Influence of abiotic stress on allelopathic properties of Amaranthus cruentus L. by INGRID ...

155 Pages·2016·2.43 MB·English

by  Ingrid Allemann

Influence of abiotic stress on allelopathic properties of
Amaranthus cruentus L.
by
INGRID ALLEMANN

Submitted in fulfilment of the requirements for the degree
Magister Scientiae
in the
Faculty of Natural and Agricultural Sciences
Department of Plant Sciences
University of the Free State
Bloemfontein
JUNE 2016

Supervisor: Co-supervisor:
Dr M.E. Cawood Dr J. Allemann
Department of Plant Sciences Department of Soil, Crop and Climate
Sciences
UFS UFS
Declaration

I declare that the dissertation hereby submitted by me for the MSc degree at the
University of the Free State is my own independent work and has not previously
been submitted by me at another university/faculty.
I further more cede copyright of the dissertation in favour of the University of the
Free State.
Acknowledgements

 I would like to thank the Dean’s office (Faculty of Natural and Agricultural
Sciences) for funding to help me complete my studies.
 I am sincerely indebted to Dr M.E. Cawood and Dr J. Allemann for their
supervision, guidance, patience and helpful criticism throughout my study.
 My gratitude also goes to the Department of Agriculture, University of the Free
State, South Africa, for providing the climate controlled chambers and help
with getting soil that was used in this study.
 I thank Prof. W. Swart, Plant Pathology, for allowing me to use part of his
laboratory for my experiments.
 I thank Dr A. Biljon, Plant Breeding, for giving me a helping hand with
understanding the HPLC.
 I am deeply grateful to my family members, especially my mom Anette and
dad James, my two sisters Melanie and Elaine, my brother in law Jac, my
Ouma and Oupa, Uncle, Aunt and two nieces, for their unconditional love and
encouragement and always listening to me complain. I love you all.
 To all my friends in the department for always helping and lending a shoulder
to cry on. All the best to you all.
 En die beste vir laaste Andri en Linde. My twee beste pelle in die wêreld. As
dit nie vir julle was nie so ek nooit klaar gemaak het nie. Ek is baie lief vir julle.
Table of contents

Chapter 1: Introduction and rationale
1.1 Introduction 1
Objectives 3
References 4
Chapter 2: Literature review
2.1 Amaranthus 7
2.1.1 General 7
2.1.2 Origin and history 8
2.1.3 Environment 10
2.1.4 Uses of the genus Amaranthus 11
2.1.4.1 As a food crop 11

2.1.4.2 Medicinal uses 14

2.1.5 Amaranthus cruentus 15
2.2 Phytochemistry 16
2.2.1 Chemical composition of amaranth 17
2.2.1.1 Carotenoids 17
2.2.1.2 Phenolic compounds 19
2.2.1.3 Steroids 21
2.2.1.4 Terpenoids 21
2.2.1.5 Ascorbic acid 21
2.2.1.6 Betacyanins 22
2.2.1.7 Alpha spinasterol 22
2.2.1.8 Spinoside, Amaranthoside and Amaracine 22
2.2.1.9 Antioxidant nutrients 22
2.3 Allelopathy 23
2.3.1 Amaranth allelopathy 28
2.4 Effect on agriculture 31
2.4.1 Crop rotation 32
2.5 Environmental factors 33
2.5.1 Abiotic factors 33
2.5.1.1 Temperature 34
2.5.1.2 Water 34
2.5.1.3 Light 36
2.5.2 Biotic factors 36
2.5.2.1 Pathogens 37
2.5.2.2 Herbivores 37
2.6. Vegetables 38
2.6.1 Pepper (Capsicum annuum L.) 38
2.6.2 Tomato (Solanum lycopersicum L.) 38
2.6.3 Lettuce (Lactuca sativa L.) 38
2.6.4 Cucumber (Cucumis sativus L.) 39
References 40
Chapter 3: Materials and methods
3.1 Materials 62
3.1.1 Plant material 62

3.1.2 Other materials 62

3.2 Methods 63

T3.e2r.i1a lT emperature stress treatment 63
3.2.2 Preparation of crude plant extracts 63
3.2.3 Total phenolic concentration 63
3.2.4 Total flavonoids 64
3.2.5. Chromatography techniques 64
3.2.5.1 Thin Layer Chromatography 64
3.2.5.2 Antioxidant and antibacterial activity 65

3.2.5.3 High Pressure Liquid Chromatograph 65
3.2.5.4 Gas Chromatography and Mass Spectrometry 66
3.2.6 Allelopathy 66
3.2.6.1 Leaf litter 67
3.2.6.2 Extracts 67
3.2.6.3 Growth conditions and growth measurement 67
3.2.7 Statistical analysis 68
References 69
Chapter 4: Results and discussion
4.1 Plant survival and yield after temperature stress treatment 71
4.2 Extraction of plant material 73
4.3 Total phenolic and flavonoid concentration 75
4.4 Chromatography 76
4.4.1 Thin Layer Chromatography 76
4.4.1.1 DPPH antioxidant activity 82
4.4.1.2 Antibacterial activity 83
4.4.2 High Pressure Liquid Chromatography 84
4.4.3 Gas chromatography and mass spectrometry analysis 89

4.5 Allelopathy 95
4.5.1 Phytotoxicity of plant litter 95
4.5.1.1 Germination percentage 95
4.5.1.2 Hypocotyl length 99
4.5.1.3 Radicle length 102
4.5.2 Phytotoxicity of extracts 106
4.5.2.1 Germination percentage 106
4.5.2.2 Hypocotyl length 108
4.5.2.3 Radicle length 110
References 113
Chapter 5: General discussion and conclusion
5.1 General discussion and conclusion 122
5.2 Survival and chemical composition 122

5.2.1 Optimal temperature 122
5.2.2 Heat stress 123

5.2.3 Cold stress 124

5.3 Phytotoxicity 125

5.3.1 Germination percentage 125

5.3.2 Hypocotyl length 126

5.3.3 Radicle length 127

References 129
Summary 131
Opsomming 134
Dr J Allemann
List of
Tables & Figures
List of Tables

CHAPTER 2
Table 2.1: Species of amaranth, their origin and use.
9
Table 2.2: Composition of species of grain amaranths.
13
CHAPTER 4

Table 4.1: Total and percentage surviving A. cruentus plants at cold
71
(14/7°C), optimum (28/21°C) and hot (40/33°C) temperatures.

Table 4.2: Influence of temperature on total fresh and dry leaf yield, leaf
72
yield per plant as well as percentage water in fresh leaves.

Table 4.3: Plant extracts recovery obtained by different solvents.
74
Table 4.4: Total phenolic and flavonoid compounds in temperature
75
stressed amaranth leaf material.

Table 4.5: Colour and R values of compounds in the methanol-water leaf
f

extracts of the different temperature treated A.cruentus plants,
79

visualised by p-anisaldehyde spray reagent on TLC.

Table 4.6: Colour and R values of compounds in the DCM leaf extracts of
f

the different temperature treated A.cruentus plants, visualised
81
by p-anisaldehyde spray reagent on TLC.
Table 4.7: GC-MS results of compounds present in optimal temperature

92
treated DCM leaf extract of A. cruentus.

Table 4.8: GC-MS results of compounds present in cold temperature
93
treated DCM leaf extract of A. cruentus.
Table 4.9: GC-MS results of compounds present in hot temperature
94
treated DCM leaf extract of A. cruentus.
i