Ethylene Inhibitors Increase Net Assimilation Rate and Cotton Boll Dry Matter Under Drought

Although the ethylene inhibitors role on reduction rate of boll abscission in cotton plants submitted to drought is being recently reported, its effects on photosynthesis performance and on cotton boll dry matter across the sympodial branch is scarce. Thus, the objective of this study was to evaluate the cotton photosynthesis and its boll dry matter performance across the reproductive branches via positional mapping in plants sprayed with ethylene inhibitors and submitted to water deficit. 1-methylcyclopropene (1-MCP), an inhibitor of ethylene action and aminoethoxyvinylglycine (AVG), an inhibitor of its synthesis, were sprayed on cotton plants alone and in association. Treatments were composed by (T1) control, where deionized water was sprayed; (T2) sprayed with AVG at 0.15 g a.i. L-1; (T3) 1-MCP at 0.076 g a.i. L-1; (T4) AVG at 0.15 g a.i. L-1 plus 1-MCP at 0.076 g a.i. L-1; (T5) AVG at 0.15 g a.i. L-1 twice at each seven days; (T6) 1-MCP sprayed at 0.076 g a.i. L-1 twice using the same interval and (T7) AVG at 0.15 g a.i. L-1 plus 1-MCP at 0.076 g a.i. L-1 twice at each seven days. The ethylene inhibitors sustained higher photosynthesis performance and higher boll dry mass across reproductive branches independent of compound, its combination or entries number. Highlight that a AVG (T2) or its 1-MCP association in two entries (T7) showed the best performance for dry matter accumulation, especially in the two first reproductive branches, while they maintained the highest photosynthesis rates at the end of stress period.