Nutritional Stress and Ethylene Evolution by Young Cotton Bolls1

Abstract

Previous results have shown that a nutritional stress increases the rate of young boll abscission from cotton (Gossypium hirsutum L.) plants. Tests were conducted to determine whether a nutritional stress affects the rate of ethylene evolution by 4‐day‐old bolls. Fruiting cotton plants were subjected to conditions that should decrease photosynthesis (dim light, short days), increase respiration (long warm nights), or change the demand for products of photosynthesis (partial boll removal, changing boll load during a growing season).As little as one day of dim light caused a measurable increase in ethylene. Partial boll removal slightly decreased the effects of subsequent exposure to dim light. Bolls from plants exposed to three consecutive long warm nights produced more ethylene than bolls from control plants. Rate of ethylene evolution by bolls of field‐grown plants increased almost eightfold from June 25, when the boll load was light, to July 30, when the boll load was heavy.Sugar analyses indicated significant negative correlations between sugar content of bolls and their rate of ethylene evolution.The results indicate that a nutritional stress increased rates of ethylene evolution by young cotton bolls. This additional ethylene is probably a causal factor in the increased rates of boll abscission that occur when cotton plants are subjected to conditions that promote a nutrltional stress.