Gas exchange and yield response to foliar phosphorus application in Phaseolus vulgaris L. under drought

this study was conducted to evaluate the effect of foliar pi application on gas exchange and yield of bean genotypes submitted to a mild water deficit at the pre-flowering stage. in the first experiment, when extra pi (10 g.l-1) was sprayed on leaves during water stress or during recovery, there was no effect on gas exchange or yield in the a320, carioca and ouro negro genotypes. however, net co2 assimilation (a) of a320 and ouro negro was less affected, but not significantly, than carioca at the end of the stress, when pi was supplied five days before water deficit. in the second experiment, two different doses of pi (10 and 20 g.pi l-1) were sprayed five days before water deficit on the carioca genotype. during the last three days of the mild water deficit, a values were significantly higher for the pi20 treatment when compared to the control plants without extra pi supply. the intrinsic water use efficiency for plants receiving pi20 was significantly higher than for the other treatments. in addition, seed dry weight per plant was higher for plants receiving pi20 dose than for plants with pi10 and its control.