Chamberlayne and Banko, 2003; Differing Blanketflower Cultivar and Ecotype Hilgers et al., 2005; Keever and Responses to Plant Growth Regulators Olive, 1994; Kim et al., 1999; Latimer et al., 2006). To our knowledge, no information has been reported Helen E. Hammond1,5,7, Richard K. Schoellhorn2, for chemical plant growth regulation Sandra B. Wilson3,6,8, and Jeffrey G. Norcini4,6 of blanketflower, with the exception of ‘Burgundy’ blanketflower (G. ·grandiflora), of which G. pulchella ADDITIONAL INDEX WORDS. Gaillardia pulchella ‘Torch Flame’, ethephon, is a parent. Thomas et al. (1998) and uniconazole, growth retardant, native plants, Sumagic, Florel, firewheel Latimer et al. (1999) found that PGR response of burgundy blanketflower SUMMARY. Two different plant growth regulators were applied to ‘Torch Flame’ blanketflower (Gaillardia pulchella) and a native blanketflower ecotype to reduce varied by application rate, application pedicel elongation and final production size. Uniconazole was applied as a spray at number, and PGR type. We con- 60, 120, and 180 mgÁL–1 or as a drench at 6, 12, and 24 mgÁL–1 one and two times ducted a preliminary study with a per plant. Ethephon was applied as a spray at 500 and 1000 mgÁL–1 one and two blanketflower ecotype (G. pulchella) times per plant. When applied as a spray, uniconazole had no effect on torch and a cultivated selection of ‘Torch blanketflower, but when applied as a drench, growth indices were reduced by 12% Flame’ blanketflower (G. pulchella)to to 30% without delayed flowering. When treated with ethephon spray, torch determine how three commercially blanketflower was 15% to 25% more compact than untreated controls, but flowering available PGRs [daminozide (B-Nine; was delayed. The blanketflower ecotype did not respond to uniconazole or Uniroyal Chemical Co., Middlebury, Ethephon treatments, regardless of the application rate, number, or method. CT) daminozide/chlormequat chlo- ride (Cycocel; Olympic Horticultural lanketflower is an herbaceous University of Georgia, Colorado Products Co., Mainland, PA), and annual in the Aster family. It State University, North Carolina paclobutrazol (Bonzi; Syngenta Crop Bis native throughout Florida State University, Auburn University, Protection, Inc., Greensboro, NC)] (Wunderlin and Hansen, 2004) and Pennsylvania State University, and affect plant growth and flowering, most of the United States (U.S. even in Canada at the University of and found none of these PGRs to be Department of Agriculture, 2006), Guelph. In 2005, The University of effective in controlling plant growth with cultivated varieties grown world- Florida ‘‘trialed’’ 23 blanketflower (Danielson, 2005). The cultivar wide. Using blanketflower (Gaillar- cultivars and ecotypes and found that Torch Flame is a Ball Selection (Ball dia pulchella) and common gaillardia two of the Florida ecotypes (from FloraPlant, West Chicago) character- (G. aristata) as parents, more than Leon and Okaloosa counties) had ized by having heat-tolerant, long- 30 cultivars have been produced that greater or equal landscape impact lasting blooms with trumpet-shaped vary in floral attributes, flowering than many of the cultivated selections ray florets in hues of yellow, red, time, vegetative characteristics, cold (Danielson, 2005). and orange on well-branched, up- tolerance, and landscape performance Many of the blanketflower culti- right plants. The Florida ecotype has (Schoellhorn, 2004). The ornamental vars available today can be propagated a looser growth habit and fewer ray value of blanketflower is further by seed in addition to cuttings. florets that are horizontally oriented. revealed by its use in many state Although relatively easy to produce, There is a potential market for local or university trial gardens including blanketflower is fast growing and can regional ecotypes in landscape plant- quickly reach a cumbersome size for ings as public awareness and use of Indian River Research and Education Center Journal handling and shipping. Applications native species has become more wide- Series No. R-080702. of plant growth regulators (PGRs) spread (Florida Wildflower Advisory We gratefully acknowledge Bob Weidman and Seth may help to extend the amount of Council, 2004; Hammond et al., Hammond for greenhouse assistance, and Carolyn Bartuska for statistical expertise. We thank Ball Flora- time these plants can be held before 2007; Norcini and Aldrich, 2004). Plant for donating unrooted cuttings. distribution and sale, to improve vi- In addition to daminozide, 1Department of Environmental Horticulture, P.O. sual quality, and to facilitate shipping. daminozide/chlormequat chloride, Box 110670, Gainesville, FL 32611 There are many PGRs available for and paclobutrazol, two other com- 2Proven Winners, 7421 NW 176th Street, Alachua, use on ornamental crops, but their monly used chemical growth retard- FL 32615 effectiveness is often species or even ants are uniconazole (Sumagic; Valent 3Department of Environmental Horticulture, Indian cultivar specific (Barrett, 2001; USA Corp., Walnut Creek, CA) and River Research and Education Center, University of Florida-IFAS, 2199 South Rock Road, Fort Pierce, FL 34945 4Department of Environmental Horticulture, North Florida Research and Education Center, University Units of Florida-IFAS, 155 Research Road, Quincy, FL 32351-5677 To convert U.S. to SI, To convert SI to U.S., multiply by U.S. unit SI unit multiply by 5Graduate Research Assistant. –1 6 10 % mLÁL 0.1 Associate Professor. 3.7854 gal L 0.2642 7Current address: Faculty Extension Assistant, MD 28.3495 oz g 0.0353 Cooperative Extension, 18330 Keedysville Road, 1 ppm mgÁL–1 1 Keedysville, MD 21756. 0.1019 qt/100 ft2 LÁm–2 9.8170 8Corresponding author. E-mail: [email protected]fl.edu. ( F – 32) O 1.8 F C (1.8 · C) + 32
552 • October–December 2007 17(4) Ethephon (Florel; Southern Agricul- index. Height was measured from the torch blanketflower plants drenched tural Insecticides, Palmetto, FL). soil level to the highest vegetative with uniconazole (Table 1). Unico- Similarly to daminozide, uniconazole point. Width was measured first at nazole-drenched plants had signifi- inhibits the synthesis of gibberellins, the widest vegetative point passing cantly lower growth indices and dry but often at a lower concentration through the center of the plant, and weights, with greater compactness and with greater efficacy (Barrett, a second measurement was taken per- than control plants. Increasing the 2001). Ethephon is an ethylene- pendicular to the first. Growth index rate linearly decreased the growth releasing compound that has been was calculated as [(height + average index and dry weight of plants. Dry used to suppress height in some spe- width)/2]. Visual compactness was weight was reduced by 16% to 31%, cies (Krug et al., 2006; Rademacher, assessed on a scale from 1 to 3 points, compared with untreated controls, 1991). The objective of the current where 1 point is not compact, 2 without significantly affecting flower- study was to determine whether uni- points is somewhat compact, and 3 ing (Table 1, Fig. 1). A second drench conazole or ethephon, used at vary- points is highly compact. At 3 weeks, had no effect on growth, and delayed ing rates with one or two applications, the total number of flowers having at flowering at 4 weeks. As a spray, can reduce plant size of cultivated and least one fully expanded ray floret was uniconazole was ineffective in reduc- noncultivated forms of blanketflower. counted for each plant. All but one ing growth of torch blanketflower plant from each block was severed (data not presented). Also, regardless Materials and methods at the crown (soil level), placed into of application rate, number, or Torch blanketflower cuttings individual paper bags, and oven-dried method (spray or drench), unicona- (Ball FloraPlant) were rooted in at 70 C for 1 week, after which dry zole did not affect blanketflower eco- Fafard no. 2 medium (Conrad Fafard, weights were recorded. Flower num- type growth (data not presented). Agawam, MA) in 72-cell trays. Seeds ber of the remaining plants was Plant responses to foliar or of a Florida blanketflower ecotype counted again at 4 weeks. Plants were drench applications of the same PGR were collected from a native popula- arranged in a completely randomized often vary as a result of differences tion in Crestview, FL (Okaloosa block, with three blocks having three in absorption rates and translocation. County) and sown in Fafard no. 2 replications of each treatment. The Unlike ethephon, uniconazole can medium in 128-cell trays. Seed trays study was repeated once with similar be applied as a media drench or foliar and cuttings were kept under inter- results. Values presented are from the spray. Because it is xylem transported mittent mist (10 s every 20 min) for first study. Data were subjected to to the growing points, applications 10 d, then moved to a greenhouse, analysis of variance, and main effects to the leaves do not actively move to where they were watered with 150 of treatments were partitioned into other parts of the plant (Whipker mgÁL–1 20N–4.3P–16.6K liquid fer- single df (orthogonal contrasts) at et al., 2003). Although foliar sprays tilizer (20–10–20; The Scotts Co., P £ 0.05. of uniconazole did not affect plant Marysville, OH). Rooted cuttings (3 growth of blanketflower in our study, weeks old) or seedlings (8 weeks old) Results and discussion Kim et al. (1999) found foliar spays of were transplanted into 1-gal contain- UNICONAZOLE. Nonsignificant uniconazole to be more effective in ers filled with Fafard no. 2 medium rate · drench number interactions reducing total plant height of bleed- and manually drip irrigated (until occurred for each measured trait of ing heart (Dicentra spectabilis) than runoff) as needed. Nine plants having 8 to 16 expanded leaves with visible roots at the edge of the substrate were Table 1. Growth index, dry weight, compactness rating, and flower number assigned randomly to each treatment. of ‘Torch Flame’ blanketflower drenched with uniconazole (n = 9). On 11 July 2005 (1 week after trans- Dry Compactness Flowers Flowers planting to 1-gal containers), unico- Drenches Growth wt rating at 3 wk at 4 wk nazole-P was uniformly applied (2 qt/ Rate (mgÁL–1)z (no.) indexy (g)x (1–3 scale)w (no.) (no.) 2 100 ft ) with a CO2 sprayer at 60, 120, and 180 mgÁL–1, or as a drench Control — 31.8 15.4 1.0 4.7 9.5 at 6, 12, and 24 mgÁL–1. Ethephon 6 1 29.2 14.9 1.3 3.5 11.0 was applied (3 qt/100 ft2) using a 6 2 26.7 12.9 1.4 3.2 5.0 –1 12 1 25.8 12.4 1.4 4.3 9.5 CO2 sprayer at 500 and 1000 mgÁL . A spray adjuvant CapSil (Aquatrols, 12 2 25.9 15.1 2.2 2.7 3.5 Cherry Hill, NC) was added to ethe- 24 1 21.9 10.7 2.7 3.2 5.5 phon solutions at 0.5 mLÁL–1. The 24 2 22.5 12.4 2.4 2.3 5.0 second uniconazole and ethephon Contrasts application (for treatments that re- Control vs. others ** * ** NS NS ceived two applications) was applied Rate L** L* L** NS NS 1 week after the initial treatment. Drench no. NS NS NS NS * Distilled deionized water was applied Rate vs drench no. NS NS NS NS NS z1mgÁL–1 = 1 ppm. as a control and used to make all other yGrowth index was calculated by the equation (height + average width) O 2. solutions. x1 g = 0.0353 oz. After 3 weeks, the height and wVisually assessed on a scale where 1 point is not compact, 2 points is somewhat compact, and 3 points is highly compact. perpendicular width of each plant NS,*,**Nonsignificant or significant at P £ 0.05 or 0.01 respectively. were measured to obtain a growth L, linear.
• October–December 2007 17(4) 553 RESEARCH REPORTS media drenches. Likewise, Gibson and Whipker (2001) reported that increas- ing the foliar spray concentrations of uniconazole (2, 4, 8, 16, and 32 mgÁL–1) linearly reduced plant height of both ‘Osaka White’ and ‘Nagoya Red’ ornamental cabbage (Brassica oleracea var. acephala). In their review of Asteraceae responses to PGRs, Latimer et al. (2006) re- ported that the effective spray rates of uniconazole varied widely from less than 15 mgÁL–1 to more than 80 mgÁL–1. Although a single spray application of 45 or 60 mgÁL–1 uni- conazole moderately reduced plant height of ‘Burgundy’ blanketflower (Latimer et al., 1999), ‘Goblin’ blan- ketflower (G. ·grandiflora) was not responsive (Latimer et al., 2006). Also, although not an objective of our study, it is of interest to men- tion residual PGR effects and post- greenhouse performance. Latimer et al. (1999) reported that the com- paction of uniconazole-treated bur- gundy blanketflower did not persist Fig. 1. (A, B) Response of ‘Torch Flame’ blanketflower drenched with uniconazole through 5 weeks after treatment and 21 21 did not affect subsequent landscape at 0, 6, 12, or 24 mgÁL once (A) or twice (B). 1 mgÁL = 1 ppm. performance. As compared with foliar sprays, medium drench applications of uni- Table 2. Growth index, dry weight, compactness rating, and flower number conazole are sometimes more effec- of ‘Torch Flame’ blanketflower sprayed with Ethephon (n = 9). tive because they are taken up by the Dry Compactness Flowers Flowers roots and xylem transported up the Spray Growth wt rating at 3 wk at 4 wk stems to the growing points (Barrett, Rate (mgÁL–1)z (no.) indexy (g)x (1–3 scale)w (no.) (no.) 2001). Also, it has been suggested Control — 26.3 8.9 1.2 2.3 12.3 that uniconazole drenches may affect 500 1 22.6 6.1 2.0 0.0 7.3 cell elongation or division during 500 2 20.8 6.5 3.0 0.0 0.0 flower development at a lesser extent 1000 1 22.2 7.5 3.0 0.0 0.7 than sprays, thus hastening flowering 1000 2 19.4 5.9 3.0 0.0 0.0 in some species (Barrett, 2001; Starman, Contrasts 1991). Starman (1991) applied one Control vs. others ** ** ** ** ** and two foliar sprays and single Rate NS NS ** NS ** drenches of uniconazole to ‘Yodel Spray no. ** NS ** NS ** Blue’ lisianthus (Eustoma grandiflo- Rate vs. spray no. NS *** NS ** rum) and found that uniconazole z1mgÁL–1 = 1 ppm. drenching did not delay flowering, yGrowth index was calculated by the equation (height + average width) O 2. whereas foliar spray applications x1 g = 0.0353 oz. wVisually assessed on a scale where 1 point is not compact, 2 points is somewhat compact, and 3 points is highly did. Similar to sprays, drenches are compact. species and cultivar specific. Whipker NS,*,**Nonsignificant or significant at P £ 0.05 or 0.01 respectively. et al. (1995) drenched potted ‘Red Pygmy’ and ‘Golden Emblem’ dahlia (Dahlia variabilis) with uniconazole significantly lower growth indices double-spray applications at 500 and and found that only ‘Red Pygmy’ and dry weights, with greater com- 1000 mgÁL–1, plants were 1.7 to 2.5 responded enough to the treatment pactness than control plants. Increas- times more compact than untreated to be considered marketable. ing the rate had no effect on growth controls, but flowering was delayed. ETHEPHON. Significant rate · index or dry weight, but did increase Ethephon reduced torch blanket- spray number interactions occurred visual compactness. A second spray flower dry weight by as much as 34% for dry weight, visual compactness, application had no effect on dry (double application at 1000 mgÁL–1) and flowering of torch blanketflower weight or flower number (at 3 weeks), compared with untreated controls plants sprayed with ethephon (Table but did reduce growth index and (Table 2, Fig. 2). In a study using 2). Ethephon-treated plants had visual compactness. With single- or several different container-grown
554 • October–December 2007 17(4) increased rates from 6 to 24 mgÁL–1, but a second application is not war- ranted. Although ethephon reduced growth of torch blanketflower at 500 and 1000 mgÁL–1, flowering was delayed. Based only on flowering at 4 weeks after PGR application, ethe- phon-sprayed plants were considered less marketable compared with uni- conazole-drenched plants. It should be noted that our experiments were conducted during mid summer in Florida, therefore recommended rates may need to be lowered for northern growers.
Literature cited Barrett, J. 2001. Mechanisms of action, p. 32–47. In: M.L. Gaston (ed.). Tips on regulating growth of floriculture crops. Ball Publishing, Batavia, IL. Chamberlayne, C.L. and T.J. Banko. 2003. Growth response of container- grown herbaceous perennials to Ethe- phon, daminozide, paclobutrazol and uniconazole. Southern Nursery Assn. Res. Conf. Proc. 48:267–271. Danielson, H.H. 2005. Production and performance of Gaillardia cultivars and ecotypes. Dept. of Environ. Hort., Univ. of Florida, Gainesville, FL. MS thesis. Florida Wildflower Advisory Council. 2004. History. 19 Mar. 2006.
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Krug, B.A., B.E. Whipker, I. McCall, and Norcini, J.G. and J.H. Aldrich. 2004. tors. Southern Nursery Assn. Res. Conf. J.M. Dole. 2006. Narcissus response to Establishment of native wildflower plant- Proc. 43:286–290. plant growth regulators. HortTechnology ings by seed. 19 Mar. 2006.
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