Physiological parameters and green grain yield of cowpea under water deficit

Abstract

The objective of this study was to evaluate the leaf area, total chlorophyll content and leaf water potential, correlating them with cowpea (Vigna unguiculata (L.) Walp.) yield, under different water depths. The experiment was carried out at Embrapa Meio-Norte, in Teresina, PI, Brazil, from September to November 2009. The BRS Guariba and BRS Paraguaçu cultivars were used. Five irrigation depths based on fractions of reference evapotranspiration (25, 50, 75, 100 and 125% ETo) were applied. A randomized block design in split plots was used with four replications. The leaf area index showed decreasing linear effect for the lowest depth of irrigation and quadratic for the other depths. The chlorophyll levels showed a quadratic effect. There was an average reduction of 13.8 and 18.8% for the total concentration of chlorophyll, 116% for the leaf water potential, 70% for yield green grain, between the lowest and highest blade for BRS and Guariba BRS Paraguaçu, respectively. The yield of green grain is positively correlated with leaf water potential, leaf area index and total chlorophyll content.