Temperature effect on bulb development at the end of the bulb preparation phase and during storage

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Introduction

Lachenalia pot plant production is a fairly new industry in South Africa and in the world and therefore a brief survey of the taxonomy, morphology and ecology will help the reader to obtain a better understanding ofthe rest of this thesis. Furthermore, the research program and production system, which is currently managed by the ARC – Roodeplaat Vegetable and Ornamental Plant Institute in South Africa, will be descrjbed. Finally, the importance of temperature in bulb growth and development will briefly be discussed.

Taxonomy

The genus Lachenalia Jacq.f ex Murray belongs to the family Hyacinthaceae (Duncan,1988) which was previously part of the family Liliaceae, sensu lata (Dahlgren, Clifford and Yeo, 1985). It is the largest genus in the family consisting of approximately 110 species (Duncan, 1988). According to Duncan (1992) a high degree of morphological variation, which exists within several species and the existence of many intermediate forms between related species, as well as the difficulty of identifying distinguishing characteristics that canbe applied to delimit these species, has resulted in problematic taxonomy.

Description

The Lachenalia plant is a small bulbous geophyte. The storage organ is a true bulb with dry membranous tunics, which protect it from drying out and from physical injury. The genus exhibits a variety in leaf number per plant. In some species, the mature bulb produces one to two leaves, while others may produce up to eight leaves. Even in leaf shape the species differ from robust and broad to short and cylindrical.

Production System

Lachenalia varieties are mainly produced in the summer rainfall area where winters are more severe than in natural habitats, although these plants have seldom been lost during cold spells. This production situation developed primarily due to the breeding program that was conducted at ARC – Roodeplaat, which is situated in the proximity of the majority of flower and bulb growers in South Africa.

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CHAPTER 1
1.1 Taxonomy
1.2 Description
1.3 Distribution and Habitat
1.4 Establishment of the Lachenalia research program
1.5 Production system
1.6 Influence of temperature on bulb growth and development
1.7 The aimof this study
1.8 References
CHAPTER 2
2.1 Summary
2.2 Introduction
2.3 Materials andMethods
2.4 Results and Discussion
2.4.1 Bulb growth
2.4.2 Bulb structure
2.5 Conclusion
2.6 References
3.1 Summary
3.2 Introduction
3.3 Materials andMethods ,
3.4 Results and Discussion
3.4.1 Bulb growth
3.4.2 Root growth
3.4.3 Leaf growth
3.4.4 Whole plant growth
3.4.5 Growth of inflorescences
CHAPTER 3
3.5 Conclusion
3.6 References
CHAPTER 4 Temperature effect on bulb development at the end of the bulb preparation phase and during storage
4.1 Summary
4.2 Introduction
4.3 Materials andMethods
4.4 Results and Discussion
4.5 Conclusion
4.6 References
CHAPTER 5
5.1 Summary
5.2 Introduction
5.3 Materials andMethods
5.4 Results and Discussion
5.4.1 Starch
5.4.2 Soluble sugars
5.5 Conclusion
5.6 References
CHAPTER 6
6.1 Summary
6.2 Introduction
6.3 Materials andMethods
6.3.1 Flower quality
6.3.2 Plant quality
6.4 Results and Discussion
6.4.1 Planting and flowering date
6.4.2 Flower quality
6.4.3 Number of inflorescences
6.4.4 Keeping abilityof the inflorescences
6.4.5 Leaf quality
6.4.6 Spotting on leaves
6.4.7 Bulbs
6.4.8 Roots
6.5 Conclusion
6.6 References
CHAPTER 7
7.1 Summary
7.2 Introduction
7.3 Materials andMethods
7.4 Results and Discussion
7.4.1 Bulb fresh mass and size versus quality and keeping ability of pot plant
7.4.2 Leaf number and total leaf area versus number of inflorescences
7.5 Conclusion
7.6 References