‘糯米糍’荔枝碳素营养储备动态与坐果的关系

Seasonal Changes in Carbon Nutrition Reserve in Nuomici Litchi Trees and Its Relation to Fruit Load

以10～12年生的‘糯米糍’荔枝(Litchi chinensis Sonn.)为材料,研究了高产树(60～65kg·株-1)和低产树(5～10kg·株-1)不同部位(叶片、各级枝条和主干)碳素营养储备(淀粉)的差异及季节动态;分析了不同果实发育阶段树体碳素营养水平与坐果率的关系。结果表明,果实成熟时高产树各部位的淀粉含量均低于低产树,而可溶性糖含量高于低产树。果实采收后,低产树早于高产树抽发新梢。入冬季前(11月底前),低产树和高产树分别抽发了3次和2次秋梢。7～11月秋梢生长发育期间,高产树和低产树均无显著淀粉积累,11月中旬以后枝梢生长停滞期间,各部位,尤其是4cm直径以内的枝条大量积累淀粉,在花穗发育前达到高峰。之后,随花穗发育、开花及坐果而持续降低。高产树和低产树各部位淀粉高峰并无明显差异,表明坐果量对树体碳素营养储备的累积并无明显的长期影响。叶片、主枝和主干积累的淀粉含量较低,总体相对稳定;而4cm直径以下的枝梢淀粉含量变化剧烈,说明这些枝梢是更为活跃的碳素储备库。本研究还表明,坐果早期(花后3周内)枝条(2cm直径)的淀粉含量与该枝条上最终坐果率呈显著正相关,而果实发育中期(花后8周)枝条淀粉含量与坐果率无关,说明早期果实发育一定程度依赖树体碳素营养储备,而中后期果实发育几乎不依赖树体储备。

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 long-term 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 during mid 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 at mid to late stages.