Louisiana State University LSU Digital Commons
LSU Historical Dissertations and Theses Graduate School
1966 Part I. The Life History of Amphibromus Scabrivalvis in Louisiana. Partii. Some Studies of the Autecology and Chemical Composition of Amphibromus Scabrivalvis. Wayne Thomas Flinchum Louisiana State University and Agricultural & Mechanical College
Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_disstheses
Recommended Citation Flinchum, Wayne Thomas, "Part I. The Life History of Amphibromus Scabrivalvis in Louisiana. Partii. Some Studies of the Autecology and Chemical Composition of Amphibromus Scabrivalvis." (1966). LSU Historical Dissertations and Theses. 1122. https://digitalcommons.lsu.edu/gradschool_disstheses/1122
This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Historical Dissertations and Theses by an authorized administrator of LSU Digital Commons. For more information, please contact [email protected]. This dlsMrUtlon h u been microfilmed exactly es received ® —6442 FLINCHUM, Wayne Thomas, 1937- PART I. THE LIFE HISTORY OF AMPHIBROMUS SCABRIVA LVT3 IN LOUISIANA. PART II. SOME STUDIES OF THE AUTECOLOGY AND CHEMICAL COMPOSITION OF AMPHIBROMUS SCABRIVALVIS.
Louisiana State University, Ph.D., 1966 B otany
University Microfilms, Inc., Ann Arbor, Michigan PART I. THE LIFE HISTORY OF AMPHIBROMUS SCABRIVALVIS IN LOUISIANA PART II. SOME STUDIES OF THE AUTECOLOGY AND CHEMICAL COMPOSITION OF AMPHIBROMUS SCABRIVALVIS
A Dissertation
Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy
in
The Department of Botany and Plant Pathology
by Wayne Thomas Flinchum B.S., N. C. State College, 1960 M .S., Louisiana State University, 1962 January, 1966 PLEASE NOTE: Plate pages are not original copy. They tend to "curl" due to glue used for mounted illustrations. Filmed in the best possible way. University Microfilms, Inc, ACKNOWLEDG EMENT
The author wishes to express his appreciation to Dr. J. B.
Baker for his counsel in the execution of these studies, for his interest and guidance during the course of this research and the preparation of this manuscript. Acknowledgement is also made to
Dr. W. C.Normand and Dr. L. C. Standifer for helpful advice and criticism relating to experimental work.
Acknowledgement is also extended to Dr. C . A. Brown for the loan of a photograph.
This work was conducted while the author was a recipient of a Louisiana State University assistantship. This financial assistance is gratefully acknowledged.
The author also expresses his appreciation to his wife and his daughter for encouragement while a graduate student.
ii TABLE OF CONTENTS
Page
ACKNOWLEDGEMENT...... ii
LIST OF TABLES...... v
LIST OF PLATES...... vii
LIST OF FIGURES...... ix
ABSTRACT...... x
PART I
INTRODUCTION...... 1
LITERATURE REVIEW...... 2
DEVELOPMENT AND STRUCTURE OF VEGETATIVE PARTS...... 4
Definition of Terms...... 4 General Growth C h aracteristics...... 5 Seed Germination and Seedling Development ...... 8 Tiller Formation...... 8 R o o ts...... 12 R hizom e...... 12 C u lm ...... 14 L eaf...... 20
DEVELOPMENT AND STRUCTURE OF THE INFLORESCENCE .... 24
Intravaginal Inflorescence ...... 24 Terminal Inflorescence...... 32
SUMMARY AND CONCLUSIONS...... 38
PART II
INTRODUCTION...... 42
LITERATURE REVIEW...... 43
iii P age
MATERIALS AND METHODS...... 57
Study of the Rate of S p read ...... 57 Study of the Effect of Photoperiod...... 59 Study of the Effect of Light Intensity...... 61 Study of the Effect of Clipping ...... 62 Studyof the Chemical Composition of Enlarged Internodes . . . 62
RESULTS AND DISCUSSION...... 67
Results from the Rate of Spread S tudy ...... 67 Results from the Photoperiod Study ...... 78 Results from the Light Intensity S tu d y...... 83 Results from the Clipping Study ...... 87 Results from the Chemical Composition of Enlarged Internode Study ...... 91
SUMMARY AND CONCLUSIONS...... 95
LITERATURE CITED...... 98
BIOGRAPHY...... 103
iv LIST OF TABLES
TABLE Page
1. Effect of three treatments on the per cent of nodes producing tillers on A. scabrivalvis culm s ...... 17
2. The average length of internode, leaf sheath, and leaf b la d e ...... 21
3. The average number of florets per node and the average awn length of florets at each node ...... 29
4. Average dry weight and average number of tillers per square foot and average dry weight per tiller at the first sampling period ...... 69
5. Analysis of variance of dry weight data per square foot at the first sampling period ...... 69
6. Analysis of variance of tiller production per square foot at the first sampling period ...... 69
7. Average number of tillers per square foot at the second sampling period ...... 70
8. Analysis of variance of tiller production per square foot at the second sampling period ...... 70
9. Average number of tillers per square foot at the third sampling period ...... 76
10. Analysis of variance of tillers per square foot at the third sampling period ...... 76
11. Effect of two photoperiods on tiller production ...... 81
12. Dry weight and tiller production in A. scabrivalvis grown under various light intensities...... 85
13. Analysis of variance for dry weight of A. scabrivalvis when grown 8 weeks under various light intensities . . . 86
v TABLE Page
14. Analysis of variance for tiller production in A. scabrivalvis when grown 8 weeks under various light intensities ...... 86
15 . Average number and per cent of tillers produced per plant, when clipped weekly ...... 87
16. Analysis of variance of tillers produced on clipped plants ...... 89
17. Amount of alcohol soluble sugars in enlarged basal internodes of A. scabrivalvis ...... 94
vi LIST OF PLATES
PLATE Page
1. Growth and morphological habit of,A. scabrivalvis ... . 7
2. A germinating basal seed of A. scabrivalvis ...... 9
3. Longitudinal section through a germinated basal seed of A. scabrivalvis ...... 10
4 . Young seedling of A. scabrivalvis showing the first leaf extended through the coleoptile ...... 10
5. Close view of a basal stem area showing tillering, swelling of internodes, and a short rhizome ...... 11
6. Stems of A. scabrivalvis connected by rhizomes ..... 13
“7. Cross section of an enlarged basal internode ...... 16
8. The method of tiller production on summer produced culms of A. scabrivalvis ...... 18
9. The production of tillers and adventitious roots on a summer produced culm of A. scabrivalvis ...... 19
10. Vegetative apex of A. scabrivalvis cut transversly. The youngest leaf has not sheathed the apex com pletely, and there is a transverse section of a tiller enclosed by the first le a f...... 22
11. Transverse section of the middle part of a leaf of A. scabrivalvis ...... 23
12. A basal inflorescence on the node below the first elongated internode behind the leaf sheath ...... 25
13. Immature male and female flower parts of a basal flo re t...... 26
14. Lower stem of .A. scabrivalvis showing inflorescences behind the leaf sheaths ...... 27
v ii PLATE P age
15. Lower three Internodes of an A. scabrivalvis stem showing arrangement of inflorescences at the nodes .... 28
16. A comparison of awn length between a basal floret and a terminal floret of A. scabrivalvis ...... 31
17. A complete terminal inflorescence of A. scabrivalvis collected in May...... 33
18. A comparison of spikelet size and number of florets between a basal and a terminal spikelet of A. scabrivalvis ...... 35
19. A view of a basal inflorescence composed of one flo re t...... 36
20. A comparison of seed size produced on basal and terminal inflorescences ...... 37
21. The effect of clipping on production of tillers and enlargement of internodes ...... 90
v iii UST OF FIGURES
FIGURE Page
1. Effect of seeding rate on tiller production at three sampling periods ...... 77
2. Effect of photoperiod on tiller production during an 18 week period, sampled every 2 weeks ...... 82
ix ABSTRACT
Amphibromus scabrivalvis (Trin.) Swallen, a member of the
Gramineae family,, endemic to South America is now established in
Tangipahoa Parish, Louisiana. A. scabrivalvis is a perennial possessing a rhizome-tiller complex, an adventitious root system, intravaginal inflorescences at the nodes over the entire length of the stem, as well as a terminal inflorescence. Also, the lower internodes of the stem may swell or enlarge after elongation.
The most active growth in the life cycle of A. scabrivalvis is from late October or early November to May or June. However, A. scabrivalvis remains more or less dormant during the cold weather of winter, but as soon as spring temperatures become favorable vigorous growth and the production of rhizomatous tillers, the major means of spread during the growing period, is resumed. Growth of
A. scabrivalvis after May or June appears to be vegetatively without the initiation of floral parts.
In auteocology studies, tillering is significantly affected by stand density, reduced light intensity and weekly removal of top foliage. Interruption of the dark phase also has an effect on tiller production.
x Analysis of hot alcohol extracts of enlarged basal internodes of
A. scabrivalvis indicates that reducing sugars and sucrose do not make up the bulk of the dry weight. Tests of enlarged basal internodes for
starch were also negative.
xi PART I: THE LIFE HISTORY OF AMPHIBROMUS SCABRIVALVIS IN LOUISIANA
INTRODUCTION
During previous years grasses not endemic to the United States have been introduced and established intentionally. However, unwanted nonendemic grasses have appeared in the United States also. One such grass is Amphibromus scabrivalvis (Trin.) Swallen, a member of the Gramineae family originating in South America.
The time and method of entry of A. scabrivalvis into the United
States is unknown but in the late 1950's it was discovered, established and actively growing, in a strawberry field in Tangipahoa Parish,
Louisiana. On strawberry farms which are infested with this grass the cost of production has increased because of the extra labor and time needed to control it. Plastic mulch instead of the usual pine-
straw mulch gives effective control under the plastic, but a cheaper and more effective means of controlling A. scabrivalvis is needed.
To effectively control any weed a knowledge of its growth habits is helpful. Therefore, this dissertation represents the author's endeavor to obtain a clearer insight into the life history of A_. scabrivalvis in
Louisiana.
1 LITERATURE REVIEW
The original description and the naming of the genus Amphibromus is credited to Nees (40). According to Black (7) amphi in Greek means about and bromos means oat. Species belonging to this genus have been reported in South America, New Zealand, Tasmania, and
Australia. Swallen, in a 1931 publication on the technical descrip tion of this genus and related species, listed only five species: A.
Neesii, A. scabrivalvis. A. fluitans. k. quadridentulus, and A. recurvatus. In his technical description he placed this genus in the
Festuceae tribe because the glumes are much shorter than the spikelet.
Black, in his book. The Flora of South Australia. places the genus Amphibromus in the Aveneae tribe because of the twisted awn which rises from between two teeth or lobes at the summit of the lemma.
He further states that four species are endemic in Australia and New
Zealand, and gives a description of three species one of which is A.
Archeri. Swallen did not list this species when he described the species of the genus.
Gardner (15) in his book Flora of Western Australia, gives a technical description of the genus Amphibromus and states that three species are endemic to Australia. He places this genus in the Aveneae tribe generally on the characteristics of its geniculate twisted awn which he feels affords a more satisfactory character for tribe place
ment than that of the comparative length of the glumes. Cockayne (10)
cites A_. fluitans in his book The Vegetation of New Zealand, but does
not refer it to any tribe and labels it "the rare grass."
According to Swallen, scabrivalvis could be found in open
grassland from Peru to Uruguay and Chile, and in the late 1950's, he
identified a specimen growing in Tangipahoa Parish, Louisiana, as
A. scabrivalvis. DEVELOPMENT AND STRUCTURE OF VEGETATIVE PARTS
Definition of Terms
Since some of the terms used in this manuscript may have been employed elsewhere with different meaning, and others are new, it is necessary to define the exact manner in which all terms will be used.
Seedling: A young plant which develops directly from the seed is a seedling. The young plant will be regarded as a seedling up to the time when lateral tillers appear, or until internodes of the primary shoot become elongated.
Plant: All the growing shoots and roots which have developed from a single seed, or as the case may be, from the detached part of another plant is a plant.
Tiller: A stem with its attached roots, leaves, buds, and inflorescences which has developed from an axillary bud is a tiller.
The term tiller may be applied from the time when the axillary bud has expanded.
Stem: The axis of the shoot including the proaxis, enlarged internode, culm, and inflorescence is a stem.
Culm: the part of the stem which is composed of elongated, cylindrical, hollow internodes is the culm. 5
Proaxis: The part of the stem below the enlarged or elongated
Internode which is composed of compacted nodes and internodes is
called the proaxis.
Rhizome: That part of the tiller which remains underground is
a rhizome.
Terminal Inflorescence: That visible open panicle which is pro
duced at the top of the culm is the terminal inflorescence.
Intravaginal Inflorescence: Those inflorescences that are pro
duced at each node of the culm which remain enclosed within the leaf
sheath are intravaginal inflorescences.
Basal Inflorescence: Those spikelets produced underground at
the lower two or three enlarged or elongated internodes are labeled as
basal inflorescences.
Basal Seed: Those seeds produced in a basal inflorescence are
basal seeds.
Basal Floret: Those florets produced in a basal inflorescence are
basal florets.
General Growth Characteristics
Swallen describes A. scabrivalvis as a perennial, but on agri
cultural land in Louisiana it grows as a winter annual. On undisturbed
land it has been observed to grow during the summer months, but
terminal inflorescences are only produced during the months of May
and June. A. scabrivalvis is located in the strawberry area of Louisiana and is well adapted to the cultural practices used in the production of strawberries. When the soil is prepared in the fall to receive the strawberry transplants A., scabrivalvis will make an appearance. The infestation of A. scabrivalvis may be from two different sources: one, vegetatively from buds on plant parts left in the soil and, or secondly, from seeds produced during the preceding spring.
Regardless of plant origin A. scabrivalvis remains more or less dormant during the cold weather of winter, but as soon as spring weather becomes favorable, vigorous growth and tillering is resumed.
When the internodes begin to elongate, the lower first, second, and in some instances the third, internode may enlarge or become swollen, and the buds at the nodes will initiate inflorescences at each node over the entire length of the stem. During May and June the terminal open panicle is visible at the top of the culm.
The general growth habit of A_. scabrivalvis is illustrated in
Plate 1. The leaves are arranged in two ranks, succeeding ones being on alternate sides of the stem. Stems with a terminal inflorescence usually attain a height of 65-120 cm. or more above the soil line, with a bluish-green foliage color during active growth which turns brown after panicle emergence. Plate 1. Growth and morphological habit of A. scabrivalvis . Seed Germination and Seedling Development
A germinated seed or caryopsis from a basal inflorescence is shown in Plate 2. The coleoptile and the coleorhiza develop at approximately the same rate, but the radicle emerges before the first leaf. A thin section through the median longitudinal plane of a germi nated A. scabrivalvis caryopsis can be found in Plate 3. The section clearly shows the structure found in a germinated caryopsis, such as: endosperm, coleoptile with its enclosed leaf primordia, apical meristem of the shoot, radicle, and scutellum. A young seedling with the first leaf just emerged through the coleoptile appears as in Plate 4. Adventi tious roots form on the first or cotyledonary node very soon after germination. After approximately three weeks growth the seedling was in the three-leaf stage. Under greenhouse conditions the first tiller was visible when the plants were in the four-leaf stage, but under these same conditions it required 13 weeks of growth before the first internode began to elongate.
Tiller Formation
Tillers are produced from buds on nodes in a zone between the first node and the first elongated internode. The nodes in the proaxis area are very close together or compacted due to the very short inter nodes; and Plate 5 shows a proaxis with several tillers. The bud which becomes a tiller is covered by an organ called a prophyllum.
At first the prophyllum completely covers the bud, but later opens as Plate 2 . A germinating basal seed of A. scabrivalvis (X 23). Plate 3. Longitudinal section through a germinated basal seed of A. scabrivalvis (X 39).
P la te 4 Young seedling of scabrivalvis showing the first leaf extended through the coleoptile (X 7). 11
Plate 5. Close view of a basal stem area showing tillering, enlarge ment of internodes, and a short rhizome (X 4). A. short rhizome; B. enlarged internode; C . basal inflorescence. 12 the tiller develops. As the tiller elongates, the prophyllum can be observed on the lower regions, and is very similar to the coleoptile of the seedling. Development of the tiller is very similar to that of a seedling, and mature plants are indistinguishable as to origin.
These secondary shoots, or axes, in turn, may produce branches of a third order from buds produced on its proaxis. All tillers are pro duced extravaginally, that is they pierce through the base of the surrounding leaf-sheath to reach the exterior.
Roots
The primary root of A. scabrivalvis appears to have a limited role in the growth of the plant. Once the primary root breaks through the coleorhiza it may produce some lateral roots, but they never appear to attain any importance. The major root system of A. scabrivalvis is derived from adventitious roots which arise in the basal intercalary meristem of the lower internodes of the stem. Plate 1 illustrates the importance of the adventitious root system to A. scabrivalvis.
Adventitious roots may occur at nodes in association with the tillers, but they may form independently of tillers.
Rhizome
When an axxillary bud initiates a tiller, the internode connecting the primary plant and the axis of the tiller has been labeled a rhizome
(Plate 6). Usually this connection is just an elongated internode Plate 6. Stems of A. scabrivalvis connected by rhizomes. 14 which is connected to the primary shoot from an intercalary meristem,
and the other end has a node or compacted zone of nodes and inter
nodes above which there is a growing point, but occasionally there
is a node or nodes on the rhizome. Also the internode or rhizome may
be short as shown in Plate 5, as compared to those in Plate 6.
Culm
The culm of A. scabrivalvis found in Louisiana contains up to .
ten or more elongated internodes. Culms vary in length according to
the time of year they are produced. Those produced during the spring
are much longer than those produced during the summer even though
they contain approximately the same number of elongated internodes.
The total number of internodes and nodes including those of the pro
axis has not been ascertained. The culm is composed of alternating
nodes and internodes with the internodes cylindrical and hollow. The
average length of elongated internodes and their position with respect
to the culm can be found in Table 2. The longest internodes are located
towards the terminal end of culm and shorter internodes at the basal
end.
Under greenhouse conditions, the internode begins to elongate
after approximately 13 weeks of growth in plants produced from seeds.
After the lower intemodes elongate, they may become enlarged or
swollen (Plate 5). The pattern of enlargement is not always the same.
From one to three internodes may swell, or the first internode alone may swell, or the first internode may swell and the second and third remaining unchanged, while the fourth enlarges. Most of the enlarged internodes remain underground, but above ground swollen internodes have been observed. The enlarged internode is hollow in the center and has scattered vascular bundles (Plate 7). Whether the enlarged internode serves as a storage organ has not been definitely established.
Labeling of the enlarged internodes as corms is equivocal because the
structure of the enlarged internode satisfies some definitions of a corm but not others.
As previously mentioned in the section on general growth charac teristics A. scabrivalvis produces inflorescences at the nodes during the spring. Therefore a study of the buds at the nodes on culms pro
duced during the summer and early fall was undertaken. In the middle
of October, culms of A. scabrivalvis were cut at ground level from an
area which had been clipped back to 2 inches on May 29 of the same
year. The leaves were removed from each culm and the culms were
subjected to one of three treatments as follows: (1) culm left intact
with growing point attached, (2) culm left intact except growing point
removed, (3) culm dissected between each node with growing point on
the terminal piece of the culm. Each culm was placed between two
pieces of germination paper and enclosed in a clear plastic box with
a tight fitting lid. The plastic box was transferred to a growth room
adjusted to a constant 30°C. The number of nodes, number of tillers Plate 7 . Cross section of an enlarged basal internode (X 40). 17 produced, and the per cent of nodes producing tillers is shown in
Table 1. Treatment 1, which had the growing point attached and the stem not dissected had the lowest number of nodes producing tillers which was approximately 20 per cent. There was very little difference in the per cent of nodes producing tillers between treatment two and three with 42.8 and 43.9 per cent, respectively. In Plate 8 the method of tillering, which was similar on all culms, can be noted and Plate 9 shows a view of nodes producing tillers as well as adventitious roots.
There was no set pattern for tiller production on any culm under any treatment, since tillers could be found on any node of the culm regard less of treatment. Although there appeared to be no set pattern for tiller initiation, it can be noted in Table 1 that there was a reduction in the per cent of nodes producing tillers where the growing point was attached and the culm not dissected. This indicates that there may be some apical dominance exerted over the culm when the growing point is attached.
Table 1. Effect of three treatments on the per cent of nodes producing tillers on A. scabrivalvis culms.
No. of No. of Per Cent of Nodes Treatment Nodes Tillers Producincr Tillers 1 43 12 27.9 2 35 15 42.8 3 41 18 43.9
♦Treatments were: (1) Growing point and culm intact. (2) Growing point removed, culm intact. (3) Growing point on top internode, culm dissected. 18
Plate 8. The method of tiller production on summer produced culms of A. scabrivalvis. Plate 9. The production of tillers and adventitious roots on a summer produced culm of A. scabrivalvis . 20
Leaf
The leaf of &. scabrivalvis consists of a sheath, blade, and a thin, rather soft, and more or less translucent ligule. No auricles are formed at the junction of the leaf and blade. The leaves are formed on the stem in two ranks, one at each node. Each sheath is rolled around the node in the opposite direction from that of the preceding one. Leaf sheaths are longer than the internodes, with the exception of the inter- node just under the terminal inflorescence.
Data recorded on the leaves of randomly selected A. scabrivalvis stems with expanded terminal panicles can be found in Table 2. As the length of the internode generally decreased from the terminal inflores cence down the culm, the leaf sheath although longer than the internode, decreased also. In contrast to this the length of the leaf blade increased from the top of the stem down to the bottom. The width of the leaf blade measured across at the mid-point ranged from 3-5 mm, and the ligule ranged from 5-14 mm.
The manner in which the leaves are rolled around one of the margins enclosing the stem tip is shown in Plate 10. Three leaves are formed and a fourth is in the process. The coleoptile encloses all the leaves and a tiller initial can be seen between the first and second leaf. A cross section of a portion of a leaf blade is shown in Plate 11.
The ridges are the upper surface of the leaf blade and the smooth side is the lower surface. There is one vascular bundle in each ridge of the blade which has no prominent midrib. 21
Table 2. The average length of internode, leaf sheath, and leaf blade.
Av. Length of Av. Length of Av. Length of Internode Internode in cm Leaf Blade in cm Leaf Sheath in cm
1 26.9 3.3 20.7
2 15.2 7.5 15.0
3 10.5 13.6 12.0
4 8.8 18.8 11.1
5 6.5 21.9 11.3
6 6.5 22.1 10.8
7 5.7 24.2 10.7
8 3.5 25.5 10.3
9 4.1 22.0 9.0
10 1.3 --
*Nodes or Internodes are numbered beginning just under the terminal inflorescence. 22
Plate 10. Vegetative apex of A. scabrivalvis cut transversly. The youngest leaf has not sheathed the apex completely, and there is a transverse section of a tiller enclosed by the first leaf (X 94). Plate 11. Transverse section of the middle part of a leaf of A. scabrivalls (X 110). DEVELOPMENT AND STRUCTURE OF THE INFLORESCENCE
Intravaqlnal Inflorescence
When the first internode elongates, the bud at the node enclosed in the leaf sheath is initiated to produce a floret. A young spikelet produced behind the leaf sheath on the first elongated internode is shown in Plate 12, and Plate 13 shows the male and female parts of a floret produced on the first node. There are three stamens, and one pistil composed ot an ovary and two styles with plumose stigmas.
Inflorescence produced at the nodes below the growing point remain enclosed within the leaf sheath and are not visible until the sheath is removed or decays. The lower portion of a culm with the sheaths removed from the first two internodes, and the next two sheaths pulled back to expose the inflorescence enclosed is shown in Plate 14.
The inflorescences are produced two ranked and alternately, the same as the leaves {Plate 15). They are always produced on the node oppo site where the margins of the sheath overlap.
The average number of florets produced per node and the average awn length of the florets from randomly selected stems with an expanded terminal inflorescence can be found in Table 3. The number of nodes producing inflorescence below the soil line varied from three to four.
Floret production per node increased with increasing node height from
24 Plate 12 . A basal inflorescence on the node below the first elongated internode. A. Leaf sheath, B. Elongated internode, C. Basal inflorescence. Plate 13. Immature male and female flower parts of a basal floret (X 46). Plate 14. Lower stem of A. scabrivalvis showing inflorescences behind the leaf sheaths. A. Floret behind the leaf sheath, B. Leaf sheath. 28
Plate 15. Lower three internodes of an A. scabrivalvis stem showing arrangement of inflorescences at the nodes. A, B, and C are basal inflorescences. 29
Table The average number of florets per node and the average awn length of florets at each node.
Av. No. of Av. Length of Node Florets/Node ______Awn in mm
1 1.0 0.00
2 1.4 0.00
3 1.5 0.12
4 2.0 0.50
5 2.6 1.49
6 4.8 2.82
7 6.8 — 4.24
8 9.2 4.72
9 10.6 5.70
10 5.6 5.58
12.60 30 the ground, with one exception, the node just below the terminal inflorescence always had fewer florets than did some of the nodes lower down the stem. Floret production was always the greatest on the second node below the terminal inflorescence.
As presented in the review of literature some workers believe that the genus Amphlbromus belongs to the Aveneae due to the charac teristics ot the awn. It can be observed in Table 3 that there is no awn on the lemma of the floret produced on the first two nodes and it is only rudimentary on the florets of the third and fourth node. Length of the awn on the florets produced at the other nodes attained a length of only half that of the awns of the florets produced in the terminal inflorescence. A comparison of awn length on florets produced in the terminal inflorescence and at one of the lower nodes of the stem is shown in Plate 16 .
An attempt was made to determine the germination of seeds pro duced at each node of the stem and the terminal inflorescence. Seeds produced at each node of the stem and the terminal inflorescence were collected on May 10 and allowed to dry under room conditions. On
May 25 the seeds were placed in petri plates containing one piece of filter paper and 4 ml of distilled water and transferred to the growth room adjusted to 80°F. No seeds germinated over a period of 10 days regardless of where they were produced. Plate 16. A comparison of awn length between a basal floret and a terminal floret of A. scabrivalvis. A second experiment was undertaken with seeds produced on the first elongated internode. The seeds were placed under three different temperatures and two light conditions. The temperatures were continuous
60, 70, and 80°F, under no light and under 12 hours of 420 ft-c of white light. No germination occurred under any treatment, but basal seeds collected during December germinated 100 per cent in July under 70°F and 420 ft-c of white light. Also, basal seeds collected during early summer, washed, dried, and stored under room conditions, gave almost 100 per cent germination when used as a plant source for an experiment in October. It appears from the above results that seeds of A. scabrivalvis may have an after-ripening period.
Terminal Inflorescence
The apical meristem of A_. scabrivalvis ceases to produce foliage leaves and initiates an inflorescence which usually appears in May or
June (Plate 17). Terminal inflorescence may vary in length up to 25 cm.
Spikelets located at the bottom of a terminal inflorescence usually contain only three florets and average about 16 mm in length including the awn, while those spikelets located midway on the panicle contain four florets and average about 18 mm. Spikelets located at the terminal end of the inflorescence usually contain between five and six florets and are up to 25 cm in length.
Regardless of location on the terminal inflorescence, the length
of the first glume ranged between 5 and 5 .5 mm, and that of the second Plate 17. A complete terminal inflorescence of A. scabrivalvis collected in May. 34 glume between 5.5 and 7.0 mm. The number of nerves of the first glume is one or three and of the second glume three or five while the number of nerves of the fertile lemma is seven or nine. These measurements are within those given by Swallen in his description of this grass.
A comparison of a spikelet produced on the first elongated inter node containing one floret and a spikelet produced on the terminal inflorescence containing five florets is shown in Plate 18. One similarity is that the glumes on both spikelets are shorter than the first floret, and a dissimilarity is the absence of an awn on the basal spikelet as com pared with an awn on each floret of the terminal spikelet. Data recorded as to length of floret on either basal or terminal inflorescence indicates that on the average florets on the terminal inflorescence are 8.05 mm in length while basal florets are 7.5 mm long (Plate 19).
Seeds or caryopses oi A. scabrivalvis vary in size depending on the area of the stem where they are produced. Seeds produced on the first elongating internode are the largest, and those produced on the terminal inflorescence are the smallest. A comparison of five seeds produced at either location is shown in Plate 20. 35
Plate 18. A comparison of spikelet size and number of florets between a basal and a terminal spikelet of A. scabrivalvis. 36
Plate 19. A view of a basal inflorescence composed of one floret. 37
0 \
Plate 20. A comparison of seed size produced on basal and terminal inflorescences (X 6). A. Terminal seeds; B. Basal seeds. SUMMARY AND CONCLUSIONS
Amphlbromus scabrivalvls is a perennial possessing: a rhizome- tiller complex, an adventitious root system, inflorescences at the nodes over the entire length of the stem, as well as a terminal inflorescence. Also, the lower internodes of the stems may swell or enlarge after elongation.
In Louisiana on land used for strawberry production, growth of
A. scabrivalvls is more similar to a winter annual than a perennial, but on land not disturbed by tillage it will tiller and form new plants during the summer also.
During late October or early November A. scabrivalvls appears in the strawberry transplant bed probably from two sources, buds on plant parts left in the soil and seeds produced during the preceding growing season.
scabrivalvls remains more or less dormant during the cold weather of winter, but as soon as spring weather becomes favorable vigorous growth and tillering are resumed.
During the period of internode elongation, after approximately
13 weeks of growth, intravaginal inflorescences are produced at the nodes, and the lower internodes may or may not swell or enlarge.
38 39
During May and June a terminal open panicle is visible at the top of the stem.
The buildup and spread of this grass during the growing season is by rhizomatous tillers .
Culms of A_. scabrivalvls produced during the spring, although containing approximately the same number of nodes and internodes as summer culms, are longer due to greater elongation of the internodes.
Extravaginal tillers are produced from axillary buds located on the proaxis.
The primary root of A. scabrivalvls appears to have a limited role in the growth of the plant and is replaced by adventitious roots which arise in the basal intercalary meristem of the lower internodes and nodes of the stem.
In a germinating seed the coleoptile and the coleorhiza develop at approximately the same rate, but the radicle emerges before the first leaf.
The enlarged basal internodes as well as the other internodes of the culm are hollow.
The buds on the nodes of culms produced during the summer can be induced to produce tillers. If the growing point is left attached to the culm there is a reduction in the number of nodes producing tillers as compared to the number produced when it is removed.
The leaf of A. scabrivalvls consists of a sheath, blade, and a thin rather soft, and more or less translucent ligule. The leaves are 40 formed on the stem in two ranks. Sheath length is usually shorter than blade length and both are influenced by location of the leaf on the culm.
The upper surface of the leaf consists of a number of ridges with a vascular bundle in each and a smooth lower surface with no prominent midrib.
Three or four nodes below the soil line produce intravaginal inflorescences.
The number of florets per inflorescence is influenced by node location with the number of florets usually increasing towards the terminal inflorescence.
There is no awn on the lemma of the floret produced on the first two nodes and only a rudimentary awn on the florets of the third and fourth node. Awn length on the florets produced at the other nodes of the stem attain only half the length of that of the awn on the florets produced in the terminal inflorescence.
All efforts to germinate freshly collected air dried seeds failed, but basal seed collected in December gave 100 per cent germination the following July. There appears to be an after-ripening period in the seeds of A. scabrivalvis.
Terminal inflorescences usually appear in May and June, and their length varies up to 25 cm, and the number oi florets in the spikelets vary from three to six.
The glumes are shorter than the first floret regardless of where the floret is produced on the plant. • Basal florets are slightly shorter than florets in the terminal inflorescences.
Seeds produced on the first elongating internode are the largest, and those produced on the terminal inflorescence are the smallest.
Due to the rapid rate of growth and the prolific production of reproductive structures, spread of this plant to other areas in
Louisiana could easily occur. PART II: SOME STUDIES OF THE AUTECOLOGY AND CHEMICAL COMPOSITION OF AMPHIBROMUS SCABRIVALVIS
INTRODUCTION
Survival of a plant species depends on the ability of the plant to reproduce. The rate of spread of a plant species depends on several factors, such as environment and the plant's ability to pro duce organs of dissemination. The effectiveness of a plant's ability to reproduce vegetatively may be influenced by the storage of reserve carbohydrates.
As was pointed out in Part I of this manuscript, the buildup and spread of A_. scabrivalvls during the growing season is by rhizomatous tillers. It was also noted that A_. scabrivalvis has the unusual ability to produce seeds over the entire length of its stem.
Some of the studies in Part II deal with the relation between the growth of A. scabrivalvls and its environment.
Since the first, and sometimes more, of the basal elongated internodes of A. scabrivalvls swell or become enlarged, some studies were undertaken to determine what compound or compounds make up the bulk ot their dry w eight.
42 LITERATURE REVIEW
Investigations of Rate of Spread
The inherent ability of a plant to reproduce itself vegetatively or otherwise with great rapidity enhances its ability to infest other area£. In a study on nutsedge (Cvperus rotundus L.) in Georgia,
Hauser (21, 22) investigated its establishment and spread from space-planted tubers. He observed that at the end of one season of growth, tubers planted one foot apart produced 3.09 million plants and 4.42 million tubers and bulbs per acre, as compared to tubers planted three feet apart, which produced 2.32 million plants and
2.76 million tubers and bulbs. During the second season the number of plants increased 66 per cent in the area with one-foot spacing
(from 3 .09 to 5.14 million) and 84 per cent in the three-foot area
(from 2 .32 to 4 .27 million). The differences recorded from the two spacings at the end of the second season of growth were not as great as they were at the end of the first season of growth.
In a growth rate test with New York strains of nutsedge, it was found that the vegetative development slowed after 2 months as day length decreased, but that nutlet production increased steadily.
Eleven weeks after planting, the yield of tubers from individual seedlings averaged 152 (1). Tumbleson and Kommedahl (42) reported
43 44 that a single tuber usually produced from zero to seven shoots; however, they obtained in an area of .about 34 square feet an accumulative total of 1918. plants and 6864 tubers from a single tuber in one year's time.
Investigation of Effects of Photoperiod on Tillering
The effects of photoperiods on different plants have received much attention since the initial work of Garner and Allard (16).
Guitard (17) determined the effects of two temperatures and three photoperiods when applied at three stages of growth of spring barley.
Stage I was from seedling to internode elongation; Stage II was from internode elongation to heading, and Stage III was from heading to maturity. He found that a significantly greater number of tillers was “ produced by plants grown under 8 to 24 hour photoperiods during
Stage I. However, no photoperiod or temperature treatment during
Stages II or III influenced the total number of tillers produced.
Newell (29) tested tiller production of bromegrass in the green house under long-day conditions (16 hour) at high temperature
(75-85°F) and low temperature (55-65°F), and under a natural day
(9 1/2 to 11 hours) at the same two temperatures. He obtained an average of 6.3 tillers per plant at the low temperature treatment as compared to 4.3 per plant at the high temperature (75-85°F). Those plants growing under a 16-hour photoperiod produced 4.9 tillers at the low temperature treatment and 4.3 per plant at the high tempera ture . 45
Misra (25) subjected two varieties of rice, TN 32 and TA 64 to a
10-hour photoperiod for one month when they were 10, 20, 30, 40 and
50 days old. He conducted a second experiment in which he increased the exposure of the seedlings until the panicle emerged. In both cases he found that 10-hour photoperiod treatment reduced tiller development of those seedlings exposed 30 days or less in age. He concluded that the tiller production in the older seedlings was probably due to tillers initiated prior to treatment.
Wiggins and Frey (49) conducted an experiment to determine tiller production in oats. Their photoperiod treatments were 9 hours, 9 hours plus 1 hour at midnight, 12, 15, 18 and 24 hours at two tempera tures, 58 and 70°F. No head-producing tillers were formed under photoperiod treatments of 9 and 12 hours at either temperature. How ever, a photoperiod of 9 hours plus 1 hour in the middle of the dark phase formed head-producing tillers. In contrast Riddel and others
(33) found that in wheat shortening or breaking the dark period resulted in the differentiation of fewer vegetative nodes prior to the induction of flowering. They concluded that breaking of the dark phase may accelerate nodes already differentiated at the time of treatment.
Peterson and Loomis (30) tested the effects of photoperiod and temperature on shoot production of three strains of Kentucky blue- grass. The two temperature treatments were a minimum of 55.8°F and a maximum of 65 .4°F for the low temperature and 61.2°F minimum 46 and 74.7°F maximum for the high treatment. Photoperiods were 11, 15, and 19 hours. Shoot number was recorded at 25, 50 and 105 days. At, the end ot 25 days the average number of shoots per pot of the three strains for the three photoperiods and two temperatures were: 11-hour photoperiod high temperature 66.3 shoots and for low temperature
64.5, 15-hour photoperiod had 63.6 shoots for the high and 62.2 for the low temperature, 19-hour photoperiod had 57.3 for the high tempera ture and 61,9 for the low temperature. There was no significance in number of shoots between temperature and photoperiod at the end of
25 days. At the end ot 50 days there was a significant difference between photoperiods. The 11-hour photoperiod had the highest number of shoots with 104.7 for the high temperature and 112.1 for the low temperature. At the end of 105 days there was a significant difference between photoperiods. The 11-hour photoperiod had a high of 160.8 shoots for the low temperature and 142.2 for the high and the
15-hour photoperiod had 114.4 for the low and 116.4 for the high temperatures, while the 19-hour photoperiod had 116.7 for the low temperatures and 10b. 1 for the high temperature.
Yellow foxtail (Setaria lutescens) was grown under long day and
short day photoperiods (3). At the end of 8 weeks plants subjected to long day conditions had produced an average of 2.2 tillers per plant, while those plants receiving a short day photoperiod had an average
of 4 .0 tillers per plant. Schreiber (35) studied the development of giant foxtail (Setaria laberii) under several temperatures and photoperiods. Temperature treatments were 50, 60, 70 and 80°F, and the photoperiods were 8,
12, 16 and 20 hours. He noted that no tillering occurred in plants grown at 80°F with photoperiods of 20 and 16 hours, while at 12 and
8 hours tillering had occurred. The response was similar at 70°F, but no tillers were produced at 60 and 50°F.
Investigation of the Effect of Light Intensity on Tillering and Drv Weight
The intensity of the light a plant receives greatly influences its growth. In a Maryland experiment (3), the effects of shading upon the development of yellow foxtail (Setaria lutescens) were established. Shading or reduced light intensity significantly decreased number ot tillers, and dry weight per plant. At 60 per cent shading the dry weight was decreased two-thirds while at 90 per cent the dry weight was almost negligible. The number of tillers produced under 0, 60, and 90 per cent shade were 6.1, 2,4, and 2.7, respectively. Very similar results were obtained with giant foxtail
(Setaria faberii).
In a Rhode Island experiment (1), nutsedge was exposed to 8,
48, and 100 per cent of the normal light in a greenhouse. The reduc tion in light intensity greatly reduced plant size and vegetative shoots.
After 12 w eeks, the average weight of plants for the 8, 48, and 100 48 per cent levels were 5, 25, and 135 grams, respectively, and the average number of vegetative shoots per plant was 1,2, and 22.
At low light intensity, photoperiod had a significant effect on shoot formation.
Moggs (26) reported on an experiment involving apple trees which received 100, 78, 41 and 24 per cent of natural daylight. He found that shading reduced weight oi new stems. Total dry weight ot new stems were 151, 127, 52 and 17 gm, respectively in accordance with the amount of light received.
Wiggans (50) subjected oats to treatments of 0, 50, 75 and 90 per cent shade and reported that increased shade resulted in decreases in number of head-bearing tillers, and in dry weight of the grain and straw ,
Watkins (47) used bleached sheeting over wooden frames to reduce normal light intensity from 10,5 00-4,000 down to 800-300 ft-c over bromegrass plots. He concluded that shading decreased the number
ot shoots and further reduced the dry weight.
Burton (8) noted that when he used one, two, or three layers of
open-mesh cotton cloth he reduced the light to 64, 43 and 29 per cent
of that of normal light. Bermuda grass growing under these treatments
decreased the forage yield as shade increased.
Dibbern (12) observed only ten clones of bromegrass were alive
out of 23 clones when allowed to grow one year under one layer of cloth or 732 ft-c (14 per cent of normal sunlight) and no clones survived when grown under two layers or 251 ft-c (5 per cent of normal sunlight).
Pritchett and Nelson in a similar experiment (32) grew bromegrass under one, two, three, and four layers of muslin which reduced the light intensity to 757, 422, 257 and 157 ft-c, respectively as compared to full greenhouse light of 2,833 ft-c. They discovered that the dry weight of the plants decreased as the light intensity was reduced.
Investigation of the Effect of Clipping on Tillering
Plants respond differently to mowing, grazing or clipping back to a desired height. To some plants clipping may serve as a method of control and not to others. One of the influences that loss of top foliage has on plants is on tillering ability.
Wagner (44) determined the effects oi one or two clippings at different intervals oi time on tiller production of orchard grass.
Treatments included clipping the grass back to the height of 2 inches at 20, 40, 60 and 90 days after emergence. The data were taken 130 days after emergence in one set of the grass, and in another set the grass was clipped back to 2 inches at 20, 40 and 60 days after emergence and then clipped a second time and the data taken 130 days after emergence. The number of tillers per plant of uncut orchard grass increased very little from 60 to 90 days, but pronounced increases occurred between 90 and 130 days. However, clipping reduced the number of tillers in 130-day old orchard grass to such an 50 extent that when cut twice there was no tiller increase in plants between
60 and 130 days.
Robertson (34) studied the effect of frequent clipping on the development ot five grasses: Bouteloua gracilis, Bromus lnermls,
Holcus sorahum sudanensis. Koeleria cristata. Poa pratensis and
Stipa sparta. Sudan grass was cut 3 cm above the soil level and all the others were cut 1.5 cm above the soil level as soon as they reached grazing height. Tiller production was reduced in ail the grasses, but tiller production in sudan grass was the most affected with unclipped plants having 11 per plant as compared to 1.5 tillers per clipped plant.
Davis (11) clipped reed canary grass back to 1, 2, 3, 4 and 5 inches every time the grass reached 10 inches high. The number of tillers was reduced from an average of 10.7 per plant for the 5-inch treatment down to G.b for the 1-inch treatment.
Harrison (20) undertook an experiment in which he studied the
effects of three clipping heights on red fescue which was cut 16 times
between April 15 and July 15 to heights of one-fourth inch, one and
one-half inch, and three inches. He found that red fescue tillered
more when cut to one-fourth inch than when cut back to the other two
heights.
Langer (23) noted in timothy and meadow fescue that there was 51 a reduction in the number of tillers following weekly cuts over a 4- week period.
Washko (46) studied the effects ot grazing on winter small grain in Tennessee. Sheep were used as grazing animals and he adjusted the number of animals on each plot so that they would remove all the available forage in 24 hours. He found that grazing reduced tillering
8 to 25 per cent and postponed ripening 2 to 8 days in oats, rye, barley, and wheat.
In an experiment in Connecticut (3) where yellow foxtail was clipped back to a 2-inch height, the formation of tillers was not pre vented, and these tillers produced seed heads.
Horsenettle (Solanum carolinense) was clipped at the soil level
15, 20, 25 and 30 days after emergence. The average number of shoots produced were 0.25, 1.00, 1.7 and 3.0 corresponding to the increase in number of days after emergence before being cut (2).
Dibbern (12) planted smooth bromegrass in the greenhouse on
April 27 and 28 and on June 30 he clipped all vegetation back to 2 inches above the soil level. On July 13 he measured the number of stems and found there was a 76 per cent reduction in the number ot stem s.
Caro-Costas and Chandler (9) concluded that cutting molasses grass back to 0-3 inches would severely reduce its growth and eventually death would occur if treatments were continued very long. ; 52
Investigation of Carbohydrates of Grass Culms
The first node of timothy grass culms becomes enlarged and Evans
(14) has suggested the name "haplocorm" to be the swollen part near the base of the stem. He further states that it is usually composed ot
one,, less frequently two, and rarely three swollen internodes. Harper
and Phillips (19) believe it to be a storage organ and have carried out
some experiments on the chemical composition of the "haplocorm."
In an attempt to learn what changes occur during the winter, a collec
tion was made in October and another of over-wintered "haplocorms"
from the same area in May ot the following year. They found glucose
to make up O.b per cent of the dry weight in October and increased to
0.7 per cent in May, while fructose increased from 1.40 to 5.18 per
cent and sucrose from 2.8 to 5 .15 per cent. The greatest change was
in fructosan content which changed from 47.7 to 17.5 per cent of the
dry weight from October to May. In a second experiment they studied the
changes in chemical composition during the growing season from May 30
to October 25. May 30 was found to be the time when new "haplocorms"
were large enough to be sampled satisfactorily. It was found that in
May, glucose made up 5 .74 per cent of the dry weight while fructose,
sucrose, and fructosans were 1.71, 4.64 and 1.9 per cent, respec
tively ot the dry weight. On June 3 glucose made up 6.25 per cent of
the dry weight but decreased steadily down to 2.10 per cent by June 30;
while fructose was 1.36 per cent of the dry weight on June 3, but it decreased to 0.14 per cent by June 30. Sucrose made up 6.56 per cent
of the dry weight on June 3, and Increased slightly during the first hall
ot the month, but decreased to 4.00 per cent ot the dry matter by
June 30. Fructosan content was 11.1 per cent, and increased steadily
during the month of June to 47.0 per cent by June 30. From July 25 to
October 25 glucose content remained less than 1 per cent of the dry weight and made up 0.22 per cent ol the dry weight on October 25;
while fructose remained less than 1 per cent from July to September,
but it increased to 3 .22 per cent ol the dry weight by October 25.
Sucrose content fluctuated some between July and October from a low
of 1.41 per cent August 2 to a high of 4.44 per cent of the dry weight
on October 25 . The fructosan content fluctuated during the time from
July to October with a high of 53.6 per cent ol the dry weight on
September 17 to a low ol 38.3 per cent ol the dry weight on October 25.
Trowbridge and others (41) reported that no starch is produced
in the "haplocorm" during the storage process. Phillips and Smith
(31) also report they found no starch in timothy. Waite and Boyd (45)
tested four grasses including timothy and stated that they found starch
only in the seeds ot the four grasses. They also determined sucrose,
reducing sugars, which they called hexoses, and fructosan content
from the earliest spring growth to autumnal senescence (April to
October). The three other grasses they tested were fescue, cocksfoot,
and rye-grass. The maximum sucrose was found in June for fescue. 54
timothy, and cocksfoot of 6, 5 and 5 per cent, respectively, and In
May for rye-grass ot 9 per cent. Hexoses were at a maximum also
in June for fescue, timothy, and cocksfoot of 5, 4 and 4 per cent ot
the dry matter while rye-grass had 2.59 per cent all the time.
Fructosan was highest in fescue in the June-July period of 16 per
cent; while the content was highest in timothy and cocksfoot in
August of 28 and 20 per cent, respectively. Rye-grass had the highest
fructosan content in June of 32 per cent.
Smith and others (36) determined total available carbohydrates
ot timothy stem bases, and found about 50 per cent of the dry weight
to be carbohydrates during June was compared to 20 per cent during
May. They also found another peak in late August or early September
ot 45 per cent.
Morosov (27) determined the amount of monosaccharides and
-aucrose of the shortened internodes of three grasses, Bromus inermis.
Lolium pluenne. and Festuca pratensis. at three stages of growth;
tillering, flowering, and fruiting. He did not determine fructosan
content. He found that monosaccharides and sucrose content was
highest in ail three species during flowering measuring 0.17, 1.10
and 1.40 per cent of dry weight for Bromus, Lolium, and Festuca.
respectively. Sucrose content accounted for 2.90, 1.32 and 6.15 per
cent, respectively ot dry weight for the three grasses during flowering. 55
Baker and Garwood (6) estimated the amount of sucrose, glucose, fructose and the fructosan content of cocksfoot stubble (lower 1 inch of stem) when cut frequently or infrequently. They found that regard less of cutting treatment sucrose, glucose and fructose content was low in May, about 0.7 per cent of dry weight and increased to about
3.5 per cent in July. The percentage of fructosans ranged from 1.9 to
16.6 according to month and cutting treatment.
Lindahl and co-workers (24) studied the carbohydrate reserves
of switch cane (Arundinaria tecta) and found only simple sugars,
starch , polysaccharides and no fructosans .
Sullivan and Sprague (39) found that the lower 1 1/2 inches of three-month old rye-grass stubble or stem had a fructose content of
1.79 per cent of dry weight, while glucose, sucrose and fructosan
content was 2.01, 6.08 and 15.04, respectively. Later Sprague and
Sullivan (38) ascertained that the lower stubble of orchard grass con tained reducing sugars of 0.7 per cent of the dry weight and a sucrose
and fructosan content of 2.6 and 36.2 per cent, respectively.
Dodd and Hopkins (13) noted that blue grama grass (Bouteloua
gracilis) contained soluble sugars, fructosan and starch in the roots,
rhizomes and crowns. Weinmann and Reinhold (48) found starch in
large amounts in the stems of Cvnodon dactvlon and in moderate
amounts in Digltaria trlcholaenoides and Eraqrostis chalcantha and no
starch in Brachlarla serrata. Harpechloa flax and Hvparrhenla hirta. 56
Archbold (5) found the maximum fructosan content in the lower stems of wheat and rye in a May-June period and in the June-July period for oats and barley. He had concluded earlier (4) that the greatest accumulation of fructosan in any internode ot barley stem occurs after its growth has ceased. MATERIALS AND METHODS
Study of the Rate oi Spread
This investigation was conducted on the experimental research farm in Lintonia soil. The experimental design was a randomized block with three blocks of three treatments per block. Each block had three plots ot 10 x 10 feet with one-foot borders on all sides.
The prepared soil received the equivalent of 1000 pounds of commer cial 8-8-8 fertilizer broadcast over the area and thoroughly disked, after which the soil surface was leveled and smoothed by hand raking.
Then the entire experimental area was fumigated with methyl bromide at the rate of 2 pounds per 100 square feet to kill any existing vegeta tion as well as weed seeds in the soil.
Seeds ot A. scabrivalvis used in this study were from dried underground nodes which had previously been collected from the soil during the summer ot 1963, washed and dried on the greenhouse bench, and stored at room temperature in the laboratory. Seeds were removed
from the underground nodes by hand. On October 22, 1963, blocks one
and two were planted, and on October 25, 1963, block three was
planted. Treatments consisted ot one, two, or four seeds per square
foot. To obtain accurate spacing of the seeds, a 10 x 10 frame of
3/4" x 2" wood was constructed and bisected at one-foot intervals with a cotton cord to obtain 100 one-foot squares. Plots which received the treatment of one seed per square foot had the seed placed by hand in the center of the foot square. Plots which received two seeds per square foot had the square foot area divided into two equal triangles and the seeds placed in the center of each triangle.
Those plots which received seeds at the rate of four per square foot had the square foot divided into four equal squares and the seeds placed in the middle of each six-inch square. With the aid of permanent corner stakes, it was possible to place the frame at a later date in the exact position as when the plot was planted.
On March 17, 1964, the first count of tillers was recorded as well as green and dry weight. For this first sampling, the frame was placed over the plot and three randomly selected foot-squares were dug up, placed on a wire screen, and washed gently with a garden hose until all soil was gone. The grass was blotted dry and the green weight measured to the nearest tenth of a gram on an Ohaus balance.
The number of tillers was recorded; the grass was dried in a forced air oven at 70°C for 48 hours and immediately weighed upon removal from the oven on an Ohaus balance to the nearest tenth of a gram.
On May 29, 1964, all growth was clipped back to 2 inches with a Gravely mower equipped with a front mounted sickle cutter bar. On
June 3, 1964, a second counting of tillers was taken. This time the frame was placed over the plot and the number of tillers in three 59 randomly selected one-foot squares was counted and recorded on a tally. This procedure was followed for all treatments in all blocks.
Approximately one year after the start of the experiment on
October 30, 1964, a third count of tillers was conducted in a manner very similar to the June count except only those squares to be counted were clipped back to 2 inches with the aid of a pair of scissors.
Study of the Effect of Photoperiod
To study the effect of light on scabrivalvis . an experiment was carried out in the greenhouse during the spring of 1963. Seeds collected during the summer of 1962 from underground nodes were used as a source of plant material. Nine-inch pots holding approximately
15 pounds of growth medium were used for growing the grass. The growth medium was composed of one-half river soil and one-half peat
moss fertilized at the rate of 1,000 pounds of 8-8-8 fertilizer per
acre.
The light used to interrupt the dark phase was from three
Sylvania Gro-Lux flourescent tubes. The light fixture was attached
to a wood frame approximately 36 inches above the tops of the pots.
The wood frame was five feet long and 4 feet high with a "A” type
roof one and one-half feet high in which the light fixture was attached.
The entire box was covered with black six-mil plastic. The sides and
ends of the box were constructed so that they could be removed during
the day and the plastic on the roof could be rolled up, therefore 60 causing very little reduction in the amount of light the plants received during the day. The plants which received no light during the dark cycle were also placed under a similar box.
Twenty pots were filled to within one inch of the top with growth medium. Each pot received seven A. scabrivalvis seeds on February 2,
1963. Due to irregular germination each pot was thinned to five seedlings, and on February 14, the treatments were started. Ten pots were placed in the photoperiod box to receive 9 hours of daylight and one and one-half hours of light in the middle of the dark phase. The sides, ends and top were removed at 8 A.M. and replaced at 5 P.M.
Ten pots received 9 hours of daylight with no additional light during the dark phase. To insure that the plants would receive only
9 hours of light they were covered at 5 P.M. and uncovered at 8 A. M. thereby giving an uninterrupted dark phase of 15 hours.
The plants were watered from the top in the morning and again in the afternoon just before they were covered for the beginning of the dark phase.
On February 28, 1963, one pot from each treatment was emptied, the seedlings washed and the number of tillers produced by each plant was recorded. After the data had been recorded, the plants were dried and mounted. This procedure was followed every two weeks until eight pots from each treatment had been emptied. The remaining two pots in each treatment were used to determine reproductive activities under the different treatments. 61
Study of the Effect of Light Intensity
To study the effects of light intensity on A. scabrivalvis, an experiment was carried out in the greenhouse during the spring of
1963. Seeds collected during the summer of 1962 were used as source of plant material. The pot size, planting rate and date, germinating medium, and fertility rate were the same as in the photoperiod study.
Light intensity was reduced with varying layers of grade 50 cheese cloth placed on wood frames 30 inches high and 60 inches long.
Fifteen pots were filled to within one inch of the top with the growth medium. Each pot received seven A. sabrivalvls seeds on
February 2, 1963 . Due to erratic germination each pot was thinned to four seedlings as soon as germination was complete, and this con stant number maintained by removing the seedlings that emerged later.
The treatments were started on February 14 , 1963 . Five pots of grass were covered with two layers of cheesecloth, and five pots were covered with four layers. The remaining five pots were not covered with cheesecloth and were used as a check.. To ascertain the amount of light the plants in each condition were receiving, the light was measured over the center pot with a Weston Illumination Meter Model
756. The amount of light received by the check was 5600 ft-c, while under two layers of cheesecloth it was 2200 ft-c, or 39 per cent, and further reduced to 1180 ft-c, or 21 per cent, under four layers.
The pots were watered from the top twice daily, which appeared sufficient. The grass was allowed to grow 8 weeks after the treatments 62 were initiated. At the end of this period the pots were emptied and the gresh weight of the entire plant measured, and the number of tillers per grass plant were recorded. The intact plants were dried in a forced air oven for 48 hours at 70°C, and the dry weight recorded immediately upon removal from the oven.
Study of the Effect of Clipping
This experiment was conducted in the greenhouse during the
spring of 1963. The A. scabrivalvis seedlings were obtained from
seeds collected during the summer of 19 62 and stored at 2°C. The pot
size, planting rate and date, germinating medium and fertility rate are the same as in the photoperiod study.
The four treatments were: (1) not clipped, (2) clipped back to
2 inches, (3) clipped back to 4 inches, and (4) clipped back to 6 inches. The pots were arranged on a greenhouse bench in a randomized block design. The grass in the pots which received treatments two, three and four was clipped with a pair of scissors as soon as the grass reached its respective height. After the first clipping, the grass was
clipped back once a week. This allowed the grass to produce some
new growth each week. The experiment was terminated on July 9,
1963, when all the pots were emptied and the data recorded.
Study of the Chemical Composition of Enlarged Internodes
Selected enlarged basal stem internodes of A. scabrivalvis collected on May 13, 1964, were used in this study. A small clump of grass was removed from the soil and washed gently with water until all roots and stems were exposed. Swollen basal internodes were selected, freed of nodal tissue, rewashed, and blotted dry. Six lots of approxi mately 5 grams each were weighed; three of these were used to deter mine dry weight and per cent of water contained in the tissue, and the other three lots were used for sugar determination.
Those lots on which dry weight was to be determined were placed on tared watch glasses, the enlarged internodes were cut into small pieces with a sharp scalpel to insure faster drying, and were placed in an oven and dried for 24 hours.
Those lots on which sugar determination was to be estimated were macerated in 80 per cent ethanol with a Servall mixer for 1 minute. After the internodes were ground, the mace and alcohol were transferred to a flask. The mixer cup and blades rinsed three times with 80 per cent ethanol and added to the flask also. It was then necessary to bring the final concentration of the alcohol in the flask to 80 per cent. The contents of the flask were refluxed gently for
3 hours. After 3 hours, the contents of the flask were filtered while hot through a Buchner funnel using a water aspirator. The drained mace was washed with three small portions of hot 80 per cent ethanol, and the washings combined with the filtrate. The filtrate was transferred to a Claisen flask and concentrated under reduced pressure at no higher temperature than 45°C to approxi mately the volume of the total amount of water in the sample. Two hundred ml of distilled water was added to the flask and again concen trated to a very small volume. The contents of the Claisen were transferred to a 100 ml volumetric flask; as well as the water used in washing the flask. Distilled water was added to bring the contents to standard volume, and a drop of toluene was added before storage under refrigeration to await sugar determination.
Reducing sugars were estimated by the Somogyi-Nelson technique.
The reagents were prepared according to Somogyi (37) and Nelson (28).
Twenty ml of the alcohol-free extract was pipetted into a 50 ml volu metric flask, and slightly less than 10 ml of a saturated solution of neutral lead acetate was added and the contents thoroughly mixed.
After 5 minutes had elapsed, 20 ml of a saturated solution of disodium phosphate were added and the contents mixed again. The contents were increased to volume with water. The water-clear fluid above the white precipitate was decanted and placed in a centrifuge tube, and centri fuged for 2 or 3 minutes in an unrefrigerated centrifuge. The super- nate was clear, and there was a small amount of white precipitate in the bottom of the tube.
Reducing sugars were determined on duplicates of two lots of enlarged internodes. Two ml of the clear supernate was pipetted into 65
a test tube which contained 2 ml of Somogyi's copper reagent. Each tube was swirled after the addition of the copper reagent exercising
care to avoid splashing any onto the higher walls of the tubes. After thorough mixing each tube was capped with a marble and plunged into
a rapidly boiling water bath for exactly 10 minutes. At the end of 10 minutes the tubes were removed simultaneously and, at once, immersed
in ice water to cool. After cooling, 2 ml of Nelson's chromogen was
added to each tube and mixed by swirling. The tubes were allowed to
stand for 5 minutes, diluted with distilled water to 20 ml, stoppered with parafilm and inverted several times to mix thoroughly. A blank was prepared in a similar manner except that 2 ml of distilled water replaced the 2 ml of alcohol-free, clear, sugar supernate.
A Bausch and Lomb Model 340 Spectrophotometer set at a wave
length of 620 mu wag utilized to record transmission and optical
density. The blank was used to "zero" the instrument on 100~per
cent transmission and "zero" optical density. The amount of sugar was determined from a standard curve obtained from the data recorded
from glucose solutions containing 0, 5, 10 and 20 ug of glucose.
When testing the enlarged internodes for sugar, a test was made
with iodine-potassium iodide for starch. Thin cross sections were
placed in a spot plate and treated with dilute I 2KI.
Carbohydrates of the enlarged basal internodes were determined
by the method presented by Umbreit, Burris, and Stauffer (43). The anthrone reagent was prepared by the addition of 20 g of anthrone dissolved in one liter of 95 per cent sulfuric acid. Three ml of the alcohol-free, clear, sugar supernate, used in the reducing sugar test, was pipetted into a test tube containing 6 ml of the anthrone reagent,
The. solutions were mixed thoroughly at once by swirling and placed in a boiling water bath for 3 minutes. After 3 minutes the tubes were removed and cooled in an ice-water bath. The intensity of the color was measured as with the reducing sugar test except that the wave length was 660 mu instead of 620 mu. The blank was prepared in a similar manner except water replaced the sugar solution. However, the color was too intense when the anthrone reagent was used as first described; therefore , the anthrone reagent was diluted by a factor of
2 parts of anthrone reagent to 1 part of water. The test was repeated using the diluted reagent.
A glucose standard curve was made using samples containing
0, 20, 40 and 60 ug of glucose. RESULTS AND DISCUSSION
Results from the Rate of Spread Study
This study was conducted to determine the extent and rate of tiller production in a given time and area. Dry weight of the entire plant produced on a given area was also recorded for the first sampling period.
The condensed results from the first sampling period, approxi mately 5 months after the planting date, can be found in Table 4. The experiment was conducted as a randomized block design and statis tically evaluated by analysis of variance (Table 5 and 6). The F value of 14.67 for dry weight (Table 5) exceeds the value necessary to indicate significance at the 1 per cent level. As shown in Table 4 the average dry weight produced by each square foot which received one seed per square foot is 8.55 gm or 76.4 per cent of the dry weight pro duced per square foot of plots receiving two seeds per square foot.
The dry weight produced on plots receiving one seed per square foot was only 29.7 per cent of the dry weight produced on the area receiving four seeds, which produced an average of 28.75 gm per square foot.
The squares receiving two seeds produced 38.3 per cent as much dry weight as those squares receiving four seeds per square foot.
67 The number of tillers produced under each treatment for the first sampling period is shown in Table 4. The F value of 12.68 for yield of tillers (Table 6) exceeds the value necessary to indicate signifi cance at the 1 per cent level. As shown in Table 4, more tillers were produced per square foot area as the number of seeds per square foot increased. The difference in tiller production between one and two seeds per square foot was not as great as the difference between two and four seeds per square foot. One seed per square foot produced an average of 28 .6 tillers or 65 .7 per cent as many tillers as two seeds per square foot. Two seeds produced only 41.1 per cent as many tillers per square foot as did four seeds per square foot. The one seed treatment produced 27 per cent as many tillers as the four seed treat ment.
When the number of tillers are estimated on an acre basis, one seed per square foot would have produced a total of 2,117,016 tillers, whereas the treatment of two and four seeds would have produced a total of 3,223,440 and 7,840,000, respectively.
The average number of tillers produced per square foot of soil area at the time of the second sampling is shown in Table 7, and the
F value of 12.82 is highly significant (Table 8). The average number of tillers produced was 95.3, 123.5 and 138.2 for the treatments of one, two and four seeds per square foot, respectively. One seed per square foot treatment produced 77 .1 per cent as many tillers as did 69
Table 4 . Average dry weight and average number of tillers per square foot and average dry weight per tiller at the first sampling period.
No. of Seeds Av. Dry Weight in Av. No. of Tillers Av. Dry Weight perSq. Ft. Gms per So. Ft. per Sq. Ft. per Tiller (Gm)
1 8.55 48.6 .117
2 11.05 74.0 .125
4 28.75 180.0 .131
Table 5. Analysis of variance of dry weight data per square foot at the first sampling period.
Degrees of Sum of Mean F F Components Freedom Squares Square Obtained Required (.01)
Blocks 2 105.86 - - -
Treatment 2 727.58 363.79 14.64 8.65
Error 4 99.2 24.8 - -
Total 8 932.64
Table 6. Analysi s of variance of tiller production per square foot at the first sampling period.
Degrees of Sum of Mean F F Components Freedom Squares Square Obtained Required (.01)
Blocks 2 1971 985 .5 -- Treatment 2 29126 14563 12.68 8.65
Error 4 4594 1148.5 --
Total 8 35691 70
Table 7. Average number of tillers per square foot at the second sampling period.
Number of Seeds Average Number of Tillers per per Square Foot Square Foot______
1 95.3
2 123.5
4 138.2
Table 8. Analysis of variance of tiller production per square foot at the second sampling period.
Degrees of Sum of Mean F F Components Freedom Sauares Square Obtained Reauired (.01)
Blocks 2 5.91 - - -
Treatment 2 2847 1423.5 12.82 8.65
Error 4 444.28 111.07 _—
Total 8 3297.19 the treatment of two seeds per square foot and 68.9 per cent as many tillers as the treatment of four seeds per square foot. The difference between yield of tillers from the area receiving two seeds per square foot and the area receiving four seeds per square foot was not as great as the difference in the number of tillers produced between the treatment of one and two seeds per-square foot. Two seeds per square foot produced 89.4 per cent as many tillers as did four seeds per square foot. On an acre basis one seed per square foot produced the equivalent of 4,251,268 tillers while two and four seeds per square foot produced 5,379,660 and 6,019,992, respectively.
Yield of tillers per square foot for the third sampling period, approximately 1 year after planting, is shown in Table 9. The trend of tiller production is the reverse of what it was for the first two sampling periods. However, the F value of 11.52 (Table 10) is significant at the 1 per cent level. Treatment of one seed per square foot had the highest average yield of tillers, 144.16, while treatments of two and four seeds per square foot had tiller yields of 106.55 and
105.3, respectively. Two seeds per square foot produced only 73.9 per cent as many tillers as the treatment of one seed per square foot, and four seeds per square foot produced slightly less than the treat ment of two seeds per square foot. On an acre basis one seed per square foot produced 6,279,610 and two and four seeds per square foot produced 4,631,218 and 4,586,868 tillers, respectively. 72
If one assumes that all seedlings have the same tillering rate it would appear that the treatment of one seed per square foot would produce 50 per cent as many tillers or dry weight per square foot as the squares having received the treatment of two seeds per square.
Also, it would probably be expected that squares receiving one seed per square foot would produce 25 per cent as many tillers or dry weight as the squares receiving four seeds per square foot. The difference between two and four seeds per square foot treatment would be 50 per cent as well.
Figure 1 shows the average number of tillers produced under each treatment at the three sampling periods. Tiller production on squares which received one seed per square foot is almost linear over the three sampling periods. This was not found to be true for the other treat ments . Production on the squares receiving two seeds increased over the number produced at the first sampling period, but the increase was not linear. Squares having the treatment of four seeds per square had a higher production of tillers at the first sampling period that was recorded for any other treatment at any other sampling period.
When comparing the actual percentage with the hypothetical percentage required between squares receiving treatments of one and two seeds per square foot at the first sampling period, the percentage obtained (65 .7) is higher than the percentage required (50.0). This indicates that either one seed per square foot produced more tillers 73 than would be expected, or two seeds per square foot did not produce as many tillers as would be expected, or both conditions may contribute to the results. However, it appears from the percentage (41.1) obtained between two and four seeds per square foot that tiller production under treatments of two seeds per square was low, since the per cent of tillers (24) obtained between treatment one and four is very close to the hypothetical value of 25 per cent.
Data obtained at the second sampling period was much harder to interpret since no percentages obtained were close to the hypothetical values. The number of tillers produced in the second sampling for the treatment of one and two seeds increased over the number recorded for the first sampling period. The treatment of four seeds per square foot produced more tillers than the squares which received the treatment of one and two seeds per square foot, but the number was less than the number recorded for this treatment at the first sampling period.
As mentioned previously the curve indicating tiller production from squares receiving one seed per square foot is linear whereas the curve for treatment of two seeds per square foot is not linear (although still higher than for one seed per square foot). Although tiller pro duction on the squares which received four seeds per square foot was greatly reduced, the total number of tillers produced was still greater than for the other two treatments . At the end of the third sampling period the plots receiving the treatment of four seeds per square foot had the lowest number of tillers recorded. There was also a reduction in the number of tillers pro duced in the third sampling period on those plots receiving the treat ment of two seeds per sqxiare foot; however, the total number is slightly more than for four seeds per square foot and less than the number on squares receiving one seed. The number of tillers pro duced at the third sampling period was highest for the treatment of one seed per square foot, but not as high as the number of tillers produced in the first sample period for the treatment of four seeds per square foot.
Explanation of this reduction in total number of tillers produced in the second and third sampling period for the treatment of four seeds per square foot and in the third period for the treatment of two seeds per square foot can only be postulated. It could possibly be a matter of continuing competition between the tillers, which showed up first in those plots with the highest tiller count. If this was the sole answer, another sampling period could substantiate this since those plots receiving the treatment of one seed had a tiller production rate at the third sampling period between the rate of the other two treat ments when their tiller production started decreasing. There is also the possibility that some of the older stems had died and decayed or were broken during the clipping process just before the data was 75 recorded for the second sampling period. However, this would not be altogether true for the third sampling period since most or all of the tillers were produced after the second sampling period and were still actively growing.
Another possible explanation is that .A. scabrivalvis may pro duce a substance that is toxic to itself or can become toxic by a buildup from a certain number of tillers. This appears plausable since there was a reduction of tillers after the first sampling from the treatment of four seeds per square foot when the number had reached a high of 180. This same trend was followed in those plots which received two seeds per square foot in the third sampling period after a high of 123 tillers in the second sampling period. As mentioned previously another sampling period would be necessary to partially answer this question since tiller production on the squares receiving the treatment of one seed per square foot is in the range in the third sampling period where the other two treatments began to decline.
Any factor that influences the growth of A. scabrivalvis or its tillering ability would affect the amount of dry weight it would pro duce . In Table 4 it was noted that four seeds per square foot produced the most tillers as well as the most dry weight per square foot. Two seeds per square foot produced 1.4 times as much dry weight and 1.5 times as many tillers as did the treatment of one seed per square foot.
Four seeds per square foot produced 3 .4 times as much dry weight and 76
Table 9. Average number of tillers per square foot at the third sampling period.
Number of Seeds Average Number of Tillers per per Square Foot Square Foot______
1 144.16
2 106.55
4 105.30
Table 10. Analysis of variance of tillers per square foot at the third sampling period.
Degrees of Sum of Mean F F Components Freedom Sauares Sauare Obtained Reauired (.01)
Blocks 2 3038.33 - - -
Treatment 2 2300.82 1150.41 11.52 8.65
Error 2 199.56 99.79 *
Total 8 5538.71 Figure 1. Effect of seeding rate on tiller production at three three at production tiller on rate seeding of Effect 1. Figure Av. No. of Tillers per Square Foot 100 120 160 140 180 40 20 60 80 apig periods. sampling -76 6-3-64 3-17-64 Date Sampled Date 10-30-64 = □ pr qae foot square per 4 1 e sur foot square per 78
3.9 times as many tillers as did the one seed treatment. Whereas four
seeds per square produced 2.6 times as much dry weight and 2.4 times
as many tillers as did the two seed treatment.
Although the average total dry weight per square foot increased
as the average total number of tillers produced increased, the average
dry weight per tiller did not. As noted in Table 4 the dry weight per
tiller in the treatment of one seed per square foot was the lowest
(0.117 gm) with the dry weight per tiller in the treatment of two seeds
per square foot (0.125 gm) slightly less than the dry weight per tiller
of the treatment of four seeds (0.131 gm) which was the highest. The
differences obtained between treatments were not significant.
Results from the Photoperiod Study
Table 11 represents the data of eight sampling periods to deter
mine the number of tillers produced under different photoperiods. As
indicated in Figure 2 the number of tillers under each treatment in
creased for the first six sampling periods. Those plants which
received an interrupted dark phase, or two dark periods in 24 hour
cycle of 6 1/2 and 7 hours, did not have an increase in tiller produc tio n between the sixth and seventh sampling period, but remained the
same. However, between the seventh and eighth sampling period there
was an increase in the amount of tillers produced. Those plants which
were grown under conditions of a long night (15 hours) showed a decline in the number of tillers produced between the sixth and seventh sampling period, with an increase between the seventh and eighth sampling period to the highest number produced for either photoperiod.
Figure 2 also shows that a greater number of tillers were produced by those plants which did not have an interrupted dark phase, than by those plants which received an additional one and one-half hours of light after the first 7 hours of the dark phase. The effect of photo periods on tiller production in A. scabrivalvis agrees with the results some researchers have found, and disagrees with what others have found with other plants. Newell (29) observed that bromegrass tillered more when grown under conditions of long uninterrupted dark phases and at a temperature of 55-65°F, while Riddell and others (33) noted that wheat subjected to a break in the dark period resulted in the differentiation of fewer vegetative nodes . However, a break in the dark phase of oats caused an increase in the production of head- producing tillers rather than a decrease (49).
Other than the slight reduction in the number of tillers per plant, breaking of the dark phase with one and one-half hours of light had no visible effects. Plants under either photoperiod began tillering when they were in the four-leaf stage, or at the first sampling period, and were producing secondary tillers by the third sampling period. By the sixth sampling period, the first internode began elongating and enlarg ing in the plants under both photoperiods. At the last sampling period 80 the first and second internodes had elongated and enlarged in the older tillers of both treatments, but no seeds were formed under either treatment.
The reduction in the number of tillers produced per plant which received light in the middle of the dark phase may be similar to the response Riddell and his co-workers observed of wheat which was subjected to an interrupted dark phase. There may have been a reduc tion in the number of vegetative buds initiated, since there was no difference as to time of tiller initiation under either photoperiod.
In Figure 2 the reduction in number of tillers produced per plant at the seventh sampling period for the treatment of a long dark period is probably not due to the treatment, but to other factors. Pot arrangement and removal in both photoperiod enclosures was the same and all pots were planted at the same time; therefore, the reduction in the number of tillers per plant in the pot at this sampling period was not a loss in number of tillers as indicated by the graph, but rather a failure in number produced over the entire time before this
sampling period. The plants which received the interrupted dark phase at this same sampling period had the same number of tillers as did the pot sampled at the sixth period. Since the plants under both treatments were in the same position, and neither increased in number of tillers produced during the two-week period, it appears that 81 the reason may be due to positional effects or other environmental factors rather than treatment effects.
Table 11. Effect of two photoperiods on tiller production.
9 Hr. Light 9 Hr. + 1/2 Hr. Light Date No Tillers/Plant No Tillers/Plant Sampled ______(Av. 5 PI.) ______(Av. 5 PI.) ______
2-28-63 0.6 0.4
3-14-63 2.6 _ 1.6
3-28-63 4.0 2.8
4-11-63 8.8 6.0
4-25-63 9.8 6.8
5-9-63 14.0 9.6
5-23-63 9.8 9.6
6-6-63 14.4 10.8 Figure 2. Effect of photoperiod on tiller production during an an during production tiller on photoperiod of Effect 2. Figure Av. No. of Tillers per Plant/per Pot 10 12 14 16 0 2 4 6 8 18 week period, sampled every every sampled period, week 18 1 • A= light rs. h 9 “ O 2 9 + 1 apig Period Sampling
3 1/2 r. light hrs. 4 5 6 2 weeks. 7 8 82 83
Results from the Light Intensity Study
Table 12 shows the dry weights obtained and tillers produced by
A. scabrivalvis in 8 weeks when grown under various light intensities.
The F value obtained for the difference between treatments for the dry weight is not significant (Table 13). However, the F value obtained for differences between treatments for tiller production exceeds the F value at the 1 per cent level (Table 14).
Although there is no significant difference in dry weight between the light treatments, those pots which were not under cheesecloth pro duced the greatest amount of dry weight (Figure 7). Those pots which were under four layers of cheesecloth or which received only 21 per cent as much light as those not under cheesecloth produced more dry weight of grass than did those pots under two layers of cheesecloth or which received 39 per cent as much light as the control. Dry weight of the grass in pots under four layers of cheesecloth was 84.6 per cent as much as that produced in pots under no cheesecloth; whereas, the dry weight of grass produced in pots under two layers was only 74.4 per cent as much.
Although the differences found for the effect of shade on dry weight are not significant,^hey do agree with what other workers have found
(1, 3, 8, 26, 32, 47, 50). The reason for dry weight produced under four layers of cheesecloth being higher than the dry weight under two layers is not understood. It is possible that the experiment was not 84 conducted over a long enough period for significant differences to appear, and that the greater amount of dry weight produced under four layers is due to chance alone, having no real significance for 8 weeks of growth.
The effect of reduced light on tillering of A. scabrivalvis is shown in Table 12, The F value obtained exceeds that required for the 1 per cent level of significance (Table 13). Grass plants without a cheese cloth covering produced the greatest number of tillers per plant; whereas, seedlings grown under four layers of cheesecloth which received 21 per cent of the light received by plants not covered had a slightly higher average number of tillers per plant than did those growing under two layers of cheesecloth and receiving 39 per cent of the amount of light received with no cheesecloth. Tillering was reduced by approximately
37 per cent under four layers of cheesecloth and approximately 40 per cent under two layers when compared to tillering of plants with no covering.
The reduction in tillering under reduced light intensity is similar to what other researchers have found in plants (1, 3, 47, 50). However,
Hamilton and Bucholtz (18) report an increase in Veronica peregrina.
Polygonum persicaria. and Oxalls stricta seedlings in shaded plots as compared to unshaded.
The slight increase (3 per cent) in average number of tillers pro duced per plant under four layers of cheesecloth over the number 85 produced under two layers would also cause the Increase in dry weight per pot above that produced under two layers. Reasons as to why there was a higher average number of tillers produced under four layers than under two layers of cheesecloth are hard to ascertain. It is possible that when light reduction reached 60 per cent, further reduc tion to approximately 80 per cent by two more layers of cheesecloth was more beneficial than inhibitory. It may be that four layers of cheesecloth produced a more favorable plant environment than did two layers even though light was further reduced. Temperatures were possibly different; amount of transpiration and evaporation could have differed under the two treatments. Perhaps if the experiment had been conducted over a longer period of time the plants grown under 80 per cent light reduction would have stopped tillering altogether and possibly died while those grown under 60 per cent light reduction might have been able to main tain themselves.
Table 12 . Dry weight and tiller production in A. scabrivalvis grown under various light intensities.
No. of Layers Amount of Light Dry Weight per Pot No. of Tillers per of Cheesecloth Received in (%) in (Gm^ Av. 5 Pots Plant Av. 20 Plants
0 100 3.52 9.40
2 39 2.62 5.85
4 21 2.98 6.15 86
Table 13. Analysis of variance for dry weight of A. scabrivalvis when grown 8 weeks under various light intensities.
Source of Degrees of Sum of Mean F F Variation Freedom Squares Square Obtained Required (.05}
Among 2 2.05 1.025 2.92 3.74
Within 12 4.24 0.352
Total 14 6.28
Table 14. Analysis of variance for tiller production in A. scabrivalvis when grown 8 weeks under various light intensities.
Source of Degrees of Sum of Mean F F Variation Freedom Squares Square Obtained Required (.05}
Among 2 38.77 19.38 17.46 6.51
Within 12 1.11 — — -
Total 14 54.12 87
Results from the Clipping Study
Weekly clippings affected the number of tillers produced over an 18 week period. Tabular results are shown in Table 15. The F value of 15.66 for yield of tillers (Table 16) exceeds the value neces sary to indicate significance at the 1 per cent level.
As can be seen in Table 15, plants that were cut back weekly to a height of 2 inches had the lowest number of tillers produced per plant. Tiller production of plants receiving this treatment produced only 21.9 per cent as many tillers as did those plants that were not cut back. Plants cut back to 4 inches weekly were not as seriously affected as those cut back to 2 inches. Plants cut back to 4 inches produced approximately 53 per cent as many tillers as did the control plants. The least affected plants were those clipped weekly to 6 inches. Although the plants clipped to the 6-inch stage weekly were the least affected, they produced only approximately 64 per cent as many tillers as did the control plants. These data agree with most of the work reported by other researchers (11, 12, 23, 34, 44, 46); how ever, Harrison (20) noted that red fescue tillered more when cut back to one-fourth inch than when cut back to the 3 inch stage.
A possible explanation for the degree of reduction in tillering with respect to the severity of the clipping treatment could be correlated with the loss of photosynthetic area. The shorter the grass was clipped, the larger the loss of area for carbohydrate production and the higher the 88
per cent of tiller reduction became. Those plants that were clipped
back to 2 inches survived and did produce some tillers which seemed
to indicate that there was enough photosynthetic area to produce enough
carbohydrates to maintain the primary seedling with excess to allow for
tillers to be produced. As photosynthetic area increased so did tiller
production.
Another interesting point is that those plants cut back to 2 and 4
inches did not produce enlarged basal internodes, while thgse plants
cut back to 6 inches and those not clipped at all did produce these
structures. Data on the number of enlarged internodes produced were
not recorded, but Plate 1 shows a comparison between the four treat
ments. Since plants clipped back to 6 inches had a 36 per cent tiller reduction, it is possible that there was also a reduction in the number
of internodes swollen when compared to the check because of the loss
in photosynthetic area. Absence of enlarged internodes on those plants cut back to 2 and 4 inches further supports the suggestion that these enlarged intemodes may function as storage organs. The presence of
enlarged intemodes in those plants cut back to 6 inches indicates the
possibility that although there was a loss in photosynthetic area, some
plants were producing enough carbohydrates in order that some could be
stored. 89
Table 15. Average number and per cent of tillers produced per plant, when clipped weekly.
Height Clipped No. of Tillers per Tillers as (Inches) Plant &v. 8 PI.) % of Check
2 9.38 21.9
4 22.75 53.2
6 27.63 64.3
Unclipped 42.75 100.0
Table 16. Analysis of variance of tillers produced on clipped plants.
Sources of Degrees of Sum of Mean F F Variation Freedom Squares Square Obtained Required (.0 D
Blocks 1 105.13 - -
Treatment 3 1139.19 379.73 15.66 8.65 V Error 3 72.81 24.27
Total 7 1317.13 90
Plate 21. The effect of clipping on production of tillers and enlarge ment of internodes. Left to right, clipped back to 2, 4, and 6 inches, and not clipped. 91
Results for the Chemical Composition of Enlarged Internode Study
The results of the sugar analysis on enlarged basal internodes collected in May can be found in Table 17. Reducing sugars are recorded as well as total sugars. According to Waite and Boyd (45) extractions with hot 80 per cent alcohol will contain only glucose, fructose, and sucrose, but they also note that a very small amount of fructosan may be in the extract.
From Table 17 it is readily seen that the reducing sugars make up only a very small per cent of the dry weight of the enlarged basal internodes. They contribute an average of 0.057 per cent or less than one-tenth of 1 per cent of the dry weight. It can also be noted in
Table 17 that total sugars make up a very small amount of total dry weight of the enlarged intemodes. Total sugars make up an average of 1.49 per cent of the dry weight.
Since the test of fresh material indicated that there was no starch in A_. scabrivalvis enlarged internodes, the question arises as to the nature of the bulk of the dry weight in these swollen inter nodes. The Somogyi-Nelson is specific for reducing sugars and the anthrone reagent according to Umbreit (43) will react with mono-, di-, and polysaccharides, dextrins, dextrans, starches, gums and gluco- sides. Since starch was not present it also seems from the low yield that no other polysaccharide was present, and if so, in very small amounts. Therefore, it is probably valid to assume that total sugars as recorded include only glucose, sucrose, and fructose, and it can be assumed that the carbohydrate which makes up the bulk of the dry weight is not alcohol soluble. One example of an alcohol insoluble sugar which has been shown to occur in certain grasses in high con centrations is fructosan {4 , 5 , 6 , 19 , 45).
Fructosans are water soluble and would not have shown up in these tests since only the alcohol extract was analyzed for sugars.
If fructosans were present in A. scabrivalvis internodes they would have remained in the mace that was discarded and would have been extracted only-if water instead of alcohol had been used.
Other explanations for these extremely low values for reducing sugars could be due to time of year and age of material sampled. A. scabrivalvis begins vigorous growth in early spring and by the middle of May many terminal inflorescences can be observed as well as those seeds produced at each node. These swollen intemodes may act as storage organs for reserve carbohydrates, and particularly in this case as alcohol insoluble carbohydrates. Harper and Phillips (19) noted when they analyzed swollen basal intemodes of timothy from
May until October, that the per cent of dry weight attributed by the reducing sugars was low in September making up only 0.36 per cent
of the dry weight while fructosan content made up 50.8 per cent. In
May when the intemodes began to enlarge the reducing sugars made
up more of the dry weight than did fructosan, 7 .45 per cent as 93 compared to 1.9. Morosov (27) observed that the reducing sugar content of Bromus inermis, Lolium oerenne. and Festuca pratense was low during fruiting, tillering and flowering. Therefore, the low reducing sugar content in A. scabrivalvis could be related to the pro duction of the seeds at each node over the entire length of the culm.
In light of the seasonal fluctuations in carbohydrate content of grasses found by other researchers, it is quite evident from this
study that a more thorough knowledge of the carbohydrate content of A_i_ scabrivalvis during one entire growing period is needed. 94
Table 17. Amount of alcohol soluble sugars in enlarged basal inter- nodes of A. scabrivalvis.
Sugar in Mg/G Sugar Per Cent Sugar Lot Dry Weight Drv Weight
Reducing 1 0.44 0.04
2 0.70 0.07
Total 1 13 .80 1.38
2 16.10 1.61 SUMMARY AND CONCLUSIONS
An experiment was conducted for one year to determine the number of tillers A. scabrivalvis would produce per square foot from three seeding rates. At the end of approximately 5 months of growth plots receiving four seeds per square foot produced more tillers than the treatments of two and one seed. When the number of tillers are projected on an acre basis, one seed per square foot would have pro duced a total of 2,117,016 tillers; whereas, the treatment of two and four seeds would have produced a total of 3,223,440 and 7,840,000 tillers, respectively.
The average dry weight per square foot was higher at the first sampling period on those plots receiving four seeds per square foot than on those which received two or one seed. There was very little difference between average dry weight of treatments when expressed on a per tiller basis.
At the second sampling period after approximately 8 months of growth there was an increase in the number of tillers produced per plot receiving treatments of one and two seeds over the number recorded for the first sampling period. There was a decrease in the number of tillers per plot which received the treatment of four seeds-*-
Although there was a decrease in the number of tillers at the second
95 96 sampling from the number recorded for the first sampling period for the treatment of four seeds per square foot, the number of tillers produced was higher than for the other two treatments.
At the third sampling period, after approximately one year of growth, those plots receiving one seed per square foot had the highest number of tillers, and the plots receiving four seeds had the lowest number of tillers. The plots which received the treatment of two seeds produced approximately the same number of tillers as the treatment of four seeds.
Tiller production on plots which received one seed per square foot increased almost linearly over the three sampling periods, whereas tiller production on the plots receiving the treatment of two and four seeds was not linear, but reached a maximum and then decreased.
Plots receiving the treatment of four seeds per square foot had the highest production of tillers at the first sampling period as was recorded.
In photoperiodic studies breaking of the dark phase with one and one-half hours of light reduced tiller production in A. scabrivalvis when compared to an uninterrupted dark phase. There was no other apparent difference in plant development due to photoperiod.
The production of dry weight of A. scabrivalvis was not signi ficantly reduced when grown under reduced light intensity. Tiller production was significantly decreased when light intensity was 97
reduced. Seventy-nine per cent light reduction by cheesecloth had no
greater effect on tillering than did 61 per cent.
A. scabrivalvis plants which were cut back to 2 inches weekly
yielded fewer tillers than those plants cut back to 4 or 6 inches or
controls which were not cut back. Plants cut back to 6 inches
produced more tillers than those plants cut back to 2 or 4 inches
while plants not cut back produced the greatest number of tillers.
Control plants and the plants cut back to 6 inches produced enlarged
basal intemodes, while those cut back to 2 and 4 inches did not.
The bulk of the dry weight of the enlarged internode is not due
to alcohol soluble sugars or starch. Analysis of hot alcohol extracts
of enlarged basal intemodes indicated that only a very small per cent
of the dry weight is due to reducing sugars (0.057 per cent). Total
alcohol soluble sugars make up only 1.49 per cent of the dry weight.
A test of fresh enlarged intemodes indicated that there was no starch
present. LITERATURE CITED
1. Anonymous. 1962. Life history studies as related to weed control in the northeast. 1 Nutgrass. Northeast Regional Publication. Rhode Island Agri. Exp. Sta. Bui. 364.
2. Anonymous. 1962 . Life history studies as related to weed control in the northeast. 3 Horse Nettle. Northeast Regional Publication. Rhode Island Agri. Exp. Sta. Bui. 368.
3. Anonymous. 1963. Life history studies as related to weed control in the northeast. 2 Yellow Foxtail and Giant Foxtail. North east Regional Publication. Rhode Island Agri. Exp. Sta. Bui. 369.
4. Archbold, H. K. 1938. Physiological studies in plant nutrition. VII. The role of fructosans in the carbohydrate metabolism of the barley plant. Part 2. Seasonal changes in the carbohy drates, with a note on the effect of nitrogen deficiency, Ann. Bot. N. S . 2: 403-435 .
5. Archbold, H. K. 1940. Fructosans In the monocotyledons. A review. New Phytologist 39: 185-219.
6. Baker, H. K., and E. A. Garwood. 1961. Studies on the root development of herbage plants. V. Seasonal changes in fructosan and soluble-sugar contents of cocksfoot herbage, stubble and roots under two cutting treatments. J. Brit. Grassland Soc. 16: 263-267.
7. Black, J. M. 1943. Flora of South Australia. Part 1. K. M. Stevenson, Government Printer. 253 pp.
8. Burton, G. W . , J. E. Jackson, and F. E. Knox. 1959. The influence of light reduction upon the production, persistence and chemical composition of coastal bermuda grass, Cvnodon dactylon. Agron. J. , 51: 537-542 .
9. Caro-Costas, R., and J. Vicente-Chandler. 1961. Cutting height strongly affects yield of tropical grasses. Agron. J. 53: 59-60.
98 99
10. Cockayne, L. 1958. The Vegetation of New Zealand. Hafner Pub. Co. New York. 456 pp.
11. Davis, W . E. P. 1960. Effect of clipping at various heights on characteristics of regrowth in reed canary grass (Phalaris arundinacea L.). Can. J. Plant Sci. 40: 452-456.
12. Dibbern, J. C. 1947. Vegetative responses of Bromus inermis to certain variations in environment. Bot. Gaz. 109: 44-58.
13. Dodd, J. D. , and H. H. Hopkins. 1958. Yield and carbohy drate content of blue grama grass as affected by clipping. Trans. Kans. Acad. Sci. 61: 280-287.
14. Evans, M. W. 1927. The life history of timothy. U. S. D. A. Bui. 145 0.
15. Gardner, C. A. 1952. Flora of Western Australia. Vol. 1, Part 1. Gramineae. W. H. Wyatt, Pub. Government Printer. 400 pp.
16. Garner, W. W ., and H. A. Allard. 1920. Effect of the relative length of day and night and other factors of the environment on growth and reproduction in plants. J. Agri. Res. 18: 553- 606.
17. Guitard, A. A. 1960. The influence of variety, temperature, and stage of growth on the response of spring barley to photoperiod. Can. J. Plant Sci. 40: 65-80.
18. Hamilton, K. C. , and K. P. Buckholtz. 1955.Effect ofrhizomes of quackgrass (Aqropvron repens) and shading on the seedling development of weedy species. Ecology, 36: 304-308.
19. Harper, R. H., and T. G. Phillips. 1943. Part II. Storage organs. New Hamp. Agri. Exp. Sta. Tech. Bui. 81.
20. Harrison, C. M. 1931. Effect of cutting and fertilizer applica tion on grass development. Plant Physiol. 6: 669-684.
21. Hauser, E. W. 1962. Establishment of nutsedge from space- planted tubers. Weeds. 10: 209-211.
22. Hauser, E. W. 1962 . Development of Purple nutsedge under field conditions. Weeds. 10:315-321. 100
23. Langer, R. H. M. 1959. A study of growth in swards of timothy and meadow fescue II. The effects of cutting treatments, J. Agri. Sci. 52: 273-281.
24. Lindahl, I., R. E. Davis, andW. O. Shepherd. 1949. The application of the total available carbohydrate method to the study of carbohydrate reserves of switch cane (Arundlnara tecta). Plant Physiol. 24: 285-294.
25. Misra, G. 1955. Photoperiodism in rice: VII. Photoperiodic response of two early varieties of rice. Agron. J. 47: 393-395.
26. Moggs, D. H. 1960. The stability of the growth pattern of young apple trees under four levels of illumination. Ann. Bot. 24: 434-450.
27. Morosov, A. S. 1939. Storing of carbohydrates by forage grasses. Comptes. Rend. Acad. Sci. U.R.S.S. 24: 407-409.
28. Nelson, N. 1944. A photometric adaptation of the Somogyi method for the determination of glucose. J. Biol. Chem. 153: 375-380.
29. Newell, L. C. 1951. Controlled life cycles of bromegrass, Bromus inermis Leyss. , used in improvement. Agron. J. 43: 417-424.
30. Peterson, M. L. , andW. E. Loomis. 1949. Effect of photoperiod and temperature on growth and flowering of Kentucky bluegrass. Plant Physiol. 24: 31-43.
31. Phillips, T. G., and T. O. Smith. 1943. The composition of timothy Part 1. Young grass and hay. New Hamp. Agri. Exp. Sta. Tech. Bui. 81.
32. Pritchett, W. L. , and L. B. Nelson. 1951. xhe effect of light intensity on the growth characteristics of alfalfa and brome grass. Agron. J. 43: 172-177.
33. Riddell, J. A., G. A. Gries, and F. W. Stearns. 1958. Develop ment of spring wheat: I. The effect of photoperiod. Agron. J. 50: 735-738.
34. Robertson, J. H. 1933 . Effect of frequent clipping on the develop ment of certain grass seedlings. Plant Physiol. 8: 425-447. 101
35. Schreiber, M. M. 1965 . Development of giant foxtail under several temperatures and photoperiods. Weeds. 13: 40-43.
36. Smith, D. , G. M. Paulsen, andC. A. Raquse. 1964. Extraction of total available carbohydrates from grass and legume tissue. Plant Physiol. 39: 960-962.
37. Somogyi, M. 1945. A new reagent for the determination of sugars. J. Bio. Chem. 160: 61-68.
38. Sprague, V. G., andj. T. Sullivan. 1950. Reserve carbohydrates in orchard grass clipped periodically. Plant Physiol. 25: 92- 102.
39. Sullivan, J. T., and V. G. Sprague. 1943. Composition of the roots and stubble of perennial ryegrass following partial defolia tion. Plant Physiol. 18: 656-670.
40. Swallen, J. R. 1931. The grass genus Amphibromus. Amer. J. Bot. 18: 411-415.
41. Trowbridge, P. F., L. D. Haig, and C. R. Moulton. 1915. Studies of the timothy plant. Part II. The changes in the chemical com position of the timothy plant during growth and ripening, with a comparative study of the wheat plant. Mo. Agri. Exp. Sta. Res. Bui. 20.
42. Tumbleson, M. E., and T. Kommedahl. 1961. Reproductive poten tial of Cvperus esculentus by tubers. Weeds 9: 646-653.
43. Umbreit, W. W ., R. H. Burris, and J. F. Stauffer. 1957. Manometric Techniques. 3rded. Burgess Pub. Co., Minneapolis, Minn. 338 pp.
44. Wagner, R. E. 1952. Effects of differential clipping on growth and development of seedling grasses and legumes. Agron. J. 44: 578-584.
45. Waite, R., andj. Boyd. 1953. The water-soluble carbohydrates of grasses. I. Changes occurring during the normal life-cycle. J. Sci. Food Agri. 4: 197-204.
46. Washko, J. B. 1947. The effects of grazing winter small grains. Agron. J. 39: 659-666. 102
47. Watkins, J. M. 1940. The growth habits and chemical composi tion of bromegrass, Bromus lnermis L ey ss., as affected by different environmental conditions. Agron. J. 32: 527-537.
48. Weinmann, H., and Leonora Reinhold. 1946. Reserve carbohy drates in South African grasses. J. S. Agrican Bot. 12: 57-73.
49. Wiggans, S. C., and K. J. Frey. 1957. Tillering studies in oats II. Effect of photoperiod and date of planting . Agron. J. 49: 215-217.
50. Wiggans, S. C. 1959. Responses of oat plants to various per centages of continuous shade. Bot. Gaz. 121: 55-60. BIOGRAPHY
4
Wayne Thomas Flinchum was born on August 13, 1937, in
Carthage, North Carolina. He was graduated from Carthage High
School in June, 1955, and entered North Carolina State College in
September, 1955 . He received a Bachelor of Science degree in
February, 1960.
He entered Louisiana State University in June, 1960, as a
Graduate Research Assistant in the Department of Botany and Plant
Pathology. He received the Master of Science degree in June, 1962.
He is a candidate for the degree of Doctor of Philosophy in January,
1966.
103 EXAMINATION AND THESIS REPORT
Candidate: Wayne Thomas Flinchum
Major Field: Botany
Title of Thesis: Part I. The Life History of Amphibromus Scabrivalvis in Louisiana Part II. Some Studies of the Autecology and Chemical Composition of Amphibromus Scabrivalvis Approved:
[or Professor and Chairman
Dean of the Graduate School
EXAMINING COMMITTEE:
c.
r
Date of Examination:
December 16, 1965