GAS EXCHANGE AND PHOTOSYNTHETIC EFFICIENCY IN COMMON BEAN ECOTYPES GROWN IN A SEMIARID ENVIRONMENT

Abstract

Common bean has a significant economic and social importance, although its yield is considered low in Brazil, due to environmental conditions and low technology level on farming. So, the use of promising cultivars may be a strategy to improve its cultivation in the Brazilian semiarid region. This study aimed to evaluate gas exchange, instantaneous water use efficiency, leaf area, biomass, leaf water content, and photosynthetic efficiency in three common bean ecotypes (Eco₁ = G2227, Eco₂ = BRA 130583 and G6490, and Eco₃ CIAT BAT = 477) cultivated in the semiarid region of the Paraíba State, Brazil. A randomized blocks design with three replications was used. The CO₂ assimilation rate, transpiration, intercellular CO₂ concentration, instantaneous carboxylation efficiency, instantaneous water use efficiency (from 9 a.m. to 10 a.m. and from 10 a.m. to 11 a.m.), leaf area, leaf area index, leaf water content, and photosynthetic efficiency were analyzed. The common bean ecotypes showed variations in the gas exchange rate and instantaneous water use efficiency along the day, under the environmental semiarid conditions of the Paraíba State. The leaf area and photosynthetic efficiency did not differ significantly in the conditions studied. The G2227 ecotype showed the best physiological responses, concerning CO₂ assimilation and carboxilation efficiency, besides presenting a smaller variation for instantaneous water use efficiency, from 9 a.m. to 11 a.m., pointing out a better adaptation level to semiarid conditions and cultivating potential.