外源抗坏血酸对离体苹果叶片衰老的影响

Effects of Exogenous Ascorbic Acid on Senescence of Detached Apple Leaves

以苹果(Malus domesticaBorkh.)品种‘嘎拉’秋梢成熟叶片为试材,在5mmol.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(0～72h)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 AsA on ascorbate zyme for ascorbic acid biosynthesis were investigated glutathione cycle and activity of GalLDH - a key enduring 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 lipid peroxidation and decreased H2 02 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 of monodehydroascorbate reductase （ MDHAR）, and decreased ratio of oxidized glutathione （GSSG） , then increased AsA content and regeneration ability accordingly. However, exogenous AsA inhibited the activity of L-galactono-1, 4-lactone dehydrogenase （GalL- DH） in the beginning of senescence and decreased ability of AsA synthesis, but later maintained higher activity of GalLDH.