Abstract:This paper studied the relative expression of Mn-SOD, Cu/Zn-SOD and CAT mRNAs and the changes of SOD, Mn-SOD, Cu/Zn-SOD and CAT activities in grafted and own-rooted cucumber leaves under low temperature stress, and their relation s with the cold resistance of cucumber. For both grafted and own-rooted cucumbe r leaves, the relative expression of Mn-SOD and Cu/Zn-SOD mRNAs under low temp erature stress was respectively accordance with the changes of Mn-SOD and Cu/Zn -SOD activities, while the expression of CAT mRNA was not accordance with the c hange of CAT activity. The relative expression of Mn-SOD and Cu/Zn-SOD mRNAs a nd the activities of SOD, Mn-SOD and Cu/Zn-SOD in grafted cucumber leaves were higher than those in own-rooted cucumber leaves, while the MDA content and ele ctrolytic leakage were in adverse. The higher SOD activity regulated by the high er SOD mRNAs expression in grafted cucumber leaves might be the key factor of gr afted cucumber having a higher cold resistance to low temperature stress than ow n-rooted cucumber. The relative expression of CAT mRNA was slightly higher in f unctional leaves but lower in young leaves of grafted cucumber, while less diffe rence was observed in CAT activity, comparing with own-rooted cucumber, which i llustrated that low temperature stress had lesser effects on the relative expres sion of CAT mRNA and the activity of CAT in grafted cucumber leaves.