The Effects of Silver Nitrate and Ethrel on the Flower Sex Expression in Balsam Pear (Momordica charantia L.) ‘Abashi’

Abstract

We examined the effect of ethylene on sex differentiation in balsam pear (Momordica charantia L.) flowers, two cultivars ‘Abashi’ and ‘Chofuku’ (only autumn cropping) with different pistillate flower differentiation characteristics were treated with silver nitrate (AgNO₃) and ethrel. AgNO₃ induced hermaphroditic flower differentiation in the main vines of ‘Chofuku’ near the 20th node. The concentration and the frequency of treatment were correlated with hermaphroditic sex differentiation. Frequent treatments with high concentrations of AgNO₃ inhibited ethylene action in the plants. AgNO₃ had no effect on pistillate flower differentiation in the spring cropping of ‘Abashi’, but increased the number of pistillate flowers in the fall cropping when applied at high concentrations. Repeated high concentration applications markedly increased the effect. Treatment with low concentrations of ethrel tended to lower the position of pistillate flower nodes in ‘Abashi’. Repeated treatment with low concentrations of ethrel somewhat increased the ratio of pistillate flower differentiation in the main vines, and a single low concentration treatment of ethrel somewhat increased the ratio in secondary vines. However, the ratio remained low near the 15^th node and above. Sensitivity to AgNO₃ thus varies by cultivar and by season. As well the effect of ethrel on flower bud sex differentiation was less pronounced in balsam pear than in other Cucurbitiaceae, suggesting that balsam pear is unusually sensitivity to ethylene.