Activities of Antioxidant Enzymes and Photosynthetic Characteristics in Grafted Watermelon Seedlings under NaCl Stress

The changes of protective enzyme activities,lipid peroxidation and photosynthetic characteristics were studied in grafted and own-root watermelon seedlings under NaCl stress using calabash cultivar 'Chaofengkangshengwang' as stock and salt intolerant watermelon 'Xiuli' as control.The results showed that the growth of both grafted seedlings and own-root seedlings were significantly decreased.Although the photosynthesis of grafted and own-root seedlings were suppressed under NaCl stress,the performance of the grafted seedlings were superior to that of own-root seedlings in net photosynthetic rate,stomatal conductance,intercellular CO2 concentration,transpiration rate and chlorophyll contents.Besides,the activities of superoxide dismutase(SOD),peroxidase(POD),and catalase(CAT) in leaves of grafted seedlings were significantly higher than those of own-root seedlings.Malondiadehyde(MDA) content in leaves of grafted seedlings was significantly lower than that in own-root seedlings.The results suggested the grafted watermelon seedlings had the well salt tolerance by obtaining higher activities of antioxidative enzymes to scavenge active oxygen specie(ROS) and therefore reducing oxidative damage and keeping higher photosynthetic rate to increase tolerance of NaCl stress in grafted seedling.