Abstract:

Watermelon male sterile line Se18 was used as the testing material，changes in antioxidant
enzymes activities and endogenous hormones contents in the lamina and flower bud of this line were
studied. The results showed that the activities of SOD and POD in sterile watermelon plants were markedly increased，while the activity of CAT was declined. However，the activity of CAT in fertile
watermelon plants was markedly increased，while the activities of SOD and POD were declined.
Moreover，the contents of IAA，ABA，GA3，ZR，JA，BR and IPA exhibited different variation trends
between sterile and fertile plants throughout the whole male flow buds development stage，and the
difference in contents between them was also significant at each stage. The declining of IAA，GA3，BR and
IPA contents and rising of JA content might be closely connected with the occurrence of watermelon male
sterility. But the declining of JA，BR，GA3 and IPA contents and rising of IAA and ZR contents in fertile
watermelon plants. Significant declining of IAA，ZR and BR and distinctive rising of ABA and JA contents
in the lamina of sterile plants were observed. Inconsistent variation trend was found in terms of
IAA/ABA，IAA/GA3，IAA/JA，IAA/ZR，IAA/BR，IAA/IPA，ABA/GA3 and ABA/ZR between the male
sterile and fertile plants and the difference was great. Therefore，we speculated that the changes in
antioxidative enzymes activities and abnormal endogenous hormones levels might be responsible for the
occurrence of male sterility in watermelon.

Key words: watermelon, recessive nuclear male sterility, bud, antioxidant enzyme, endogenous
hormone