Drought Effects on Gas Exchange, Chlorophyll, and Plant Growth of 1-Methylcyclopropene Treated Cotton

Drought impacts cotton (Gossypium hirsutum L.), affecting 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. The objective of this study was to examine the effects 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 x 2 factorial design in a split-block arrangement with five 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). The 1-MCP increased water use efficiency (WUE) in well-watered plants at 1 DAT. Many of the yield components, plant mapping, and biomass parameters investigated were adversely affected by drought. However, drought increased specific leaf weight (SLW), chlorophyll (Chl) content, and harvest index. The 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 effects of drought on gas exchange when water stress started to impact cotton plants. Additionally, 1-MCP had little or no positive effect on plant mapping, dry matter partitioning, and Chl content.