Growth studies on defoliated Lotus pedunculatus cv. 'Grasslands Maku' : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University, Palmerston North, New Zealand

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CV . I GRASs LANDS HAKU I •

A thesis presented in partial fulfilment of the requirements for the degree of

Doctor of Philosophy at

Massey University Palmers ton North

New Zealand

GAVIN WILLIAM SHEATH April , 1973

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ABSTRACT

This thesis reports on a series of experiments designeG to study the response of 'Grasslands Maku' to defoliation and thereby extend the understanding of growth and production of Lotus peduncuZatus . Morphol

ogical s truc turing , production and nonstructural carbohydrate sta tus of 'Grasslands Maku' were assessed for different defolia tion regimes in

two separate field experiments . The rela tive importance of several residual plant fac tors and assimilate partitioning in early shoot regrowth, was s tudied in controlled environmental conditions .

i

In the first field experiment, seasonal differences in the partitioning of growth were recorded , with the spring to mid-summer

period being dominated by aerial shoot growth and the late-summer , autumri period by underground growth. Of the underground components, rhizome growth was the most responsiv� to seasonal and defoliation changes and it was this horizontal stem system that formed the basis of basal shoot initia tion .

Canopy growth became increasingly dominated by rhizome shoo ts as cutting height and frequency decreased and s tubble shoo ts, stubble and dead matt r declined . Following defolia tion, regrowth was consistently slow during the first two to three weeks; thus produc tion increases were achieved where regrowth intervals were extended and subsequent, higher growth rates were allowed to be ex�res��d. Higher cutting improved shoot regrowth, particularly in the stubble shoot pool, but increased within-canopy dry matter losses that were related to death and decomposi tion processes, resulted in little, if any improvement in net produc tivity .

Shoot regrowth responses resulting from highet cutting were primarily related to increa�es in the size of the residual shoot pools from which ,

regrowth commenced . Residual shoot number and individual size were

therefore important determinants of early regrowth . Any direct influence of residual nonstructural carbohydrate status on regrowth appeared to be principally confined to the rhizome shoot pool for the first few days of regrowth . The importance of accumul.ated starch would appear t o be related to the provision of metabolic substrate for underground respiration during late au tumn to early spring .

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Where defoliation is incomplete, residual stubble would appear to be an important source of current and redistributed assimilates du�ing early regrowth. Following defoliation, redistribution of carbon compounds to shoot growth was principally confined to the rhizome shoot pool .

Total shoot growth increasingly dominated the partitioning of current assimilates as plants recovered from de1oliation . Where defoliation is incomplete it is proposed that assimil ate ucilization is a more important l imitation to early shoot regrowth than assimilate supply.

The defoliation responses recorded with 'Grasslands Maku' in these

ex�eriments are finally considered with regard to the role of L. pedunculatus in agriculture . Management guidelines are proposed and improved re�·Jwth characteristics , necessary for any further extension of L. peduncu latus into grasslands farming, are suggested.

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TABLE OF CONTENTS

Chapter 1: I ntroduc tion and Objec tives

Chapter 2: Literature Review

2.1 Lotus pedunculatus (syn . Lotus u liginosus . ) 2.2 Plan t component growth pat terns and

iii

Page 1

4 4

relationships . 10

2.2.1 Growth of shoo ts . 11

2.2.1.1 Lotus cornicu latus 11

2.2.1.2 Medicago sativa 12

2.2.1.3 Coroni l la varia 14

2.2.2 Growth of underground organs 15 2.2.2.1 Seasonal effects on underground

organs 15

2.2.2.2 Defoliation effects on

underground organs 16

2.3 Defoliat ion management and herbage dry mat ter

production 17

2.3.1 General concept s 17

2.3.2 Lotus corniculatus 18

2.3.3 Medicago sativa 20

2.3.4 Coroni l la varia 22

2.4 Nonstructural carbohydrates 22

2.4.1 Seasonal changes in nonstructural carbohydrates

2.4.2 Defoliation effects on nonstructural carbohydrates

2.4.3 Nonstructural carbohydrates and plant regrowth

2.5 Carbon partitioning in plants 2.5.1 Carbon distribution 2.5.2 Carbon redistribution

Chapter 3: Morphological characteristics of Lotus peduncu latus cv . 'Grasslands Maku'

3.1 Introduction 3.2 Experimental 3.3 Result s

23 24

25 27 27 29

31 31 32 37

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3.3.1 Underground plant components 3.3.1.1 Primary crown and taproot 3.3 .1.2 Rhizome

3.3.1.3 Fibrous root 3.3.2 Final canopy components

3.3.2.1 Final shoot growth

Page 37 3 9 42 45 46 46 3.3.2.2 Final stubble and \.L!ad matter 48 3.3.3 Final shoot numbers and characteristics 50

3.3.3.1 Stubble shoots 3.3.3.2 Rhizome shoots

3.3.3.3 Rhizome shoot initials

3.3.3.4 Crown shoots and crown shoot initials

3.3.4 Residual shoot numbers

50 52 55

56 56 3.3.4.1 Residual stubble shoot numbers 60 3.3.4.2 Residual rhizome shoot numbers 60 3.3.4.3 Residual crown shoot numbers 61 3.4 Discussion

3.4.1 Underground plant components 3.4.2 Crown and taproot

3.4.3 Rhizome 3.4.4 Fibrous root 3.4.5 Stubble shoots 3.4.6 Rhizome shoots

Chapter 4: Defoliation management and herbage dry matter production of Lotus peduncu la tus cv . 'Grasslands

�1aku'

4.1 Introduction 4.2 Experimental

4.2.1 Experiment 1 4.2.2 Experiment 2 4.3 Results

4.3.1 Experiment 1

61 61 63 64 64 6 7 6 8

71 71 72 72 72 75 75 4.3.1.1 Net herbage production 75 4.3.1.2 Regrowth cycles: (i) spring

regrowth cycle; (ii) summer

regrowth cycle 7 6

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4 .3 .2 Experiment 2 4 . 3 . 2 . 1

4 .3 . 2 .2 4 . 3 . 2 . 3 4 .3 .2 . 4 4 . 3 . 2 .5 4 .3 .2 .6

Treatment Treatment Treatment Treatment Treatment Treatment

RS SAS 6S 61 SAL LS 4 . 3 .3 Winter production of 4 . 4 Discussion

4 . 4 . 1 Stubble shoots 4 . 4 . 2 Rhizome shoots

Experiment

4 . 4 .3 Secondary axillary shoots 4 . 4 . 4 Stubble and dead matter 4 . 4 .5 Leaf area

4 . 4 . 6 Net canopy growth 4 . 4 . 7 Proposed management

1 and 2

Chapter 5: Nonstructural carbohydrate levels in Lo tus peduna- u latus cv . 'Grasslands Maku'

5. 1 Introduction 5 .2 Experimental 5 .3 Results

5 .3 . 1 Experiment 1

5 . 3. 1. 1 Central system total nonstruct

ural carbohydrates

5 . 3 . 1 .2 Peripheral system total non

structural carbohydrates 5 . 3 .2 Experiment 2

5 . 3 .2 . 1 Spring sampling 5 .3 .2.2 Autumn sampling 5 . 4 Discussion

Chapter 6: The importance of several residual plant factors in determining early regrowth in Lotus pedunaulatus cv . 'Grasslands Maku'

6 . 1 Introduction

Page 77 82 86 87 9 1 92 96 97 9 8 9 9 1 0 1 102 1 03 1 04 1 05 1 07

109 109 1 1 0 1 12 112 1 14 1 16

1 1 9 1 1 9 12 1

125 125

V

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6 .2 Experimental 6 .3 Results

6 . 3 .1 Shoot regrowth 6.3 . 2 Shoot ntnnbers

6 .3 .3 Residual leaf area, stubble weight and underground weight

6 .3 . 4 Nonstructural carbohydrate status 6 . 4 Discussion

Chapter 7 The partitioning of

c14

labelled assimilates in defoliated Lotus peduncula tus 'Grasslands ��ku'

7 .1 Introduction 7 .2 Experimental 7 .3 Results

7 .3 .1

c14

Distribution experiment 7 .3 .2

c14

Redistribution experiment 7 . 4 Discussion

7 . 4 .1

c14

Distribution experiment 7 . 4 .2

c14

Redistribution experiment Chapter 8: General Discussion

Acknowledgements Bibliography Appendices

Page 126 128 128 133

137 139 1 4 4

1 50 1 50 1 51 1 54 1 54 160 168 168 171 174

1 82 1 83 1 97

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Table 1

2 3 4 5 6 7

8 9 10 11 12 1 3 1 4 1 5 16 17 1 8 1 9

20

. 21

22 23 24 25

vii LIST or TABLES

Page Plant densities for pre-autumn and post-

winter samplings . 40

Total underground dry weight . 40

Crown plus tapro t dry weight . 4 3

Rhizome dry weight· 4 3

Fibrous root dry weight . 45

Percentage contribution of stubble and rhizome shoots

to final canopy weight . 47

Percentage contribution of stubble and dead matter

to final canopy weight . 49

Number of final stubble shoots . 51

Number of final rhizome shoots . 51

Number of rhizome shoot initials . 55

Number of final crown shoots and crown shoot initials . 58

Residual shoot numbers . 59

Net herbage production in Experiment

1 .

76 Leaf area indices during a spring and summer regrowth

cycle of Experiment 1 . 79

Total and component dry matter production in

Experiment 2 . 81

Net dry matter production during winter in

Experiment 1 and 2. 97

Nonstructural carbohydrate status of the central plant

system in Experiment 1 . 115

Nonstructural carbohydrate status of the peripheral

plant system in Experiment 1 . 117

Nonstructural carbohydrate status of the rhizome and above-ground fractions of the peripheral

system sampled on 6 / 4 /76 . 11 8

TNC concentrations and dry weights of underground

organs during late spring and autumn in Experiment 2. 120 Total, stubble and rhizome shoot dry weights . 129 Shoot dry weight relationships with regrowth time. 132 Individual stubble and rhizome shoot dry weights . 134 Stubble and rhizome shoot numbers . 136 Leaf area of stubble, stubble shoots and rhizome

shoots . 138

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Table 26 27 2 8

2 9 30

31 32 33

34

35

Stubble and total underground dry weights Dry weights of plant components during

regrowth in the

c14

Distributition experiment Specific activities of plant components in the

c14

Distribution experiment

Absolute activity of plant components in the

cl4

Percentage distribution of total plant activit y between components in the

c14

Dry weights of plant components during regrowth in the

c14

Redistribution experiment

Specific activity of plant components in the

c14

Absolutle activity of plant components in the

c14

Percentage distribution of total plant activity between components in the

c14

Activity levels of plant components, as a

percentage of their original activity on day 0,

page 139 1 5 5 1 56 1 57

1 58

161 162 164

165

in the

c14

Redistribution experiment 167

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LIST OF FIGURES Figure

1

A diagramatic representation of the morphology of 'Grasslands Maku', Lotus peduncuZatus .

2 To tal underground weight per plant a t six-weekly

· harvest dates .

3 Net herbage production during a six week spring period in Experimen t 1 .

4 Net herbage production during a six week summer period in Experiment 1 .

5 Componen t dry mat ter yields for treatments RS (A) and SAS (B ) .

6 Shoot numbers and LAI for treatments RS

(h)

and SAS (B ) ^•

7 Component dry mat ter yields for treatments 6S (A) and 61 (B) .

8 Shoot numbers and LAI for treatments 6S (A) and 61 (B ) .

9 Component dry mat ter yields for treatments SAL (A) and LS (B) .

10 Shoo t numbers and LAI for treatments SAL (A) and LS (B ) .

11 TNC status of residual plants following cut ting.

1 2 RGR uf collective to tal (A) , stubble (B ) and rhizome (C) shoo t pools .

13 RGR of individual stubble (A) and rhizome (B ) shoots .

14

Nons tructural carbohydrate levels in stubble shoo ts (A) ; rhizome shoots (B) ; stubble (C) ; rhizome (D ) ;

ix Page

35 38 78 80 84 85 89 90 94

95

113

131 135

and crown plus taproo t (E) ^. 1 4 2 & 143 1 5 Percentage distribution of total plant activity in

collective components of high and low cut plants in the cl4 Distribution experiment

16 Percent age distribution of to tal plant activity in collective components of high and low cut plants in

159

the c14 Redis tribut ion experiment . 166

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Plate 1 .

2 .

3 and 4 .

5 . 6 . 7 .

8 . 9 .

10 .

1 1 .

1 2 . 1 3 . 1 4 .

LIST OF PLATES

A multicrown and taprooted plant linked by woody rhizome growth; considered as one plant

Page

unit. 41

Primary crown and forked taproot; pink crown

shoot initials are also evident . 4 1 Rhizome components: non-woody rhizume; woody

rhizome with a swollen nodal region and concentrated shoot locii; basal portion of a terminal rhizome

shoot. 44

A stubble node possessing three axillary shoots at different stages of development.

Contrasting leaf and stem complements in rhizome shoots and stubble shoots during early regrowth . A rhizome shoot characteristically dominating two stubble shoots and a rhizome shoot with a basal underground portion.

Two rhizome shoots and several rhizome shoot initials at different stages of development.

Early rhizome shoot development ranging from

a leafy orthotropic rhizom� shoot to an underground rhizome shoot initial .

Stages of abnormal rhizome shoot initials;

apical death; subtended axillary bud development;

resumed rhizome shoot initial growth .

A spreading, open plant habit, typical of 9 . 5 cm cutting

(

LF

)

where underground growth was

extensive .

Intermediate plant habit of 5 . 0 cm cutting

(MF).

A compact plant habit resulting from 1 . 5 cm cutting and reduced rhizome expansion

(

^SF

)

^.

A dorsal view indicating concentrated shoot locii at swollen rhizome nodes distant from the crown.

53 5 3

54 54

5 7

65 65 66

66

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L I S T OF APPENDICES

Appendix Page

1

2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3

Percen tage soil mo is ture during 1 9 7 5 / 7 6 for 0-5 cm , 5- 1 5 cm and 1 5-30 cm depths

Met eorological measurements , D . S . I . R , Palmers ton North Res idual and f inal dry mat ter levels o f Experiment 1.

Res idual and f inal leaf area indices o f Experiment 1 . Growth rates in treatment RS

Growth rates in t reatment SAS Growth rat es in trea tment 6S G rowth rates in treatment 61 Growth rates in treatment SAL Growth rates in trea tment LS

Environmental de tails of the controlled c l imates in Experiment 3 and 4 .

Leaf to stem dry weigh t ratios of s tubb l e , s tubb le shoots and rhizome shoots .

Experimental details of the

c14

Redistribution and

1 9 7 1 9 8 199 200 20 1 W 2 2 0 3 204 205 206 207 208

D i s t r ibut ion experiment s . 209

14 To tal plant l eaf area in the

c14

Dis tribution experiment 2 10 1 5 Rhizome and c rown plus taproot TNC in the c14

Redis tribut ion exper iment 2 10

x i