Pg. 20-23 Seasonal changes in starch reserves in litchi, cv. HLH Mauritius

Like in all woody plants, carbohydrates are also important in the growth of litchi trees. There are strong seasonal influences in carbohydrate reserves which reflect the growth stages of a tree, such as vegetative shooting, flowering and fruit growth. The starch reserves of HLH Mauritius litchi trees were determined as part of an orchard management program. Wood samples from the main branches of trees of various treatments were taken up to ten times a year according to certain phenological stages of the trees. Starch content varied from year to year and within a year, reflecting alternate bearing and tree phenology. Vegetative growth, flower panicle development and rapid fruit growth resulted in reduced starch reserves, whereas rest phases, such as the period prior to flower panicle development and periods between vegetative flushing, caused starch reserves to increase again.

Summary:

• Carbohydrates, especially starch, are vital for the growth stages of litchi trees, such as vegetative growth, flowering, and fruit development.
• Starch reserves in HLH Mauritius litchi trees show strong seasonal fluctuations reflecting tree phenology and alternate bearing patterns.
• Starch levels decrease during periods of vegetative growth, flower panicle development, and rapid fruit growth, while they increase during rest phases such as before flower panicle emergence and between vegetative flushes.
• Study conducted on 18-year-old HLH Mauritius trees in Nelspruit from 2005 to 2009 as part of an integrated orchard management program.
• Wood core samples were taken multiple times per year from main branches to analyze starch content in relation to key phenological stages.
• Starch content varied both within and between years, influenced by crop load (on-year versus off-year) and phenological growth.
• High yields deplete starch reserves post-harvest, while low yields allow starch recovery during late fruit development.
• Efficient control of post-harvest vegetative flush, such as by using Ethepon, influences starch dynamics and crop yield.
• Flower initiation and early panicle development are associated with starch accumulation, while flowering causes slight starch depletion likely due to combined demand and lower photosynthesis from environmental stress.
• Rapid fruit growth between September and November significantly reduces starch reserves, with higher crop loads causing greater depletion.
• Alternate bearing impacts starch reserve levels, with lower reserves observed after high yield years.
• Orchard management practices such as flush control, irrigation, fertilization, and pruning can help manage starch reserves to support critical growth stages.
• Further research is needed to clarify if starch levels at specific times can predict crop size.