrition suggested that there were different mechanisms involved.
In this second group of experiments (experiments 4 and S), there were three objectives. The first was to determine whether senescence symptoms observed in postproduction on heavily fertilized potted chrysanthemums conformed to the standard physiological definition, by exhibiting a rapid decrease in chlorophyll content. The second was to reproduce the results observed in Experiment 3 in an open production system in which plants were irrigated from overhead. Finally, an attempt was made to demonstrate that N was the principal nutrient responsible for differences in postproduction quality in previous experiments.
Materials and Methods
Experiment 4. This experiment was begun April 11,1991, using the cultivar
'Spirit*. There were three treatments: Osmocote 14-14-14 incorporated at the recommended rate (- 7.1 kg CRF/m1 or about 500 mg N/0.5 liter pot), Osmocote at 4x the recommended rate (~ 28.5 kg CRF/m1 or about 2.0 g N/0.5 liter pot), or Peter's 20-10- 35
20 Peatlite injected into the irrigation stream at every irrigation at 300 mg N/Iiter - but no
Osmocote. Each treatment was replicated three times in a randomized complete block
design. Each of the nine treatment/replication combinations was assigned a flow and ebb
bench in a blocked fashion, with 60 plants per bench. All plants were irrigated from overhead and the leachate allowed to run off. At harvest, 12 plants were sleeved, boxed, and moved to postproduction. In addition, foliar and growing medium samples were submitted from each treatment/replication (experimental unit) to the Research and
Extension Analytical Laboratory in Wooster, Ohio. Foliar samples were also taken at eight weeks into production. Plant growth responses measured at harvest included: plant height and diameter, flower diameter, total leaf number and area, average leaf area, and dry weights of leaves, stems, flowers, and roots.
Postproduction longevity of the inflorescences was recorded. Also, beginning at harvest and repeated every 3 to 4 days in postproduction, mature leaves from the terminal and basal portions of a plant from each experimental unit were analyzed for chlorophyll content. A different plant from each experimental unit was used each measurement period.
Two terminal leaves (minus petioles) were removed from the plants. Fresh weights of both leaves were recorded. One leaf was dried and reweighed to serve as a reference for calculating chlorophyll content on a dry leaf weight basis. The second was then cut up and placed in a centrifuge tube. The tube was filled with enough distilled water to bring the leaf/water volume to 4 ml (it was assumed that weight of leaf pieces in grams was equal to its water content in ml). Sixteen ml of 100% acetone were added to leaf tissue in the 36 tube, which was then homogenized with a Polytron homogenizes. The homogenate was
mixed with 10 ml of 80% acetone used to rinse the blades after homogenizing, and was then centrifuged at 5000 rpm for 5 minutes. Chlorophyll content was measured in a spectrophotometer (Shimadzu UV-Visible recording spectrophotometer) by diluting 1 ml of the supernatant with 2 ml of 80% acetone and measuring light absorption at 700.0,
663.2,646.8, and 470 nm. Chlorophyll content (pg/g) was determined from a program in the spectrophotometer based on equations of Lichtenthaler ( 1987), The procedure was repeated, taking a lower leaf from the branches of the same plant. Chlorophyll content, presented in the results section, is based on leaf fresh weights rather than dry weights. The reason for this is that data for fresh and dry weights of the reference leaves were missing for several of the measurement periods.
Experiment S. There were only two treatments in this experiment, each with 3 replications arranged in a randomized complete block design. Hydro-Sol, a Grace-Sierra water soluble product with a ratio of 5-11-26, was the principal fertilizer used. It is commonly used in hydroponic crop production. When injected into the irrigation stream at recommended rates it furnishes adequate levels of all nutrients except N and Ca.
Hydro-Sol provides no Ca at all and only 50 mg N/liter, with KNO, being the source of the N. Its use in this and following experiments allowed the manipulation of N source and rate while keeping levels of all the other nutrients constant. To provide Ca, approximately
870 mg gypsum was topdressed to each pot in both treatments. 'Spirit' in the first treatment was fertilized from a concentrate solution containing 16 g Hydro-Sol and 1.8 37 g urea/L. In the second, the concentrate contained 16 g Hydro-Sol and 12.1 g NH4NO/L.
The concentrated fertilizers were applied to plants by injecting them into the irrigation stream with a hose-on that had a dilution ratio of 16:1. This yielded a final N concentration of 100 mg N/L (1 N O /: 1 N H /) for the first treatment, and 400 mg N/L
(9 N O /: 7 N H /) for the second. The goal was to vary the total N availability but keep the relative proportion of NO / to N H / (or urea) approximately equal.
Plant responses measured in this experiment were the same as those in Experiment
4, except that no chlorophyll analysis was conducted.
Results:
Experiment 4. The Peter's WSF and high Osmocote treatments produced fuller, more aesthetically pleasing plants than did the recommended Osmocote rate. However, just as in the closed system, flowers declined faster in postproduction, about 3 to 4 days for the high Osmocote rate and 7 days for the WSF. Plants fertilized with WSF had the highest foliar N levels, followed by the high and then the recommended Osmocote rate treatments. Fertilizer treatment had no significant impact on total leaf number per plant, but plants that had the higher total foliar N levels (WSF and high Osmocote treatments) also had higher total and average leaf areas and total leaf dry weights. They also had the lowest root fresh and dry weights (Table 6). This was true especially in those plants fertilized with WSF which, despite fungicide drenches, exhibited some significant root necrosis. Table 6. Exp 4. 'Spirit* growth responses to Osnocotc 14-14-14 it two riles and to Peter's 20-10-20 Peallite
Plant Plant Flower Avgleaf Avgleaf Stem fresh Shoot dry Flower Flower height diameter diameter Leaf fresh wt dry wt weight weight fresh wt dry wt Fertilizer treatment (an) (an) (an) number (mg) (mg) (R) (g) (g) (g)
Osmocote 1 g N /p o t 27.8 233 13.4 56 398 75 20.8 5.65 75.0 1249 Osmocote 4 g N / pot 29.9 26.7 145 56 705 95 305 6.94 920 11.48 Peter's 300 mg N / liter 27.0 255 135 51 838 114 27.6 5.10 695 1256
LSUnum (w C. V.z) 1.77 1.9 055 59.0 103 527 0.95 738 —
Root fresh Root dry Average Postprod Medium Medium Medium Medium Medium weight weight leaf area Floral life Medium EC NO,* P K Ca Fertilizer treatment GO (8) (on*) (days) pH (dSAn) (mg/kg) (mg/kg) (mg/kg) (mg/kg)
Osmocote 1 g N /p o t 134.1 26.0 11.1 27 6.13 1.00 13 3 8.0 44.7 773 Osmocote 4 g N / pot 1085 185 162 22 439 426 186.7 413 2380 2803 Peter's 300 mg N / liter 43.1 63 16.6 19 4.90 4.60 460.7 48.0 505.0 1173
LSDnum (or C.V.Z) 302 0 3 ) 13 29 056 (25) (37) (28) (47) 0 6 ) _
Foliar N FoIiarN ©disbud @harvest Foliar P FoliarK Foliar Ca Foliar Mg Foliar Fe Foliar Mn Foliar Zn Foliar Na Fertilizer treatment (*) (*) (* ) <%) (*> (%) (mg/kg) (mg/kg) (mg/kg) (mg/kg)
Osmocote 1 g N /p o t 3.77 264 0.42 3.68 1.18 031 572 96.7 41.9 19.0 Osmocote 4 g N /p o t 5.52 433 0.88 5.11 1.42 051 60.1 3103 793 24.8 Peter's 300 mg N / liter 736 6.75 1.73 6.70 0.85 031 88.1 207.9 53.9 413
LSDmon (or C.V.Z) 0.45 059 026 0.43 033 0.12 17.8 926 16.4 8.6 z C.V “ Coefficient of Variability expresses the standard deviation as a percent of the general mean of the dependant variable. It is presented for those dependant variables where heterogeneity of variance violated the assumptions of ANOVA, rendering F test a levels questionable. 39
Based on guidelines for individual nutrients for chrysanthemum published by Dole and
Wilkins (1989), foliar nutrient levels for all plants fell in what could be considered an acceptable range with the following exceptions: the N level in low Osmocote plants at harvest was notably below the suggested range of 4.0 to 6.0%, while the level in the WSF plants at both disbud and harvest was high. In addition, the P level in the WSF plants was a little above the suggested 0.2 to 1.2% range. The floral growing medium analysis highlighted some problems. The low Osmocote growing medium had low Ca levels and very low NO/ and K levels. The high Osmocote media had low pH and high soluble salt and P levels as did the WSF pots. In addition, the WSF pots also had high K content
(Table 6). As expected, postproduction longevity declined as N in the leaves increased.
The correlation was rather strong (Table 7). There was a hint of chlorosis in a few of the lower leaves of the lx Osmocote plants, but the most significant symptom of decline in all the plants, including the lx Osmocote plants, was a wilting of the foliage and inflorescences. This was followed by a necrosis of the petiole and base of the leaf blade.
In addition to foliar N, a number of the other plant growth parameters that were measured also correlated well with postproduction flower longevity (Table 7). As root dry weight and pH dropped, and medium N and soluble salt levels increased, postproduction flower longevity declined.
Chlorophyll content in the top mature leaves changed very tittle during postproduction, even alter the flowers had declined. No measurements for the Peter's fertilized plants were Table 7. Exp 4. Coefficient of Determination (0 between postproduction flower longevity a n d ... ______
Root dry weight 0.768 Foliar N 0.783 Medium NO/ 0.763 Soluble salts 0.637 PH 0.508 Foliar Ca/Na ratio 0.789 df«7. All correlations were significant (psO.01, except pH - p<0,05). iue . x. Clrpyl otn (gg effeh egt o Sii' during 'Spirit' of weight) fresh leaf (mg/g content Chlorophyll 4 Exp. 6. Figure postproduction.
mg/g leaf fresh weight mg / g leaf fresh weight ■s* Osm 1 kg N/cu m •v- Osm 4 kg N/cu m N/cu kg 4 Osm •v- m N/cu 1kg ■s* Osm 2.5 1.5 0 2 Peters' 300 mg N/liter mg 300 Peters' Top leaves Top Bottom leaves Bottom Weeks in postproduction in Weeks Weeks in postproduction in Weeks 42 taken during the fourth week of recording because all the leaves on these plants had declined. Similar observations were made with the bottom mature leaves, with some differences. First, chlorophyll content in lx Osmocote leaves appeared to be below those of the other treatments during most of postproduction. This is not surprising considering the fact that N content in the leaves of these plants was below the recommended range.
Chlorophyll content in these leaves, however, did not decline during the period of measurement in postproduction. Second, lower mature leaves of the 4x Osmocote fertilized plants had permanently wilted before the last measurement period.
Experiment 5. Though there was a significant difference in the N levels in the foliage and growing medium between the two treatments, there was not the range of separation that I had expected in foliar N levels. Foliar N levels in both treatments were above the guidelines suggested by Dole and Wilkins (1989). This translated into plants that were observationally and statistically indistinguishable. There were actually
larger relative differences between the two treatments in foliar levels of other nutrients
(e.g. P and K). Still there was a difference in postproduction longevity of 3 to 4 days
(Table 8).
The growing medium analyses revealed that nutrient levels in the pots of the two treatments conformed to expectations. The NO,‘ levels in the high N fertigation treatment were ~3x that of the lower N treatment. There were no significant differences between the levels of P and K, and only a slight difference for Ca (Table 8). The growing medium
P, K, and soluble salt levels in both treatments were high. Table 8. Exp.5. 'Spirit' growth responses i t moderate and high levels ofN fertility.
Plant Plant Total leaf Avgleaf Root dry Foliar Foliar Foliar height diameter d ij weight area weight N P K Fertilizer treatment (cm) (an) (g) (an1) 100 mg N/L 20.0 18.4 2.17 11.11 234 6.93 0.82 6.29 400 mg N/L 21.0 18.9 4.18 11.72 1.83 730 132 4.81 ** *•* rF M 2 NS NS NS NS NS Foliar Postprod. Growing Soluble Medium Medium Medium Medium a longevity medium salts NO, P K Ca Fertilizer treatment 0 9 (d«y») pH (dSAn) (mg/lcg) (mg/lcg) (mg/kg) (mg/lcg) 100 mg N/L 0.89 23 733 331 135.7 33.7 5183 98.0 400 mg N/L 1.15 19 5.90 5.70 406.7 343 4643 178.7 *••*•** •* t fm______NS NS 2 F test significant at tbe 0.05 (*), 0.01 (**), 0.001 (*•*), or not significant (NS). 44 Growing medium pH in the low N treatment was above the recommended range, while the N O / level was a little below. Discussion Visual appearance of the plants from the various treatments suggested that there was little, if any, loss of chlorophyll during four weeks in postproduction. Measurements of chlorophyll in the leaves support these observations. Again, one of the key characteristics of classical senescence is a rapid loss of chloroplast integrity and chlorophyll content. It appears that rapid postproduction decline of heavily fertilized plants that we observed in these experiments is not due to a mechanism normally associated with senescence. We were able to reproduce the accelerated loss of postproduction keeping quality in an overhead irrigation open production system that was observed in previous subirrigation studies. This was important for future studies in which control of individual nutrient levels, facilitated by this production system, would be evaluated. The variations between the two treatments in Experiment 5, in foliar nutrient levels, and growing medium pH and soluble salt levels may be due, at least indirectly, to increased N fertilization. Roude et a). (1991a) found that, as the level of Peter's 20-10-20 and Osmocote 14-14-14 increased from 1.3 to 2.6 to 5.2 kg N/m1, the pH of three different types of growing medium (Vergo Clay Mix, MetroMix 350, and 1 peat: 1 perlite: 1 sand) dropped. This was true of pots in which 'Copper Hostess' (ra=0.42) and Tip' (i*=0.60) chrysanthemums were grown. However, Roude et al.(1991a), found no correlation 45 between fertilizer concentration and medium pH for pots in which the cultivar Tridon' was grown. Lang and Elliot (1991) found that, as the N H /:N O / ratio increased from 1:3 to 3:1 (at 210 mg/L total N), or as total N was doubled from 210 to 420 mg/liter total N (NH/:NO/ ratio remained constant); pH dropped. In a second paper Roude et al. (1991b) found that, as the N H /:N O / ratio increased from 0.0:1.0 to 1.0:0.0 and from 0.0:1.0 to 0.4-.0.6 (total N remained constant at 300 mg N/liter and 3.06 g N/pot, respectively), pH dropped from 7.1 to 3.6 and from 7.2 to 6.6. A number of researchers have reported an inhibition of NO/ uptake with increasing N H / concentration. Elliot et al. (1983) reported that the proportion of NO / uptake by Dendrcaithemagrandiflora cv. 'fiesta' produced with constant levels of NO/ decreased as N H / levels increased. Rufty et al. (1982) reported the same with com, as did McCrimmon et al. (1992) with Tenncross' creeping bentgrass (Agroslispalustris). With the inhibited N O / uptake and enhanced N H / uptake, soil reaction becomes more acidic as the roots export protons to facilitate N H / uptake, or when N H / releases protons as it is absorbed as neutral NH, molecules. Source of N fertilization is often cited as a significant influence on the uptake of other nutrients (Marschner, 1885), Ammonium generally may inhibit uptake of other cations and enhance anion uptake, while NO/ favors anion uptake. In experiment 5, higher P and lower K levels were found in the treatment receiving moreNH/, but the other cations were also found in higher levels in the foliage. From these two experiments, the level of N nutrition has been implicated as a contributor to the loss of postproduction longevity, but not as the principal cause. CHAPTER IH Foliar Carbohydrate Levels as Indicators of Postproduction Longevity The visual symptoms of rapid decline in heavily fertilized 'Spirit* observed in the previous experiments did not appear to fit the mold of classical senescence. This decline appears to be closely associated to the level of N fertility. How docs a high level of fertility, presumably high N fertility, cause the accelerated rate of decline in a postproduction environment? In Experiment 6, two possible explanations were to be evaluated. Nutritional research with various turfgrass species has demonstrated deleterious effects of excess fertilization. Excess N increases the rate of protein synthesis and carbohydrate utilization (Beard, 1973). This depletes and diverts the allocation of carbohydrate reserves required for respiration and tissue maintenance to the detriment of roots. The result is a pushing of the top growth at the expense of the root system, which predisposes the turfgrass to stress if the weather or cultural practices become less than ideal (Beard, 1973). Westhafer et al. (1982) evaluated three different turfgrass species, Poapratensis 'Baron', Poa auma, and Agrostispaluslris 'Penncross', produced under two different NO/-N levels, 5 and 10 mM They found that total soluble carbohydrates as well as the individual components, fructose, glucose, sucrose, and fructans, all were lower in the roots, stems, and leaves of plants produced at 10 mM N O / compared to those 46 47 produced at 5 mM. Potted chrysanthemums do not exhibit the same type of indeterminate polycarpic habit of turfgrass, since they are produced as a determinate monocarpic crop. But it is possible that a similar adjustment occurs in the carbohydrate level or the caibohydrate/protdn ratio due to excessive N. In the greenhouse under ideal conditions, i.e. high light intensity and ample moisture, sufficient carbohydrate is produced to support various physiological processes required to maintain the plant. Low light intensity levels and possible periodic water stress, due to erratic irrigation, typical of most discount storc/home/office environments, are not conducive to the same rate of photosynthesis. Perhaps, as the rate of respiration exceeds photosynthesis, carbohydrates are depleted to the point that physiological processes in the plant slow or become unresponsive to environmental stress signals. This study was designed to evaluate the potential link between N levels and postproduction longevity. The coefficients of determination (r3) between foliar N level and postproduction longevity in Experiment 3 (0.93) and in Experiment 4 (0.89) strongly implied that such a link exists. The second possible explanation evaluated was soluble salt problems. In Experiment 4, we found a strong negative correlation between salt levels in the growing medium and postproduction longevity (r2 = 0.64). Roude et al. (1991a, 1991b) noted a decrease in postproduction flower quality occurred in response to increasing N concentrations or percentage ofN H / as the N source. This was accompanied by an increase in the soluble salts content of the growing medium. Gerberick (1989) found that discontinuing water soluble fertilizer use at the time of disbud resulted in significantly lower soluble salts levels 48 (in addition to lower foliar N levels) and increased flower keeping quality. The association between soluble salts and postproduction longevity may only be indirect, i.e. the electric conductivity goes up in direct response to increasing fertilizer levels, and postproduction longevity goes down due to the same cause. Increased growing medium ECs, however, may have raised the osmotic potential of the medium to the point that water uptake was inhibited and some root injuiy occurred. Data from Gctbcrick’s (1989) work appear to both support and disprove this possibility. Treatments included plants that were fertilized until harvest, bud color, disbud, or until harvest, with the growing medium leached until the salt level was the same as that found in the bud color fertilizer termination treatment. He found that while flower keeping quality of'Spirit' for the harvest-leaching treatment matched that for the bud color termination treatment in one trial, in a second, longevity was shortened, matching that for the harvest termination treatment. In addition to the possible water relations and root injury that may occur due to lowering of the osmotic potential of the growing medium associated with increased electric conductivity, salts, particularly Na, may afreet the physiology of the root. A model has been proposed which describes Na displacing Ca at the plasmalemma, and perhaps at intracellular membranes, affecting structural stability and membrane functions such as uptake of Na, K, Ca and other nutrients (Lfluchli, 1990; Lynch et al., 1989) and perhaps the membrane-mediated seconded messenger system. In the last 10 to 15 years, a number of researchers have implicated Ca as having a larger role in plant function than previously realized. Calcium stabilizes associations between the head groups of 49 phospholipids, particularly in the plasmalemma. Calcium is also postulated to be a key component in the cellular second messenger system, allowing plants to respond to exogenous stimuli (Ferguson and Drobak, 1988; Poovaiah, 1988; Einspahr and Thompson, 1990). Experiment 6 was designed to evaluate the hypothesis that excessive N depletes carbohydrate reserves, predisposing plants to postproduction decline. The potential value of periodic foliar Ca sprays on postproduction keeping quality was also evaluated. Materials and Methods Experiment 6 was begun April 4,1992 using the cultivars 'Spirit' and Torch'. There were four fertilizer main plot treatments for each cultivar and two Ca subplot treatments. The main plots were replicated three times, utilizing a total of 12 flood and ebb benches. Two of the replicates were run in one house and the third in an adjacent house maintained under as nearly identical, growing conditions as was possible. A total of 1,200 plants were used. The four main plot treatments were: 1. Osmocote 14-14-14 at 7.1 kg/m1 preplant incorporated into the growing medium (~ 53% NO,'). 2. 100 mg per liter total N (- 56% NO,*) from 16 g Hydro-Sol/L, 1.33 g urea/L, plus 0.67 g NHjNO/L, diluted 16:1 with a hose-on during fertigation. 3. 400 mg per liter total N (56% NO,*) from 16 g Hydro-Sol/L, plus 12.12 g NH4N O /L, diluted 16:1 with a hose-on during fertigation. 4. 400 mg per liter total N (60% NO,') from 32 g Peter's 20-10-20 Peatlite/L, diluted 16:1 with a hose-on during fertigation. so Treatments 2 and 3 received 870 mg gypsum/pot topdressed. Since these were the critical treatments, an attempt was made to hold the NOj'/NH 4* ratio constant, while varying the total amount ofN supplied. Treatments 1 and 4 were added as moderate and high fertilization controls. Half of the plants on each bench were sprayed with distilled water on a weekly basis beginning at disbud to harvest. The other half were sprayed with 400 mg/Iitcr CaCI2. Data recorded included plant height and diameter, inflorescence diameter, days to flower, and days to floral and foliar postproduction decline. Also, average leaf number and area, as well as lea£ stem, root and inflorescence fresh and dry weights of three plants per treatment/replication were recorded. Floral growing medium samples were taken at the main plot level, but foliar analyses were done at harvest for both main and subplot treatments. Foliar samples were taken at harvest and 2 weeks into postproduction for chlorophyll, starch, total soluble carbohydrates (TSC) and soluble protein measurements. Chlorophyll levels in mature leaves from the top portions of plants were determined using the procedure described in Experiment 4. The pellet left in the centrifuge tubes afler the chlorophyll/acetone supernatant had been removed was washed in 80% acetone and centrifuged three times. Pellets were transferred to glass tubes that had been dried overnight at 40 to 50°C, cooled in a sealed desiccator and weighed. The tubes plus pellets were dried, cooled and reweighed. The difference in tube weights was used to calculate starch on a per dry leaf weight basis. The starch in the pellets was solubilized by placing 20 ml distilled water in each tube and placing the tubes in a hot bath (98°C) for 10 minutes. Tubes were removed from the hot bath and briefly placed in an ice bath to bring them 51 down to room temperature, and 25 pi amylogfucosidase was then added to each tube. Tubes were held overnight to allow the enzyme ample time to break the starch down to glucose. The following day, glucose levels were determined by preparing the samples and glucose standards according to the steps outlined in a Sigma Diagnostics Glucose kit (Procedure No. 510) and measuring light absorption at 450 nm. Two subsamples were generated from each sample prior to the use of the glucose kit to help serve as a check for procedural errors. If significant discrepancies were observed between the two subsamples, additional subsamplcs were run. Soluble protein and TSC were assayed by homogenizing the second leaf samples in 20 ml phosphate buffer solution and centrifuging at 4,000 to 5,000 rpm for five minutes. Two subsamples were prepared from each sample by placing 0.1 ml phosphate buffer (to serve as a blank), diluted albumin stock (0,05 ml albumin plus 0.05 ml distilled water to yield 100 pg protein), or buffer/leaf extract. To each tube, 5 ml Bradford protein reagent was added. The tubes were allowed to stand for about 5 minutes. The standard and leaf extracts were measured against the blanks at 595 nm. Protein concentration (mg/ml) for each leaf extract was determined by multiplying the leaf extract absorption units by the concentration of protein standard (1 mg/ml) and dividing by the protein standard absorbance. Total soluble protein content per gram leaf fresh weight was determined by multiplying the protein concentration (mg/ml) by the total leaf extract (20 ml phosphate buffer plus the fresh weight (g) of the leaf samples converted to ml) divided by the leaf fresh weight. This was then converted to a per g leaf dry weight basis. Total soluble carbohydrates were measured by placing 50 pi of buffered leaf extract in two glass tubes (i.e. two subsamples per sample) and diluting it with 1.95 ml distilled water. Tubes containing 2 ml diluted leaf buffer extract, sucrose standard (0.02 mg/ml), or distilled water blanks were placed in an ice bath. Five ml of sulphonatcd a- naphthol reagent (Devor, 1950) was added to each tube with a rapid delivery pipette. The tubes were individually shaken to mix the reagent and sample, then placed in a 98°C water bath for 10 minutes and returned to the ice bath for 5 minutes. Absorbance at 555 nm was read in the spectrophotometer. Total soluble carbohydrates per leaf sample was calculated in a manner similar to that for total soluble protein. Results Results in Tables 9 and 12 show that as in previous experiments, plants fertilized at the higher rates tended to be larger (plant volume - calculated by multiplying the area equivalent to plant diameter by the height) and more robust and succulent (larger average and total leaf dry weights and average leaf area). For 'Spirit', plants fertilized at higher rates were darker green in color (higher chlorophyll content per unit leaf area). Torch' foliage is naturally dark green, even under low to moderate nutritional levels and color did not intensify at higher nutritional levels. Postproduction foliar longevity also decreased with an increase in fertilizer levels. There was larger root mass (total root dry weight) for the Osmocote treatments for both cultivars. The other treatments were statistically similar to each other. Foliar nutrient levels (TablelO) and growing medium pH and nutrient levels were similar to those observed in previous studies. Table 9. Exp. 6. Impact of fertilizer regimes on chrysanthemum production and postproduction characteristics. Plant Average Average leaf Chlorophyll Postproduction volume leaf area dry weight content longevity Treatment (dm*) (cm2) (mg/cm2) (Mg fax?) (days) ’Spirit’ Osmocote 7.1 kg/m5 11.1 13.5 5.1 49.7 55 Hydro-Sol 100 mg N/L 8.4 12.6 5.2 55.5 44 Hydro-Sol 400 mg N/L 10.6 17.9 8.3 78.2 28 Peter's 400 mg N/L 10.8 16.6 6.2 68.3 21 LSDflum 1.9 4.0 2.0 13.1 5 Torch' Osmocote 7.1 kg/m1 9.6 12.9 7.6 66.1 59 Hydro-Sol 100 mg N/L 9.3 14.7 8.0 69.0 55 Hydro-Sol 400 mg N/L 13.5 15.8 7.3 67.0 40 Peter's 400 mg N/L 15.7 23.6 10.3 62.7 26 LSDflmn 1.8 2.2 1.1 NS 8 Table 10. Exp 6. Foliar and growing medium nutrient levels at harvest Foliar ______Growing medium N P K Ca Mg Mn N P Ca K Treatment (%) (%) (%) (%) (%) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) pH ’Spirit’ Osmocote 7.1 kg/m3 3.7 0.67 4.7 1.81 0.40 133 43 31 164 98 5.9 Hydro-Sol 100 mg N/L 5.4 0.59 6.5 1.08 0.52 14 55 39 94 473 7.1 Hydro-Sol 400 mg N/L 6.5 1.31 6.0 1.33 0.63 267 274 34 150 362 5.0 Peter's 400 mg N/L 7.0 1.52 7.6 0.90 0.30 43 293 48 54 503 5.4 LSDrajK1 (orC.V.z) 0.6 0.26 0.71 0.22 0.12 88 (82) (48) 0.43 ... m Torch’ Osmocote 7.1 kg/m1 4.0 0.64 5.0 1.49 0.50 150 22 15 114 49 6.0 Hydro-Sol 100 mg N/L 5.5 0.52 6.6 0.96 0.62 17 49 48 101 483 6.9 Hydro-Sol 400 mg N/L 6.8 1.07 6.0 1.46 0.95 260 257 41 128 334 5.0 Peter's 400 mg N/L 7.6 1.25 8.4 0.90 0.58 183 334 48 64 575 5.5 LSDrnM> (or C.V.z) 0.6 0.21 0.83 0.18 0.15 52 (89) 7 — (63) 0.21 z C.V ■ Coeffideal of Variability expresses tbe standard deviation as a percent of the general mean of the dependant variable. It is presented for those dependant variables where heterogeneity o fvariance violated the assumptions of ANOVA, rendering F test a levels questionable. Starch content at harvest in both cultivars receiving Osmocote was significantly higher than for any other treatment There were no significant differences between the two Hydro-sol treatments at harvest in either cultivar (Table 11). By two weeks into postproduction, starch levels in both cultivars had dropped to minimal levels. Total soluble caibohydrates in the high Hydro-sol treatment for Torch' appeared higher than levels for any of the other treatments at harvest for the same cultivar, but statistically there was no difference between the two Hydro-Sol treatments. Other than that one exception, there were no differences in TSC levels among treatments in a given measurement period for cither cultivar. There was a trend, however in the two weeks between harvest and postproduction measurements, for caibohydrates to decline for all treatments. There were no significant differences observed in soluble protein content among treatments; there appeared to be no decline during the two weeks in postproduction. There were some differences in chlorophyll content in the leaves of'Spirit' among treatments, but there were no observations of a decline in chlorophyll content over time among any of the treatments for either cultivar. Calcium chloride spray treatments in this experiment had no impact on any of the production, postproduction, or nutritional variables that were recorded. Discussion The results obtained from this experiment do not support either hypothesis put forward. Correlations between postproduction longevity and leaf carbohydrate or between postproduction and carbohydrate/protein ratios were very low, and in most cases were not significant (Table 13). Examination of foliar carbohydrate levels (including starch and 5 6 TSC), both at the end of production and two weeks into postproduction, reveals few differences between the two Hydro-sol treatments within a given time period. The TSC level at the end of production for the cultivar Torch1 appeared to vary, although the difference was not statistically significant. Leaves of plants produced with Hydro-sol at 400 mg N/L contained 60 % more TSC than plants produced with lower N rate. Had the first hypothesis been valid, I would have expected the lower N Hydro-sol treatments in both cultivars to have had higher TSC levels. It is interesting to note, however, that the starch levels for the Osmocote treatments in both cultivars at the end of production were significantly higher than the others. Trusty and Miller (1991), working with the chrysanthemum variety Tavor1 produced with 300 mg N/L found that both leaf starch and TSC levels dropped significantly during the first four days in postproduction and thereafter remained relatively constant. This decline in leaf carbohydrate levels, however, was not accompanied by leaf senescence or loss of turgor. They also found that "a substantial amount of free sugar (and starch) remained in the inflorescences at the onset of (flower) wilting and senescence." A direct connection or correlation between the time of carbohydrate depletion and loss of floral/foliar turgjdity in postproduction was not apparent. Their results suggest that neither foliar nor floral carbohydrate content at harvest would be reliable indicators of keeping quality potential, even if the expected carbohydrate differences had been observed between treatments in this current study. Foliar soluble protein content in plants fertilized with Hydro-sol at 400 mg N/L was statistically similar to that in plants fertilized at 100 mg N/L. Again, this is contrary to 5 7 what I would have expected. Woodson et al. (1984) found that although there was a significantly higher level of NO,' reduction in the leaves of the variety 'Indianapolis White* maintained at 200 mg per liter N compared to those maintained at 50 mg per liter N during the early vegetative stages of growth, NO/ reductase activity in the two treatments was statistically indistinguishable from the time of first observable flower bud color through harvest. This observation may offer at least a partial explanation for similarities in soluble protein content in the leaves among treatments in this experiment. Since NRA dropped significantly before the reproductive stage began, and appeared to be relatively insensitive to N fertilization rate by that time, one might expect little difference. That is, difference in foliar NO/ reductase activity (NRA) between the two N treatments were not statistically significant by day 60, and leaves of both treatments had lost significant N content to the inflorescence. It doesn't appear to be a complete explanation however, because even in their study, foliar levels of reduced N were much higher in the high N treatment. The lack of plant response to Ca containing sprays in this experiment is far from definitive, given the crude, exploratory nature of the treatments, but they certainly lend no support to the Ca membrane displacement-second messenger hypothesis proposed. Table 11. Exp 6. Influence of fertilizer kvds on leaf starch, tod] soluble carbohydrate, soluble protein, and chlorophyll content measured at the end of production and again after two weeks in postproducdoo. Total soluble Soluble Starch carbohydrates protein Chlorophyll (mg/gdiywt) (mjz/stdrywt) (mgfgdxywt) (mg/gdrywt) Treatment Prod Past Prod Post Prod Post Prod Post 'S pirit1 Osmocote7.1 kg/in* 266 0.7 31 19 2 2 3 28.9 9 3 9.6 Hydro-Sol 100 mg N/L 49 2 3 39 19 273 2 0 3 103 10.8 Hydro-Sol 400 mg N/L 83 1.8 38 12 26.4 24.7 12.4 11.7 Peter’s 400 mg N/L 69 2.2 31 23 27.1 34.9 123 134 Ftesfc Between Hydro-Sol T its, 100 v.s. 400 mg N/L NS NS NS NSNS NS •* NS C. V. for all treatments 86 92 35 50 29 47 14 10 Torch* Osmooote7.1 kgfo’ 159 0.8 37 21 213 14.4 8.7 10.4 Hydro-Sol 100 mg N/L 68 1.6 42 22 18.5 30.6 9.7 11.4 Hydro-Sol 400 mg N/L 92 5.1 67 21 323 2 4 3 134 103 Peter’s 400 mg N/L 37 1.2 25 21 19.4 18.4 93 10.4 Ftest Between Hydro-Sol Trts, 100 v.s. 400 mg N/L NS NS NS NS NS NS ** NS C. V2. for all treatm ents 77 170 44 61 41 47 20 9 z C.V « Coefficient ofVariability expresses the standard deviation as a percent of the general mean of the dependant variable. It is presented for those dependant variables where heterogeneity of variance violated the assumptions of ANOVA, rendering F test a levels questionable. Table 12. Exp 6. Responses of selected leaf root, and growing medium parameters to differed fertilizer regimes. Total leaf Total root Soluble Postproduction diyw rigbl dry weight Root/leaf salts longevity Treatment fe) (B) ratio fdS/in) (days) ’S pirit' Osmocote 7.1 kg/m’ 3 3 16.8 4.75 2.7 55 H ydro-Sd 100 mg N/L 3.1 5.7 1.82 3.1 44 Hydro-Sol 400 mg N/L 7.1 6 3 0.87 4 3 28 P eter's 400 mg N/L 5 3 5.0 0.96 3 8 21 LSDmim 2 3 4 3 0.84 1.8 5 Torch* Osmooote 7.1 kg/m* 4.4 19.8 4.47 1.7 59 Hydro-Sol 100 mg N/L 5.1 7 3 1.45 3.1 55 Hydro-Sol 400 mg N/L 5 3 6.8 139 3.7 40 P eter's 400 mg N/L 11.0 6.4 039 4.4 26 LSD fr m 3 3 6 3 0 34 3 2 8 60 Tabic 13. Exp 6. Relationships between postproduction longevity and other selected plant measurements. t2 between foliar ^between foliar postproduction postproduction Degrees of longevity longevity Dependent variable freedom 'Spirit* Torch* Foliar N 22 0.92 **•* 0.86 *•• Foliar P 22 0.70 ••• 0.74 ••* Foliar K 22 0.56 •** 0.59 *♦* Foliar Ca 22 0.54 ••• 0.17 NS pH 10 0.32 NS 0.38* Soluble salts 10 0.33* 0.57 ** Medium N03” 10 0.73 •** 0.89 •** Medium Ca 10 0.25 NS 0.18 NS Root diy weight 22 0.54 **• 0.37 ** Root/leaf ratio 22 0.57*** 0.47 *** Starch 22 0.36* 0.21 NS Total soluble carbohydrates (TSC)22 0.01 NS 0.01 NS Starch+ TSC/protcin ratio 22 0.18 NS 0.09 NS Foliar Ca/Na ratio 22 0.44* 0.96 ••* z Correlations were significant at the 0.001 (***), 0.01 (**), or 0.03 (*), or not significant (NS). Correlations of postproduction longevity with foliar and growing medium variables (except pH) were negative in value. CHAPTER IV: Evaluation or Root Carbohydrate Levels and Root Function As A Mechanism Of Accelerated Decline in Well Fertilized Chrysanthemums In Experiment 6 it was concluded that hastened postproduction decline associated with excess N nutrition was not due to depletion of total soluble carbohydrates (TSC) or alteration of the TSC/soluble protein ratio. It is conceivable, that rather than looking at the leaves, the focus should have been on the roots. Several aspects of the data support this possibility. First, it was noted in Experiment 6, and in previous studies that there was some root dieback at harvest, particularly in plants that received high N treatments. This dieback progressed during postproduction. Second, the symptoms of decline in 'Spirit1, loss oftuigor despite adequate medium moisture levels, suggests the possibility of reduced water uptake by the roots. Third, there were significant correlations in previous experiments between postproduction longevity (PPL) and root diy weight, root/leaf ratio, and soluble salts. It is also conceivable that much of the problem of lost postproduction longevity was due to increased NH4* present in the high N treatments. Roude (1991b) reported that PPL of'Iridon* declined by seven days when the N H //N 03’ ratio increased from 0:1 to 0.5:0.5 to 1:0 (total N =300 mg/L). While it is true that it takes more energy 61 62 (ATP, carbohydrates) to convert NO]* into organic nitrogen (it is converted to NH3 as an intermediary), much, perhaps most, of it is transported in the xylem to the leaves. There it maybe stored in vacuoles or it may converted into organic N. Woodson and Boodlcy (1984) reported that 70% or more of the nitrate reductase activity occurs in chrysanthemum foliage. Ammonium, on the other hand, is tone to the plant unless it is rapidly incorporated into an organic N form in the roots. As discussed in chapter 3, high N H / levels can stimulate N H / uptake and suppress N O / uptake in some plants. The enhanced N H / uptake would require greater carbohydrate reserves in the roots to supply the energy and carbon skeletons needed to convert N H / to organic N. Ammonium has been shown to increase root respiration while NO/ has not (Matsumoto and Tamura, 1981 in Marschner 1986). Talouizte et al. (1984 in Marschner, 1986) reported that N H / fertilization resulted in lower soluble carbohydrates in roots compared to the carbohydrate levels in roots of plants fertilized with NO/. The objective of this last experiment was to evaluate the impact of high N O / vs high N H / fertilization on postproduction keeping quality and on root TSC levels and TSC/soluble protein ratios. Materials and Methods This seventh experiment was begun 24 September, 1993. It was designed as a two way factorial experiment for each cultivar, ’Spirit* and Tridon*. There were three N rate/source by two fertilizer termination treatments, with four replications per treatment and 18 subsamples (1 chrysanthemum per 11.5 cm plastic geranium pot « 0.5 liter) per 63 replication. The three fertilizer treatments were: 1. 100 mg total N/L, 25 mg NH/-N/L. This was supplied by 16 g Hydro-Sol/L, and 2.42 g NH4NOj/L mixed in a 19-liter bucket and diluted 16:1 as it was injected into the irrigation stream. Gypsum was topdressed at 870 mg topdressed per pot at the beginning of the experiment to supply calcium. 2. 400 mg total N/L, 100 mg NH/-N/L, This was supplied by 16 g Hydro-Sol/L, 9.7 g NHjNOj/L, and 15.5 g Ca(NO,)i/L mixed in a 19-liter bucket and diluted 16:1 as it was injected into the irrigation stream. Gypsum was added to each pot as in treatment 1. 3. 400 mg total N/L, 20 mg NH/-N/L. This was supplied by 16 g Hydro-Sol/L and 36.1 g CafNOjyL mixed in a 19-liter bucket and diluted 16:1 as it was injected into the irrigation stream. Treatment 2 supplied four times the total N (and N H /) of Treatment 1, but the percent of the total N supplied as N H / in these two treatments was about the same. Treatments 1 and 3 supplied about the same amount of NH /, but the total N and the percent o fN H / differed by a factor of four. The two fertilizer termination treatments consisted of plants that were fertilized until harvest and those that were fertilized until the bud color stage. Plants that were only fertilized until bud color were irrigated with tap water after that point. Data recorded included: plant height, plant diameter, inflorescence diameter, days to flower, leaf number, leaf area, leaf, stem, inflorescence, and root fresh and dry weights 64 at harvest, foliar nutrient analysts and growing medium nutrient analysts at harvest, floral and foliar postproduction longevity, and root fresh and dry weights 2 and 4 weeks into postproduction. Foliar and growing medium analyses were conducted at harvest on 'Spirit' only. A second trial was begun 6 weeks after the first. The parameters for the second trial were the same as for the first with a few exceptions. There were only 10 subsamples per replicate; leaf area, and stem and flower weights were not recorded. Root weights and total root N content were determined at harvest and at the end of weeks 1 and 2 in postproduction for 'Spirit' and at harvest and weeks 1,2,4, and 5 for 'Iridon'. Starch at harvest, and total soluble carbohydrates and soluble protein levels at harvest and one and two weeks postproduction were determined for 'Spirit'. Sampling for root N, TSC, soluble protein, and starch was done by taking one plant per treatment/replication at harvest and one and two weeks postproduction. Roots were washed, blotted dry between paper towels, and weighed (fresh weight). Approximately 1 to 1.5 grams was taken, weighed, placed in a plastic bag and frozen for later analysis. The remaining roots were placed in a drying oven (55°C) and then reweighed. Dry weight was estimated for the frozen portion of the root system using the ratio of the fresh and dry weights and the fresh weight of the frozen portion. The dried portion of the root system was then sent to The Research Extension Analytical Lab at Wooster for total N determination. The procedure for determining TSC, soluble protein and starch was essentially the 65 same as that used for the leaves in Experiment 6, except that starch was determined using the pellet that remained in phosphate buffer tube after TSC and soluble protein levels had been determined. The pellet was rinsed three times in an 80% acetone solution at which point the protocol indicated in Experiment 6 was followed. Finally, average daily transpiration rate was calculated for each cultivar while in postproduction. This was done by weighing two pots for each treatment/replication after irrigation (after they had drained) and reweighing at one to two day intervals until the pots were to be irrigated again. From the total water loss from each pot between irrigations was subtracted the average water loss from four pots in which the plants had been cut off at the crown. The purpose was to calculate a total water loss due to transpiration. Finally, total water loss for each irrigation period was divided by the total number of days during that period to calculate the average daily transpiration rate. All plants of a given cultivar were watered when any of that cultivar began to show wilt or when the weights of any of the pots indicated that wilt was imminent. The number of days between irrigation ranged between four and eight. One 'Spirit' plant from each treatment/replication at harvest and at one week postproduction was taken to the laboratory of Dr. Robert Joly at Purdue University to measure the hydraulic conductivity of the stems and root systems. Dr. Joly has set up a computerized pressure bomb that allows the analyses of 6 root/stem samples in a run. Unfortunately, the system could not be adapted to generate reliable readings with the chrysanthemum samples. 66 Results The cultivar 'Spirit' in both trials responded to the different fertilizer treatments in a manner consistent with results in previous experiments. Table 17 shows that the 'Spirit' foliar N levels for both the low and high N treatments in both trials was in the high end of the acceptable range. Although nutrient analyses were not conducted on the foliage of'Iridon' in either trial, they were grown on the same benches, under the same cultural conditions as the 'Spirit' and probably also contained high foliar nutrient levels. The high nutrient levels in the leaves of all treatments probably account for the laclc of meaningful differences in overall plant size, as well as little contrast between leaf and root fresh and dry weights. The data presented in Table 14, for the cultivar 'Spirit', presents some interesting trends (some were significant) among the treatments. First, consistent with research by Gerberick (1989) and Nell (1989), 'Spirit' fertilized until budcolor exhibited better postproduction quality (lasted longer in the postproduction room) than those fertilized through harvest. As in previous studies, plants that received the lower rate of N lasted longer in postproduction than the high N treatments. Treatments that received 400 mg N/L, with a quarter of it as N H /, declined 4 to 10 days sooner than plants that received the same amount of total N but only 5 % of it as N H /. In fact, total N H / that the plant was exposed to appeared to have more impact on postproduction longevity, in these trials, than did the total amount of N. This pattern was also observed (though not always with statistical significance) for root and leaf weights. Plants that received high N/high N H / 67 generally had larger leaf areas, leaf fresh and dry weights, but smaller root fresh and dry weights than the other treatments. Plants that received the high N/low N H / treatments had root/shoot ratios that were comparable to those of the low N treatments. The correlation between postproduction longevity and root dry weight and root shoot ratios in both trials involving 'Spirit' was, however, extremely low (r2 s 0.05). This is a distinct change from previous studies where the correlations were significantly stronger. The correlations between PPL and foliar N levels were still significant (trial 1: r2 = 0.79; trial 2: r3 - 0.55), but not as high as in previous studies (Table 20). The impact of fertilizer treatments on postproduction longevity, leaf area and leaf weights of fridon1 (Table 15) followed the same pattern as observed on 'Spirit*. However, differences in fertilizer treatments seemed to have little effect on root fresh or dry weight of'Iridon'. The growing medium analysis of 'Spirit' (Table 16) that received the high N treatments had pH, soluble salts, and NO/ levels that varied somewhat in magnitude between the two trials of Experiment 7. Growing medium supporting plants that received the lowN treatment and the high N/high N H / treatments through harvest in the first trial yielded analytical results similar to those in Experiments 5 and 6, with one exception. The pH drop in this trial did not appear to be as precipitous as in the two previous experiments. This might be explained by the fact that there was not as much N H / in the high NfV treatment in this experiment as previously. In the second trial of Experiment 7, where more total N (and therefor more total N H /) appeared to be in the pots, the pH did drop 6 8 as observed in the two previous experiments. The higher levels of nutrients in the second trial of Experiment 7 did not seem to have a major impact on the nutrient levels in the plant, as foliar nutrient levels in the two trials were similar to each other, and to levels observed in Experiments 5 and 6. In the discussion section for Experiment 5 it was mentioned that a number of researchers have reported an inhibition of NO/ uptake with increasing N H / concentration. Such an effect might explain some of the differences observed between the high N/high N H / and the high N/low NH / treatments. The greater growing medium NCV availability and pH drop may reflect preferential uptake of N H / for the high N H / treatments. However, the foliar nutrient levels did not show the variation in this study that were observed in previous studies, or that is normally associated with preferential N H / uptake. 'Spirit1 and 'Iridon' behaved differently in postproduction in response to the different fertilizer treatments. First, 'Spirit* declined more rapidly in postproduction than did 'Iridon'. Second, the symptoms of decline differed sharply. Flowers and foliage of 'Spirit' lost turgor and wilted, although there was ample water in the growing medium. The younger and older foliage showed the wilting symptoms first, with leaves from the middle portion of the stems exhibiting symptoms last. There was very little chlorosis or marginal necrosis associated with this decline; necrosis was first observed at the junction of the petiole and leaf blade. 'Iridon', like 'Spirit', exhibited very little chlorosis, but there was also no loss of leaf or flower turgor. Instead, marginal necrosis was evident on all the foliage, though it was far more evident on the youngest and oldest foliage. This was 69 followed by a collapse and drying (but not a wilting) of the upper and lower foliage. Thrips damage masked symptoms of decline in Iridon* flowers, but it appeared that the lower or outer rows of ray florets also collapsed, dried and darkened in color. Symptoms of decline in Torch' in Experiment 6 were intermediate between those observed for 'Spirit' and 'Iridon' here. Torch' exhibited loss of foliar and floral turgor and marginal leaf necrosis, but not the foliar collapse. There were other distinctions between the two cultivars in this experiment in postproduction (Table 18). The root systems of'Spirit' displayed a rapid loss of root fresh and dry weight by the end of the second week in postproduction. Root weight declined fastest in plants fertilized with high N/high N H /. Much of the loss in root weight in this cultivar was due to root dieback. Even at harvest plants fertilized with high N/high N H /, especially if fertilized until harvest exhibited significant root dieback. This dieback progressed in postproduction to the point that by the end of the second week almost no white viable roots remained on the high N/high N H / plants fertilized until harvest. Root systems of'Spirit' receiving the other fertilizer treatments also showed dieback, becoming most prominent about the time the leaves collapsed. Roots systems of plants fertilized with the high N/Iow N H / showed an intermediate response in postproduction. Root systems of'Iridon' showed very little necrosis even 5 weeks into postproduction. And there were no clear effects of fertilizer treatment on root weights. The pattern of average daily water usage in postproduction (Fig. 7) was generally consistent with other results. Water usage, for both cultivars, was greatest for low N 70 plants followed by high N/Iow N H / and then high N/high N H /. Also, plants fertilized only to bud color tended to transpire at a higher rate than those fertilized to harvest. Plants that sustained the highest transpiration rates, survived the longest in postproduction. The pattern of transpiration did not, however, match the pattern of total plant fresh weights at harvest. Plants that received high N/high N H / generally had the highest total fresh weights; but they also had the lowest root fresh weights, and lowest transpiration rates. Plants that received high N/low N H / generally had the lowest total plant fresh weights but had intermediate transpiration rates in postproduction. Both cultivars showed an initial increase in transpiration rate in postproduction. Though not measured, the transpiration rate of plants while sleeved, boxed and in the dark (no photosynthesis and high C 02 in the stomatal cavity resulting in closed stomata), was probably veiy low. Perhaps there was a gradual acclimation to the low light levels with limited photosynthesis resulting in gradual stomatal opening and increased transpiration. Both cultivars showed a drop in average daily transpiration, which was slight in 'Iridon* while in 'Spirit' it was much sharper and corresponded to the period when root decline was accelerating. Transpiration in Iridon', especially for the low N H / treatments, then increased on a daily basis until the last recording period. The second rise in 'Iridon* transpiration is difficult to explain. The differences among treatments, however, may be explained by the fact that it was during this period that leaves of the high N/high N H / started to collapse. Results of the total N, soluble protein and total soluble carbohydrate analyses run on the roots are presented in Table 19. With one exception, the only differences noticed 71 among treatments or over time was the increase in TSC levels for all treatments and soluble protein for the two high N/Iow N H / treatments at the end of the second week in postproduction when roots were decaying. TSC levels of the low N treatments were significantly higher than the other treatments at harvest. By the end of the first week in postproduction the difference had disappeared. No starch (data not presented) was observed in roots of any of the treatments at harvest. Discussion: The symptoms of decline exhibited by the two cultivars in this study were different. * Spirit* exhibited a loss of turgor, as in previous experiments, while marginal necrosis and then leaf collapse were the symptoms ‘Iridon' exhibited. These different symptoms may still have resulted, directly or indirectly, from the same cause. The range o fN H / toxicity symptoms that have been reported on chrysanthemum and poinsettia include both root dieback and foliar marginal necrosis (Fleming et at., 1987; Cox and Seeley, 1984). Variable chrysanthemum cultivar sensitivity to ammonium toxicity has also been reported (Fleming et a!., 1987). The range of symptoms that have been observed in this set of experiments on the cultivars 'Bright Golden Anne', 'Spirit', Torch1, and 'Iridon' might all fit under the umbrella of ammonium toxicity. There are difficulties, however, in attributing all the problems we have observed in postproduction just to the level of ammonium in the irrigation solution during production. First, though keeping quality varied among fertilizer rate/source treatments, the actual symptoms of decline in high N produced plants within a given cultivar did not TabIcI4. Exp7. Response of •Spirit* it harvest to different nitrogen rates, sources, and termination periods. Plant Leaf fresh Leaf dry Root F re d Root Dry Root/ Foliar Floral Height Weight Weight Weight Weight Shoot longevity longevity Treatment (cm) (8) (8) f t) (8) ratio (days) (days) 'Spirit' - First trial 100 mg/1 N (25 mg/1 NH4) until bud color 20.1 22.5 2.0 2 8 J 3 3 1.6 38 29 100 mg/1 N (25 mg/1 NH4) until harvest 20.8 203 1.9 27.7 3Z 1.7 30 25 400 mg/1 N (100 mg/1 NH4) until bud color 20.5 263 2.4 2Z9 Z 7 1.1 21 19 400 mg/1 N (100 mg/1 NH4) until harvest 193 23.4 Z 0 18.0 Z 4 1Z 14 13 400 mg/1 N (20 mg/1 NH4) until bud color 19.4 20.4 1.9 25.1 3.0 1.6 30 27 400 mg/1 N (20 mg/1 NH4) until harvest 20.4 20.9 Z1 23.0 2 3 1Z 25 23 F-Tests Rate/Source NS * NS NSNS NS *** Fcrt termination NSNSNS NSNS NS *** *** Interactioo NS NS NSNS NS NS NSNS LSD (0.05) 4.44 5.6 3 3 'Spirit1 - Secood trial 100 mg/1 N (25 mg/1 NH4) until bud color 19Z 14.4 1.4 173 1.77 13 43 100 mg/1 N (25 mg/1 NH4) until harvest 20.0 13.9 1.4 18.4 1.99 1.4 43 400 mg/1 N (100 mg/1 NH4) until bud color 18.6 15.6 1.7 14Z 1.67 1.0 37 400 mg/1 N (100 mg/1 NH4) until harvest 17.1 10.7 1Z 8.6 1Z2 1.1 25 400 mg/1 N (20 mg/1 NH4) until bud color 18.5 10.9 1Z 13.4 1.69 1.4 40 400 mg/1 N (20 mg/1 NH4) until harvest 193 11.0 1Z 14.4 1.64 1.4 31 F-Tests Rale/Source •• • NS •• NS NS *** Fattcrminalioo NS NS NS NS NS NS •* Interaction * NSNS NS NS NS NS LSD (0.05) 1.25 3.20 4.63 6.8 Table 15. Exp7. Response ofTridon' at harvest to different nitrogen rates, sources, and tammatioo periods. Plant Leaf fresh Leaf dry Root Fresh Root Dry Foliar Height W right W right W right W right longevity Treatment (cm) fe> (ft) (8) (fD (days) Tridan' - F irst trial 100 mg/1 N (25 mg/1 NH4) until bud color 17.8 26.1 2 3 30.8 3.8 44 100 mg/I N (25 mg/1 NH4) until harvest 17.8 29.6 2 3 303 3.7 47 400 mg/1 N (100 mg/1 NH4) until bud color 17.1 31.8 3 6 28.0 3 3 33 400 mg/1 N (100 mg/I NH4) until harvest 18.3 3 1 3 3 7 29.0 3.8 23 400 mg/1 N (20 mg/1 NH4) until bud color 16.9 2 4 3 2 3 29.1 3.6 41 400 mg/1 N (20 mg/1 NH4) until harvest 173 2 5 3 3 6 30.0 4.0 34 F-Tests Rate/Source NS NS NSNS **• Fattennmatioo NS NS a NS NS •*« Interactkn NS NS NSNS NS LSD (0.05) 3.19 0 3 5 4.0 Iridoo' - Second trial 100 mg/1 N (25 mg/1 NH4) until bud color 203 193 1.7 15.6 1.8 59 100 mg/1 N (25 mg/1 NH4) until harvest 19.8 21.6 1 3 153 1.8 56 400 mg/1 N (100 mg/1 NH4) until bud color 19.0 21.0 3 0 153 3 0 43 400 mg/1 N (100 mg/1 NH4) until harvest 18.8 183 1.8 153 3 0 37 400 mg/1 N (20 mg/I NH4) unto bud color 193 173 1.7 13.0 1.6 59 400 mg/1 N (20 mg/1 NH4) until harvest 18.7 173 1.8 15.4 1.9 49 F-Tests Rate/Source NS • NSNS NS •** Fert tammatioo NS NS NSNS NS * Intoactioo NS NS NSNSNSNS LSD (0.05) 3.48 8.8 Table 16. Exp7. Growing medhim analysis at harvest Soluble salts N 03 P K Ca Mg pH (dShn) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) 'S p irit' F irst trial 100 mg/1 N (25 mg/1 NH4) until bud color 7 3 1.0 233 133 1135 933 39.8 100 mg/1 N (25 mg/1 NH4) until harvest 7.0 15 665 253 1843 114.0 51.3 400 mg/1 N (100 mg/1 NH4) until bod color 7.0 2.0 162.0 6 5 116.0 264.8 42.8 400 mg/1 N (100 mg/I NH4) until harvest 6 5 4.0 3353 2 8 3 247.8 280.8 67.8 400 mg/1 N (20 mg/1 NH4) until bud oolcr 7.1 13 103.8 53 935 179.0 265 400 mg/1 N (20 mg/1 NH4) until harvest 6.6 2.8 2883 105 1755 3S4.0 4 5 3 F-Tests Rste/Souroe • Fcrt termination • • Interaction NS LSD (0.05) 0 3 6 C.V.2 57 83 74 48 59 38 ‘Spirit1 Second trial 100 mg/1 N (25 mg/1 NH4) until bod color 7 3 1.1 2 1 5 6 5 9 1 5 7 9 3 40.8 100 mg/1 N (25 mg/1 NH4) until harvest 6.8 23 98.8 223 261.0 199.0 74.8 400 mg/1 N (100 mg/1 NH4) until bud o dor 6.4 33 2615 73 1303 412.0 100.8 400 mg/1 N (100 mg/1 NH4) until harvest 5 5 6 5 7645 263 3313 735.8 163.0 400 mg/1 N (20 mg/1 NH4) until bud o d o r 73 2.1 1665 2.8 1065 240.0 615 400 mg/1 N (20 mg/1 NH4) until harvest 6 3 6.1 6395 123 295.0 6195 1225 F-Tests Rate/Souroe F at lamination **• Interaction NS LSD (0.05) 0 3 0 C.V.Z 66 93 70 52 74 51 z C. V - Coefficient of Variability expresses the standard deviation ts a percent of tbc general mean of tbe dependant variable. It is presented for those dependant variables where heterogeneity of variance violated the assumptions of ANOVA, rendering F test a levels questionable. Table 17. Exp7. Foliar raafysia at harvest. N (total) P K Ca Mg Fe Na Treatment (percent) (percent) (percent) (percent) (mg/kg) (mg/kg) (mg/kg) 'S p irit' F irst trial 100 mg/1 N (25 mg/I NH4) until bud color 6.1 1.1 6.6 1.6 0.48 122 217 100 mg/1 N (25 mg/1 NH4) until harvest 6.8 13 7.0 1.7 051 135 268 400 mg/1 N (100 mg/1 NH4) untfl bod color 7.8 1.6 5.7 2 3 0 5 5 114 416 400 mg/1 N (100 mg/1 NH4) until harvest 8 3 1.7 6.1 1.9 0 5 7 128 469 400 mg/1 N (20 mg/I NH4) until bud color 6.7 1.0 5.6 3 5 0.49 106 285 400 mg/1 N (20 mg/1 NH4) until harvest 7.1 1.1 5.6 3.9 0.49 116 307 F-Testo Ralc/Souroc **** ••• **m F eit tenninatioQ NS *• NSNS *** NS Interactioa * NS NS * NSNS NS LSD (0.05) 0.16 0.16 0.36 0 3 0 .068 7.9 'Spirit' Second trial 100 mg/1 N (25 mg/1 NH4) until bud o d o r 6.0 1.0 7.1 3 0 0.48 121 302 100 mg/1 N (25 mg/1 NH4) until harvest 6.1 0.9 7 3 1.9 0.46 120 324 400 mg/1 N (100 mg/1 NH4) until bud color 6.4 13 5 3 3 8 0 5 8 119 278 400 mg/1 N (100 mg/1 NH4 ) until harvest 6.7 13 5 5 3 9 0.70 124 283 400 mg/1 N (20 mg/1 NH4) until bod color 5.9 0.8 5 3 3.1 053 111 271 400 mg/I N (20 mg/1 NH4) until harvest 6 3 1.0 5.6 3 3 0 5 6 115 276 F -T esti Rate/Source **#•* •a NS Ferttamimtioo *** * * NS NS NS NS Interaction NS ** NSNS NS NS NS LSD (0.05) 0 3 0.11 0 3 7 0 3 3 0.120 7.6 — Table 18. Exp7. Response ofSpirif and Iridon' roots at harvest and during postproduction (PP) to different nitrogen rales, sources, md termination periods. Harvest 1 Wk Postproduction 2 WkPostproduction Fresh Wt D iyW t Fresh Wt Dry Wt Fresh Wt Dry Wt Treatment GO (8) GO GO (8) GO 'Spirit' - Second trial 100 mg/I N (25 mg/1 NH4) until bod color 173 1.77 16.7 1.83 11.0 1.03 100 mg/1 N (25 mg/1 NH4) until harvest 18.4 1.99 14.9 1.63 134 136 400 mg/1 N (100 mg/1 NH4) until bud color 143 1.67 10.1 130 6 3 0.74 400 mg/1 N (100 mg/1 NH4) until harvest 8.6 1.22 8.4 130 3.4 033 400 mg/1 N (20 mg/1 NH4) until bud color 13.4 1.69 13.6 133 8.8 0.96 400 mg/1 N (20 mg/1 NH4) until harvest 14.4 1.64 11.4 1.43 8 3 0.88 F-Tests Rate/Source a* NS ••• NS •** m F at termination NSNSNS NS NSNS Interaction NS NS NS NSNS NS LSD (0.05) 4.63 3.78 4.42 0.50 lWkPP 2 WlcPP 4 W kPP 5 W kPP . FW*DW* FW DW FW DWFW DW FW DW GO fa) GO fa) _ (8) (8) (8) (8) (8) (8) Iridon' - Second trial 100 mg/1 N (25 mg/1 NH4) until bud color 15.6 1.8 133 1.49 143 131 16.1 1.91 14.0 133 100 mg/1 N (25 mg/1 NH4) until harvest 153 1.8 130 1.45 11.0 1.15 13.1 1.46 133 135 400m g/l N (100 mg/1 NH4) until bud color 153 3 0 137 1.60 133 1.45 10.9 138 14.3 1.69 400 mg/I N (100 mg/I NH4) until harvest 153 3 0 11.1 1.41 10.1 1.15 9.6 130 103 1.17 400 mg/1 N (20 mg/1 NH4) until bud color 13.0 1.6 138 131 13.0 1.42 15.8 1.99 133 1.47 400 mg/1 N (20 mg/I NH4) until harvest 15.4 1.9 123 133 10.6 137 137 1.74 143 1.48 F-Tests Rate/Source NS NS NS NS NSNS NS NS NS NS Fert termination NS NSNS NS * NS NS NS NS NS Interaction NSNSNS NS NS NS NS NS NS NS LSD (0.05) 3 3 5 1 FW (fresh w eight), D W (thy weight) Table 19. Exp7. ‘Spirit1 total root N. total aolublc proton and total soluble carbohydrates it harvest, 1 «nd 2 weeks postproduction. ______Harvest______1 Week Postproduction 2-Wfffc Pwtprcfocfon Total Root N Protein Total Root N Protein Total Root N Protein Treatment (%) ______(tng/g) ______(w ifi______(mg/g) ‘Spirit* • Second trial 100 mg/1 N {25 mg/1 NH4) until bud color 2.2 3.8 1.9 5.2 2.1 6.9 100 m g'! N (25 mg/1 NH4) until harvest 2.0 53 Z1 6 3 2.1 8.8 400 mg/1 N (100 mg/1 NH4) until bud color 2 3 43 2.1 4.6 Z3 7.8 400 mg/1 N (100 mg/1 NH4) until harvest 2.0 3.8 Z1 4.7 Z 6 73 400 mg/1 N (20 mg/1 NH4) until bud color 2.1 5.1 Z1 4 3 Z3 113 400 mg/1 N (20 mg/1 NH4) until harvest 2.3 63 23 53 ZO 16.6 F-Tcsts Rate/Source NS NSNS NS * NS F at lamination NS NSNS NSNS NS Interaction NS NSNS NS NSNS LSD 10.05) • 0 3 4 Total Soluble Carbohydrate Total Soluble Carbohydrate Total Soluble Carbohydrate (w ifi (mgfc) (m g/fl *Spirit‘ * Second trial 100 mg/1 N (25 mg/1 NH4) until bud color 52 1.9 9.4 100 mg/1 N (25 mg/1 NH4) until harvest 4.7 2.4 10.0 400 mg/1 N (100 mg/1 HH4) until bud color 3.0 23 5.4 400 mg/1 N (100 mg/1 NH4) until harvest 2.4 Z1 4 3 400 mg/1 N (20 mg/1 NH4) until bud color 3.7 1.9 9.9 400 mg/1 N (20 mg/1 NH4) until harvest 2.6 22 9.7 F-Tests Rale/Source • NS NS Fed termination NS NS NS Interaction NS NS NS LSD (0.05) 1.85 78 20 15 10 5 0 Irrigation period in postproduction — 100:25-BC *«* 100:25-H — 400:100-BC — 400:100-H 400:20-BC — 400:20-H 30 •• 25 ■■ 10 •• Irrigation period in postproduction 100:25-BC — 100:2541 -^400:100-BC ♦ 400:100-H -*r- 400:20-BC -*-400:20+1 Figure 7. Exp7. Average daily transpiration rates for 'Spirit1 (top) and 'Iridon* (bottom) during postproduction. Note: Treatment 100:25-BC - 100 mg N/L — 25 mg/L of it from N H /, fertilized until bud color, -H * fertilized until harvest Treatments 400:20(or 100)* 400 mg N/L » 20 (or 100) mg/L of it from NH/. Tabic 20. Exp 7. Relationships between postproduction longevity and other selected plant measurements for ‘Spirit’ both trials. r2 between foliar r2 between foliar postproduction postproduction Degrees of longevity longevity Dependent variable freedom first trial second trial Foliar nitrogen 22 0.79 ***z 0.55 *** Foliar phosphorus 22 0.44 ••• 0.29** Foliar potassium 22 0.08 NS 0.29 ** Foliar calcium 22 0.00 NS 0.30** pH 22 0.42 *•* 0.41 *** Soluble salts 22 0.44 •** 0.44 *** Medium nitrogen 22 0.40 ••* 0.50 *** Medium phosphorus 22 0.07 NS 0.11 NS Medium potassium 22 0.I6NS 0.22* Medium calcium 22 0.22* 0.52 *** Root dry weight 22 0.03 NS 0.06 NS Root fresh weight 22 0.12 NS 0.23 •* Root/shoot ratio 22 0.04 NS 0.02 NS Total root N at harvest 22 0.04 NS 1 Correlations were significant at the 0.001 (***), 0.01 (•*), or 0.05 (*), or not significant (NS). Correlations of postproduction longevity with foliar and growing medium variables (except pH) were negative in value. 80 vary. Second, though plants fertilized with high N/low N H / declined most rapidly in postproduction, plants fertilized with high N/high N H / also declined more rapidly than plants grown under low N conditions. It is conceivable that hastened decline in high N/low N H / plants may be due in limited part to denitrification. The medium in the pots did not remain continuously wet, but perhaps it remain moist for periods long enough for denitrifying bacteria to convert some of the excess nitrates to nitrites. Nitrites cause toxicity problems for a number of plants (Zsoldos, et al., 1993). These points suggest that either high N and high N H / have similar modes of toxic action on the plant or they both affect a common intermediary which then influences postproduction longevity. In this experiment, the energy reserve at the end of production, as expressed by root TSC levels and/or TSC/soluble protein ratios, was postulated as the common intermediary. However, neither variable served as a practical indication of potential longevity in the postproduction environment. Because neither of the hypotheses suggested in this manuscript were supported by the experiments that were conducted, I can only speculate about the cause(s) of decline and why symptoms varied between cultivars. 'Spirit' roots, whatever the physiological mechanism, may be particularly prone to N H /, pH, or EC induced problems. With increased rates o f root mortality and decomposition, hydraulic conductivity of the root system drops sharply, resulting in the wilting symptoms observed. 'Iridon' roots may be much more tolerant o f potential N H / and related medium problems. Decline may result from uptake and translocation of the NH, to the foliage were N H / toxicity, its symptoms and repercussions develop. General Discussion Results of the seven experiments showed that the accelerated decline in postproduction did not fit the standard pattern of senescence. Senescence in flowers and leaves is marked by a rapid loss of macromolecules, including soluble proteins and RNA, along with an increase in hydrolase activity. In leaves there is also a rapid decline in the rate of photosynthesis and loss of chlorophyll as the chloroplasts disintegrate; in consequence leaves become chlorotic (Woolhouse, 1978; Thomas and Stoddard, 1980; Stoddard and Thomas, 1982; Mei and Thimann, 1994). Little foliar chlorosis developed on any treatments that received moderate to high amounts of fertilizer in any of the experiments. ‘Bright Golden Anne’ (‘BGA’), ‘Spirit’, and ‘Iridon* that received 250 mg N per 0.5 liter pot (0.5x Osmocote or from starter WSF alone) in the first two experiments did exhibit some chlorosis in postproduction. However, a loss of postproduction longevity (PPL) was not seen until N level (from Osmocote 14-14-14) was reduced to 125 mg N per 0.5 liter pot in Experiment 3. In these plants, pronounced chlorosis suggested that N deficiency had accelerated the rate of natural decline or senescence. In Experiment 4, terminal and basal leaves of plants that had received moderate to high levels of fertilizer during production were monitored during postproduction. Basal leaves of plants that received Osmocote at 500 mg N/0.5 L pot (7.1 kg N/m* = lx) did 81 82 develop some chlorosis in postproduction. These leaves (Figure 6) also contained less chlorophyll on a per fresh weight basis during postproduction than leaves from plants receiving more N. Chlorophyll content in the terminal leaves remained relatively constant throughout postproduction. These visual and analytic results strongly imply that the mechanism of accelerated decline in moderate to well fed plants differs from standard senescence. In Experiment 6 (Table 11), soluble protein and chlorophyll levels did not drop during the first two weeks in postproduction, lending additional support to this conclusion. Symptoms of decline observed in the four chrysanthemum cultivars varied. The principal symptom in 'Spirit’ and ‘BGA’ was a loss of turgor in the flowers and foliage. Necrosis developed later at the base of the wilted leaves, i.e. at the petiole/leaf lamina junction. Necrosis of florets that had already wilted developed at the base of the florets. ‘Iridon’ foliage exhibited marginal necrosis followed by a collapse and drying of the remaining leaf lamina. Unlike ‘Spirit’, there was very little wilting at any point during foliar decline of ‘Iridon’. The inflorescences also exhibited a collapse and drying of the florets with no wilting. Symptoms of decline in ‘Torch’ were intermediate, and included some marginal necrosis and then wilting. Although not well described, decline in other chrysanthemum postproduction studies fit within this range of symptoms (Roude, et al., 1991a and 1991b; Gerberick, 1989; Nell et al. 1990). Throughout the series of experiments, total foliar N and growing medium nitrate levels inversely correlated most consistently with PPL (r2 ranging from 0.55 to 0.92, and 83 from 0.40 to 0.89 respectively). Additional dependent variables that were inversely correlated with PPL included: foliar P (r2 = 0.29 to 0.79), foliar K (? = 0.08 to 0.63), soluble salts (r2 ® 0.33 to 0.64). Growing medium pH (r2 = 0.32 to 0.51), root dry weight and root-to-shoot ratio positively correlated with PPL through the first six experiments (r2 *= 0.37 to 0.77, and 0.47 to 0.55 respectively), but not significantly in the last experiment (r2 s 0.06). Much evidence suggests that N is a principal cause of the accelerated rate of decline. Foliar N and growing medium nitrate levels consistently inversely correlated more closely with PPL than any other dependant variable that was evaluated. In the first four experiments, N availability was crudely varied by controlling the total amount of commercially formulated fertilizer applied to the media. As N availability increased, so also did P and K. This would explain the close relationship between PPL and P, K and soluble salts in those eariy studies. In the last study, nutrients other than N applied to the medium were fixed across treatments, with only the total amount of N and the N source ratio varying. In that study, foliar N and medium nitrate correlated better with PPL than P or K. Soluble salts, because of the salt effect of NO / and N H ,\ still correlated well also. Finally, the effects of N03‘:N H / ratios and concentration on medium pH could explain the correlation observed between pH and PPL (Roude et al., 1991a, 1991b; Lang and Elliot, 1991; Elliot et al., 1983; Rufty et al., 1982; McCrimmon et al., 1992). Nitrogen also appears to provide a link for the correlation observed between root dry weight and PPL in the first six experiments. Marschner (1986) has noted that for most 84 plants, low levels of N favor a high root/shoot ratio, while high N levels favor a lower ratio, i.e. less roots, more top growth. Trewavas (1985) has suggested that an explanation might be found in an old concept for which there is some supporting evidence. Low available N (high C/N ratio) that “root growth is promoted because the root competes more effectively for the nitrate it is absorbing and because compositionally it is high in C/N.” With a low C/N ratio the shoot, which naturally has a lower C/N ratio due to the photosynthetic apparatus, more effectively competes for the photosynthates when N levels arc high - stimulating top growth. Gutshick (1987) has postulated that under conditions of low N, the plant devotes a significant portion of its available energy resources “looking" for additional N, i.e. increasing its root to shoot ratio. The correlation between dry root weight and PPL however, breaks down in the last experiment, perhaps because o f a confounding effect of varying N source ratios. In the first six experiments, the amount of N was varied, but the proportions of NO / and NH4+ remained relatively constant (« 53 to 60%). In the last study both total N concentration and NOj'/NH/ proportions varied. It was hypothesized that high N levels hasten decline by drawing on carbohydrate reserves, that could prolong vigor in a stressful postproduction environment, to provide carbon skeletons and energy for conversion of NOj* and NH/ to organic N. The hypothesis was not borne out by the results of Experiment 6. Starch, and/or total soluble carbohydrate levels at harvest had been expected to serve as predictors of postproduction longevity (PPL), i.e. plants that received high N fertility should have had the lowest starch, 85 TSC, and carbohydrate/soluble protein ratios. There was no correlation between total carbohydrates and treatment fertilizer level during production, and both starch and TSC dropped to very low levels by the end of the first two weeks in postproduction. This is consistent with the results of Trusty and Miller (1991). In the several experiments using ‘Spirit*, it was observed that plants receiving higher rates of N also had smaller root systems (root dry weights) at harvest, and that there was a higher percentage of root necrosis. Plants began to lose turgor as the percentage of root necrosis increased. These observations suggested a second hypothesis. Ammonium fertilization depletes carbohydrates in the roots (Chi, 1976). The plants use the carbohydrates to provide the carbon skeletons and energy to convert NH3, which is toxic to the plants, to amino acids and other organic N forms. Excessive uptake of NH, may overwhelm the roots resulting in direct root necrosis and reduced water uptake. Many potted crops, including mums, respond differently to N H / and MO)*. Tsujita (1974) found that chrysanthemums were larger and more full, but also more prone to breakage, when produced with NH / or N H / plus NO / ( i 25% N H /) compared to plant produced with NO/ alone. Ammonium can cause problems, especially in winter when the soils are cooler and nitrification is slowed. Ammonium is toxic to a plant and is normally incorporated rapidly into an organic N form in the roots. Nitrate, however, is nontoxic and maybe reduced in the roots or transported to the leaves for reduction (- 70% of NO/ reductase activity in chrysanthemums normally occurs in the leaves - Woodson and Boodley, 1984) or stored in vacuoles. Therefore, although fewer carbohydrates are 86 involved in converting Nil, to organic N, N H / potentially puts a greater demand on root carbohydrates. It has also been shown to raise root respiration and lower soluble carbohydrates (Matsumoto and Tamura, 1981, in Marschner 1986; Talouizte et al., 1984, inMarschner, 1986). High N/high N H / treatments did decrease PPL for both ‘Spirit* and ‘Iridon' in both trials compared to high N/low N H / or low N treatments. A distinction in PPL between the low N and high N/low N H / (N H / concentrations were 25 and 20 mg/L, respectively) did exist but was it was much less pronounced. Terminating fertilizer applications at bud color, especially for the high N/high N H / treatments, extended PPL. For ‘Spirit', the problem with excess N H / was readily seen in the roots. There was some root necrosis in all treatments as plants started to decline, but those that received the high N/high NH / treatments had already shown some significant necrosis by harvest. ‘Iridon* roots exhibited very little root decline regardless of the N concentration or source, even after leaves had begun collapsing. However, marginal necrosis and tissue collapse are symptoms that have been associated with N H / toxicity on chrysanthemums and poinsettias (Fleming et al., 1987; Cox and Seeley, 1984). One factor that did appear to track very closely with PPL in the last experiment was average daily transpiration rate. For both ‘Spirit’ and ‘Iridon’, plants that lasted the longest in postproduction also had the highest average daily transpiration rate. This observation held despite the fact that root dry weight correlated veiy poorly with PPL. Water uptake is a passive process, but it occurs more rapidly in healthy, vigorous roots 87 than in stressed or dying roots. Root dysfunction may have resulted from excessively low in some of the treatments receiving high levels ofN H /. It is also conceivable that NH / , perhaps accompanied by other monovalent cations displace CaJt from the polar head groups of the plasma membrane of root cells, disrupting membrane function and perhaps the Ca second messenger system, resulting in a weakened root system. Such a scenario could explain the extensive root dicback in ‘Spirit* and wilting of leaves and inflorescences as the plants declined. The persistent relative vigor and function of the ‘Iridon* root systems would offer some explanation for this cultivar retaining foliar and floral turgor long after ‘Spirit’ had permanently wilted. Based on reduced levels of transpiration, 'Iridon* docs appear to suffer some loss of root vigor, but the overall symptoms of decline imply that high N and high N H / adversely affect the cultivar in other ways. Abstract This effort evaluated the production and postproduction response of potted chrysanthemum to controlled-relcasc fertilizers (CRF) in a flood and ebb system, established a distinction between classical senescence and accelerated decline, and determined whether hastened decline in well fertilized chrysanthemums was due to carbohydrate depiction in the leaves or roots as plants incorporate NO,*, and especially NH4* into organic compounds. Osmocote 14-14-14 and Nutricote 14-14-14 Type 100 at rates up to 14.2 kg CRF/m1 (2x rate), produced quality plants without loss of postproduction longevity (PPL). Not until rates of 28.5 kg CRF/m1 was any loss of PPL recorded. Symptoms of hastened decline in heavily fertilized chrysanthemums did not include chlorosis, loss o f chlorophyll or soluble protein typically associated with senescence. Symptoms of decline varied with cultivar and ranged from a loss of turgor in the foliage and inflorescences (despite moist growing medium) followed later by necrosis at the base of the leaf blade, to a marginal leaf necrosis followed by a collapse and drying (but no wilting) of leaves and florets. Total foliar N content and growing medium NO,* consistently correlated with PPL. Fertilizer termination and NH//NO,’ ratio also influenced PPL. Plants fertilized to 88 89 budcolor persisted 3 to 11 days longer than those fertilized until harvest. Plants produced with 400 mg N/L (20 mg NH/-N/L) lasted one to two weeks longer than plants produced with 400 mg N/L (100 mg NH/-N/L). Growing medium EC and pH, root dry weight and foliar P and K also correlated with PPL, though less consistently. Root dry weight decreased with increasing N H /. Root mortality increased with total N, N H /, or fertilizer duration for some but not all cultivars. Transpiration rate in postproduction generally matched postproduction trends; plants that lasted longer in postproduction had higher rates of transpiration throughout postproduction. Contrary to expectations, foliar and root carbohydrate levels were not affected by the level of nitrogen fertilization or by N H //NO/ ratio, even though PPL was. These experiments imply a strong relationship between the amount, source, and duration of N fertilization with PPL, but the mechanism was not identified. APPENDICES Additional Data 90 Tablc21. Exp. 1. Bright Golden Anne' chrysaitlg num growth response to four rates of two controlled release fertilizers (CRF), both without 20-10-20 water sohAlefatilim^WSF) @ 400mg N/L during the first five irri potions. Avg. Avg. Avg. Plant Plant Flower leaffiesh leaf dry leaf height diameter diameter Days to weight weight area Treatment (an) (cm) (cm) flower (mg) (mg) (g) Qsmocote 14-14-14 Olcg/m* 17.8 12.7 53 1223 130 40 33 3.6kgAn> 27.1 20.9 123 91.0 550 110 143 7.1kgte* 30.2 26.0 12.6 863 940 120 23.0 14.2 lcg/m* 31.2 28.0 12.7 810 1320 140 27.4 Rale2 L**Q* LQ** LQ C" LQ**C* LQ** LQ** LQ** Nutricote 14-14-14 Tvne 100 OlcgAn* 163 11.4 53 1215 140 40 3 3 3.6kgAn* 25.2 21.8 123 91.0 600 100 13.6 7.1kgfa* 283 24.0 118 833 740 110 17.4 M ^lcgto1 30.9 28.2 128 823 1,190 130 25.9 Rate2 LQ" LQC" LOC** LQ** L** L** L** 2 Rate and F tests significant at 0.001 (••*),0.01 (•*) or0.05 (•), or not significant (NS). Rate linear (L), quadratic (QX or cubic (C). Table 21 Exp. 1. Bright Golden Anne' chtysantbemum growth response to four rates of two controlled release fertilizers (CRF) both with 20-10-20 water ^hAlejatilizg^WSF)@jOOmg N/L during the first five irrigations- ______ Avg. Avg. Avg. Plant Plant Flower leaf fresh leafdiy leaf height diameter diameter Days to weight weight area Treatment (cm) (cm) (an) flower (mg) (mg) (g) Osmocote 14-14-14 Olcg/m* 293 20.7 103 943 650 120 16.7 3.6 kg/m1 33.0 24.8 123 89.0 890 110 212 7.1 kg/in* 33.8 27.8 12.2 913 1,100 120 26.8 141 kg/m* 34.1 29.0 118 853 1,380 150 30.9 Rale2 L* LQ** L* NS L** NS L** Nutricote 14-14-14 Time 100 Okgfa* 303 23.4 10.6 99.0 710 130 181 3.6 lcg/m* 313 28.8 13.0 97.0 1,050 130 25.1 7.1 kg/in* 31.4 28.9 123 833 1,000 100 24.7 MlkgAn* 30.9 30.3 116 810 1180 140 28.8 Rate* NS L**Q* L*0**C* L* L* NS L* * Rate and F tests significant at 0.001 (*•*), 0.01 (**)cr 0.05 (•), or not significant (NS). Rale linear (L), quadratic (Q), or cubic (C). Table 23. Exp. l.ANOVA(sndOmegiSquarrd)chartfor,BrigtiGoldco Anne'chrysanthemum parameters measured. CRF “ Controlled Release Fertilizers (Osmocote 14*14-14 v* Nutricote 14-14-14 Type 100). WSF ” water soluble fertilizer (@ 400 mg N/L) injected or not injected during the first five irrigations. Rate B amount of CRF incorporated into the growing medium. Avg. Avg. Avg Plant Plant Flower kaffiesh leafdiy leaf bdgfat diameter diameter Days to weight weight area F tests (Omega Squared)Y (cm) (cm) (cm) flower (a) (R) (g) CRF*WSF*RATH •(.01) NS NS NS NS NS NS CRF*WSF NS •(.02) NS NS NS NS NS CRF*RATE NSNS NS NS NS NS NS WSF*RATE *••(.18) •••(.08) *••(20) •••(.21) NS •*(20) *(.04) CRF NS NS NS NS NSNS NS WSF •••(.33) •**(-21) ••*(.07) *(■03) •••(.18) *(.17) ***(23) RATE •••(.40) *••(.65) ••*(.71) •••(.64) *••(.67) •**(28) ***(28) z Rate and F tests significant at 0.001 (•••),0.01 (••) or 0.05 (•), or not significant (NS). Rate linear(L), quadratic (Q), or cubic (C). Y Omega Sq. is a measure ofthe proportion of total variance that is attributable to eachefTect or interaction. wvo Table 24. Etqp. 1. 'Bright Golden Ante? cbysantbcmum pas^roductkn flower He ( m days) in response to four rates of taro controlled release fiatflizas (CRF) PostproductioQ longevity Postproductioo longevity CRF without WSF CRF with WSF Treatment (days) (d*ys) Osmocote 14-14-14 Okgftri* __ r 21.6 3.6kgAn> 21.7 27.7 7.1 kg/m’ 23.8 17.7 14.2 kgto* 25.4 23J2 Rale L* c»»* Nutricote 14-14-14 Tvoe 100 Okg/m1 __ T 20.1 3.6 kg/m1 20J 22_5 7.1 kg/m5 21.7 18.6 14.2 kgfa* 20.4 20.4 Rale NS C* * Rale and F tests significant at 0.001 (***), 0.01 (*•) cr 0.05 (*), or not significant (NS). Rate linear(L), quadratic (Q), or cubic (C). 1 Postproducrioo life of flowers Out received no WSF were analyzed separately from those that did, because flowers of Ox Osmocote and Nutricote were deemed unacceptable. Table 25. Exp 2. Production end postproduction response o f‘Spirit’ to three rites (0.5,1.0, and 2.0 the recommended rate) of Osmocote 14-14-14(100- 120 day release period) and two Osmooote-bke control release fcrtilizris (CRF) also with ratios of 14-14-14, but with release periods of40-60 days and 70-90 days. Plant Plant Flower Floral Avg leaf Avg leaf Foliar Rate beigbt diameter diameter longevity area dry wt nitrogen Fertilizer (lento*) (cm) (an) (cm) O o> 1 ! (days) (cm1) (mg) (percent) CRF-40 3.6 23.9 21.6 105 80 16 9.7 45.7 5.18 7.1 24.0 21.9 105 81 12 11.1 50.6 5.78 14.2 22.9 215 14.4 78 13 9.0 605 7.10 CRF-70 3.6 20.1 19.1 10.0 78 17 8.6 43.1 4.77 7.1 24J2 21.1 115 75 14 115 495 5.74 14.2 21.6 20.1 9.8 80 12 10.7 49.8 6.43 Osmocote 3.6 20.8 19.4 10.4 75 20 105 47.0 4.83 7.1 245 22.2 10.7 73 18 11.0 49.0 5.99 145 22.0 21.9 105 74 12 15.1 71.4 6.80 ANOYA (Omega Sal* F a t NS NS NS NS NSNS NS *(•04) Rate Q« Q* NS NS NS NS L** L***(.75) Q**(.09) F a t x Rate NS NS NS NS NS NS NS NS 2 Omega Sq. is a measure of the proportion of total variance tbit is attributable to each effect or interaction. Rale and F tests significant it 0.001 (•**), 0.01 (**) or 0.05 (•), or not rignificant (NS). Rale linear(L), quadratic (Q), oc cubic (C). Table 26. Exp 2. Production and postproductioQ response erf Tridon' to three rates (03,1.0, and 2.0 the recommended rate) of Osmocote 14-14-14(100- 120 day release period) and twoOsmooole-like control release fertilizers (CRF) also with ratios of 14-14-14, but with release periods of40-60days and 70-90 days.______ Plant Plant Flower Floral Avg leaf Avg leaf Foliar Rale hejghl CRF-40 3.6 22.1 19.7 8.7 81 7 110 47 1 557 7.1 21.0 2 1 J 9.1 80 7 16.7 605 5.91 14 1 16.0 20.6 8.7 79 15.9 611 7.14 CRF-70 3.6 19.4 19.9 8.4 81 7 11.9 551 5.58 7.1 18.8 21.7 8.9 79 7 14.1 591 5.79 14.2 17.6 20.4 8.8 77 13.1 575 6.13 Osmocote 3.6 18.1 18.7 8.7 80 7 105 44.4 5.54 7.1 18.6 191 8.8 78 7 110 501 612 14 1 16.9 20.5 8.9 76 9 155 61.7 6.82 ANOVA (Omega SqY Fert NS NS NSNS NS **C19) NS NS Rate L**(J4) Q** Q** L* NS L***(.24) L** L*** Fert x Rate **(.12) NS NS NS NS NS NS NS 2 Omega Sq. is a measure of the proportion of total variance that is attributable to each effect or interaction. Rate andF tests significant at 0.001 (**•), 0.01 (*•) or 0.05 (*),or not significant (NS). Rate linearfL), quadratic (Q), or cubic (C). Table 27. Exp 3. Production and postproductioo response of'Spirit* to three riles (0.25.1.0, «od 4.0 tbc recommended rate) of Osmocote 14-14-14 (100- 120 day release period) and two Osmocote-lib: control release fat2izers(CRF) also with ratios of 14-14-14, but with release periods of 40-60 days and 70^90 days. u j ■ Pu Jj Iff Plant Flower Postprod Avg leaf Avg leaf Avg leaf Rate diameter diameter Days to floral life area fresh wt dry wt Fertilizer OcgAn*) (cm) (cm) flower (days) (cm?) (mg) (mg) CRF-40 1.8 21.8 15.9 10.1 77 31 7.7 251 54 7.1 26.7 206 10.8 73 37 12.4 516 90 286 256 22.7 11.4 70 23 11.4 540 80 CRF-70 1.8 20.1 14.2 9.9 77 30 5 6 174 40 7.1 27.4 19.8 106 73 37 11.6 433 76 286 26.8 22.2 11.8 70 27 136 618 91 Osmocote 1.8 22.2 16.8 10.1 77 29 7.0 234 52 7.1 28.7 206 11.1 73 37 116 432 81 286 26.0 22.7 11.4 70 18 126 630 92 ANOVA (Omega SqY Fert NS NS NS NS *(04) NS NS NS Rate Linear •*•(.14) *••(.67) *•*(.43) •*•(.73) •**(.52) •**(67) *•*(.64) •*•(.78) Quadratic •••(6 9 ) *•*(60) NS •*•(.15) •••(3 1 ) •••(62) *•*(.18) •••(.04) Fert x Rale NS NS NS NS •<<*> NS NS NS z Omega Sq. is a measure of tbc proportion of total variance that is attributable to each effect or interaction. F tests significant at 0.001 (•**). 0.01 (**) or 0.05 (*), or not significant (NS). ! i i Table 28. Exp 3. Foliar nutrient levels at harvest (plusN at disbud) in response cf’Spirit' to three rales (0.25,1.0, and 4.0 the recommended rate) of Osmocote 14-14-14 (100-120 day release period) and two Osn»ootc-4ike control release fertilizers (CRF) also with ratios of 14-14-14, but with release periods of 40-60 days and 70-90 days. ______ Nitrogen Rate at disbud Phosphorus Potassium Calcium Magnesium Iron Manganese Zn Fertilizer (kg/m1) (percent) i f f (percent) (percent) (percent) (ppm) (PP«n) (ppm) (ppm) CRF-40 1.8 3 3 23 0.35 3.44 1.07 030 84 47 30 7.1 5 2 3.8 0.73 433 1.43 0.45 91 178 40 283 6.6 5.8 137 531 133 031 80 288 49 CRF-70 1.8 2.9 2.4 037 3.60 1.10 031 61 51 24 7.1 5.0 3.9 0.59 40.7 1.41 0.44 86 142 38 28.5 63 53 1.07 4.97 135 0.60 88 281 71 Osmocote 1.8 3.8 23 0.40 339 1.08 031 70 54 24 7.1 5.1 3.6 0.75 3.97 1.45 037 87 156 35 28.5 7.1 6 2 130 5.06 138 033 83 274 78 ANOVA (Omegn S tf F a t *(•02) NS •(.04) NSNS NSNS NS NS Rate Linear ***(.81) ***(.91) ***(.87) ••*(.85) •(.11) *••(.72) NS **•(.65) *** Quadratic •*•(.12) *•*(.05) ••(.02) **(.04) *•*(.65) •**(.19) • ••*(.01) NS Fert x Rate NS *(01) *(•02) NSNS *(.01) NS NSNS 1 Omega Sq. is a measure ofthe proportion of total variance that is attributable to each effect or interaction. F testa significant at 0.001 (*•*), 0.01 (**) or 0.05 (*), or not significant (NS). vo 00 t Table 29. Exp 6. Impact of Osmocote 14-14-14, Hyro-Sol at two rates or N, and to Pete's 20-10-20 Peatlite fertilizer regimes on ’Spirit' production and postproduction characteristics and growing medium nutrient levels. Plant Plant Flower Days Avg leaf Avg leaf Average Root dry Postprod height diameter diameter to Leaf flesh wt dry wt leaf area weight foliar life Fertilizer treatment (cm) (cm) (cm) flower number (mft) (mg) (cm1) (g) (days) Osmocote 0.5 gN/pot 25.0 23.S 14.0 86 51 461 69 135 16.8 55 Hydro-Sol 100 mg/liter N 222 21.9 13.9 81 48 458 65 126 5.7 44 Hydro-Sol 400 mg/liter N 24.1 23.7 145 80 48 851 148 17.9 6 2 28 Peter's 400 mg/IiterN 23.6 24.1 143 81 50 717 104 16.6 5.0 21 LSDm pr, (or C. V.r) 23 1.7 5.1 ,T1 230 60 3.9 45 53 Leaf dry Root Chlorophyll/ Chlorophyll/ Medium Medium Medium Medium Medium wt/area to shoot leaf dry wt leaf area Medium EC NO,* P K Ca Fertilizer treatment (mg/cm2) ratio (mg/g) (mg/cm2) pH (dS) (PPtn) (ppm) (ppm) (Ppm) Osmocote 0 5 g N/pot 5.06 4.74 93 49.7 5.9 27 43 31 98 164 Hydro-Sol 100 mg/liter N 5.18 1.82 105 555 7.1 3.1 55 39 473 94 Hydro-Sol 400 mg/liter N 831 0.87 124 782 5.0 4 2 274 34 362 ISO Peter's 400 mg/liter N 6.24 0.96 125 683 5.4 3.8 293 48 503 54 LSD ^ (orC.V.2) 1.98 0.84 3.7 13.1 0.43 1.8 (82) — (48) (48) z C V « Coefficient of Variability expresses the standard deviation as a percent ofthe general mean ofthe dependant variable. It is presented for those dependant variables where heterogeneity of variance violated the assumptions of ANOVA, rendering F test o levels questionable. vo vo Table 30. Exp 6. *Spirif Foliar nutrient levds at harvest and leaf starch, total soluble carbohydrate, soluble protein, and chlorophyll content it harvest anl at two weeks into postproduction (postp). Foliar N Foliar P Foliar K Foliar Ca Foliar Mg Foliar Fe Foliar Mn Foliar Zn Foliar Na Fertilizer treatment (%) (%) <%) (* ) <%) (ppm) (ppm) _ (ppm) (ppm) Osmocote 0.5 gN/pot 3.66 0.67 4.72 1.81 0.40 79 133 37 93 Hydro-Sol 100 mg/liter N 536 0.59 634 1.08 032 101 14 37 98 Hydro-Sol 400 mg/liter N 6-53 131 6.02 133 0.63 141 267 47 112 Peter's 400 mg/liter N 7.01 132 7.64 0.90 030 105 196 48 90 0.62 0.26 0.71 032 0.119 44 *** 9 NS Starch / leaf dry wt Carbohydrate / leaf dry wt Protein/leaf dry wt Chlorophyll/leaf dry wt harvest 2 wkspostp harvest 2 wkspostp harvest 2 wkspostp harvest 2 wkspostp Fertilizer treatment (mg/g) (mg/g) (mg/g) (mg/g) (mg/g) (mg/g) (mg/g) (mg/g) Osmocote 0 3 g N / pot 266 0.7 31 19 223 28.9 93 9.6 Hydro-Sol 100 mg/litcr N 49 23 39 19 273 203 103 10.8 Hydro-Sol 400 mg/liter N 83 1.8 38 12 26.4 24.7 12.4 11.7 Peter's 400 mg/liter N 69 23 31 23 27.1 34.9 123 12.4 Ftest: Between Hydro-Sol Trts, 100 v.s. 400 mg/L N NS NSNS NSNS NS •* NS C.V.2 for all treatments 86 92 35 so 29 47 14 10 2 C.V. “ Coefficient of Variability expresses the standard deviation as a percent of the general mean of tbc dependant variable. It is presented for those dependant variables where heterogeneity of variance violated the assumptions of ANOVA, rendering F test a levels questionable. Tablc31. Exp 6. Impact of Osmocote 14*14-14, Hyro-Sol at two rates or N, and to Peter’s 20-10-20 Peallite fertilizer regimes ca Iridoo’ production and Plant Plant Flower Days Avg leaf Avg leaf Average Root dry Postprod height diameter diameter to Leaf fresh wt dry wt leaf area weight foliar life Fertilizer treatment (cm) (cm) (cm) Gower number (mg) (mg) (an?) (g) (days) Osmocote 0.5 gN/pot 25.6 21.8 10.7 86 45 548 99 12.9 19.8 59 Hydro-Sol 100 mg/liter N 23.2 22.6 10.7 83 44 704 118 14.7 7.4 55 Hydro-Sol 400 mg/liter N 25.8 25.8 11.0 81 45 699 119 15.8 6.8 40 Peter's 400 mg/liter N 25.5 27.9 103 87 46 1,334 241 23.6 6.4 26 LSEWorCV.*) 2.46 130 — 33 — 210 (44) 223 (62) 8.1 Leaf dry Root Chlorophyll/ Chlorophyll/ Medium Medium Medium Medium Medium wt/area to shoot leafdry wt leaf area Medium EC NO,- P K Ca Fertilizer treatment (mg/an1) ratio (mg/g) (mg/an1) pH (dS) (ppm) (ppm) (ppm) (ppm) Osmocote 0 3 g N/pot 7.63 4.47 8.7 66.1 6.0 1.7 22 15 49 114 Hydro-Sd 100 mg/liter N 8.07 1.45 9.7 69.0 6.9 3.1 49 48 483 101 Hydro-Sol 400 mg/liter N 7.33 139 124 67.0 5.0 3.7 257 41 334 128 Peter's 400 mg/liter N 1032 039 9 2 627 5 3 4.4 334 48 575 64 LSDmrm(orC.V.z) 1.01 024 — — 031 (41) (89) 7.4 (63) — z C.V m Coefficient of Variability expresses the standard deviation as a percent of the general mean of the dependant variable. It is presented for those dependant variables where heterogeneity of variance violated the assumptions ofANOVA, rendering F test g levels questionable. Tabic 32. Exp 6. IridoD' Foliar numenl levels at harvest and leaf starch, total soluble carbohydrate, soluble protein, aod chlorophyll content at harvest ant at two weeks into postprodocdoo (postp). Foliar N FoliarP FoliarK Foliar Ca Foliar Mg Foliar Fe Foliar Mn Foliar Zn Foliar Na Fertilizer treatment (%) (%) (%) (%) <%) (ppm) (ppm) (ppm) (ppm) Osmocote 0.5 g N / pot 3.96 0.64 5.03 1.49 050 77 150 54 81 Hydro-Sol lOOmg/lherN 5.51 031 6.64 0.96 0.62 95 17 37 91 Hydro-Sol 400 mg/liter N 6.82 1.07 5.96 1.46 0.95 114 260 49 247 Peter's 400 mg/liter N 7.65 1.25 8.40 0.90 .058 139 183 62 664 LSIWorC.V*) 0.55 0.21 0.83 0.18 0.15 21.0 (61) 7 3 (95) Starch / leaf dry wt Carbohydrate/leaf dry wt Protein/leafdry w t Chlorophyll / leaf dry wt harvest 2 wkspostp harvest 2 wkspostp harvest 2 wkspostp harvest 2 wkspostp Fertilizer treatment______(ms/e) (mg/g) ______(mg/g) (mg/g) ______(mg/g) (mg/g) ______(mg/g) (mg/g) Osnoco(e7.1 kg/m* 159 0.8 37 21 213 14.4 8.7 10.4 Hydro-Sol 100 mg/liter N 68 1.6 42 22 185 30.6 9.7 11.4 Hydro-Sol 400 mg/liter N 92 5.1 67 21 325 243 12.4 103 Pete's 400 mg/liter N 37 13 25 21 19.4 18.4 9 3 10.4 Ftcst: Between Hydro-Sol Trts, 100 v j . 400 mg/L N NS NS NSNSNS NS ** NS C. 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