نبذة مختصرة : The effects of abscisic acid (ABA) on aquaporin content, root hydraulic conductivity (Lpr), whole-plant hydraulic conductance and leaf growth are controversial. We addressed these effects via a combination of experiments at different scales of plant organisation, and tested their consistency via a model. We analysed under moderate water deficit a series of transformed maize (Zea mays L.) lines, one sense and three antisense, affected on the NCED gene expression and which differed in the concentration of ABA in the xylem sap. In roots, the mRNA expression of most aquaporin PIP genes was increased in S plants and decreased in AS plants. The same pattern was observed for the protein contents of 4 PIPs. This resulted in more than 6-fold differences between lines in Lpr under both hydrostatic and osmotic gradients of water potential. This effect was probably due to differences in aquaporin activity because it was nearly abolished by an H2O2 treatment, which blocks the water channel activity of aquaporins. The hydraulic conductance of intact whole plants was affected in the same way when measured either in steady state conditions or via the rate of recovery of leaf water potential after rewatering. The recoveries of leaf water potential and elongation upon rehydration differed between lines and were accounted for by the experimentally measured Lpr in a model of water transfer. Overall, these results suggest that ABA has long-lasting effects on plant hydraulic properties via aquaporin activity, which contributes to maintenance of a favourable plant water status.
Processing Request
No Comments.