Abstract:

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.

Key words: grafted cucumber, low-temperature stress, AsA-GSH cycle, relative expression, activity