Physiological and biochemical characterization of contrasting cowpea genotypes for drought tolerance

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Abstract
The objective of this study was to understand the physiological and biochemical mechanisms of drought tolerance in contrasting cowpea genotypes. The experiment was carried out in a greenhouse at the Federal University of Ceará, State of Ceará, Brazil. A stress-tolerant (Pingo de Ouro 1.2) and sensitive (Santo Inácio) cowpea genotype was grown under total irrigation (control), moderate water deficit, severe water deficit and re-irrigation after severe water deficit to study its mechanisms of water drought tolerance. The experimental design was completely randomized in a 4x2 factorial scheme, with five replications. The factors corresponded to irrigation regimes and genotypes. The results indicated that the main mechanisms of drought tolerance in cowpea include greater leaf water potential and electron transport rate under conditions of severe water deficit. In addition, maintaining the chlorophyll content, increasing the content of carbohydrates and amino acids in the leaves for osmotic adjustment, less damage to the cell membrane and greater recovery capacity after rehydration were observed as the main mechanisms. Therefore, Pingo de Ouro 1.2 was more tolerant of water stress.