Effect of Ethylene Inhibitor 1-MCP (Methyl Cyclopropene) On Soybean Flower and Pod Abortion Under High Temperature Stress.

In soybean high temperature stress causes early senescence of leaves and abortion of flower, and pods through enhanced ethylene level. Thus, we hypothesize that foliar application of ethylene inhibitor (1-MCP) can alter leaf senescence and flower and pod abortion. The objectives of this research was to determine the effect of ethylene inhibitor on physiological and biochemical traits associated with leaf senescence, flower and pod abortion under ambient and high temperatures. Soybean cultivars K03-2897 and LS03-4993 were grown up to full bloom at optimum temperature (28/18ºC). At full bloom one half of plants in each genotype were exposed to 1000 ppb of 1-MCP gas for 5 hours. Each set of treated and untreated plants were exposed to optimum or high temperature stress (38/28ºC). The high temperature stress treatment was imposed for 14 d after exposure to 1-MCP. During the stress and recovery data on physiological and biochemical parameters, flower abscission and pod set were recorded. Exposure to high temperature stress decreased photosynthetic rate, stomatal conductance, chlorophylls content and Fv/Fm ratio by about 19, 12, 20, 5 and 7%, respectively, compared to optimum temperature. High temperature stress significantly increased flower and pod abscission and decreased pod-set (by 22%) when compared to optimum temperatures. However, foliar spray of 1-MCP improved gas exchange, chlorophylls content and Fv/Fm ratio and decreased pod abortion compared to unsprayed control under high temperature stress. These preliminary results suggest that application of 1-MCP can decrease rate of leaf senescence and increase pod-set under high temperature stress in soybean.