1-Methylcyclopropene and Aminoethoxyvinylglycine effects on yield components of field-grown cotton Efeitos de 1-Methylcyclopropeno e Aminoethoxyvinylglycina sobre componentes de rendimento de algodoeiros crescidos sob condi es de campo

Biotic and abiotic stresses can alter the hormone balance and trigger the activation of pathways involved in the cotton stress responses, resulting in the abscission of squares, flowers and young bolls and consequent reductions in the seed cotton yield and fiber yield. As part of the mechanism that primarily regulates the protective response of plants against stresses, ethylene is considered a key hormone involved in this response, and increased ethylene synthesis has been observed when plants are subjected to stress. Thus, the development of strategies aimed to mitigate their negative effects can reduce the shed rate of reproductive structures and positively impact cotton productivity. For this purpose, 1-methylcyclopropene (1-MCP), a compound that inhibits the action of ethylene, and aminoethoxyvinylglycine (AVG), an ethylene synthesis inhibitor, were sprayed on cotton plants to investigate their effects on the seed cotton yield (SCY), fiber yield (FY), fiber percentage (% Fiber) and final stand of plants (STAND) during two cotton growth seasons (2010 and 2011). To this end, experiments were performed in a randomized complete block design with five replicates. Our results demonstrate that the inhibitors of ethylene synthesis and action increased the seed cotton and fiber yield during both growing seasons. The results obtained after AVG spraying in the initial reproductive phase (first square emission) presented the highest values for the cotton yield components and are the first record of the success of this method in Brazil. A ocorrência de estresses bióticos e abióticos pode alterar o balan o hormonal e desencadear a ativa o de vias envolvidas nas respostas do algodoeiro a estresses, resultando na abscis o de bot es, flores e ma s em desenvolvimento e em menor rendimento de algod o em caro o e de fibras. Como parte desses mecanismos que primariamente regulam as respostas protetivas da planta contra estresses, o etileno é considerado um horm nio chave, envolvido nessas respostas e aumentos em seu nível de síntese têm sido verificados em plantas submetidas a quaisquer tipos de estresse. Assim, o desenvolvimento de estratégias objetivando mitigar os seus efeitos negativos poderia reduzir a taxa de queda de estruturas reprodutivas e impactar positivamente na produtividade de fibras. Com esse propósito, 1-methylcyclopropeno (1-MCP), um composto inibidor da a o do etileno e aminoethoxyvinylglycina (AVG), um inibidor da sua síntese foram aplicados sobre o algodoeiro para investigar seus efeitos sobre o rendimento de algod o em caro o, de fibras, a perce