Hormonal Changes in Developing Fruits of Seedless Mutant of Watermelon

Seedless plants '406S' and seeded plants '406F',offsprings of a radiated mutant '406' were taken as materials.With the method of morphology and ELISA,the dynamic changes of the fruit growth of watermelon were studied as well as the endogenous hormones in pulp and seed.The results showed that the vertical and horizontal diameter of two types fruits presented similar changes as single S-curves with'slow-quick-slow'growth patterns,while the fruit weight and seed growth are different.The '406S' fruit weight increased with constant rate relatively,and its seeds degenerated in 15 days after pollination(DAP) following the size and weight decreased,whereas the fruit weight of '406F' changed'quick-slow-quick'like double S-curve,with seed size and quality increased rapidly at developmental stages.Furthermore,the value and the peaks of hormones in seedless and seeded fruits differ during its growth period.'406S' pulp contained high contents of ZRs and GAs in 0～3 DAP and high IAA in 3～15 DAP.However,'406F' pulp contained high contents of ZRs and GAs in 6～21 DAP,and the changes of GAs coincided with the development of fruit shape.During seed development,the levels of IAA,GAs,ZRs in the seeds of '406S' were relatively low,except the ABA content increased larger with the degradation process of seeds,but they were all high and fluctuated greatly at different developing period in '406F'.In conclusion,the results indicated that the mechanism of fruit development of seedless and seeded watermelon varied,the four types hormones in pulp of '406S' and '406F' made greater impact on the fruit weight than that on the fruit shape.The endogenous hormones in seeds were related closely to the growth and development of itself,but for abortive seeds of seedless watermelon,it did not affect the fruit development.