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Cotton Response to High Temperature Stress During Reproductive Development

Temperature is a primary controller of the rate of plant growth, developmental events, and fruit maturation. Increased temperatures from global climate change are projected to cause substantial losses in crop productivity by the end of the twenty-first century. Elevated temperatures affect all stages of cotton development, but the crop seems to be particularly sensitive to adverse temperatures during reproductive development. In Arkansas, temperature stress is considered to be one of the main factors affecting cotton yield. Environmental stress during floral development is a major reason for the disparity between actual and potential yields. Field and growth chamber studies were conducted with the objectives of investigating the effects (1) of high temperature stress during flowering and early boll development on early seed growth, (2) of foliar-applied 1-Methylcyclopropene (1-MCP) on the growth and yield of field grown cotton, and (3) investigate the amelioration of high temperature stress in cotton flowers and young cotton fruit using 1-MCP. In growth room studies high day temperature (38 o C) compared to the control temperature (32 o C) resulted in increased glutathione reductase (GR) activity and decreased ovary carbohydrate concentrations. In field studies GR activity, calcium and carbohydrate concentrations of ovaries and leaves were not significantly affected by applications of 1-MCP. Yield parameters of lint, seed, and seedcotton were also not affected by 1-MCP applications in Marianna, whereas in Fayetteville yield was significantly increased. The increases in yield in Fayetteville were attributed to higher temperatures during the reproductive period when the 1-MCP applications were made. Overall the studies show that foliar applied 1MCP may potentially help to ameliorate the effects of high temperature on cotton, but may also exhibit no effect or a negative effect on non-stressed cotton. This thesis is approved for recommendation to the Graduate Council.