Comparison of antioxidant activities and endogenous hormone levels between bush and vine-type tropical pumpkin (Cucurbita moschata Duchesne)

A bush-type plant was selected from a cultivar ‘Cga’ of tropical pumpkin (Cucurbita moschata Duchesne) in order to study and compare the bush and vine habit of C. moschata in terms of various physiological and biochemical characteristics. During the internode development of the bush and vine-type plants in C. moschata, the metabolism of reactive oxygen species (hydrogen peroxide, H2O2; and superoxide anion radical, O2−), the activities of some antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT; and ascorbate peroxidase, APX), and the levels of some endogenous hormones (gibberellin A3, GA3; gibberellin A4, GA4; and indole-3-acetic acid, IAA) were compared. Bush plants were found to have a significantly higher O2− level than vine plants at 28 days after germination (DAG) and onwards. Moreover, there was no significant difference of H2O2 level between the two genotypes until 32 DAG, in which the difference was significant at 32 DAG. In both genotypes, no significant differences of SOD activity were observed, and this was opposite to APX activity in which significant differences were observed during almost the whole sampling stages. What's more, APX activity of bush plants was significantly higher than that of vine plants at 24, 28, 32, and 36 DAG. CAT activity showed the same trend for the two genotypes. Quantitative analysis by enzyme-linked immunosorbent assay (ELISA) indicated that the internodes of bush plants contain lower levels of GA3, IAA, and GA4 than those of vine plants in C. moschata. In addition, GA3 deficiency was also found in the leaves and roots of bush plants. In conclusion, this work provided some new information about different levels of endogenous chemicals in pumpkins with differing growth habits.