Abstract: Taking grafted and ownroot cucumber (Junlv No.3) plants as test materials, the changes of their leaf Cu/Zn-SOD, Mn-SOD and CAT mRNA relative expression, leaf SOD, Cu/Zn-SOD, Mn-SOD and CAT activities, leaf MDA content, and leaf electrolytic leakage under NaCl stress were studied. The results showed that under NaCl stress, grafted cucumber had a higher relative expression of its leaf Cu/Zn-SOD, Mn-SOD and CAT mRNA, and higher activities of its leaf SOD, Cu/Zn-SOD, Mn-SOD and CAT, compared with ownroot cucumber, which suggested that the higher relative expression of Cu/Zn-SOD, Mn-SOD and CAT mRNA in grafted cucumber leaves resulted in the higher activities of their SOD, Cu/Zn-SOD, Mn-SOD and CAT. With the NaCl stress prolonged, the relative expression of Cu/Zn-SOD, Mn-SOD and CAT mRNA in both grafted and own-root cucumber leaves had an increasing rend, but the changing trend of Cu/Zn-SOD, MnSOD and CAT activities were not the same as that of mRNA, indicating that the activities of SOD and CAT were also regulated by other factors. The leaf MDA content and electrolytic leakage of grafted cucumber were lower than those of ownroot cucumber, suggesting that grafted cucumber had a higher scavenging metabolism, which could decrease oxidative damage and increase its salt-tolerance.

Key words: nitrogen form, NO₃^--N, NH₄⁺-N, yield, quality, nutrient absorption.