Ecophysiological Studies and Tree Manipulation for Maximisation of Yield Potential in Avocado (Persea Americana Mill.)

Anthony W. Whiley. 1994. ECOPHYSIOLOGICAL STUDIES AND TREE MANIPULATION FOR MAXIMISATION OF YIELD POTENTIAL IN AVOCADO (Persea americana Mill.). PhD. Thesis. Department of Horticultural Science. University of Natal. Pietermaritzburg, South Africa. 175 pages.

TABLE OF CONTENTS

ABSTRACT		i
DECLARATION		iii
ACKNOWLEDGMENTS		iv
INTRODUCTION		1
UNIT ABBREVIATIONS		4
CHAPTER
1. LITERATURE REVIEW		5
	1. 1 ENVIRONMENTAL PHYSIOLOGY	5
	1. 1. 1 Irradiance	6
	1. 1. 2 Temperature	9
	1. 2 CARBOHYDRATE CYCLING IN TREE FRUIT CROPS	12
	1. 3 AVOCADO AND TRUNK-INJECTED PHOSPHONATES	14
2. PHENO/PHYSIOLOGICAL MODELS		18
	2. 1 AVOCADO PHENOLOGY	19
	2. 2 INTEGRATION OF PHYSIOLOGY WITH PHENOLOGY MODELS	22
	2. 2. 1 Introduction	22
	2. 2. 2 Methods and Materials	22
	2. 2. 3 Results and Discussion	28
3. LEAF AND SHOOT PHYSIOLOGY IN RELATION TO CO₂ ASSIMILATION AND FRUIT RETENTION		42
	3. 1 DYNAMICS OF GROWTH AND CO₂ ASSIMILATION OF THE FRUITING SPRING SHOOT	42
	3. 1. 1 Introduction	42
	3. 1. 2 Materials and Methods	43
	3. 1. 3 Results	44
	3. 2 CO₂ ASSIMILATION OF CV. HASS LEAVES IN RELATION TO IRRADIANCE, CO₂ PARTIAL PRESSURES AND TEMPERATURES	48
	3. 2. 1 Introduction	48
	3. 2. 2 Materials and Methods	50
	3. 2. 3 Results	52
	3. 3 EFFECT OF PRE-ANTHESIS DEFOLIATION OF TREES AND THE INFLUENCE OF INDETERMINATE INFLORESCENCES ON FRUIT RETENTION	58
	3. 3. 1 Introduction	58
	3. 3. 2 Materials and Methods	59
	3. 3. 3 Results	60
	3. 3. 4 Discussion	63
4. GAS EXCHANGE OF DEVELOPING FRUIT		72
	4. 1 CARBON DIOXIDE EXCHANGE OF DEVELOPING FRUIT	72
	4. 1. 1 Introduction	72
	4. 1. 2 Materials and Methods	73
	4. 1. 3 Results	75
	4. 1. 4 Discussion	79
	4. 1. 5 Conclusion	81
5. CARBON PARTITIONING IN CONTAINER-GROWN AVOCADO TREES		83
	5. 1 ¹⁴C-PHOTOSYNTHATE PARTITIONING IN AVOCADO TREES AS INFLUENCED BY SHOOT DEVELOPMENT	83
	5. 1. 1 Introduction	83
	5. 1. 2 Materials and Methods	84
	5. 1. 3 Results and Discussion	86
	5. 1. 4 Conclusions	88
6. FRUIT SIZE, YIELD AND STARCH CYCLING IN RELATION TO DELAYED HARVEST OF EARLY AND LATE MATURING AVOCADO CULTIVARS		90
	6. 1 EFFECT OF DELAYED HARVEST ON SUBSEQUENT AND FRUIT SIZE OF EARLY (‘Fuerte’) AND LATE (‘Hass’)YIELD MATURING AVOCADO CULTIVARS	90
	6. 1. 1 Introduction	90
	6. 1. 2 Materials and Methods	91
	6. 1. 3 Results	94
	6. 1. 4 Discussion	108
	6. 1. 5 Conclusions	113
7. TRANSLATION OF PHENO/PHYSIOLOGICAL RESEARCH INTO MANAGEMENT STRATEGIES		114
	7. 1 CONTROL OF PHYTOPHTHORA ROOT ROT WITH TRUNK-INJECTED PHOSPHONATE	114
	7. 1. 1 Introduction	114
	7. 1. 2 Materials and Methods	116
	7. 1. 3 Results and Discussion	119
	7. 1. 4 Conclusions	128
	7. 2 EFFECT OF SPRING APPLIED NITROGEN AND PACLOBUTRAZOL ON ‘HASS’ YIELD AND FRUIT SIZE	129
	7. 2. 1 Introduction	129
	7. 2. 2 Materials and Methods	130
	7. 2. 3 Results and Discussion	134
	7. 2. 4 Conclusions	141
GENERAL DISCUSSION AND CONCLUSION		142
SUMMARY		150
LITERATURE CITED		157
APPENDICES		175