Group Title: Effects of soil temperature gradient on growth and carbohydrate and nutrient element levels in three warm-season turfgrasses /
Title: Effects of soil temperature gradient on growth and carbohydrate and nutrient element levels in three warm-season turfgrasses
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Title: Effects of soil temperature gradient on growth and carbohydrate and nutrient element levels in three warm-season turfgrasses
Physical Description: xii, 92 leaves : ill. ; 28 cm.
Language: English
Creator: Seitz, Garry Lee, 1945-
Publication Date: 1974
Copyright Date: 1974
 Subjects
Subject: Grasses   ( lcsh )
Agronomy thesis Ph. D
Dissertations, Academic -- Agronomy -- UF
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
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Thesis: Thesis--University of Florida.
Bibliography: Includes bibliographical references (leaves 86-91).
Statement of Responsibility: by Garry Lee Seitz.
General Note: Typescript.
General Note: Vita.
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Bibliographic ID: UF00098180
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 000413435
oclc - 38038745
notis - ACG0517

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EFFECTS OF SOIL TEMPERATURE GRADIENT ON GROWTH AND CARBOHYDRATE

AND NUTRIENT ELEMENT LEVELS IN THREE WARM-SEASON TURFGRASSES














By

CARRY LEE SEITZ


A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF

THE UNIVERSITY OF FLORIDA

IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE

DEGREE OF DOCTOR OF PHILOSOPHY








UNIVERSITY OF FLORIDA

1974
















ACKNOWLEDGEMENTS


I wish to thank Dr. S. H. West and Dr. G. C. Horn for serving as

Chairmen of my Supervisory Committee. A special and sincere thanks is

extended to Dr. J. N. Joiner for his guidance and patience during

preparation of this manuscript.

I would also like to thank Dr. W. L. Currey, Dr. O. C. Ruelke,

Dr. G. S. Smith and Dr. J. W. Strobel for their guidance and suggestions

during the course of this research. Appreciation is extended to others

at Ornamental Horticulture Greenhouses and Research Unit for their

contribution.

And deepest appreciation is extended to my wife Betty for her

support and understanding without which this degree would not have been

accomplished.

















TABLE OF CONTENTS


Page


ACKNOWLEDGEMENTS . . . . . .


iii


LIST OF TABLES. . . . . . . . . . . . . .

LIST OF FIGURES . . . . . . . . . . . . .


ABSTRACT . . . . . . . .


INTRODUCTION . . . . . . . . . . . . .


REVIEW OF LITERATURE . . . . .


Temperature Effects on Turfgrasses . . . . . .
Shoot Growth . . . . . . . . . .
Root Growth . . . . . . . . . . .
Carbohydrate Levels . . . . . . . . .
Elemental Nutrition . . . . . . . . .
Cultural Practices. . . . . . . . . .

METHODS AND MATERIALS . . . . . . . . . . .


Temperature Gradient Plate Experiments.
Stolon Experiment . . . . . .
Field Study . . . . . . .

RESULTS . . . . . . . . . .

Temperature Gradient Plate Experiments.
Stolon Experiment . . . . . .
Field Study . . . . . . .


DISCUSSION. . . . . . . . . . . . . . .

Effects of Soil Temperature Gradient . . . . ...
Shoot Growth . . . . . . . . . .
Verdure Growth. . . . . . . . . . .
Stolon and Rhizome Growth . . . . . . .
Root Growth . . . . . . . . . . .
Winter Root Growth in Field . . . . . . . .
Seasonal Grass Growth . . . . . . . . . .
Cultural Practices . . . . . . . . . .

SUMMARY . . . . . . . . . . . . . .


. . xi


1


S. . 2


. . . . . 27

. . . . . 27
. . . . . 64
. . . . . 73


. . . . . .
. . . . . .
. . . . . .


















Page

LITERATURE CITED . . . . . . . . . . . . 86

BIOGRAPHICAL SKETCH .. .... ...... ... ... ... .. 92















LIST OF TABLES


Table Page

1 Mean soil temperatures in three experiments
utilizing temperature gradient plate apparatus. . . 18

2 Mean clipping dry weights (gms) of bahiagrass
as affected by a gradient of soil temperatures .. .. 28

3 Mean clipping dry weights (gms) of St. Augustinegrass
as affected by a gradient of soil temperatures. ... .29

4 Mean clipping dry weights (gms) of bermudagrass as
affected by a gradient of soil temperatures ...... 30

5 Total clipping and mean verdure dry weights of bahia,
St. Augustine, and bermuda grass as affected by a
gradient of soil temperatures . . . ... .. .... 31

6 Mean rhizome, stolon and root dry weights of bahia,
St. Augustine and bermuda grass as affected by a
gradient of soil temperatures . . . . . .. 33

7 Total dry weight of plant tissue of bahia, St.
Augustine and bermuda grass as affected by a
gradient of soil temperatures . ... .. ... .. .39

8 Mean percent Total Nonstructural Carbohydrates (TNC)
in clippings averaged for all harvest dates and mean
percent TNC in verdure tissue of bahia, St. Augustine
and bermuda grass as affected by a gradient of soil
temperatures. . . .. . . . . . . . 45

9 Mean percent Total Nonstructural Carbohydrates (TNC)
in rhizomes, stolons and roots of bahia, St. Augustine
and bermuda grass as affected by a gradient of soil
temperatures. . . . . . .. . . . . . 50

10 Total Nonstructural Carbohydrates (TNC) content per
pot of clippings averaged for all harvest dates as
affected by a gradient of soil temperatures ...... .52

11 Mean Total Nonstructural Carbohydrate (TNC) content
per pot in verdure, rhizome and stolon tissue of
bahia, St. Augustine and bermuda grass as affected
by a gradient of soil temperatures. . . . . ... 54












12 Mean Total Nonstructural Carbohydrate (TNC) content
per pot in roots and overall total of tissues of
bahia, St. Augustine and bermuda grass as affected
by a gradient of soil temperatures. . . . . ... 57

13 Analysis of variance table for content of nutrient
elements in bahia, St. Augustine and bermuda grass
tissue. . . . . . . . . ... ..... .61

14 Content of nutrient elements in bahiagrass verdure
tissue as affected by a gradient of soil temperatures .62

15 Content of nutrient elements in bahiagrass rhizomes and
roots as affected by a gradient of soil temperatures. . 63

16 Content of nutrient elements in St. Augustinegrass
verdure and stolon tissue as affected by a gradient
of soil temperatures. . . . . . . . . ... 65

17 Content of nutrient elements in bermudagrass verdure
and rhizome tissue as affected by a gradient of soil
temperatures. . . . . . . . . ... . .66

18 Mean root length and dry weight of bahia, St.
Augustine and bermuda grass initiated on stolons
or rhizomes and affected by a gradient of soil
temperatures for six days . . . . . . .... 67

19 Mean monthly combustionable carbon root weight for
bahia, St. Augustine and bermuda grass from fertilizer
field study (averaged over five fertilizer treatments
and four replications). . . . . . . . ... 74

20 Mean content of nutrient elements in leaf tissue
taken from bahia, St. Augustine and bermuda grass
four weeks after termination of fertilizer field
study . . . . . . . . . . . . 74

21 Mean content of nutrient elements in bahia, St.
Augustine and bermuda grass top tissue taken three
weeks after termination of fertilizer field study . . 74


vii


Table


Page















LIST OF FIGURES


Figure Page

1 Experimental, compartmentalized temperature
gradient plate apparatus containing four pots
of grass per temperature treatment. . . . . ... 15

2 Pots of grass in one temperature compartment
showing surface insulation used to maintain
temperature levels. . . . . . . . . ... 16

3 Sample of pots used in the experiments, with
aquarium air stone in bottom to facilitate
drainage and prevent sand media loss. . . . ... 17

4 Fiberglass template and scissors used in harvesting
clippings at a specific cutting height. ...... 20

5 Initial rhizome and stolon pieces of bahia, bermuda,
and St. Augustine grass (left to right) utilized in
stolen experiment . . . . . . . .... 23

6 Rhizome and stolon pieces suspended in water-
filled tube used in stolon experiment . . . ... 24

7 Plots of bahia, St. Augustine, and bermuda grass
utilized in outside winter fertilizer rate and
ratio experiment. ................. . 26

8 Total clipping dry weight of bahia, St. Augustine,
and bermuda grass as affected by a gradient of
soil temperatures . . . . . . . . 32

9 Mean verdure dry weight of bahia, St. Augustine,
and bermuda grass as affected by a gradient of
soil temperatures . . . . . . . . ... 35

10 Mean dry weight of stolons or rhizomes of bahia,
St. Augustine, and bermuda grass as affected by
a gradient of soil temperatures . . . . ... 36

11 Mean root dry weight of bahia, St. Augustine,
and bermuda grass as affected by a gradient
of soil temperatures . . . . . . . ... 37












12 St. Augustinegrass root sections taken from grass
plugs maintained on soil temperature gradient
apparatus for seven weeks . . . . . .... 38

13 Total dry weight of plant tissue of bahia, St.
Augustine, and bermuda grass as affected by
a gradient of soil temperature. .... . . . 40

14 Bahiagrass plugs and roots after eight weeks growth
on soil temperature gradient apparatus. . . . ... 41

15 St. Augustinegrass plugs and roots after seven weeks
growth on soil temperature gradient apparatus . .. 42

16 Bermudagrass plugs and roots after five weeks
growth on soil temperature gradient apparatus .... 43

17 Percent TNC in clippings averaged over all harvest
dates of bahia, St. Augustine, and bermuda grass
as affected by a gradient of soil temperatures. ... 46

18 Percent TNC in verdure tissue of bahia, St. Augustine,
and bermuda grass as affected by a gradient of soil
temperatures. . . . . . . . . . . 47

19 Percent TNC in rhizomes and stolons of bahia, bermuda,
and St. Augustine grass as affected by a gradient of
soil temperatures . . . . . .. ... ... . 48

20 Percent TNC in roots of bahia, St. Augustine, and
bermuda grass as affected by a gradient of soil
temperatures. . . . . . . . . . .. 49

21 Mean TNC content (mgm) per pot in total clipping
yields per pot of bahia, St. Augustine, and bermuda
grass as affected by a gradient of soil temperatures. 53

22 Mean TNC content (mgm) per pot in verdure tissue of
bahia, St. Augustine, and bermuda grass as affected
by a gradient of soil temperatures, . . . .. 55

23 Mean TNC content (mgn) per pot in rhizomes and
stolons of bahia, St. Augustine, and bermuda grass
as affected by a gradient of soil temperatures. ... 56

24 Mean TNC content (mgm) per pot in roots of bahia,
St. Augustine, and bermuda grass as affected by
a gradient of soil temperatures . .. .. . 58


Page


Figure












25 Mean TNC content (mgm) per pot in plant parts of
bahia, St. Augustine, and bermuda grass as affected
by a gradient of soil temperatures. . . . . ... 60

26 Bahiagrass rhizome pieces after six days growth
on soil temperature gradient apparatus. . . . ... 68

27 St. Augustinegrass stolon pieces after six days
growth on soil temperature gradient apparatus .... 69

28 Bermudagrass stolon pieces after six days growth
on soil temperature gradient apparatus. . . . ... 70

29 Mean root dry weight (mgm) initiated on bahia,
St. Augustine, and bermuda grass rhizomes or
stolons as affected by a gradient of root
media temperatures. . . . . . . . . ... 71

30 Mean root length (mm) initiated on bahia, St.
Augustine, and bermuda grass stolons or rhizomes
as affected by a gradient of root media
temperatures. . . . . . . . . ... ... 72

31 Mean monthly combustionable carbon root weight for
bahia, St. Augustine, and bermuda grass averaged
from five fertilizer treatments in field study. ... 75


Figure


Page











Abstract of Dissertation Presented to the Graduate Council
of the University of Florida in Partial Fulfillment
of the Requirements for the Degree of Doctor of Philosophy

EFFECTS OF SOIL TEMPERATURE GRADIENT ON
GROWTH AND CARBOHYDRATE AND NUTRIENT
ELEMENT LEVELS IN THREE WARM-SEASON TURFGRASSES

By

Garry Lee Seitz

June, 1974

Chairman: Dr. S. H. West
Major Department: Agronomy

Effects of soil temperatures on growth of warm-season turfgrasses

are important from a management standpoint, thus the objective of this

work was to evaluate growth and tissue levels of carbohydrates and nu-

trient elements of 'Argentine' bahiagrass, Paspalum notatum Flugge,

'Floratine' St. Augustinegrass, Stenotyphrun secundatum (Walt.) Kuntz, and

'Tifgreen' bcrmudagrass, Cynodon idartlon (L.) Pers. X C. transvaalonsis

Davy as affected by a gradient of soil temperatures. An aluminum alloy

plate was developed ir.to a teperature gradient apparatus to maintain temp-

erature of potted grass plugs or stolons at 10 to 46C range. The three

grasses were utilized in a six-day stolen study and grass plug studies of

five to eight weeks duration. Growth was evaluated by terminal dry weight

of clippings and plant parts and analyses of tissue for nutrient element

levels and total nonstructural carbohydrates (TNC) on percent and total

weight bases. Shoot growth decreased with decreasing soil temperatures,

whereas rhizome growth increased. Higher soil temperatures were optimum

for shoot than for rhizome and root growth. TNC levels in grass tissue

responded inversely or not at all to shoot growth but responded directly

with rhizome and loot growth. Root growth had higher optimum soil temp-

eroture on short term (6-cday) than on long term bases. Carbohydrate










reserves (TNC) were preferentially utilized for shoot growth with

increasing soil temperatures but were translocated basipetally at

cooler temperatures for growth and storage in rhizome and root

tissue.


xii















INTRODUCTION


Bahia, St. Augustine, and bermuda grass constitute the most

important ornamental turfgrasses in Florida in terms of production,

acreage, and value. However, little research is available on factors

affecting growth of these warm-season turfgrasses.

Three major classes of factors affecting turfgrass growth are

climatic, edaphic, and cultural practices. These interact to form

the growing environment to which turfgrasses respond. Soil temperature,

a climatic-edaphic factor, assumes major importance since it modifies

and controls growth of almost half of the turfgrass plant tissue and

has a significant indirect effect on the other half.

Limited investigations have been accomplished in which soil temp-

eratures were monitored or evaluated on warm season turfgrass growth,

and little consideration has been extended this factor when planning and

undertaking cultural practices on such grasses. Top growth and above-

ground environmental factors have been used primarily as the indicators

for evaluation and cultural management of turfgrasses.

A better understanding of soil temperature effects on warm season

turfgrasses can lead to cultural practices which improve factors detri-

mental to winter growth and survival of these grasses. This study was

thus initiated to evaluate effects of soil temperature on total growth

and chemical composition of 'Argentine' bahia, 'Floratine' St. Augustine,

and 'Tifgreen' bermuda grass.















REVIEW OF LITERATURE

Tei: erature Effects on Turfgrasses

Shoot Growth

Plants have a range of three cardinal temperatures: Minimum temp-

erature range is the lowest et which growth occurs, optimum is range at

which growth is most active, and maximum is the highest range at which

growth can occur (45, 60). Plant cardinal temperatures vary from species

to species, within species and even between various plant parts on the

same plant (6). Beard (6) pointed out the optimum temperature for maxi-

mum shoot growth lay not be the same for maximum quality or desirability.

Numerous experiments have been reported which bracket air tempora-

ture range of 15.5 to 25C (60 to 77"F) as optimum for maximum shoot

growth of cool-season turfgrass's (6, 9, 15, 18, 28, 29, 34, 54, 60, 71).

A few studies have reported a higher temperature range of 26 to 350C

(78 to 95C) for maximum shoot growth oE warm-season turfgrasses (6, 9,

29, 35, 49). Miller (34) reported that maxirumi photosynthetic rate of

creeping bentgrass, a cool-season grasr, occurred at 250C (77F) and

maximum rate for bermudagrass, a warm-season grass, at 35'C (95F).

Cooper and Tainton (9) divided forage grasses into temperate

Festucoid grasses, having temperature optimal between 20 to 25C (68 to

770F), and subtropical or tropical ron-festucoid grasses (Panicoid and

Chloridoid species), having an optimum range between 30 to 35'C (86 to

950F). Eeard (6), in a literature review, states that temperature above

or below optimum range drastically reduced shoot growth.









Minimum and maximum temperature ranges are more difficult to

delineate than temperature optima since nutrition, hydration, humidity,

and temperature duration influence them markedly. Youngner (70) indi-

cated that bermudagrass stopped top growth and proceeded into dormancy

at approximately 10C (500F). Brown (7) observed that shoot growth of

Kentucky and Canada bluegrass continued at 4.4%C (40*F). Ketellapper

(21) concluded that soil temperature rather than air temperature was the

determining factor for induction of summer dormancy in work with Reed

Canarygrass.

Root Growth

Optimum temperatures for root growth of warm- and cool-season

grasses are as disparate as for shoot growth, but ranges are lower for

both. Beard (6), in a literature review, reported the optimum tempera-

ture range for root growth of most cool season turfgrasses was between

10 to 18.3C (50 to 650F), whereas, the optimum range for root growth of

most warm season turfgrasses was 24 to 29.5C (75 to 850F). He added

that information was limited concerning warm season turfgrasses.

Brown (7) used Cynodon dactylon and found the optimum temperature

for maximum root weight was 37.8C (1000F), and Lovvorn (28) observed

similar results with the same species, although he gave the optimum for

root growth as between 26.7 to 32.2C (80 to 900F). These early works

did not consider the fact that entire plants were subjected to the

reported temperatures and were maintained at low fertility with infre-

quent or no clipping of shoot growth.









Recently, Youngner (72) controlled air temperatures and varied

root temperatures along a gradient and showed that a soil temperature

of 23.3C (740F) provided maximum root weight and root length for

Cynodon dactylon L.

West et al. (67) grew Digitaria decumbens Stent., a warm-season

forage grass, on a gradient of soil temperatures for two weeks utilizing

terminal stolen pieces and reported that maximum root weight and length

occurred within a range of 31 to 34%C (88 to 93'F), but maximum root

number occurred between 24 to 26*C (75 to 79F). Schroder (50) grew

'Pensacola' bahiagrass, 'Coastal' bermudagrass, Pangolagrass and

'Slenderstem' digitgrass, warm-season grasses, over a range of soil

temperatures and obtained maximum root weight between 26.7 to 30C (80

to 860F) under pasture management conditions.

Root morphology was influenced by soil temperatures, according to

Beard (6), who stated, in a literature review, that optimum soil temp-

eratures produced turfgrass roots that were multibranched, thick, and

white, whereas, roots grown at temperatures below optimum were thicker,

shorter, and less to non-branched (21, 58). Beard (6) also indicated

that soil temperatures above optimum hastened maturity and senescence,

resulting in brown, spindly roots.

Seasonal variation in root growth of temperate grasses has been

documented with the findings that most growth occurred in early spring

and, to a lesser extent, in late fall when soil temperatures were low

(4, 7, 44, 56, 73).











Youngner (73) stated that little was known of seasonal root growth

patterns for warm-season grasses, but he noted that growth of stolons

and roots of such grasses occurred simultaneously throughout the summer,

thus seasonal responses may not be as obvious as with cool-season

grasses. In contrast, he felt that root initiation and subsequent

growth might occur in winter and early spring when no active top growth

was visible.

Water absorption and movement within plants might be reduced at

low soil temperatures according to Richards et al. (45),Nielson and

Humphries (41), Kramer (25), Kleinendorst and Brouwer (22), and

Mongelard and Mimura (36). Kramer (25) reported this could be caused

by factors, such as increased viscosity of water, increased viscosity

of protoplasm, decreased permeability of cells, decreased rate of move-

ment of water from soil to root, and retardation of root elongation.

Reduced water absorption can restrict growth only if transpiration rate

exceeds absorption causing wilting. Davis and Lingle (13) concluded

from work with shoot responses to root temperature in tomato that control

of shoot growth by soil temperatures was not based on mineral or water

availability to the shoot.

Nielson and Humphries (41) indicated that soil temperature

influenced soil aeration, more specifically soil oxygen concentration

and carbon dioxide tension around roots. Reduced soil temperatures

would decrease oxygen diffusion through the soil and decrease its con-

centration held in ground water, however, the importance of these factors

on root growth could not be determined.











Nielson and Humphries (41) pointed out that relationships between

root temperature and shoot growth probably were complex since optimum

root growth temperatures were lower than optimum shoot growth tempera-

tures. They further stated that critical experiments in controlled root

and shoot environments will be necessary to analyze interactions of shoot

and root growth as affected by soil temperatures.

Davidson (11) studied root shoot (R/S) ratios of twelve pasture

grasses and clover in which he evaluated five soil temperatures from 5

to 35"C with constant ambient temperature maintained. He found that

lowest R/S ratios occurred at optimum soil temperature for forage yield

and the R/S ratio increased at temperatures above or below this optimum.

Troughton (59) reported that root relative to shoot growth varied

directly with temperatures within the range of 10 to 26.7C (50 to 80"F)

when Lolium perenne L. was grown in controlled-environment cabinets.

The root to shoot ratio probably is affected by soil temperatures,

depending on whether they are more favorable for top growth or root

growth.

Carbohydrate Levels

Smith (51, 53) classified perennial grasses into two groups based

on type of nonstructural polysaccharides accumulated in vegetative plant

parts. Warm-season grasses accumulate primarily starches, while temp-

erate or cool-season grasses accumulate mostly fructosans. Mcllory (32)

classified carbohydrates into those involved in structural framework

cells and nonstructural components, such as free monosaccharides,

oligosaccharides and 'reserve' polysaccharides. Smith (52) used 'total

nonstructural carbohydrates' (TNC) as an estimate of carbohydrate

energy readily available to plants.











Carbohydrate reserves were defined by Beard (6) as those that

accumulated in permanent organs of plants in nonstructural forms and

which were available for subsequent utilization in assimilatory pro-

cesses. These reserves provide energy for periods of rapid growth,

regrowth from adverse conditions and as an energy source for respira-

tion (73).

Madison (29) indicated that as temperature rose above 35C (950F)

carbohydrate storage stopped for temperate season grasses and reserves

were used up by high respiration rate. There are differences in Q10 of

respiration and photosynthesis at different temperatures. Went (66)

proposed that the photosynthesis to respiration ratio was greater than

10 at low temperatures, but at high temperatures, respiration increased

relatively more than photosynthesis and an imbalance of carbohydrate

synthesis and utilization was attained.

Soil temperatures affect carbohydrate status of shoots of

perennial ryegrass as shown by Sullivan and Sprague (57), who reported

reduced carbohydrate content of tops as soil temperature increased from

10 to 32C (50 to 90F). Zanoni et al. (74) stated that seasonal

fluctuations in carbohydrate levels of several cool-season turfgrasses

were directly related to soil temperatures. Brown and Blaser (8) found

that growth of tall fescue or orchardgrass, cool-season grasses, were

reduced by low soil temperatures and reserve carbohydrates increased.

Schmidt and Blaser (49) reported that growth and carbohydrate

reserves in stolons of 'Tifgreen' bermudagrass were generally larger

and nitrogen content less with high than with low ambient temperatures.










Youngner (72) reported that maximum carbohydrate storage of bermuda-

grass and Kentucky bluegrass occurred at temperatures near minimum for

measurable growth. High temperatures for only a few days rapidly

depleted carbohydrate reserves.

Schmidt (47) discovered that increased air temperatures around

bentgrass decreased carbohydrate reserves but increased respiration,

shoot growth, and carbohydrate content of bermudagrass. According to

McKell, et al. (33), results with Kentucky bluegrass and 'Coastal'

bermudagrass conflicted with Schmidt's (47) in that they obtained

highest concentration of carbohydrates at the coolest temperatures.

According to Nowakowski et al. (42) total soluble carbohydrate

content of ryegrass dry matter was least at 19.5C (670F) soil tempera-

ture and largest at 11C (520F). Davidson (11) reported a decline in

total soluble carbohydrates (TSC) in ryegrass roots with increasing soil

temperatures.

Youngner (73) stated in summary that warm-season grasses accumu-

lated reserve carbohydrates at higher temperatures than cool-season

grasses and that seasonal fluctuations in carbohydrate reserves were

largely results of changes in climatic conditions. Numerous authors

agree that temperature is a major factor dictating carbohydrate accumu-

lation and utilization (7, 34, 57, 61). Youngner (73) also stated that

the maximum rate of reserve carbohydrate accumulation in cool-season

grasses occurred in late fall during periods of slow shoot growth and

gradual decrease occurred during winter with slight increase prior to the

drastic reduction due to spring regrowth after which reserves may increase

slowly into the autumn. He further stated that warm-season grasses show











a similar trend with maximum accumulation in the fall and gradual deple-

tion during winter dormancy. The only difference was a marked increase

of reserves during the summer in contrast to a decrease in cool-season

grasses. Schmidt (47) reported that carbohydrates in bermudagrass

stolons decreased during the winter and spring, increased during summer,

and reached a maximum by late fall.

Apparently carbohydrate storage capabilities of rhizomes are

several fold greater than that of roots in the warm-season grasses.

Reserve carbohydrates of cool-season grasses appear to fluctuate more

widely than that in warm-season grass species.

Elemental Nutrition

Nielson and Humphries (41) indicated that soil temperature influ-

enced plant nutrition by changing effective concentrations of soluble

nutrients in the soil or by affecting ability of plants to absorb and

utilize them. Extremes of temperature in field situations indirectly

alter mineral availability due to affects on microbial decomposition of

organic materials. They further stated that size and activity of plant

root systems determined their ability to obtain many nutrients, especially

those of low soil mobility. Therefore, if temperature restricted root

growth, nutrient absorption also would be restricted, especially if any of

these non-mobile nutrients were scarce. Kramer (25) indicated that ion

concentration in soil nutrient solution is temperature dependent and low

soil temperatures reduced ion availability and concentration.

Harrison (18) studied responses of Kentucky bluegrass to temperature

and nitrogen fertility, and his results indicated that maximum root weights

were obtained at lowest temperature 16.10C (600F) and no added nitrogen.









Nowakowski et al. (42) reported that increased soil temperature

increased total soluble-nitrogen in Italian ryegrass and decreased

protein-nitrogen whether NO or NH+ forms were applied.

A review presented by Richards et al. (45) reported that low soil

temperatures did not seriously retard absorption of N but possibly

affected the capacity of roots to reduce absorbed nitrates and convert

or assimilate them into organic nitrogenous components. Brown (7) worked

with four pasture grasses and confirmed the finding that retarded growth

from low temperatures was due to reduced rates of N assimilation rather

than restricted N absorption.

Ryegrass was grown by Parks and Fisher (43) at three soil tempera-

tures (10, 20, and 30C), and they reported increased soil temperatures

affected absorption of such divalent cations as Mg and Ca. They further

reported that K, Ca, Mg, and P contents were retarded at 100C (500F) with

largest yield of forage occurring at 200C (680F). Ehrler and Bernstein

(16), however, reported contradictory results with rice which showed no

interactions between root temperature and cation concentration or cation

ratio. They stated that low root temperature affected only K concentra-

tion and absorption sufficiently to decrease yields.

Nielson and Cunningham (40) reported increased soil temperatures

increased % Ca and % Mg in ryegrass and had little influence on concen-

tration of N, P, S, Na, and K. the lowest soil temperature (11C) grew

ryegrass with the highest Cl content. Knoll et al. (23) studied soil

temperature effects on growth of corn and concluded that P uptake

increased as soil temperatures were raised from 15 to 250C (59 to 770F).










Davis and Lingle (13) concluded after studying shoot response to root

temperature in tomato that control of shoot growth by root temperature

does not reside primarily in rates of minerals or water supply to the

shoots.

Cultural Practices

Soil temperature plays an important role in turfgrass growth and

quality, therefore, it should be considered in turfgrass management

decisions. Schmidt and Blaser (48) concluded that seasonal temperature

must be considered in timing N fertilization for bentgrass development.

Fertilizer timing and fertilizer rates and ratios must be governed to

promote such growth and quality necessary without excesses.

Close mowing height and frequency, if performed too severely,

restrict root growth for extended periods of time depending on the damage

done, according to Madison (29). When soil temperatures are above or

below optimum, root regrowth from such damage will be restricted signifi-

cantly. Should soil temperatures be optimum for maximum root growth,

mowing practices should be geared to remove the least amount of foliage

as infrequently as possible. Beard (6) indicated that cutting height of

greens can be raised to provide a measure of insulation against extremes

in high soil temperature by increasing depth of turfgrass canopy.

Irrigation can be used to reduce soil temperatures if sufficient

water is applied. Beard (5) utilized syringing (i.e., light application

of water) as a method of moderating midday heat build up in turf situations

and reported that an application of 0.25 inches of water to bentgrass turf

at noon reduced the soil temperature at the 2 inch depth by 1.60C (30F).

He also stated that a cool intense rain or frequent irrigations of 0.75

inches or more resulted in soil cooling.










Other cultural practices, such as covers and mulches, have proved

effective in altering micro-climate of close-clipped grasses (62). Covers

have been used to buffer against such extremes in cold temperature, and

treated areas are usually the first to turn green in early spring.

Watson (62) also mentioned the use of lamp black and other dark substances

as a cover over turfgrass areas to absorb radiant heat. The common

practice of topdressing greens to improve putting trueness should be

avoided during warm periods as the dark topdressing material will act

much like the lamp black and increase soil temperatures.

Electric heating cables recently have been installed below the

soil surface to raise soil temperatures sufficiently for year-round turf-

grass growth and/or prevention of soil freezing on athletic fields in

winter (1, 10, 17, 26, 30, 31). According to Beard (6) the primary

objective of soil warming is to protect against frost damage and to

maintain green color throughout winter. Soil temperature ranges of 1.7

to 7.20C (35 to 450F) are sufficient to accomplish this with cool-season

grasses, but a warmer soil temperature range of 15.6 to 18.30C (60 to 650F)

is necessary for warm-season grasses to retain green color (1, 30, 31).

Recent work has been reported which utilized growth regulators such

as gibberellic acid applications to grasses in order to maintain green

growing tissue at or below minimum temperatures (14, 20, 37, 46, 68, 69).

Other recent developments in cool temperature effects on turfgrass growth

involved the use of foams as temporary blankets for cold protection (3).















METHODS AND MATERIALS

Temperature Gradient Plate Experiments


Three experiments consisting of nine treatments each placed in

randomized block design were initiated to test effects of soil tempera-

tures on growth of 'Argentine' bahiagrass, Paspalum notatum Flugge,

'Floratine' St. Augustinegrass, Stenotaphrum secundatum (Walt.) Kuntz,

and 'Tifgreen' bermudagrass, Cvnodon dactylon (L.) Pers. X C. trans-

vaalensis Davy. Treatments were replicated four times with one pot

containing a grass plug as the experimental unit.

A temperature plate was constructed based on apparatus by Barbour

and Racine (2) and West et al. (67) to obtain a gradient of soil tempera-

tures from 10 to 46C (48 to 115F). The apparatus consisted of an alumi-

num alloy plate 75 cm x 293 cr x 1.9 cm, with 28 cm of each end immersed

in a sealed temperature controlled water bath. One bath was maintained

at 62.8C (145F) and the other at 3.3C (380F), which created a

gradient of temperatures along the plate length. Intervening plate

sections were partitioned into nine compartments by 1.9 cm wood parti-

tions at intervals of 21.6 to 29.9 cm (Figs. 1 and 2). Water filled

each corpartnent to a level of 11.1 cm to facilitate heat transfer from

plate upward, and air was bubbled for 15 seconds at intervals of 30

seconds from two locations in each compartment to prevent vertical or

horizontal temperature gradients.









Four pots of grass were immersed in each compartment, and each pot

provided with tubes draining outside the apparatus. Drain tubes were

connected to an aquarium air stone placed at the bottom of each pot to

prevent sand loss (Fig. 3).

Outsides of the apparatus were insulated with 2.54 cm thick sheets

of styrofoam, and pieces of styrofoam covered water surfaces of compart-

ments to prevent ambient temperature influence on soil temperatures.

Soil temperatures were monitored with a twenty-four-point Honeywell

recorder utilizing copper constantan thermocouples placed 7 cm below soil

surface in selected pots. Temperatures were recorded twice per hour with

reported temperatures being the mean daily temperature and maximum diurnal

flux of 20C+. Mean soil temperatures were slightly different for the

three grass experiments as shoim in Table 1.

A golf course cup cutter (plugger), 10.5 cm dia., was used to

obtain grass plugs, and attached soil was trimmed to 2.54 cm thickness.

The three grasses were cut and moved into the greenhouse at least two

weeks prior to placement on the temperature apparatus. Grass plugs were

potted in sterilized fine-grade builders sand, with bahiagrass in 14 cm

diameter pots and St. Augustine and bernuda grass plugs in 11 cm diameter

pots (1000 ml plastic beakers). Upper external surface of pot was spray

painted or covered with opaque tape to prevent sunlight reaching below

soil surface. Sod of the three grasses was obtained from Pursley Grass

Co. of Palmetto, Florida.

Grass plugs were fertilized before and after placement on apparatus

with modified Knoop's (24) nutrient solution every two days with enough

water to assure slight drainage within one minute after application.

Bahia and St. Augustine grass were fertilized with this solution at the

rate of 0.5 lb of N/1000 sq. ft./month and bermuda at twice this rate.


















































Figure 1, Experimental, compartmentali7ed temperature
gradient plate apparatus containing four pots
of grass per temperature treatment.





















































Figure 2. Pots of grass in one temperature compartment
showing surface insulation used to maintain
temperature levels.


















































Figure 3. Sample of pots used in the experiments, with
aquarium air stone in bottom to facilitate
drainage and prevent sand media loss.



























Table 1. Mean soil temperatures in three experiments utilizing
temperature gradient plate apparatus.

Soil
Temperature Treatment Experiments
(C) Number Bahiagrass St. Augustinegrass Bermudagrass

10-11 9 10C* 11 10
15-17 8 17 17 15
19-21 7 21 21 19
21-24 6 24 23 21
25-27 5 27 26 .25
27-30 4 30 29 27
31-34 3 24 33 31
37 2 37 37 37
45-46 1 45 45 46

* Temperatures were monitored 7.6 cm below soil surface.










Shoot growth measurements were accomplished with periodic clipping

at 7 or 4 day intervals by hand scissors fitted with foam rubber guards

to trap and hold cut grass blades. Clipping heights were 6.4 cm (2.5 in.),

5.1 cm (2 in.) and 1.9 cm (.75 in.) for bahia, St. Augustine and bermuda

grass, respectively. Cutting height was established using a clear rigid

fiberglass template resting on pot edges and scissors were pressed

against this plate, or pot edge in the case of bermudagrass, to maintain

reference heights (Fig. 4).

Clippings were immediately placed in a 70C oven and held for at

least 72 hours, at which time dry weights were taken and samples ground

twice in Wiley mill fitted with 20 mesh screen.

Termination of each experiment was accomplished by removing grasses

from the pots and the sand separated from the roots by repeated dips in

water baths. Roots were cut from the plugs with dissecting scissors.

The sod plug was then washed with a stream of water to remove remaining

soil, and rhizomes (bahia and bermuda grass) were cut from shoot tissue

for the various plant fractions for analysis. Tissue was then held in

70C oven for at least 96 hours before dry weights and subsequent grind-

ing was initiated as for clipping tissue.

Various methods have been presented, revised and modified for

quantitatively extracting available carbohydrate energy source (reserves)

from plant tissue (27, 38, 52, 63). The procedure of removing and

analyzing Total Nonstructural Carbohydrates (TNC) from plant tissue by

Smith (52) has been accepted and extensively used for temperate and

tropical forage grasses and was used in this study. Oven dry plant tissue

was extracted with enzymes, and the resulting reduced sugars calculated

with final determination reported as % INC of dry weight.




















































Figure 4. Fiberglass
harvesting
height.


template anj scissors used in
clippings at a specific cutting











Plant tissue was analyzed for N, P, K, Ca, Mg, Cu, Fe, Mn, and Zn

contents utilizing micro-Kjeldahl for N determination, Beckman Model DU

Flame Spectrometer for K, Ca, and Mg determinations, Bausch and Lomb

Spectronic 20 for P determinations, and Perkin-Elmer Model 290-B Atomic

Absorption Spectrophotometer for Cu, Fe, Mn, and Zn determinations (19).

No other cultural treatments were applied to grasses once on the

temperature apparatus other than application of insecticide or fungicide

for sod webworm and fungal disease control as needed.

The temperature gradient plate apparatus was located in a heated

and air-conditioned greenhouse, however, diurnal ambient temperatures

fluctuated between 15.6 and 46.1C (60 to 115F) due to radiant energy.

During the St. Augustine and bermuda grass experiments, ambient night

temperatures were slightly lower than 15.60C due to loss of normal heat

source and inadequacy of supplemental heating units. No control of

photoperiod or supplemental light was undertaken, and three grass experi-

ments were initiated in late fall and winter under short day conditions.

Respective initiation and termination dates for bahia, St. Augustine and

bermuda grass experiments were September 21 November 16, 1972, October

9 November 20, 1973, and December 10, 1973 January 12, 1974.

Stolon Experiment

A short-term experiment utilizing stolon cuttings was initiated on

the temperature apparatus to observe effects of soil temperature on root

length and root weight for six days. A randomized block design was used

with replications initiated six days apart and four samples taken per

replication.









Terminal stolons were obtained from potted plugs of each grass which

had been held and fertilized weekly in the greenhouse for at least one

month prior to cutting. Stolons of bahiagrass were cut to provide

approximately 0.6 cm rhizome and approximately 5.0 cm of shoot growth.

St. Augustine and bermuda grass stolons were cut so that each had two

nodes with the non-terminal node being stripped of its leaves (Fig. 5).

St. Augustine, bahia, and bermuda grass stolons were placed in well-

aerated, distilled water containers for 4, 3 and 1 days, respectively,

prior to initiation of experiment. Timing of duration of stolon nodes

in aerated container was determined by preliminary observation to allow

formation of root initials before placement on temperature apparatus.

At initiation of the experiment each stolon was placed in a plastic

centrifuge tube 18.7 x 111 cm filled with deionized water, and stolons

suspended by expansion of foliage (Fig. 6). Stolon tubes were immersed

in temperature compartments for six days with daily syringing and refilling

of tubes as necessary to prevent wilting. The first stolen replication

was started December 27, 1973 and fourth replication terminated

January 19, 1974 with no interruption between replications. After six

days on temperature apparatus, stolons were removed, root length measured,

and dry weights of those roots recorded. Root number was not recorded

due to variability observed in preliminary experiments.

Field Study

A completely randomized block experiment with split plot design was

initiated in which winter fertilization and fertilizer ratios were evalu-

ated as to their effect on winter root growth of the aforementioned

grasses. Main plots were grasses and subplots fertilizer treatments with

four replications.


















































Figure 5. Initial rhizome and stolon pieces of bahia,
bermuda, and St. Augustine grass (left to
right) utilized in stolon experiment.





















































Figure 6. Rhizome and stolen pieces suspended in water
filled tube used in stolon experiment. Racks
with tubes were placed on temperature gradient
apparatus.











The experimental area located at Oranmental Horticulture green-

houses was fumigated with methyl bromide September 1, 1972 and sod from

Pursley's Grass Co., Palmetto, Florida, laid two weeks later (Fig. 7).

Fertilizer treatments were begun October 24, 1972 and applied every two

weeks until May 3, 1973. Fertilizer treatment ratios (N-P-K) were

1-0-1, 1-0-0, 0-0-2, 1-0-4, and Milorganite at equivalent rates of

nitrogen. The N was derived from ammonium sulfate (NH4)2SO4 and K from

sulfate of potash magnesia K2SO4 2 Mg SO4. Rates of N were 1 lb/1000

sq. ft./month on bermudagrass and half that for St. Augustine and bahia

grasses. Rate of 0-0-2 treatment was 2 lbs/1000 sq. ft./month K for

bermuda and half that for St. Augustine and bahia grass.

Grass plugs were extracted monthly using a golf course cup cutter

and as much soil as possible washed from root systems below sod piece.

Due to inability to remove all soil particles from root systems, a deter-

mination of combustionable organic matter was recorded by taking the

difference between non-ashed weight and ashed weight.

Samples of shoot tissue were taken one month after termination of

fertilizer treatments and elemental analysis performed on this tissue as

per previous description.




















































Figure 7. Plots of bahia, St. Augustine, and bermuda grass
utilized in outside winter fertilizer rare and
ratio experiment.















RESULTS

Temperature Gradient Plate Experiments


Responses of clipping yields to soil temperature treatments are

given in Tables 2, 3, and 4 for bahia, St. Augustine, and bermuda grass,

respectively. Generally, highest yields occurred at warmer temperatures

and lowest yields at coolest temperatures. Bermudagrass clipping yields

showed a decrease of optimum temperature from December 11 to January 11

harvest date.

Total weight of top growth for each experiment showed the overall

long-term effects of soil temperature in which maximum dry weights were

attained within range of 25 to 46C (Table 5). Bahiagrass shoot weights

were much larger than St. Augustine and bermuda grass due to difference

in duration of each experiment, being 8, 7, and 5 weeks, respectively,

and differences in inherent growth rates (Fig. 8). Optimum long-term

soil temperature for top growth of bahia and St. Augustine occurred with-

in ranges of 34 to 45C, 26 to 37"C, respectively, however, bermudagrass

did not show a clear cut optimum temperature (Table 5).

Dry weights of various plant parts, other than top growth, deter-

mined at termination of experiment are presented in Tables 5 and 6.

Verdure tissue comprised top growth above rhizomes or stolons, but below

clipping height, and was mainly composed of older leaf blades and sheaths.

Cardinal temperatures for growth of such tissue were difficult to charac-

terize because bahiagrass responded to a wide range 21 to 45C, St.

Augustinegrass had an optimum at 26 to 37C, and bermudagrass, a lower

















Table 2. Mean clipping dry weights (gms) of bahiagrass as affected by a gradient of soil temperatures.

Soil
Temperature Harvest Dates (1972)
(C) Oct. 5 Oct. 12 Oct. 19 Oct. 26 Nov. 3 Nov. 9 Nov. 16

10-11 .203 g* .083 g .150 f .099 g 0.164 f .138 f 0.140
15-17 .454 f .235 f .398 e .252 f 0.453 e .330 e 0.395
19-21 .505 ef .291 ef .420 e .353 e 0.605 d .464 d 0.622
21-24 .591 de .345 de .517 de ,417 de 0.762 d .622 c 0.674
25-27 .624 ed .387 ed .594 b-d .489 cd 0.983 c .712 be 0.866
27-30 .712 be .465 be .663 a-c .562 c 1.001 be .754 b 0.785
31-34 .851 a .499 b .706 ab .736 b 1.165 ab .788 ab 0.915
37 .654 cd .523 ab .754 a .805 ab 1.293 a .898 a 1.002
45-46 .780 ab .589 a .559 cd .897 a 1.166 ab .829 ab 0.970
NS

* Means in a column followed by the same letter are not significantly different as determined by
Duncan's Multiple Range Test (5% level).















Table 3. Mean clipping dry weights (gms) of St. Augustinegrass as affected by a gradient of soil
temperatures.

Soil
Temperature Harvest Dates (1973)
(C) Oct. 15 Oct. 25 Oct. 30 Nov. 3 Nov. 7 Nov. 11 Nov. 17 Nov. 19

10-11 .0813 d* .0505 f .0530 e .0330 e .0500 e .0353 e .0863 e .0868 e
15-17 .1083 d .1460 ef .1378 de .1185 d .1408 d .1718 d .2720 d .1663 d
19-21 .1760 cd .2635 de .2303 cd .1908 c .2420 c .2405 c .3725 c .2305 c
21-24 .1320 d .2988 d .2695 bc .2380 bc .2650 bc .2838 bc .4103 bc .2528 be
25-27 .2740 bc .4333 bc .3558 ab .2828 ab .3555 a .3445 ab .4633 ab .3125 a
27-30 .2943 a-c .5095 ab .3775 a .3470 a .3893 a .3583 a .5210 a .3158 a
31-34 .3085 ab .5380 ab .4275 a .3048 ab .3445 a .3218 ab .4260 be .3465 a
37 .4138 a .6078 a .3398 ab .2823 ab .3228 ab .3383 ab .3908 be .3003 ab
45-46 .2615 be .3563 cd .2570 bc .2040 c .2543 be .2490 c .2330 d .2127 cd

* Means in a column followed by the same letter are not significantly different as determined by Duncan's
Multiple Range Test (5% level).















Table 4. Mean clipping dry weights (gms) of bermudagrass as affected by a gradient of soil temperatures.

Soil
Temperature Harvest Dates (1973-1974)
(C) Dec. 11 Dec. 15 Dec. 19 Dec. 23 Dec. 27 Dec. 30 Jan. 3 Jan. 7 Jan. 11

10-11 .0306 e* .0516 g .0313 g .0256 f .0714 e .0547 d .1307 d .1190 d .1310 d
15-17 .0453 de .0878 f .0849 f .0811 e .1515 d .1003 c .2195 a-c .2041 a-c .1988 ab
19-21 .0585 cd .1239 e .1285 e .1123 d .1600 b-d .1253 b .2619 a .2389 a .2152 a
21-24 .0628 b-d .1714 d .1761 d .1339 cd .1678 b-d .1255 b .2327 ab .2025 a-c .1924 ab
25-27 .0864 a .2065 c .2097 c .1566 c .1579 cd .1300 b .1968 bc .1949 bc .1800 a-c
27-30 .0915 a .2343 bc .2403 be .1939 b .1945 a-c .1525 a .2426 a .2073 ab .1896 ab
31-34 .0603 cd .2427 b .2149 c .1638 c .1594 b-d .1216 b .1912 bc .1646 c .1505 cd
37 .0852 ab .3086 a .2767 b .2016 b .1990 ab .1406 ab .1848 c .1719 bc .1704 bc
45-46 .0752 a-c .3131 a .3092 a .2313 a .2211 a .1229 b .1329 d .1236 d .1250 d

* Means in a column followed by the same letter are not significantly different as determined by Duncan's
Multiple Range Test (5% level).















Table 5. Total clipping and mean verdure dry weights of bahia, St. Augustine and bermuda grass as
affected by a gradient of soil temperatures.

Soil Total Clipping Dry Weight (gms) Verdure Dry Weights (gms)
Temperature
(C) Bahia St. Augustine Bermuda Bahia St. Augustine Bermuda

10-11 0.977 f* 0.476 d 0.646 d .39 c 1.3745 e 2.1179 a
15-17 2.517 e 1.261 c 1.173 c 6.8 b 1.9898 d 1.7001 a-c
19-21 3.260 d 1.946 b 1.425 b 7.6 ab 2.3693 cd 1.8654 ab
21-24 3.939 c 2.150 b 1.465 b 8.0 ab 2.5970 be 1.6779 a-c
25-27 4.655 b 2.822 a 1.519 ab 8.5 a 3.1763 a 1.4702 b-d
27-30 4.942 b 3.113 a 1.746 a 7.7 ab 3.1265 ab 1.3614 b-d
31-34 5.660 a 3.018 a 1.469 b 7.8 ab 2.5035 cd 1.1667 cd
37 5.929 a 2.996 a 1.739 a 7.7 ab 2.7213 a-c 1.0990 d
45-46 5.790 a 2.028 b 1.654 ab 7.4 ab 2.3498 cd 0.9126 d

* Means in a column followed by the same letter are not significantly different as determined by Duncan's
Multiple Range Test (5% level).













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Table 6, Mean rhizome, stolon and root dry weights of bahia, St. Augustine and bermuda grass as affected
by a gradient of soil temperatures.

Soil (gms) Root Weight (gms)
Temperature Bahia St. Augustine Bermuda
(C) Rhizomes Stolons Rhizomes Bahia St. Augustine Bermuda

10-11 10.2 ab* 1.8873 7.2477 a 0.511 f .0807 e .1537 a-c
15-17 12.1 ab 1.9770 5.5000 bc 1.581 cd .3306 ed .1886 a
19-21 10.8 ab 2.2175 5.9316 ab 2.166 a .3450 b-d .1884 a
21-24 10.2 abc 1.9880 4.7305 b-d 1.754 be .3942 a-c .1456 a-c
25-27 9.0 bc 2.1070 4.0971 cd 1.807 b ,4250 a .1676 ab
27-30 9.5 be 1.9445 5.8840 ab 1.688 b-d .4224 ab .1664 ab
31-34 9.2 bc 1.8053 3.8899 d 1.502 de .3833 a-c .1092 cd
37 8.3 c 1.6168 4.0007 cd 1.343 e .2807 d .0905 d
45-46 8.8 bc 1.7083 3.6653 d 0.299 g .0196 e .1266 b-d
NS

* Means in a column followed by the same letter are not significantly different as determined by Duncan's
Multiple Range Test (5% level).









optimum of 10 to 21C (Table 5, Fig. 9). Dry weight of verdure tissue

was positively correlated to soil temperature for bahia and St. Augus-

tine grass, and negatively correlated for bermudagrass.

Rhizome growth of bahia and bermuda grass generally responded with

decreased weights as temperature decreased, whereas St. Augustinegrass

stolon weight showed no response to soil temperature gradient (Table 6).

Fluctuations can be seen in rhizome weights of bahia and bermuda grass

between soil temperature extremes (Fig. 10).

Cardinal temperatures for root growth of bahiagrass were clearly

delineated, but this was not true for St. Augustine and bermuda grass,

since they exhibited wide ranges for these critical temperatures (Table

6, Fig. 11). Optimum soil temperature for bahiagrass root growth was

21C, whereas maximum root growth of St. Augustinegrass occurred within

a range of 23 to 34'C. Temperatures used in these studies were suffic-

iently extreme to have attained cardinal minimum and maximum temperatures

for root growth of bahia and St. Augustine grass, however, bermudagrass

did not show drastic reduction in root weight at coldest temperature

(10C) to demonstrate minimum growth level (Fig. 11). Affects of soil

temperature on root morphology are visible in Fig. 12.

Total dry weight of all plant parts, less clippings, showed addi-

tive effects of soil temperature on entire grass plug or plant (Table 7).

Optimum soil temperatures for bahia and St. Augustine grass occurred

between the extreme high and low temperatures (10 to 45C), whereas

bermudagrass showed temperature optimum at the cooler temperatures from

10 to 190C (Fig. 13). The entire grass plug with attached root system

of each grass at termination can be seen in Figs. 14, 15, and 16.























8.0 \ _,


/ Bahia

/
6.0- /

Verdure
Dry Weight
(gms)
/
4.0 /

St. Augustine

.' .. **

2.0--



Bermuda

0.0
10 15 20 25 30 3 4 45

Soil Temperature (C)

Figure 9. Mean verdure dry weight of bahia, St.
Augustine, and bermuda grass as affected
by a gradient of soil temperatures.




















\ Bahia Rhizomes




BrdRim
\*





Bermuda Rhizomes





A vK! --


St. Augustine Stolons
-. '". *


0. c ~ I


10 15 20


25 30 35 40 45


Soil Temperature (C)

Figure 10. Mean dry weight of stolons or rhizomes of
bahia, St. Augustine, and bermuda grass as
affected by a gradient of soil temperatures.


12.0+


10. oT


8.0t


Dry
Weight
(gms)


4.0F


.





















B\
/ \
I \ Bahia
f ~ '


/

/


St. Augustine
o.....* ** ..


I Bermuda


L;--4--~-----~-
0 5 20 25 30 35 40 45

Soil Temperature (OC)

Figure 11. Mean root dry weight of bahia, St. Augustine,
and bermuda grass as affected by a gradient
of soil temperatures.


2.0 4


Root Dry
Weight
(gms)


1.0 4-


0.5 4


0.0


1.5 1



















































Figure 12. St. Augustinegrass root sections taken from grass
plugs maintained on soil temperature gradient
apparatus for seven weeks. Treatment 1 was 450C,
grading to 11C at treatment 9.























Table 7. Total dry weight of plant tissue of bahia, St. Augustine and
bermuda grass as affected by a gradient of soil temperatures.

Soil Total Plant Weight (gms)
Temperature
(C) Bahia St. Augustine Bermuda

10-11 14.611 c* 3.872 d 9.634 a
15-17 20.481 a 4.994 b-d 7.427 a-c
19-21 20.566 a 5.613 a-c 8.008 ab
21-24 19.954 a 5.600 a-c 5.103 cd
25-27 19.307 ab 6.374 a 5.790 b-d
27-30 18.888 ab 6.080 ab 7.492 a-c
31-34 18.502 ab 5.174 a-d 5.188 cd
37 17.343 abc 5.154 a-d 5.214 cd
45-46 16.499 bc 4.621 cd 4.767 d

* Means in a column followed by the same letter are not significantly
different as determined by Duncan's Multiple Range Test (5% level).





















20.04-


Bahia
/ Bahia


16.0+


12.04


Bermuda




St. Augustine \ ..




~C_ i I .*


10 15 20 25 30 35


40 45


Soil Temperature (OC)

Figure 13. Total dry weight of plant tissue of bahia,
St. Augustine, and bermuda grass as affected
by a gradient of soil temperature.


Total
Plant
Weight
(gns)




















































Figure 14. Bahiagrass plugs and roots after eight weeks
growth on soil temperature gradient apparatus.
Treatment 1 was 450C, grading to 11C at
treatment 9.



















































Figure 15. St. Augustinegrass plugs and roots after seven
weeks growth on soil temperature gradient
apparatus. Treatment was 450C, grading to 11C
at treatment 9.



















































Figure 16. Bermudagrass plugs and roots after five weeks
growth on soil temperature gradient apparatus.
Treatment 1 was 46C, grading to llC at treat-
ment 9.











Carbohydrate storage levels and capacity were recorded as percent

Total Nonstructural Carbohydrates (TNC) on dry weight basis and as total

(mg) TNC per pot or experimental unit. Percent TNC evaluated the capa-

city of specific tissues in storing reserve carbohydrates.

Percent TNC of clippings averaged over the study period indicated

that bahia and St. Augustine grass stored carbohydrates in tissue at

similar levels, however bermudagrass TNC storage was consistently one

or more percent lower (Table 8, Fig. 17). Bahia and St. Augustine grass

clippings TNC levels were more responsive to soil temperatures than

bermudagrass.

TNC levels in verdure tissue indicated that bahiagrass stored

higher percentages than St. Augustine or bermuda grass (Table 8).

Bermudagrass verdure tissue showed limited responsitivity to soil temp-

eratures when evaluated by % TNC, however at lowest temperature (10*C)

the level was highest (Fig. 18). St. Augustinegrass verdure tissue had

increased % TNC as soil temperature increased, whereas bahiagrass stored

the minimum TNC within range of 24 to 370C and maximum at 100C.

Carbohydrate storage organs, such as rhizomes, stolons and roots,

exhibited sensitivity to soil temperatures by a large variation in % TNC

levels (Figs. 8 and 9). Percent TNC decreased as soil temperature

increased in the three plant tissues of the three grasses. Lowest levels

of 3.09 to 4.08% TNC in rhizomes and stolons occurred at 37 to 460C and

maximum levels of 5.93 to 12.18% TNC at 10 to 11oC. St. Augustinegrass

stolons stored less percent TNC than bahia or bermuda grass rhizomes, and

root tissue stored less TNC than rhizome or stolen tissue (Table 9).

Percent TNC of bahiagrass root tissue was lowest (1.10%) at 300C, whereas















Table 8. Mean percent Total Nonstructural Carbohydrates (TNC) in clippings averaged for all harvest dates
and mean percent TNC in verdure tissue of bahia, St. Augustine and bermuda grass as affected by
a gradient of soil temperatures.

Soil % TNC of Clippings % TNC of Verdure
Temperature
(C) Bahia St. Augustine Bermuda Bahia St. Augustine Bermuda

10-11 4.86 3.74 2.40 9.88 a* 1.40 d 4.70 a
15-17 4.63 3.81 2.34 8.07 b 1.76 cd 2.81 b
19-21 4.71 4.00 2.49 6.50 bc 2.69 be 3.02 b
21-24 4.33 4.36 2.44 6.70 b-d 2.65 bc 3.05 b
25-27 4.36 4.28 2.40 6.79 b-d 2.47 bc 2.81 b
27-30 3.99 4.16 2.16 5.96 d 2.33 bc 2.88 b
31-34 4.16 3.82 2.29 6.40 cd 2.59 bc 2.56 b
37 4.06 3.45 2.49 6.95 b-d 3.13 b 2.89 b
45-46 3.71 4.14 2.39 7.66 bc 4.76 a 2.72 b

* Means in a column followed by the same letter are not significantly different as determined by Duncan's
Multiple Range Test (5% level).























.Bahia





St. Augustine
*


9.. ,.

-=5
*
S


Bermuda









--)-~-~9= 9---~--d


1.0 L


10 15 20 25 30 35 40 45

Soil Temperature (C)

Figure 17. Percent TNC in clippings averaged over all
harvest dates of bahia, St. Augustine, and
bermuda grass as affected by a gradient of
soil temperatures.


5.0-


% TNC


0.0


















10.
\





8.0 Bahia





6.0

% TNC in
Verdure
Tissue

4.- Bermuda



\ ^ ..- *. . *

2.
..* St. Augustine




0.0
10 15 20 25 30 35 40 45

Soil Temperature (OC)

Figure 18. Percent TNC in verdure tissue of bahia, St.
Augustine, and bermuda grass as affected
by a gradient of soil temperatures.




















12.0 1


10.0 4-


8.0 -






6.0 -


4.0 4-


Bermuda Rhizomes
*


"* Bahia
Rhizomes

\


SSt. Augustine
-Stolons *- t
.
0~


2.0 4.


10 1I 2F 25 0 5 40 45


Soil Temperature (OC)

Figure 19. Percent TNC in rhizomes and stolons of bahia,
bermuda, and St. Augustine grass as affected
by a gradient of soil temperatures.


% TNC


--VlsCs~--~IP~~--- ~ II --


_25


m


r

























\ Bahia
\


St. Augustine








*


Bermud a


II


I ~ ,-

--/


0 15 20 75 0 3 445

Soil Temperature (C)

Figure 20. Percent TNC in roots of bahia, St. Augustine,
and bermuda grass as affected by a gradient
of soil temperatures.


% TNC
in Roots


2.04


- \


>1

















Table 9. Mean percent Total Nonstructural Carbohydrates (TNC) in rhizomes, stolons and roots of bahia,
St. Augustine and bermuda grass as affected by a gradient of soil temperatures.

Soil % TNC % TNC in Roots
Temperature Bahia St. Augustine Bermuda
(C) Rhizomes Stolons Rhizomes Bahia St. Augustine Bermuda

10-11 11.59 a* 5.93 a 12.18 a 5.14 a 3.82 a 3.06 a
15-17 7.34 b 3.43 bc 8.25 bc 4.27 ab 2.64 b 2.39 b
19-21 6.61 be 3.33 be 9.57 b 3.60 b 2.32 be 2.19 be
21-24 5.96 ed 2.99 be 8.85 be 2.39 c 2.39 be 1.53 f
25-27 5.60 c-e 3.59 be 8.05 be 2.31 c 2.27 be 2.04 ed
27-30 4.76 d-f 4.02 b 8.79 be 1.10 d 1.57 c 1.97 d
31-34 4.67 d-f 3.44 be 7.23 ed 1.29 ed 1.54 c 1.70 e
37 4.08 f 2.59 c 5.50 d 2.31 c 1.60 c 1.22 g
45-46 4.40 ef 3.04 b 3.09 e 1.64 ed ---** 0.67 h

* Means in a column followed by the same letter are not significantly different as determined by Duncan's
Multiple Range Test (5% level).


** Not sufficient tissue for TNC analysis.










in bermuda and St. Augustine grass, percent TNC was minimum at 45 to 46C

and 27 to 460C, respectively (Fig. 20). Maximum % TNC storage in root

tissue of the three grasses occurred at 10 to 110C.

The total TNC per experimental unit (pot) was determined by multi-

plication of % TNC level within tissue by its dry weight to give values

expressed as milligrams TNC per pot on tissue dry weight basis.

Average TNC content per pot for clipping yields collected during

the study show maxima similar to dry weight results (Table 10, Fig. 21).

No statistical analysis was performed on these data due to lack of clipping

tissue.

Table 11 presents TNC content of verdure tissue, with bahiagrass

having highest content compared with other grasses, although treatments

did not significantly affect this measurement in bahiagrass. Bermuda

and St. Augustine grass had comparable TNC content per pot within verdure

tissue, although the relationship to soil temperature was contradictory,

being negative and positive, respectively (Fig. 22).

The importance of rhizomes as carbohydrate storage organs is

apparent from data in Table 11 in which TNC weight reached maximum of

118 mgs per pot in bahiagrass rhizomes at 100C. St. Augustine stolons

stored less than half as much TNC per pot as rhizomes of other two

grasses. Weight of TNC per pot found in rhizomes and stolons of these

grasses varied. As soil temperature decreased, TNC increased, and

rhizomes and stolons were the largest reservoirs of TNC in the plant

(Fig. 23).

TNC content in roots constituted a much smaller proportion of stored

TNC than other tissues, especially with St. Augustine and bermuda grass

in which less than one milligram per pot was stored at the highest
























Table 10. Total Nonstructural Carbohydrates (TNC) content per pot of
clippings averaged for all harvest dates as affected by a
gradient of soil temperatures.

Soil Milligrams TNC per pot in clippings
Temperature
(C) Bahia St. Augustine Bermuda

10-11 4.75 1.77 1.55
15-17 11.65 4.80 2.75
19-21 15.36 7.78 3.55
21-24 17.06 9.37 3.58
25-27 20.30 12.08 3.65
27-30 19.72 12.95 3.77
31-34 23.55 11.53 3.36
37 24.07 10.34 4.33
45-46 21.48 8.40 3.95


















*


Bahia


* St. Augustine





B-u



Bermuda


i0 15 20 25 30 35 40 45

Soil Temperature (C)

Figure 21. Mean TNC content (mgm) per pot in total
clipping yields per pot of bahia, St.
Augustine, and bermuda grass as affected
by a gradient of soil temperatures.


251-


15-I-


10 -


TNC in
Clippings
(mgm)


5 .


'Ix
















Table 11. Mean Total Nonstructural Carbohydrate (TNC) content per pot in verdure, rhizome and stolon tissue
of bahia, St. Augustine and bermuda grass as affected by a gradient of soil temperatures.

Soil Milligrams TNC per pot in Vurdure Milligrams TNC per pot
Temperature Bahia St. Augustine Bermuda
(C) Bahia St. Augustine Bermuda Rhizomes Stolons Rhizomes

10-11 38.618 1.995 d* 9.937 a 118.100 a 11.107 a 88.830 a
15-17 55.085 3.625 cd 4.797 bc 88.975 b 6.757 b 46.383 b-d
19-21 56.603 6.504 be 5.933 b 70.960 bc 7.637 ab 57.540 b
21-24 53.670 6.991 b 5.150 bc 60.895 cd 6.028 b 41.825 b-d
25-27 57.338 7.879 b 4.244 be 49.880 de 6.494 b 32.995 c-e
27-30 46.885 7.287 b 3.924 bc 45.178 de 8.046 ab 51.800 bc
31-34 49.535 6.632 bc 3.044 c 42.575 de 6.204 b 28.043 d-f
37 53.938 8.611 ab 3.105 c 32.873 e 4.160 b 21.503 ef
45-46 56.463 11.171 a 2.504 c 37.965 e 5.318 b 11.303 f

Means in a column followed by the same letter are not significantly different as determined by Duncan's
Multiple Range Test (5% level).























Bahia
/ Bahia


- -4
\


- /


30+


10- .*
St. Augustine


0 *Bermuda
.


10 1'5 20 25 30 35


40 45


Soil Temperature (C)

Figure 22. Mean TNC content (mgm) per pot in verdure tissue
of bahia, St. Augustine, and bermuda grass as
affected by a gradient of soil temperatures.


TNC in
Verdure
(mgm)


















120.


100. \
\
\ \ Bahia Rhizomes
80- \


60-


40 j

TNC Content Bermuda Rhizomes .
(mgm)


20-






"- St. Augustine Stolons








Soil Temperature (OC)

Figure 23. Mean TNC content (mgm) per pot in rhizomes
and stolons of bahia, St. Augustine, and
bermuda grass as affected by a gradient of
soil temperatures.















Table 12. Mean Total Nonstructural Carbohydrate (TNC) content per pot in roots and overall total of tissues
of bahia, St. Augustine and bermuda grass as affected by a gradient of soil temperatures.

Soil Milligrams TNC in Roots Total Milligrams TNC per pot
Temperature
("C) Bahia St. Augustine Bermuda Bahia St. Augustine Bermuda

10-11 2.635 bc* 0.308 c 0.470 a 159.353 a 13.879 99.238 a
15-17 6.762 a 0.933 a 0.451 a 150.823 a 11.855 51.630 be
19-21 7.765 a 0.786 ab 0.413 ab 135.328 ab 15.502 63.886 b
21-24 4.211 b 0.966 a 0,223 c 118.778 bc 14.266 47.197 b-d
25-27 4.157 b 0.958 a 0.342 b 111.375 be 16.041 37.581 c-e
27-30 1.903 cd 0.667 a-c 0.328 b 93.965 c 16.676 56.052 be
31-34 1.840 ed 0.604 be 0.186 ed 93.950 c 14.027 31.272 d-f
37 3.047 be 0.438 bc 0.110 de 89.858 c 13.689 24.718 ef
45-46 0.544 d ---** 0.085 94.973 c 17.022 13.891 f
NS

* Means in a column followed by the same letter are not significantly different as determined by Duncan's
Multiple Range Test (5% level).

** Not sufficient tissue for TNC analysis.


















8.0-


/
I* \

6.0 /




/ Bahia
4.0 / -

TNC in /
Roots
(mgm) \


2.0/ \


I\

St. Augustine



~- t-- -. Bermuda
o\*-'-------.* "
0.0 .0
10 15 20 25 30 35 40 45

Soil Temperature (C)

Figure 24. Mean TNC content (mgm) per pot in roots of
bahia, St. Augustine, and bermuda grass as
affected by a gradient of soil temperatures.











temperature (Table 12). Total stored TNC in roots of bermudagrass was

negatively correlated with soil temperature, while bahia and St.

Augustine grass stored maximum TNC in roots at 17 to 290C (Fig. 24).

St. Augustinegrass did not respond to soil temperature in terms of

total TNC per pot less clippings, and it stored less than bermuda or

bahia grass, which increased in TNC content as soil temperatures

decreased (Table 12). Bermudagrass had the widest range of TNC levels

per pot with levels of 13.9 mg TNC at 46C to 99.2 mg at 10C. Several

fluctuations in total TNC per pot occurred in bermudagrass tissues with

these fluctuations traced to differences in rhizome dry weight and % TNC

levels (Fig. 25).

Significant effects of soil temperature on levels of nutrient

elements in tissues of the three grasses are given in Table 13. Macro-

nutrient levels in tissues were more responsive to treatment effects than

micronutrient levels with 21 out of 32 possible effects being nonsignifi-

cant at the 5% level of probability. Phosphorus and K levels were most

frequently altered by soil temperature, with Ca and Mg second in frequency

of significant variation.

Bahiagrass verdure, rhizome and root tissues, St. Augustinegrass

verdure and stolon tissues, and bermudagrass verdure and rhizome tissues

were analyzed for nutrient element content.

Bahiagrass verdure tissue had lower levels of P and K but increased

levels of Ca, Mg, Fe, and Cu at highest soil temperatures (Table 14).

N and K levels varied in rhizome tissue with N level highest at extreme

temperatures and K highest at the.lowest temperature (Table 15). Bahia-

grass root tissue varied in N, P, K, Mg, and Cu levels, but no definite

trend occurred. There was insufficient tissue at extreme temperature

treatments for analysis (Table 15).





















\


\ Bahia


Bermuda


St. Augustine

*- .. .. .** *


10 1e 2=0 2 3r 3 70 45

Soil Temperature (C)

Figure 25. Mean TNC content (mgm) per pot in plant parts
of bahia, St. Augustine, and bermuda grass as
affected by a gradient of soil temperatures.


K\


TNC in
Total Plant
(mgm)


20.


c
re























Table 13. Analysis of variance table for content of nutrient elements in
bahia, St. Augustine and bermuda grass tissue.

% ppm
Grass Tissue N P K Ca Mg Cu Zn Fe Mn

Bahiagrass Verdure +* + + + + +
Rhizome + +
Roots + + + + +

St. Augustine Verdure + + + +
Stolons + + + + + +

Bermuda Verdure + + +
Rhizome + + + +

* + indicates significant F-test value (5% level).




















Table 14. Content of nutrient elements in bahiagrass verdure tissue as
affected by a gradient of soil temperatures.

Soil
Temperature % ppm
(C) P K Ca Mg Fe Cu

10 0.36 ab* 2.15 a 0.27 d 0.79 d 183 e 29 c
17 0.41 a 1.88 a-c 0.26 d 1.10 c 293 b-d 39 be
21 0.40 a 1.82 bc 0.26 d 1.26 a-c 190 de 34 bc
24 0.31 b-d 1.68 c 0.24 d 1.19 bc 308 a-c 40 bc
27 0.33 bc 1.82 bc 0.32 cd 1.37 a 213 c-e 40 bc
30 0.29 c-e 2.06 ab 0.44 ab 1.32 ab 383 ab 45 b
34 0.28 de 1.78 bc 0.41 be 1.23 a-c 285 b-e 35 be
37 0.24 e 1.73 e 0.49 ab 1.17 bc 395 a 38 bc
45 0.27 de 1.68 c 0.51 a 1.16 bc 265 de 58 a

* Means in a column followed by the same letter are not significantly
different as determined by Duncan's Multiple Range Test (5% level).















Table 15. Content of nutrient elements in bahiagrass rhizomes and roots as affected by a gradient of
soil temperatures.

Soil Rhizome Tissue Root Tissue
Temperature % % ppm
(C) N K N P K Mg Cu

10 1.60 a-c* 0.70 a --- --- ---
17 1.53 bc 0.53 b 1.73 a 0.23 a 2.38 a 0.50 bc 41 b
21 1.48 c 0.53 b 1.68 a 0.17 b 1.71 b 0.66 a 49 a
24 1.55 be 0.58 b 1.48 ab 0.16 b 1.43 be 0.67 a 30 c
27 1.48 c 0.54 b 1.33 bc 0.16 b 1.03 d 0.59 ab 41 b
30 1.83 ab 0.53 b 1.05 c 0.19 ab 0.89 d 0.47 bc 40 b
34 1.78 a-c 0.53 b 1.65 a 0.21 ab 1.04 d 0.45 c 40 b
37 1.85 a 0.52 b 1.58 ab 0.20 ab 1.19 cd 0.46 be 46 ab
45 1.68 a-c 0.50 b --- --- --- ---

* Means in a column followed by the same letter are not significantly different as determined by Duncan's
Multiple Range Test (5% level).









St. Augustinegrass verdure and stolon tissue had variations in

levels of P, Ca, Mn, and Mg, with Ca, Mg, and M!n having generally a

positive correlation and P a negative one with soil temperatures (Table

16). K and Zn content in St. Augustinegrass stolon tissue exhibited a

positive correlation but little significance to soil temperature up to

the maximum temperature attained (I6iC).

Bermudagrass verdure and rhizome tissue had few elements which were

significantly affected by soil temperature (Table 17). Soil temperature

affected Zn and Mn in the verdure tissue with levels of these elements

being maximum at highest soil temperature. Bermudagrass rhizome tissue

varied in P, K, Ca, and Fe, with K and Ca generally lower as temperature

decreased.

Stolen Experiment

Results of a short-term (6-day) study in which root dry weight and

length were evaluated from stolon or rhizone pieces of bahia, St.

August ije, and bermuda grass ar.; shown in Table 18 and Figs. 26, 27, and

28. Optimum root medium temperatures for maximum root weights were 310C,

21 to 310C, zrd 27 to 31C for hshia, St. Augustine, and bermuda grass,

respectively (Fig. 29). Maximum temperatures for root weight were reached

at highest temperature 45C, while rainijun temperature ranged from 10 to

15C for the three grasses (Table 18).

Optimum temperatures for root length extended the ranges into higher

temperatures giving bahia, St. Augustine, and bermuda grass an optimum

temperature range of 31 to 37C, 21 to 270C, and 27 to 31CC, respectively

(Table 18). Only St. Augustinegrass root length reached its minimum and

maximum temperature, however, bahia and bcr.-da grass were close to those

cardinal points (Fig. 30).














Table 16. Content of nutrient elements in St. Augustinegrass verdure and stolon tissue as affected by a
gradient of soil temperatures.

Soil Verdure Tissue Stolen Tissue
Temperature % % ppm
(C) P Ca Mg Mn ppm P K Ca Mg Zn Mn

11 0.31 d* 0.30 c 0.44 e 78 c 0.14 be 3.31 ab 0.14 c 0.27 e 464 d 63 be
17 0.36 b-d 0.34 be 0.58 de 70 c 0.18 b 2.74 b 0.15 c 0.39 d 491 ed 40 c
21 0.46 a 0.45 ab 0.87 be 80 bc 0.22 a 4.03 ab 0.18 c 0.46 ed 528 b-d 55 be
23 0.40 ab 0.46 a 1.02 ab 78 c 0.17 b 3.42 ab 0.17 c 0.51 b-d 578 bc 80 ab
26 0.34 b-d 0.51 a 1.01 ab 83 bc 0.15 bc 3.44 ab 0.21 be 0.51 b-d 573 be 53 be
29 0.33 ed 0.45 ab 1.13 a 90 be 0.17 b 4.79 a 0.25 ab 0.63 ab 613 b 75 ab
33 0.38 be 0.55 a 1.12 a 123 a 0.15 be 4.40 a 0.29 a 0.65 a 770 a 95 a
37 0.34 b-d 0.51 a 0.95 ab 120 a 0.14 be 4.74 a 0.28 a 0.54 a-c 627 b 78 ab
45 0.31 cd 0.52 a 0.71 ed 108 ab 0.12 c 4.69 a 0.31 a 0.46 ed 500 ed 65 bc

* Means in a column followed by the same letter are not significantly different as determined by Duncan's
Multiple Range Test (5% level).

















Table 17. Content of nutrient elements in bermudagrass verdure and rhizome tissue as affected by a gradient
of soil temperatures.
Rhi~ Ti


Verdure Tissue
% N Zn ppm n ppm

2.50 ab* 445 e 130 b
2.50 ab 540 d 180 b
2.63 a 581 ed 180 b
2.38 ab 656 be 233 b
2.23 be 610 b-d 258 b
2.40 ab 624 b-d 250 b
2.40 ab 644 be 263 b
2.45 ab 691 ab 280 b
2.03 c 770 a 483 a


P K Ca


0.17
0.15
0.15
0.15
0.11
0.13
0.12
0.21
0.23


1.08 e
1.24 de
1.45 cd
1.48 ed
1.54 b-d
1.90 a
1.79 ab
1.81 ab
1.63 a-c


0.11
0.14
0.15
0.16
0.16
0.15
0.14
0.15
0.27


Soil
Temperature
(C)


zome-p ssue


Fe
Fe


* Means in a column followed by the same letter are not significantly different as determined by Duncan's
Multiple Range Test (5% level).
















Table 18. Mean root length and dry weight of bahia, St. Augustine and bermuda grass initiated on stolons
or rhizomes and affected by a gradient of soil temperatures for six days.

Soil
Temperature Root Length (mm) Root dry weight (mgm)
(C) Bahia St. Augustine Bermuda Bahia St. Augustine Bermuda

10 2.5 d* 0.0 c 7.3 g 2.0 d 0.0 d 1.5 ef
15 11.5 d 12.3 be 19.0 f 7.1 d 13.7 c 2.8 de
19 35.8 c 25.5 b 34.8 e 22.5 c 15.6 c 4.1 cd
21 35.0 c 48.5 a 50.3 d 22.7 c 26.9 ab 5.0 bc
25 43.5 c 51.5 a 59.8 cd 25.7 c 29.6 a 5.2 bc
27 66.0 b 64.3 a 71.8 ab 36.2 b 34.7 a 7.1 ab
31 104.0 a 60.8 a 77.3 a 45.8 a 28.2 a 7.5 a
37 98.0 a 52.8 a 66.0 bc 34.6 b 16.9 bc 6.0 a-c
46 5.8 d 0.0 c 5.5 g 5.1 d 0.0 d 0.0 f

* Means in a column followed by the same letter are not significantly different as determined by Duncan's
Multiple Range Test (5% level).


















































Figure 26. Bahiagrass rhizome pieces after six days growth
on soil temperature gradient apparatus. Treat-
ment 1 was 460C, grading to 100C at treatment 9.




















































Figure 27. St. Augustinegrass stolon pieces after six days
growth on soil temperature gradient apparatus.
Treatment I was 460C, grading to 100C at treat-
ment 9.


















































Figure 28. Bermudagrass stolon pieces after six days growth
on soil temperature gradient apparatus. Treatment
1 was 460C, grading to 100C at treatment 9.






















/
I \


/
SBahia

r.
r *

.4 1
*


St. Augusti


/ \


*'^ .^"-" Berud
Bermuda. *

A"~


Soil Temperature (OC)

Figure 29. Mean root dry weight (mgm) initiated on bahia,
St. Augustine, and bermuda grass rhizomes or
stolons as affected by a gradient of root media
temperatures.


504


40+


30+


Root Dry
Weight
(mgm/root)


SI'
IS

=/4


10+-


\
\
\
\
\
\
\
\
9,.
ine \ ,
\


20-J,


1A0 f5 1'9 21 25 -7 31


-~Y~-Bl;r~ou~~~uP~aurrur~C~~TRBrZ~P~BBr


J7 46


I


\


/


















100. !

SBahia

I \

80I \
1 \
Root Length p
(mm/root) Be a
Bermuda *
60- .. \





40- / St. Augustine \
40
'I



20- ,




I
10 15 19 21 25 27 31 37 46

Soil Temperature (C)

Figure 30. Mean root length (mm) initiated on bahia,
St. Augustine, and bermuda grass stolons
or rhizomes as affected by a gradient of
root media temperatures.











Bahiagrass had the highest optimum root media temperature for root

growth (weight and length) with bermuda and St. Augustine grass next.

Field Study

No significant responses occurred with bahia, St. Augustine, and

bermuda grass to five fertilizer treatments during winter months of

1972-73 as to combustionable carbon weight of root tissue. The only

differences in winter root growth were between grasses on the last four

out of five harvest dates (Table 19). Bahiagrass had highest root

weights with St. Augustinegrass second and bermudagrass third (Fig. 31).

Nutrient element analysis of leaf tissue taken one month after

termination of fertilizer treatments indicated some differences due to

fertilizer treatments and between grasses (Tables 20 and 21). Fertilizer

treatments affected N, P, Ca, and Mn levels in the three grasses, and

grasses contained different levels of N, P, K, Ca, Mg, Mn, and Cu.








Table 19. Mean monthly combustionable carbon root weight for bahia,
St. Augustine and bermuda grass from fertilizer field study
(averaged over five fertilizer treatments and four replica-
tions).

Grasses Dec. 19 Jan. 20 Feb. 23 March 28

Bermuda 0.4844 b* 0.4713 c 0.4698 c 0.6550 b
Bahia 0.7918 a 0.9345 a 0.8360 a 0.9688 a
St. Augustine 0.6975 a 0.7528 b 0.7072 b 0.9262 a







Table 20. Mean content of nutrient elements in leaf tissue taken from
bahia, St. Augustine and bermuda grass four weeks after
termination of fertilizer field study.

Fertilizer % Dry Weight ppm
Ratio N P Ca Mn

1-0-1 2.78 ab* 0.29 b 0.45 b 110 a
1-0-0 2.92 a 0.29 b 0.52 a 115 a
0-0-2 2.37 c 0.30 ab 0.50 ab 43 b
1-0-4 2.78 ab 0.31 ab 0.31 c 103 a
Milorganite 2.65 b 0.34 a 0.44 b 53 b





Table 21. Mean content of nutrient elements in bahia, St. Augustine and
bermuda grass top tissue taken three weeks after termination
of fertilizer field study.

% ppm
Grasses N P K Ca Mg Mn Cu

Bermuda 3.02 a* 0.27 b 1.82 b 0.71 a 0.33 b 115 a 24 b
Bahia 2.65 b 0.25 b 1.97 b 0.40 b 0.45 a ll a 33 a
St. Augustine 2.43 c 0.39 a 2.54 a 0.22 c 0.28 c 29 b 19 b


* Means in a column followed by the same letter are not significantly
different as determined by Duncan's Multiple Range Test (5% level).






















1.0-
/*
/ -/ .
Bahia / N /
/ N./ ,s
0.8- /
/ St. Augustine



S .

0.6- /

Combustionable
Carbon of / Bermuda
roots (gms)-

0.4-- -25






0.2-- -15

Maximum and minimum soil
temperature 10.2 en below -10
surface.
0.0
Nov. Dec. Jan. Feb. Mar.

Date of Root Harvest

Figure 31. Mean monthly combustionable carbon root
weight for bahia, St. Augustine, and bermuda
grass averaged from five fertilizer treat-
ments in field study.















DISCUSSION

Effects of Soil Temperature Gradient


Shoot Growth

Results from these experiments indicated that shoot growth was

indirectly affected by soil temperature effects on below-ground plant

parts. Total dry weight of clippings increased with increasing soil

temperatures. Bahiagrass showed highest optimum temperature, followed

by St. Augustine and bermuda grass. These results agreed with soil

temperature ranges reported by Schroder (50) for maximum shoot growth

of 'Pensacola' bahiagrass and 'Coastal' bermudagrass at 36.6 and 40.6C,

respectively, when controlled independently of ambient temperatures.

Street (55) postulated two factors about root systems which control

shoot growth: (1) Roots served as carbohydrate "sinks" or storage organs

and as assimilators for amino acid and protein synthesis since N is

absorbed by roots and translocated to shoots in organic combinations.

Therefore, roots regulate shoot growth by intensity or direction of

carbohydrate gradient. (2) Roots supplied hormonal substances to shoots

which had growth regulating effects, thus, factors which affect root

growth or function indirectly alter shoot growth.

Percent TNC of clippings showed little response to gradient of soil

temperatures, as indicated by TNC weight per pot in clipping yields curve

which closely paralleled dry weight results (Figs. 8 and 21). Nielsen and

Humphries (41) explained that temperature effects on plant growth and

carbohydrate levels were manifest in preferential utilization of available









carbohydrates for shoot growth with excesses translocated to rhizomes

and roots. Results herein showed no TNC accumulated in clippings,

except that utilized for growth, and excess TNC was translocated basi-

petally as evidenced in accumulation of TNC in rhizomes, stolons, and

roots (Figs. 19, 20, 23, and 24).

Effects of soil temperature on clipping yields appeared to be

reduction of growth at cooler temperatures and translocation of carbo-

hydrates from continued photosynthetic rates to other plant parts at

these cool temperatures. At warm, near optimum temperatures for growth,

available carbohydrates were incorporated in growth with increased

respiration, and no translocation and subsequent accumulation in other

plant parts occurred.

Verdure Growth

Verdure tissue in this study included shoot growth below clipping

height, but excluded stolons, rhizomes, and roots. Initial grass plugs

in each experiment contained a large volume of verdure tissue, thus to

obtain significant differences required large changes from initial to

final weights and TNC levels.

Maximum weights of bahia and St. Augustine grass verdure tissue

occurred within a range of 25 to 30C soil temperature, whereas

bermudagrass verdure dry weight decreased with increased soil temperatures

from 10 to 46'C (Fig. 9). Lowest dry weights of bahia and St. Augustine

grass verdure tissue occurred at 10 to 11C soil temperature. Reduction

in growth of bahia and St. Augustine grass verdure at coldest temperature

was due to root effects on shoot growth similar to clipping yield results.

Slight decreased growth of verdure tissue of these two grasses at highest

temperature was due possibly to lack of adequate root system for regulation









and assimilation of substances for further shoot growth (Figs. 9 and 11).

Possibly available carbohydrates also were utilized for growth of

clippings which had higher optimum temperature for growth.

Negative relationship of bermudagrass verdure growth and TNC weight

per pot to soil temperature was opposite or contrasted with clipping

responses, therefore, some available carbohydrates must have been uti-

lized for growth of verdure tissue at cooler temperatures instead of

translocation to rhizomes and roots. The constant level of % TNC in

verdure tissue, except at 10C, could substantiate the previous explana-

tion of growth responses, since carbohydrates were not accumulated in

clippings or verdure, except at 10C. Thus, excess carbohydrates not

utilized for shoot growth of bermudagrass were translocated basipetally

(Figs. 23 and 24). The reason for high % TNC and TNC total weight in

bermudagrass verdure at 10C could have resulted from reduced basipetal

translocation, since carbohydrates were also high in rhizomes and roots

at this temperature. Increased TNC synthesis accompanied by reduced

respiration at this temperature also would explain such accumulation at

the cold temperature.

Percent and total TNC of bahia and St. Augustine grass verdure

tissue differed from each other in response to gradient of soil tempera-

tures. Bahiagrass had maximum % TNC at 10C, which decreased to lowest

point at 300C, then increased (Fig. 18). Lowest % TNC corresponded to

greatest amount of growth, thus TNC was consumed in growth at this point.

Increased TNC level at warmer and cooler temperatures indicated increased

TNC synthesis or reduced translocation (Fig. 18). TNC weight per pot in

bahia verdure varied across the soil temperature gradient but did not

change sufficiently to provide a significant response.










TNC percent and total weight in St. Augustinegrass verdure generally

increased with increasing temperatures (Figs. 18 and 22). At higher temp-

eratures there appeared a higher rate of synthesis and accumulation of

TNC, however, as soil temperature was reduced past the point at which

maximum growth occurred, storage was reduced. This indicated that St.

Augustinegrass verdure translocated excess TNC to stolons or roots similar

to what happened in clipping tissue.

No nutrient elemental levels in any tissue of the three grasses

correlated with growth responses or to soil temperatures, although there

were significant differences in some elemental levels (Tables 13 to 17).

Lack of correlation or relationship to growth responses was probably due

to the frequency of liquid nutrient application (every two days) and to

readily soluble source of elements and the fact that none apparently were

deficient or in excess. Grass plugs were grown on pure builders sand

media, thus nutrient availability was optimum for absorption and

assimilation.

Stolon and Rhizome Growth

St. Augustinegrass stolon growth did not respond to soil temperature

gradient, although % TNC and TNC total weight did vary similarly with a

general decrease from low to high soil temperatures (Tables 6, 9, 11 and

Figs. 10, 19, and 23). TNC weight and % TNC showed similar responses

probably because most TNC was incorporated into growth of this tissue with

some accumulation at 110C.

Bahia and bermuda grass rhizome dry weights fluctuated across the

soil temperature gradient, but generally there was an inverse relationship

with growth decreasing as soil temperatures increased. When % TNC and

weight were evaluated, a more definite inverse relationship was observed,










thus showing a positive relationship of tissue growth with TNC status of

the tissue (Figs. 10, 19, and 23). This can be explained by Wardlaw's

(61) statement that carbohydrate distribution was associated with growth

rather than translocation and as temperatures were decreased there was a

shift in carbohydrate distribution from shoots to roots. At warmer soil

temperatures, shoot growth of bahia and bermuda grass was maximum, and

available TNC was incorporated into those tissues. However, as soil temp-

eratures were reduced rhizome growth was increased, and available carbo-

hydrates were translocated basipetally at expense of shoot growth.

Carbohydrate translocation thus occurred, as described by Nielsen and

Humphries (41) earlier. At cooler soil temperatures, photosynthesis

appeared to continue in shoot growth, but carbohydrate translocation was

basipetal to rhizomes and roots with little subsequent acropetal movement.

Root Growth

Root growth of bahia and St. Augustine grass was maximum at 19 to

21C and 25 to 300C, respectively, whereas bermudagrass root growth was

not statistically delineated but approached a maximum at 15 to 21C

(Table 6). Youngner (72) reported optimum soil temperature for bermuda-

grass root growth as 23.30C, whereas Schroder (50) found maximum root

weight of 'Coastal' bermudagrass at 26.90C and maximum for 'Pensacola'

bahiagrass at 300C. Minimum and maximum root growth temperatures were

attained with bahia and St. Augustine grass since very little root tissue

developed at temperature extremes (Fig. 11).

Bermudagrass root growth did not show minimum-maximum temperature

response possibly due to the fact that bermudagrass plugs were allowed

one week of root growth before being placed on temperature apparatus,

thus some root growth occurred before treatments were applied. Never-










theless, root growth of bermudagrass did appear to have a lower optimum

soil temperature than bahia or St. Augustine grass. No clear explanation

can be given for this observation except that bermudagrass verdure and

rhizome tissue also had lower optima soil temperatures than the other

grasses, indicating its genetic origin permitted cooler adaptation than

bahia or St. Augustine grass.

Percent TNC found in root systems of the three grasses indicated

general decrease as temperature increased with the highest level at 10

to 11C and lowest at 45 to 46C (Table 9). These results agree with

reports by Davidson (11) and Weinmann (64), showing high concentrations

of soluble carbohydrates at low soil temperatures. Davies (12) reported

carbohydrate levels in ryegrass to be positively correlated with growth

rate of root systems. Weight of TNC in roots of these three grasses

agreed with Davies' (12) results since there was decrease in TNC weight

as temperature was decreased or increased from optimum (Fig. 24). Expla-

nation for carbohydrate status of root systems was based on growth curves

of shoots and roots, showing a preferential translocation of carbohydrates

to growth centers. Excess TNC from shoots at cooler temperatures was

translocated to root and rhizome tissue where it was utilized for growth

and excesses stored.

Length and dry weight of roots initiated from rhizome and stolon

pieces as affected by root media temperature were evaluated over a six-

day period. Maximum root length and dry weights occurred within ranges

of 31, 21, and 27 to 370C for bahia, St. Augustine, and bermuda grass,

respectively (Table 18). Such results indicated a slightly higher

optimum soil temperature for short-term root growth than reported in

long-term grass plug experiments conducted on the same apparatus.










Beard (6) observed a similar response with bentgrass root growth in

which he reported root elongation was more rapid at high temperatures

on short-term bases of one to two weeks. West et al. (67) studied root

growth from Pangolagrass stem sections as affected by gradient of root

media temperatures for two weeks, and their results indicated maximum

root weight and length occurred at 31 to 340C, which is within the range

reported here.

An explanation for observed increases in optimum temperature for

growth in this short-term study was due probably to increased respiration

and subsequent growth, however, the study was too short to deplete

reserve carbohydrates of stolon or rhizome pieces.

Effects of long-term soil temperatures on root morphology were

identical to those reported by several authors (6, 21, and 39). Roots

were shorter, thicker, less branched and whiter at temperatures below

optimum, whereas roots were brown, spindly, and multibranched at tempera-

tures above optimum up to the maximum temperature. Minimum and maximum

cardinal temperatures for root growth appeared within the range (10 to

460C) of these studies for the three grasses. Beard (6) explained

morphological responses were caused by degree of tissue maturity. Root

maturation was accelerated by high soil temperatures which caused subse-

quent brown color and increased branching.

Winter Root Growth in Field

The field study was conducted to evaluate winter root growth of the

three warm-season grasses and to observe effects of winter fertilization

on such growth. Root growth did not respond to fertilizer rates or ratios.

There were only differences between grasses. Apparently, the soil had a

high inherent fertility level, and fertilizer treatments did not influence










growth significantly during this time of year. Grass shoots were dormant

part of the study duration, therefore, carbohydrates came from reserves

and growth was at expense of these reserves. Root growth, therefore,

responded to temperature and carbohydrate levels rather than fertilizer

treatments. Winter root growth occurred within soil temperature range

of 12.8 to 21.1C when shoot growth was reduced (Fig. 31).

Seasonal Grass Growth

There were seasonal growth responses of warm-season grasses divided

into shoot and below-ground tissue responses. Seasonal shoot growth

response agreed with findings by many authors which showed positive cor-

relations to temperatures (ambient and soil) (6, 21, and 39). Seasonal

growth responses of rhizomes and roots are not well documented, but

Youngner (72) reported root and shoot growth of bermudagrass occurred

simultaneously throughout warm season. He further stated that opposing

root-shoot growth responses did not exist to the same degree as noted in

cool-season grasses. These studies indicated that root and rhizome

growth was seasonal and opposite to that of shoot growth. Weinmann (65)

reported seasonal TAC (Total Available Carbohydrate) flux in which plant

parts of various warm-season grasses contained lowest TAC levels (8.4%)

in summer and highest (18 to 19%) TAC content in winter. Results from

these studies concurred with Weinmann's (65) observations.

Cultural Practices

Cultural practices need be initiated with ambient and soil tempera-

tures considered so as to minimize damage and/or maximize regrowth poten-

tial of turfed areas. Soil aerification which injures roots and rhizomes

should be initiated in early spring or fall when soil temperatures are

low enough to attain maximum root and rhizome regrowth. Vertical mowing






84


should be done in warm periods when shoot growth is maximum. Correc-

tions for extremely high soil temperatures can be accomplished by

periodic syringing, regardless of evidence of wilt.

More timely fertilizing, such as late fall and possibly winter

fertilization, is needed to insure adequate nutrient status for early

spring root growth. Protective covers against extremes in soil temp-

eratures could be effectively used during cool portions of the year.
















SUMMARY


Results from these experiments indicated that soil temperatures

played important roles in growth of roots and shoots. Roots appeared

to have growth regulatory effects on shoots since ambient temperatures

were not altered but soil temperatures were. Regulatory effects were

manifested in contradictory dry weight curves of roots, rhizomes, and

shoots across the soil temperature gradient. Maximum shoot dry weight

occurred when root and rhizome dry weight was lowest and was minimrum

when root and r'izome dry weight was maximum. Root dry weight did not

necessarily reflect extensiveness and activity of the root system.

Carbohydrate translocation occurred between shoots, rhizomes, and roots

with shoots and rhizomes apparently utilizing and storing carbohydrates

in higher quantities than roots. Bahia, St. Augustine, and bermuda grass

responded similarly to a g:,dient of soil temperatures, although soil

temperature optima for overall growth was highest for bahiagrass followed

by St. Augustine and bermuda grass. Overall, bahiagrass stored higher %

TNC in plant parts than St. Augustine or bermuda grass.















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