Adjustments of water-use efficiency by stomatal regulation during drought and recovery in the drought-adapted Vitis hybrid Richter-110 (V. berlandieri x V.rupestris)

The hybrid Richter-110 (Vitis berlandieri × Vitis rupestris) has the reputation of being a genotype strongly adapted to drought. A study was performed with plants of R-110 subjected to water withholding followed by re-watering. The goal was to analyze how stomatal conductance is regulated with respect to different physiological variables under water stress and recovery, as well as how water stress affects adjustments of water-use-efficiency (WUE) at the leaf level. Water stress induced a substantial stomatal closure and an increase in WUE, which interestingly persisted many days after re-watering. Stomatal conductance (gs) during water stress was mainly related to the content of abscisic acid (ABA) in the xylem, and partly related to plant hydraulic conductivity, but not to leaf water potential. By contrast, low gs during re-watering did not correlate with ABA contents, and was only related to a sustained decreased hydraulic conductivity. In addition to a complex physiological regulation of stomatal closure, gs and leaf transpiration (E) were strongly affected by leaf-to-air vapour pressure deficit (VPD) in a way dependent of the treatment. Interestingly, E increased with increasing VPD in control plants, but decreased with increasing VPD in severely stressed plants. All together, the fine stomatal regulation in R-110 resulted in very high WUE at the leaf level. This genotype is revealed to be very interesting for further studies on the physiological mechanisms leading to strong stomatal regulation and high WUE in genotypes well-adapted to drought.