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摘要
The objective of this study was to identify physiological traits that could distinguish between cotton genotypes that were tolerant or sensitive to water deficits. The experiment was conducted in a completely randomized design through a factorial combination to analyze four genotypes (BRS 187 8H and ACALA SJ-4 - water deficittolerant; CNPA 7H and SU-0450/8909 - water deficit sensitive) and two water regimes (watered/always irrigated and stressed/with a water deficit imposed at flowering). Irrigation was suspended for the plants in the water deficit treatment groups when their first flowersappeared. Leaf water potential ( pd) was monitored until the plants reached -3.0 MPa predawn, at which point leaf samples were collected for analysis. The plants were reirrigated and monitored for a recovery to 50% of leaf water potential. The maximum photochemical efficiency (Fv/Fm), chlorophyll content (SPAD index), relative watercontent (RWC), disruption of the cell membrane via membrane leakage, carbon isotope composition ( 13C), seed cotton yield and fiber quality were evaluated. The trends in membrane leakage and carbon isotope composition were different between the tolerant and sensitive genotypes under a water deficit, which makes these physiological traits suitable for screening for tolerance to water deficits in cotton. Objetivou-se identificar variaveis fisiologicas para distinguir genotipos de algodoeiro tolerantes e sensiveis ao deficit hidrico. O experimento foi conduzido no delineamento inteiramente casualizado emarranjo fatorial, sendo testados quatro genotipos (BRS 187 8H e ACALA SJ-4 . tolerante ao deficit hidrico; CNPA 7H e SU-0450/8909 - sensiveis ao deficit hidrico) e dois regimes hidricos (controle . sempre irrigado e com deficit hidrico imposto na emissao da primeira flor. Na emissao da primeira flor, a irrigacao foi suspensa para o grupo a ser submetido ao deficit hidrico. O potencial hidrico foliar foi monitorado na antemanha ate que as plantas dos cultivares em estudo atingissem -3,0 MPa, ponto no qual coletaram-se amostras foliares para analises fisiologicas. Apos, irrigou-se as plantas ate a obtencao de valor superior a 50% do potencial hidrico foliar (-1,50 MPa). Avaliaram-se a eficiencia fotoquimica maxima (Fv/Fm), o conteudo de clorofila via indice SPAD, o conteudo relativo de agua (CRA), o extravasamento de eletrolitos, a composicao isotopica do carbono ( 13C), o rendimento de algodao em caroco por planta e a qualidade da fibra. A disruptura de membrana via extravasamento de eletrolitos e a 13C apresentaram-se como potenciais indica
