The role of inorganic phosphate on photosynthesis recovery of common bean after a mild water deficit

A foliar spray of inorganic phosphate (Pi) was applied at the pollination stage of two common bean genotypes A320 and Ouro Negro, growing in pots in a greenhouse. Two days after the foliar Pi supply, a mild water deficit was imposed for 7 days and photosynthesis was evaluated during water stress and recovery. The net CO, assimilation rate (A) and stomatal conductance (g(s) were, not affected by Pi supply during the dehydration of either genotype. On the fourth day of water deficit, A320 presented a high value of A despite lower g, indicating a small effect of g, on A for this genotype, while Ouro Negro showed a low value for both A and g, However, after rehydration A and g, for A320 and A for Ouro Negro, both supplied with Pi, were higher than for non-Pi-supplied plants. In addition, the O-2 evolution (A(c)) of rehydrated A320 with foliar Pi supply was also higher than for non-Pi-supplied plants, and the non-photochemical quenching (NPQ) was higher for rehydrated A320 without foliar Pi. The results revealed an up-regulation of the recovery of photosynthesis after water deficit induced by the foliar Pi supply, which was genotype-specific. (c) 2005 Elsevier Ireland Ltd. All rights reserved.