低温胁迫对嫁接黄瓜叶片抗坏血酸-谷胱甘肽循环的影响

 为了探讨嫁接增强黄瓜抗冷性的分子机制，本试验以黑籽南瓜为砧木，‘津绿3号’黄瓜为接穗，对低温胁迫下嫁接和自嫁黄瓜幼苗叶片抗坏血酸-谷胱甘肽循环中抗氧化酶基因的表达和相关酶活性及AsA、GSH和 H₂0₂含量变化进行了研究。结果表明: 低温胁迫下, 嫁接黄瓜叶片DHAR mRNA和GR mRNA相对表达量均大于自嫁黄瓜，GalLDH mRNA和APX mRNA相对表达量均与自嫁黄瓜差异无显著差异； DHAR、GR、GalLDH和APX活性均高于自嫁黄瓜；AsA和GSH含量与AsA/DHA和GSH/GSSG比值均高于自嫁黄瓜， DHA、GSSG和H₂O₂含量均低于自嫁黄瓜。嫁接黄瓜叶片DHAR和GR较高的转录水平维持的较高DHAR和GR活性是AsA和GSH含量明显高于自嫁黄瓜的重要原因， 而嫁接黄瓜叶片较高的GalLDH和APX活性与GalLDH mRNA和APX mRNA相对表达量无关。

Effects of Low-temperature Stress on the Ascorbate-glutahione Cycle in the Grafted Cucumber Leaves

To make clear the intrinsic mechanism of cold resistance of grafted cucumber，changes of relative expression and activities of antioxidant enzymes in the AsA-GSH circle and the contents of AsA, GSH and H₂0₂ were tested in the leaves of either own-root cucumber (Junlv No. 3) or grafted plants where cucumber (Junlv No. 3) was grafted on black-seed pumpkin. Both plants were treated under low-temperature stress. The results showed that, under low-temperature stress, the relative expressions of DHAR, and GR mRNA were all higher in the leaves of grafted cucumber than that of own-root cucumber, while no significant changes were found in the relative expressions of GalLDH and APX mRNA; the contents of AsA, GSH and the ratio of AsA/DHA, GSH/GSSG were all higher in grafted cucumber than that of own-root cucumber, while the contents of DHA, GSSG and H₂O₂ were all lower. We concluded that the higher activities of DHAR and GR, which were from the higher relative expression of DHAR and GR mRNA, were mainly responsible for the higher contents of ASA and GSH in the grafted cucumber leaves. But the higher activities of GalLDH and APX have nothing to do with the relative expression of GalLDH and APX.