夏梢生长条件下树干供糖对‘砂糖橘’幼果糖代谢及脱落的影响

Effects of Trunk Injection Sucrose on Sugar Metabolism and Abscission of Fruitlet in ‘Shatangju’ under Summer Shoot Growth Condition

为探讨碳素营养在柑橘坐果中的作用,以7年生‘砂糖橘’(Citrus reticulata Blanco)为材料,在夏梢生长期采用树干注射蔗糖溶液的方式进行树体供糖处理,分析供糖对幼果糖含量、糖代谢相关酶活性及其脱落的影响。结果表明:夏梢生长促进幼果大量脱落,树干注射蔗糖可促进幼果发育和抑制幼果脱落,花后85d(夏梢生长15d)累积落果率为73.35%,比留梢对照下降10.05%。树干注射蔗糖溶液明显促进幼果中蔗糖、淀粉含量的积累,显著抑制幼果中酸性转化酶(AI)、中性转化酶(NI)活性,而对蔗糖磷酸合成酶(SPS)、蔗糖合成酶(SS)活性影响不明显。据此认为,夏梢生长条件下树干供应蔗糖溶液,通过抑制幼果中蔗糖分解酶(AI和NI)活性的方式促进蔗糖积累,从而有利于坐果。树干供糖并没有显著降低落果率,仅部分抵消夏梢生长对幼果脱落的影响,说明除糖代谢外,同时还存在其他因子参与幼果脱落的调控。

In order to reveal the roles of carbon nutrition on the fruitlet set under summer shoot growth condition of citrus, the experiment of trunk injection sucrose was carried out in 7-year old ‘Shatangju’ mandarin (Citrus reticulata Blanco) trees, and the effects of sugar accumulation, sucrose-related enzyme activities and abscission of the fruitlet were studied during the new shoot period. The results showed that, summer shoot obviously increased abscission of fruitlet, and the injecting of sucrose promoted the growth of fruitlet and decreased abscission. At the 85^th day after full blossom(15th day of summer shoot growth), the accumulative abscission rate (AAR) in trunk injection sucrose was 73.35%, which was 10.05% lower than that in the control. Trunk-injected sucrose obviously increased the contents of sucrose and starch in the fruitlet, accompanied with the inhibition of the activities of acid invertase (AI) and neutral invertase (NI), but no significant difference was observed for the activities of sucrose phosphate synthase (SPS) and sucrose synthase (SS). It suggested that the increased accumulation of sucrose by the inhibited activities of sucrose degradation enzymes (AI and NI) during injecting sucrose contributed to the fruitlet set in ‘Shatangju’ mandarin. The injection of sucrose inhibited the fruitlet abscission during shoot growth, but the exogenous sugar couldn’t fully offset the impact of summer shoot on the fruitlet abscission. Sugar metabolism was not the only factor involved in the fruitlet abscission process caused by summer shoot growth.