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 × 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 after 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.