Drought impacts cotton (Gossypium hirsutum L.), aff ecting its physiological, morphological, and agronomic parameters. Ethylene, a growth hormone, can induce fruit abscission. Ethylene inhibitors, such as 1-methylcyclopropene (1-MCP), may minimize the loss of reproductive structures. Th e objective of this study was to examine the eff ects of 1-MCP on gas exchange, plant growth/development, and yield components of cotton under drought during the reproductive phase. A 2-yr greenhouse study was conducted as a 2 × 2 factorial design in a split-block arrangement with fi ve replications. Treatments were two 1-MCP rates (0 and 2.4 g a.i. L -1 ) during a 14-h overnight incubation that were then subjected to two water regimes (control and drought). Drought started to impact gas exchange at a moderate water stress, 5 DAT (days aft er 1-MCP treatment) (-1.4 MPa). Th e 1-MCP increased water use effi ciency (WUE) in wellwatered plants at 1 DAT. Many of the yield components, plant mapping, and biomass parameters investigated were adversely aff ected by drought. However, drought increased specifi c leaf weight (SLW), chlorophyll (Chl) content, and harvest index. Th e 1-MCP improved reproductive node numbers mainly during drought, but did not lead to a better harvest index, since 1-MCP caused high fruit abscission. In conclusion, 1-MCP did not ameliorate the detrimental eff ects of drought on gas exchange when water stress started to impact cotton plants. Additionally, 1-MCP had little or no positive eff ect on plant mapping, dry matter partitioning, and Chl content.

Boll abortion is increased when cotton (Gossypium hirsutum L.) experiences various stresses during its reproductive development that can consequently reduce lint yield. Before abscission, an increase in ethylene is observed which may be assumed to be the signal necessary to initiate abscission of that particular structure. It is desirable to prevent fruit loss that may be induced by the peak in ethylene before abscission. One potential option to cope with the loss of cotton reproductive structures is the use of ethylene inhibitors. Th us, the objective of this investigation was to determine the impact of 1-methylcyclopropene (1-MCP) on growth and yield components of cotton plants treated with ethephon (ethylene synthetic hormone) under fi eld conditions. Field studies were conducted as a randomized complete block design with four replications in 2007 and 2008. Treatments were three rates of 1-MCP in combination with a surfactant applied at mid-bloom. One day later, ethephon was applied as a source of abiotic stress. At harvest, the fruit set in the upper portion of the canopy was infl uenced by 1-MCP. It had a greater number of full size, yet immature bolls, which potentially could have had a positive infl uence in the lint yield. However, ethephon caused the highest lint yield since ethephon-treated plants had more open as well as total bolls in the lower canopy at harvest. In conclusion, 1-MCP improved growth and yield components mainly in the upper portion of plants canopy at harvest, but such an improvement was not converted into lint yield. V.A. da Costa, Dow AgroSciences LLC, 13147 Jackson Rd., Sloughhouse, CA 95683; J.T. Cothren, Texas A&M Univ., 370 Olsen Blvd., MS 2474, College Station, TX 77843; J.B. Bynum, Monsanto, 700 Chesterfi eld Pkwy. West, Chesterfi eld, MO 63017.

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Upland cotton (Gossypium hirsutum L.) is an important socioeconomic crop throughout most of the southern U.S. In Texas, cotton is the lead cash crop and its productivity is often limited by abiotic stress events such as drought and elevated ambient temperatures. The objective of this study was to assess the effects of 1-methylcyclopropene (1-MCP) applications triggered by canopy temperature and forecasted ambient temperatures on field-grown cotton plants. Yield and crop morphological responses to 1-MCP applications were investigated in field studies conducted during the summers of 2012 to 2014 at the Texas A&M University Field Laboratory in Burleson County, TX. Positive effects of 1-MCP were found for fruit retention in 2013 and 2014 for both irrigated and dryland studies; however, a negative impact was found in the 2012 irrigated study. By harvest, 1-MCP applications had no effect on final cotton yield or fiber quality parameters. Applications of 1-MCP affected some morphological characteristics of cotton plants; however, it did not improve crop yield.

Cotton (Gossypium hirsutum L.) is the lead cash crop in Texas, and its productivity is often challenged by stressful environmental conditions such as high temperatures and sub-optimal water supply. The objective of this investigation was to assess the impact of 1-methylcyclopropene (1-MCP) applications triggered by canopy temperature and forecasted ambient temperatures on field-grown cotton plants. Physiological responses to 1-MCP applications were investigated in field studies conducted during the summers of 2012-2014 at the Texas A&M University Field Laboratory in Burleson County, TX. During all three growing seasons, more than 65% of the days reached temperatures above 28 °C, which indicated great potential for high temperature stress. Daily plant canopy temperature, net photosynthesis, transpiration, and photosystem II quantum yield were affected by 1-MCP treatment when plants were irrigated, but not under dryland conditions. Positive effects of 1-MCP were found for fruit retention in 2013 and 2014, for both irrigated and dryland studies, although a negative impact was found in the 2012 irrigated study. Applications of 1-MCP affected physiological characteristics; however, it did not affect crop yield.