The role of indole-3 acetic acid and acid invertase in the development of melon (Cucumis melo L. cv. Prince) fruit

Changes in indole-3-acetic acid (IAA) contents of melon (Cucumis melo L. cv. Prince) fruits were plotted during their developmental stages. The IAA content of mesocarp was almost constant during fruit development but that of seeds increased for 20 days after pollination, then decreased significantly. Hence, seeds contained much more IAA than the mesocarp throughout fruit development. The seeds may effuse IAA to the enlarging mesocarp, so that its IAA content remain constant. Exogenous application of IAA on the activities of sucrose-metabolizing enzymes, which are closely related to the sink activity of fruits, stimulated activities of the cell wall bound and soluble acid invertases, but not those of sucrose and sucrose phosphate synthases. Thus, endogenous IAA may play an important rule in the induction of cell wall bound and soluble acid invertases. We postulate that exported IAA from seeds to mesocarp stimulate cell wall bound and soluble acid invertase activities, thereby strengthening its sink activity during fruit development.