COMPARATIVE DROUGHT RESISTANCE MECHANISMS OFELEVEN MAJOR WARM-SEASON TURFGRASSES

A Dissertation

KI SUN KIM

Submitted to the Graduate College ofTexas A&M University

in partial fulfillment of the requirements for the degree ofDOCTOR OF PHILOSOPHY

May 1987

Major Subject: Agronomy

COMPARATIVE DROUGHT RESISTANCE MECHANISMS OFELEVEN MAJOR WARM-SEASON TURFGRASSES

A Dissertationby

KI SUN KIM

Approved as to style and content by:

James B. Beard(Chairman)

7J1J~~Morris G. Merkle

(Member)

~~!~

Marshall J. McFarland(Member)

~~",vLd:~Jamres L. Heilman(Member)

May 1987

ABSTRACT

Comparative Drought Resistance Mechanisms ofEleven Major Warm-Season Turfgrasses. (May 1987)

Ki Sun Kim, B.S., Seoul National University;M.S., Texas A&M University

Chairman of Advisory Committee: Dr. James B. Beard

Comparative drought resistances of eleven major warm-seasonturfgrasses were evaluated in the field after withholdingirrigation. The relative importance of the drought avoidance andtolerance mechanisms was also investigated. For the planteva.luations, visual leaf rolling and firing, leaf water potential,and visual shoot recovery were measured in the field, greenhouse,and controlled environment growth chamber studies. Both the rootingpotential and stomatal characteristics were investigated in separatestudies to assess their contributions to the drought avoidance ofeach species. Proline and abscisic acid (ABA) changes were measuredduring progressive water stress to determine their association withdrought resistance.

From the field shoot recovery data, it was found that 'Meyer'

Hi

centipedegrass [Eremocho/abermudagrasses

and 'Emerald''TifgreenI, and

'Georgia Common'

zoysiagrasses'Texturf 10'

(Zoysia sp.) , 'Arizona Common',(Cynodon sp.), and

ophiuroides (Munro.)Hack.] possessed good drought resistance, whereas 'Texas Common'

St .Augustinegrass [Stenotaphrum secundatum (Walt. ) Kuntze] and

'Tifway' bermudagrass [Cynodon dacty/on (L.) Pers. x C. transvaa/ensis

Davy] possessed poor drought resistance. 'Texas CommonI

buffalograss [Such/oe dacty/oides (Nutt.) Engelm.], 'Pensacola'

bahiagrass (Paspa/um notatum Flugge.), and 'Adalayd' seashore

paspalum (Paspa/um vaginatum Swartz) ranked in the intermediate

range. Bermudagrass and seashore paspalum had good drought

avoidance, whereas zoysiagrass, SLAugustinegrass, and buffalograss

had poor drought avoidance. Zoysisgrass and SLAugustinegrass had

good drought tolerance, whereas bermudagrass had poor drought

tolerance. Bahiagrass possessed medium drought tolerance mainly due

to a dormancy mechanism.

An extensive root system, such as deep rooting, high root dry

weight, and large number of roots, and good stomatal

characteristics, such as early closure and/or wax-covered stomata

iv

contributed to the drought avoidance mechanism. The relative

importance of each component varied among species.

There were significant correlations between shoot recovery

which represents drought resistance and plant parameters such as

leaf rolling (r=-O.59), leaf firing (r=-O.84), canopy-air

temperature differential (r=-O.64), and leaf water potential

(r=O.54) under water stress. Thus, these parameters are potential

techniques for drought resistance prediction in warm-season

turfgrasses.

DEDICATION

To my deceased mother and my lovely wife Yeu Hong

without whose sacrifices I could not have made what I am

and my son Joy J i nkyeom

who gives many things to my life

v

ACKNOWLEDGEMENTS

The author would like to express his sincere appreciation toDr. James B. Beard for his guidance and constructive criticismthroughout his studies and to Mrs. Beard for her motherly love andkindness during the stay in the U.S.

Special thanks are due to his committee members, Drs. M. G.Merkle, J. L. Heilman, M. J. McFarland, and s. M. Smith for theirassistance in the preparation of this manuscript.

Appreciation also is extended to Mr. Kil Sun Yoo and Dr. F.Fong for their technical advice during the physiologicalinvestigations, and to Dr. Helga Bhatkar in the Electron MicroscopyCenter for assisting in the SEM investigation. The author wishes toexpress his sincere gratitude to the following people who innumerous ways lent support to the completion of this dissertation:Dr. C. H. M. van Bavel, Dr. Robert L. Green, Wallace G. Menn, SamuelI. Sifers, John R. Walker, and Katherine G. Mooney.

And the author will never forget the warmest loves andencouragements from his parents, brothers, and sisters in Korea.

vi

The author would

United. States Golfthroughout this study.

like to expressAssociation for

his appreciationtheir financial

to thesupport

TABLE OF CONTENTS

CHAPTER Page

I INTRODUCTION . . . . . . . . . . . . . . . 1

II LITERATURE REVIEW 4

Drought Resistance Terminology . . . . . . . . . . . . 4 Plant Responses To Water Stress . . . . . . . . . . . 5 Mechanisms Of Drought Resistance . . . . . . . . . . . 6

Drought Avoidance . . . . . . . . . . . . . . . . 6 Drought Tolerance . . . . . 9

Measurement Of Plant Water Stress . . 15 Drought Resistance Studies In Turfgrass . . . . . . . 17

III MATERIALS AND METHODS . . . . . . . . . . . . . . . . . . 21 introduction . . . . . . . . . . . . . . . . . . . . . *&i Plant Materials . . . . . . . . . . . . . . 23 1984 Drought Resistance Greenhouse Study . . . . . . . 23

Introduction 23 Jrre—s tress culture . . . . . . . . . * . . . . . . C,J stress culture * . . . . . . . • • . * • . * . * . t̂> Parameters measured . 26

1985 Drought Resistance Field Study 29 xntr oQuction . * « « * . . * . * . . * . « « . « . &.w Pre-stress culture . . . . . . . . . . . . . . . . 31 Stress culture 32 Parameters measured 32

1985 Drought Resistance ET Study . . . . . 33 Introduction . . . . . . . . . . . . . 33 Pre-stress culture . . . . . . . . . . . 33 Stress culture • 36 Parameters measured . . . . . . . . . . . . . . . 36

1985 looting Greenhouse Study . . . . . . . 3 6 introduction • » * » • » • • * • « • • * • • • • • jt> Establishment and culture . . . . . . 37 Parameters measured . . . . . . . . 39

1985 Drought Resistance Controlled Environment Study 39

introduction . . . . . . . . . . . . . . . . . . . J9 Pre-stress culture . . . . . 39 Controlled environment growth chamber . . . . . . 40 Stress culture . . . . . . . . . . . . , 40 Parameters measured . . . . . . . . . . . . . . . 41 Proline analysis 41

CHAPTER

viii

TABLEOF CONTENTS(CONTINUED)

Page

ABA analysis .•..•••••••••••• 42Scanning electronmicroscopic investigation 45

1986 Proline Study •••••••••.••• 46Introduction •••••••••••••••• 46Pre-stress culture .••••••••.• 46Stress culture and parameters measured •••.•• 47

1986 Drought Resistance PEG Study ..•••.•.•• 47Introduction ..•• 47Pre-stress culture •••• 47Stress culture •• 48Parameters measured •••• 51

1986 Drought Resistance Field Study 52Introduction •••••••• 52Pre-stress culture •••• 52Stress culture •••••• 54Parameters measured •••••• 54

IV RESULTSAND DISCUSSION ••••• 56

v

Weather Conditions During The Field StudiesComparative Drought Resistance ••Mechanism Of Drought Resistance

Comparative drought avoidancePotential rooting •••••Stomatal characterizationAbscisic acid (ABA) analysisEvapotranspiration ••••••Polyethylene glycol studyComparative drought tolerance ••••Proline analysis ••••••••••••

Summary Of Drought Resistance And AssociatedMechanisms •••••••••••••••••.

Parameters For Drought Resistance Prediction

CONCLUSIONS

56596264666988929599

101

103109

112

REFERENCES .......................... 114

VITA ............................. 121

TABLE

LIST OF TABLES

Page

ix

1 The common, cu1tivar, and scientific names, plus theoptimum cutting heights of the major warm-seasonturfgrasses used during the 1984-1986 drought studies •. 24

2 Criteria for visual leaf firing rating used during the1984-1986 drought studies •...••••..•.•••• 27

3 Criteria for visual leaf rolling rating used during the1984-1986 drought studies ...•.••••..•.. 28

4 Components for the modified Hoagland solution usedduring the 1986 Drought Resistance PEG Study •••• 50

5 Daily air temperature, solar radiation, pan evaporation,and precipitation during the 1985 Drought ResistanceField Study •••.•....•........ 57

6 Daily air temperature, solar radiation, pan evaporation,and precipitation during the 1986 Drought ResistanceField Study •••••••••••••••••• 58

7 The comparative drought resistances, expressed aspercent shoot recoveries, of eleven major warm-seasonturfgrasses after progressive water stress during boththe 1985 and 1986 Drought Resistance Field Studies •••• 60

8 Comparative leaf firings of eleven major warm-seasonturfgrasses under progressive water stress during boththe 1985 and 1986 Drought Resistance Field Studies •••• 63

9 Changes in leaf water potentials of eleven major warm-season turfgrasses under progressive water stressduring the 1985 Drought Resistance Field Study •••• 65

10 Mean extension of the longest root, total root dryweight, and number of roots of eleven major warm-seasonturfgrasses during the 1985 Rooting Greenhouse Study ••• 67

11 Mean stomatal densities per mm2 on the adaxial andabaxial sides of leaf blades of eleven major warm-season turfgrasses during the 1985 Drought ResistanceField Study •••••••••••••••••• 70

12 Leaf water potentials of eleven major warm-seasonturfgrasses under progressive water stress during SEMstomatal investigation during the 1986 Drought

TABLELIST OF TABLES (CONTINUED)

Resistance Field Study.Page

72

x

13 Summary of stomatal characteristics of eleven majorwarm-season turfgrasses observed through a scanningelectronmicroscope (SEM) after 15 days of progressivewater stress during the 1986 Drought Resistance FieldStudy •.••••••••.• 90

14 Abscisic acid (ABA) contents in the leaves of threeturfgrass species during 13 days of progressive waterstress during the 1985 Drought Resistance ControlledEnvironment Study .••••••. 91

15 Mean evapotranspiration (ET) rates on day 1 and thecumulative ET (CET) over 13 days for ten major warm-season turfgrasses under progressive water stressduring the 1985 Drought Resistance ET Study ••.• 93

16 Comparative leaf firings and leaf water potentials ofeleven major warm-season turfgrasses after 8 days ofprogressive water stress induced by PEG during the 1986Drought Resistance PEG Study •••••••••• 98

17 Comparative leaf firings at comparable low leaf waterpotentials of nine major warm-season turfgrasses afterprogressive water stress during the 1984 DroughtResistance Greenhouse Study •••••.••••• 100

18 Leaf proline contents and leaf firings of eleven ~ajorwarm-season turfgrasses after 9 days of progressivewater stress during the 1986 Proline Study •• 102

19 Simple correlations between proline contents and leaffirings of eleven major warm-season turfgrasses afterprogressive water stress during the 1986 Proline Study. 104

20 Leaf proline contents during progressive water stressand post-stress percent shoot recoveries of threeturfgrass species during the 1985 Drought ResistanceControlled Environment Study •••••••••••.•• 105

21 Summary of the relative drought resistances, avoidances,and tolerances of the major warm-season turfgrass species. 106

22 Simple correlations of four parameters measured on days20 and 34 under progressive water stress to the droughtresistance of eleven major warm-season turfgrassesduring the 1985 Drought Resistance Field Study ••••• 110

FIGURE

LIST OF FIGURES

Page

xi

1 Schematic diagram of the 1984-1986 Drought Studies •.• 222 View of the 1985 Drought Resistance Field Study area at

the Texas A&M University Turfgrass Research FieldLaboratory •.••...••••••.•.•••••• 30

3 View of the 1985 Drought Resistance EvapotranspirationStudy area with mini-lysimeters inside the metalsleeves at the center of each sub-plot ..•••..••. 34

4 View of PVC root column facility in a greenhouse duringthe 1985 Rooting Greenhouse Study •••• 38

5 View of the turfed plastic cones standing in the PEG-nutrient solution containers during the 1986 DroughtResistance PEG Study .•••.••••.••••...• 49

6 View of the 1986 Drought Resistance Field Study area atthe Texas A&M University Turfgrass Research FieldLaboratory 53

7 Stomata and wax accumulations on the adaxial (a) and theabaxial (b) sides of a Texas Common bUffalograss leafblade through SEM after 15 days of progressive waterstress during the 1986 Drought Resistance Field Study(3000 X magnifications.) ••••••• 73

8 Stomata and wax accumulations on the adaxial (a) and theabaxial (b) sides of a Georgia Common centipedegrassleaf blade through SEM after 15 days of progressivewater stress during the 1986 Drought Resistance FieldStudy (3000 X magnification) ••••••• 74

9 Stomata and wax accumulations on the adaxial (a) and theabaxial (b) sides of an Meyer zoysiagrass leaf bladethrough SEM after 15 days of progressive water stressduring the 1986 Drought Resistance Field Study (3000 Xmagnification) ••••••••••••••••• 76

10 Stomata and wax accumulations on the adaxial (a) and theabaxial (b) sides of an Emerald zoysiagrass leaf bladethrough SEM after 15 days of progressive water stressduring the 1986 Drought Resistance Field Study (3000 Xmagnification) ••••••••••••••••• 77

11 Stomata and wax accumulations on the adaxial (a) and the

LIST OF FIGURES (CONTINUED)FIGURE Page

abaxial (b) sides of a Texas Common St.Augustinegrassleaf blade through SEM after 15 days of progressivewater stress during the 1986 Drought Resistance FieldStudy (3000 X magnification) •••••••• 78

12 Stomata and wax accumulations on the adaxial (a) and theabaxial (b) sides of an Arizona Common bermudagrassleaf blade through SEM after 15 days of progressivewater stress during the 1986 Drought Resistance FieldStudy (3000 X magnification) •••.... 79

13 Stomata and wax accumulations on the adaxial (a) and theabaxial (b) sides of a Tifway bermudagrass leaf bladethrough SEM after 15 days of progressive water stressduring the 1986 Drought Resistance Field Study (3000 Xmagnification) ••••.••••.••.•••• 80

14 Stomata and wax accumulations on the adaxial (a) and theabaxial (b) sides of a Tifgreen bermudagrass leaf bladethrough SEM after 15 days of progressive water stressduring the 1986 Drought Resistance Field Study (3000 Xmagnification) ••••••••••••••••• 81

15 Stomata and wax accumulations on the adaxial (a) and theabaxial (b) sides of a Texturf 10 bermudagrass leafblade through SEM after 15 days of progressive waterstress during the 1986 Drought Resistance Field Study(3000 X magnification) ••••••••••••••• 82

xii

16 A stoma and wax accumulation on the adaxial side of anArizona Common bermudagrass leaf blade through SEMafter 13 days of progressive water stress during the1985 Drought Resistance Controlled Environment Study(3000 X magnification) •••••••••• • 84

17 Stomata and wax accumulations on the adaxial (a) and theabaxial (b) sides of an Adalayd seashore paspalum leafblade through SEM after 15 days of progressive waterstress during the 1986 Drought Resistance Pield Study(3000 X magnification) •••••••••••••••••• 85

18 SEM view of the adaxial side of an Adalayd seashorepaspa1um leaf blade surface after 15 days ofprogressive water stress (3000 X magnification) •

19 Stomata and wax accumulations on the adaxial (a) and theabaxial (b) sides of a Pensacola bahiagrass leaf bladethrough SEM after 15 days of progressive water stress

• • 86

xiii

LIST OF FIGURES (CONTINUED)FIGURE Page

during the 1986 Drought Resistance Field Study (3000 Xmagnification) ••.•••••.•. 87

20 SEM view of the adaxial side of a Pensacola bahiagrassleaf blade surface after 15 days of progressive waterstress (3000 X magnification) ..•..•..... 89

21 Changes in the osmotic potentials of the PEG-nutrientsolution during the 1986 Drought Resistance PEG Studyin a greenhouse .................•... 97

CHAPTER I

INTRODUCTION

Water is one of the most common and important substances onthe earth's surface and is essential for the existence of life. Thek.inds and amounts of vegetation occurring on various parts of theearth's surface depend more on the quantity of water available than-on any other single environmental factor. Almost every plantprocess is affected directly or indirectly by the water supply.Water has very important roles as (a) a major constituent ofphysiologically active tissue, (b) a reagent in photosynthesis andin hydrolitic processes such as starch digestion, (c) the solvent inwhich salts, sugars, and other solutes move from cell to cell andorgan to organ, and (d) an essential component for the maintenanceof turgidity necessary for cell enlargement and shoot growth (39).

The metabolic activity of cells and plants is very closelyrelated to their water contents. Practically all land plants aresubjected to some degree of water stress. Even plants growing insoil near field capacity or in dilute water cultures developmeasurable water deficits on hot, sunny days. This occurs becausethe internal water balance and degree of water stress depend on ther~lative rates of water absorption and water loss. The plant waterbalance, therefore, is affected by a complex combination of soil,

This dissertation follows the style of the Agronomy Journal.

1

plant, and atmospheric conditions that control the rates of thesetwo partly independent, partly interdependent processes. If thewater content in most species falls much below the normal level,many physiological activities in the plant are impaired.

As much as 60 % of the water used in large urban areas duringthe hot, dry summer season is for irrigation of lawns and shrubs.In 1980, 3.5 billion m3 of water were used by the municipalities andrural communities of Texas (80). Many urban areas in Texas arevulnerable to serious water supply shortages in the immediatefuture, especially under moderate to severe drought conditions (79).

During the next two decades, overdrafts of ground water inurban areas will need to be significantly controlled throughadditional, well planned, and implemented surface-waterdevelopments, and through conjunctive use of dependable yield fromsurface-water projects and the sustained ground-water yieldsavailable to the areas. In this situation, water availability for

2

growing turf will be less and the cost will increase. Therefore,

for water conservation and the survival of turfgrasses underperiodic severe drought conditions, it is necessary to identifydrought resistant turfgrass species and cultivars, and the plantcharacteristics that are associated with better drought resistancethat can be applied to turfgrass breeding program.

Thus, the objectives of this study were:1. To establish the comparative drought resistances of

eleven major warm-season turfgrasses commonly used in

warm-humid and/or semi-arid climates.

2. To characterize the drought resistance mechanisms ofthese eleven turfgrasses in terms of the relativeimportance of the drought avoidance and droughttolerance dimensions.

3. To determine specific plant parameters associatedwith the drought resistance mechanisms of each grass.

4. To elucidate plant parameters that are effectivepredictor of drought resistance that could be used ingrass breeding programs.

3