Effects of drought on O 2 evolution and stomatal conductance of beans at the pollination stage

Abstract

The predawn leaf water potential (Ψ l), O 2 evolution (Ac) and stomatal conductance ( g s) of three bean genotypes growing in a greenhouse were evaluated in order to compare the effect of water stress induced at different ages, especially during reproductive ontogeny. There was a peak of Ac for all genotypes 30 days after sowing (DAS) at the pollination stage, and the greatest effects of drought on this parameter occurred at this stage, with a decline in Ac from a higher Ψ l (−0.35 MPa) than at the other stages (below −1.0 MPa). The Ψ l and final yield were also more reduced when drought was imposed at the pollination and flowering stages than at the vegetative or pod filling stages. During water stress, the g s of the genotypes was reduced by drought, but Ouro negro showed a different behavior in its stomatal control under drought. Firstly, with water deficit imposition, it maintained a higher g s level in the morning (9:00 h), when the vapor pressure deficit is the lowest of the day, than at midday (12:00 h) and in the afternoon (15:00 h). Secondly, after rehydration, this genotype had a higher g s than non stressed plants.