外源抗坏血酸对离体苹果叶片衰老的影响

 以苹果(Malus domestica Borkh. ) 品种‘嘎拉’秋梢成熟叶片为试材, 在5 mmol·L ^{- 1}抗坏血酸(AsA) 培养条件下, 研究了外源AsA 对离体苹果叶片衰老过程( 0 ～72 h) 中抗坏血酸—谷胱甘肽(AsA - GSH) 循环各组分和AsA合成关键酶L - 半乳糖酸- 1, 4 - 内酯脱氢酶(GalLDH) 的影响。结果表明, 外源AsA部分抑制了离体苹果叶片衰老过程中膜脂过氧化, 降低了H2O2含量, 但对表示膜损伤的相对膜透性影响不大。对AsA - GSH循环各组分来说, 外源AsA维持了叶片衰老过程中抗坏血酸过氧化物酶(APX) 和脱氢抗坏血酸还原酶(DAHR) 的高活性, 部分抑制了单脱氢抗坏血酸还原酶(MDHAR) 活性的下降, 同时降低了GSH的氧化程度, 从而提高了AsA含量和再生能力。外源AsA 在衰老前期抑制了GalLDH活性, 降低了AsA的合成能力, 而后期维持了GalLDH的高活性。

Effects of Exogenous Ascorbic Acid on Senescence of Detached Apple Leaves

Effects of exogenousAsA on ascorbate glutathione cycle and activity of GalLDH - akey enzyme for ascorbic acid biosynthesis were investigated during senescence of detached leaves of apple (Malus domestica Borkh. ‘Gala’) in this paper. The results showed that 5 mmol·L ^{- 1} exogenous AsA inhibited partially membrane lip id peroxidation and decreased H₂O₂ content, but had little effect on relative membrane permeability. Exogenous AsA maintained high activities of ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR) , but inhibited partially the activity decline ofmonodehydroascorbate reductase (MDHAR) ,and decreased ratio of oxidized glutathione (GSSG) , then increased AsA content and regeneration ability accordingly. However, exogenousAsA inhibited the activity of L-galactono-1, 4-lactone dehydrogenase ( GalLDH) in the beginning of senescence and decreased ability ofAsA synthesis, but latermaintained higher activity of GalLDH.