| dc.description.abstract | Cotton (Gossypium hirsutum L.) crops usually experience some type of environmental stress during the season. Soil moisture deficits along with high temperatures pose the biggest constraints for crop productivity. Although usually hard to distinguish between drought and high temperature stress effects, it is important to develop means to help mitigate the negative impacts of such stresses on crop productivity. The 1-methylcyclopropene (1-MCP) is an ethylene antagonist that acts by binding to ethylene receptors, thus delaying and/or diminishing its effects on plants. Recently 1-MCP became the focus of several studies due to its potential to mitigate negative impacts of abiotic stresses. The main objective of this research was to assess the impact of 1-MCP on field grown cotton. The secondary objective was to investigate the association of canopy temperature (CT), canopy temperature depression (CTD), stress degree day (SDD), thermal stress index (TSI), and crop water stress index (CWSI) with crop yield. Field studies were conducted at the Texas A&M University Field Laboratory in Burleson County, TX from 2012 to 2014. Plots were arranged in a randomized complete block design and replicated four times. Treatments consisted of 1-MCP application (25 g a.i. ha^-1) triggered by canopy temperature (28 °C) and forecasted ambient temperatures (35 and 27.8 °C). For the secondary objective treatments were two irrigation levels, namely, dryland and irrigated.
Results indicated that 1-MCP had little to no effect on the physiology and morphology of cotton at different stages of crop development. 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. Effects of 1-MCP applications during different seasons were inconsistent. Ultimately, 1-MCP treatment effects were not enough to increase final seedcotton yield under the conditions tested. Negative relationships between yield and CT (r^2 = 0.66), yield and TSI (r^2 = 0.70), and yield and CWSI (r^2 = 0.58) were found. CTD and SDD showed great distinction between the humid (2012 and 2014) and dry (2013) years, and to a lesser extent, this was also apparent for CWSI. Evidence suggests that CTD, SDD, and CWSI models should be interpreted with caution, particularly in locations where great inter-annual weather variability occurs. | en |
