Differences of Leaf Antioxidant Enzymes Activitiesand Root Vigor of Melon Seedlings under Cadmium Stress
This study explored the changes of antioxidant enzymeactivities and rootvigor in different melon seedling leaves under cadmium(Cd)stress so as to provide references for selecting Cd-resistant melon germplasm.Wild,thin-skinned and thick-skinned melons were used as experimental materials.After cultivation with different concentrations of cadmium solutions during the seedling stage,the variations in enzyme activity and root vigor in the leaves of different melon seedlings were detected.Results showed that under cadmium stress,the activities of SOD,POD,CAT,and APX in melon seedling leaves were all lower than the control without added Cd??.As the Cd??concentration increased,the SOD activity in thin-skinned and thick-skinned melon seedlings decreased significantly,while the SOD activity in wild melon seedlings slightly increased.At medium to high Cd??concentrations(50 to 100 mg/L),the SOD activity in wild melon seedling leaves was the highest,and the SOD activity in thin-skinned melon seedlings was the lowest.Under all treatments,the POD activity in wild melon seedling leaves was the highest,and that in thin-skinned melon seedlings was the lowest.With the increasing concentration of Cd2+stress,the POD activity in the leaves of different melon materials decreased,but the decrease was not significant.When the Cd2+concentration was 0 mg/L,the CAT activity in thin-skinned melon seedling leaves was the highest,while that in wild melon seedlings was the lowest.As the Cd2+concentration increased,the CAT activity in thin-skinned melon seedling leaves decreased the most.Under all treatments,the APX activity in wild melon seedling leaves was the highest,and the APX activity in thin-skinned melon seedling leaves was the lowest.The APX activity in wild melon seedling leaves decreased significantly with increasing Cd2+concentration.When the Cd2+stress concentration was 0 mg/L,the Pro content in wild melon seedling leaves was the lowest,and that in thin-skinned melon seedling leaves was the highest.As the Cd2+concentration increased,the Pro content in wild melon seedling leaves showed no significant change,while the Pro content in thin-skinned melon steadily decreased,and in thick-skinned melon,it decreased initially,then slightly increased,and decreased again.Under all treatments,the MDA content in thick-skinned melon seedling leaves was the highest.As the Cd??stress concentration increased,the MDA content in wild melon seedling leaves showed a decreasing and then increasing trend,while the MDA content in thin-skinned melon steadily decreased,and that in thick-skinned melon increased initially,then decreased,and slightly increased again.At the same Cd concentration,wild melon exhibited the strongest root vigor,while thin-skinned melon showed the largest decrease in root vigor.It can be concluded that under cadmium stress,thin-skinned melon seedlings showed the largest decrease in enzyme activity,followed by thick-skinned melon,while wild melon seedlings exhibited a relatively smaller decrease.Furthermore,wild melon consistently showed the strongest root vigor under all treatments,indicating that thin-skinned melon is more sensitive to cadmium stress,while wild melon has stronger cadmium resistance compared to thick-skinned and thin-skinned melons.
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