砂糖橘夏梢生长对果实糖代谢及脱落的影响

 以8年生‘砂糖橘’（Citrus reticulata Blanco）为试材，研究了夏梢生长对果实糖代谢及脱落的影响。结果表明，夏梢生长诱导果实大量脱落及抑制果实的生长，夏梢萌发生长6 d后落果剧增，9 d时出现落果高峰，相对落果率为7.63% · d^-1，18 d后累积落果率高达94.05%，比去梢对照增加1.58倍。夏梢生长6 d后，果实的蔗糖、还原糖含量加速下降，但18 d后糖含量恢复到去梢果实的水平。随着夏梢的生长，果实中酸性转化酶（AI）、中性转化酶（NI）的活性得到增强，淀粉酶、蔗糖磷酸合成酶（SPS）活性则被抑制，而蔗糖合成酶（SS）活性受影响不明显。因此认为，夏梢生长促进果实蔗糖分解方向的酶活性增加，加速了果实蔗糖的分解，是导致果实脱落的原因之一。

Effects of Summer Shoot Growth on Sugar Metabolism and Abscission of Fruitlet in‘Shatangju’Mandarin

The effects of summer shoot growth on sugar metabolism and abscission of fruitlet in ‘Shatangju’mandarin（Citrus reticulata Blanco）were investigated. The results showed that，summer shoot obviously increased fruitlet abscission and suppressed fruitlet growth. During 18 days of summer shoot growth，the relative abscission rate（RAR）tended to increase and subsequently decrease，with the peak of 7.63% · d^-1 at the 9th day. At the 18th day，the accumulative abscission rate（AAR）in shoot-retained treatment was 94.05%，which was 1.58 times higher than that in shoot-removed treatment. Moreover，summer shoot growth decreased the contents of sucrose and reducing sugar in fruitlet at 6th day，but no significant difference was observed for those between shoot-retained and shoot-removed treatments at 18thday. Furthermore，it was found that summer shoot increased the activities of acid invertase（AI）and neutral invertase（NI），and inhibited those of the amylase and sucrose phosphate synthase（SPS）in fruitlet. However，sucrose synthase（SS）activity was not influenced by summer shoot. Overall，these findings suggest that the accelerated decomposition of sucrose by the increased activities of sucrose degradation enzymes during summer shoot growth contributed to fruitlet abscission in‘Shatangju’mandarin.