水分胁迫期间及胁迫解除后苹果树源叶碳同化物代谢规律的研究

在苹果果实生长早期进行水分胁迫处理，研究水分胁迫期间及胁迫解除之后源叶中的不同种类碳同化物含量及相关酶活性的变化，结果表明，水分胁迫条件下源叶中总可溶性糖和还原糖积累，山梨醇含量升高；前两个干旱胁迫周期源叶中淀粉含量显著降低；水分胁迫对还原糖的影响主要是增加葡萄糖和果糖的含量，葡萄糖含量在中度胁迫时开始增加，严重胁迫时急剧升高，但果糖含量仅在轻度胁迫时显著高于对照，对蔗糖含量的影响较小。水分胁迫解除后，水分胁迫株叶片中除葡萄糖能保持一个显著高于对照的水平外，其余的糖和山梨醇均迅速地回落到正常灌溉的对照水平。同时，树体承受水分胁迫期间，源叶中的6－磷酸醛糖还原酶（A6PR）、山梨醇脱氢酶（SDH）、磷酸蔗糖合成酶（SPS）、蔗糖合成酶（SS）、中性转化酶、酸性转化酶、ADPG焦磷酸化酶（ADPGPPase）和淀粉酶等均有可能得到显著增加，并且水分胁迫解除后各种酶在短期内仍维持一个较高的活性。

Carbohydrate Metabolism in Source Leaves of Jonagold Apple Tree Under Water Stress and After Water Stress Relief

The evolution of carbohydrate and activity of the relative enzymes were studied in source leaves of Jonagold apple trees under water stress and after water stress relief． The results showed that total sugar reducing sugar and sorbitol accumulated in the leaves of the trees applied to water stress when compared with the well irrigated trees． A low level of starch was observed only on the stress trees during the two first periods of water stress． Moreover the content of glucose increased in the leaves of the trees under from a moderate to severe water stress while a high level of fructose was observed only under a slight water stress． However no effect of water stress was observed on the sucrose content in source leaves． An after－effect was obvious only on the content in glucose after removing water stress． A significant high content of glucose could be observed two days after removing water stress on the trees submitted to water stress as compared with the control trees． The activities of aldose－6－phosphate reductase and sucrose phosphate synthase ADPG pyrophosphorylase sorbitol dehydrogenase sucrose synthase neutral invertase and acid invertase might increase under water stress． Activities of some of these enzymes increased with the stress developed while that of others rose only under a severe water stress． This effect was prolonged after water stress relief for the activities of most above enzymes．