Abstract: Ten to twelve years old litchi (Litchi chinensis Sonn. ‘Nuomici’) trees with different fruit loads (60 - 65 kg·tree^{- 1} vs 5 - 10 kg·tree^{- 1} ) were used to investigate the seasonal changes in carbon nutrition reserve ( starch) in different above-ground parts, and to examine the correlation between tree carbon nutrition reserve and fruit set. The results showed that, at harvest, starch concentrations in different tree parts were all lower in the high-yield trees than in the low-yield trees, while sugar concentration showed an opposite trend. After harvest, the low-yield trees produced flush earlier than the high-yield trees. By the late November, when the trees entered growth check status, low-yield trees and high-yield trees had undergone 3 and 2
cycles of flush growth respectively. From July to November, during the flush growth period, there was no marked accumulation of starch in various parts of both low- and high- yield trees. After mid-November, starch accumulated significantly in various tree parts, especially in shoots and branches with diameter no larger than 4 cm. Starch concentration peaked prior to and decreased with panicle development from mid-Juanuary. The decline continued with blooming and fruit set. There was no significant difference in starch concentration at the peak period in various parts between the low- and the high-yield trees, suggesting that fruit load had no longterm effect in carbon nutrition reserve recharge during autumn and winter. Starch concentration was relatively low and constant in the leaf, the main branches and the trunk, while that in branches no thicker than 4 cm in diameter showed significant changes, indicating the medium to small branches played a more active role in carbon nutrition reservation and mobilization. The study also showed that starch concentration in small branches (2 cm in diameter) during early fruit set (within 3 weeks after bloom) had a significant positive correlation with final fruit set on the branches, whereas branch starch concentration duringmid fruit development stage (8 weeks after bloom) had no significant correlation with final fruit set, indicating that fruit development at early stages depend more on tree carbon nutrition reserve than atmid to late stages

Key words: litchi, carbon nutrition, tree reserve, fruit set