Effect of 1-MCP on Cotton Plants Under Abiotic Stress

Abstract

Many environmental stress factors have been identified that increase square and boll abscission and thus result in reduced cotton (Gossypium hirsutum L.) yield. Under stress conditions, ethylene, an endogenous hormone, is elicited. Ethylene peaks before abscission to promote the formation of the abscission layer and plays a major role in early season square and boll abortion. In addition, ethylene stimulates the leaf senescence process. Thus, it is desirable to protect a crop from ethylene-induced fruit loss and premature leaf senescence under stress conditions. The overall objective of this study was to test the hypothesis that the ethylene inhibiting compound 1-methylcyclopropene (1-MCP) treatment can have a beneficial effect on the physiology, biochemistry and yield traits of cotton plants under abiotic stress conditions under field and controlled environment studies. The growth chamber studies were conducted in 2011 using a randomized complete design with six replications. Cotton plants were exposed to stress conditions (heat and drought) and 1-MCP treatment at the seven-true-leaf stage. The heat stress study consisted of two 1-MCP rates (0 and 10 g a.i. ha-1) and two temperature regimes (optimum temperature: 30/20 ºC (day/night temperature) and high temperature: 40/25 ºC). The drought study consisted of two water regimes (well-watered and water-stressed) was exposed to two rates of 1-MCP (0 and 10 g a.i. ha-1). Both of the field studies were conducted with a randomized complete block design with four replications in 2010 and 2011 at the Texas A&M AgriLIFE Research Farm in Burleson County, TX. The objective of the first field study was to evaluate the ability of 1-MCP to protect cotton plants against abiotic stress imposed by a foliar treatment of ethephon. Eight treatments consisted of two 1-MCP rates (0 and 10 g a.i. ha-1) in combination of four ethephon rates (0, 146, 292, and 438 mL ha-1) were imposed at the first flower (FF) stage of crop development. The second field study investigated the effect of 1-MCP on boll development and the corresponding subtending leaves, and consisted of two 1-MCP rates (0 and 10 g a.i. ha-1) applied at 20 days after flowering. In the growth chamber study examining heat and drought, application of 1-MCP resulted in reductions of lipid peroxidation, membrane leakage, and soluble sugar content as well as increased chlorophyll content, compared to the untreated plants under stress conditions. In the field study to evaluate the effect of 1-MCP under ethephon stress, 1-MCP increased plant height and number of main stem nodes in both years. In addition, 1-MCP treated plants exhibited greater membrane integrity and increased photosystem II quantum efficiency, and thus delayed senescence in both years. This potential for yield increase was realized in 2011 with 1-MCP treatment exhibiting a higher lint yield. In 2012, although 1-MCP treatment increased number of open fruit and open fruit weight per plant, no significant yield increase was detected. In the field study to test the effect of 1-MCP on boll development and subtending leaf conditions, 1-MCP treatment increased cotton boll weight at 20 days after flowering. One probable explanation for the enhanced boll size was the healthier subtending leaves: 1-MCP-treated subtending leaves exhibited decreased membrane damage and lipid peroxidation, and higher chlorophyll content and photosynthetic efficiency.