Water deficit causes stomatal closure and reduces grapevines’ water uptake. Yet, the actual transpiration limitations during vines dehydration and rehydration are unclear. Thus, we set to explore droughts’ effects on whole-plant water uptake during water deficits and recovery. We hypothesized that discrete droughts hinder plants’ transpiration through long-term limitations to canopy development and stomatal conductance (gs).
We constructed large (2 m3) lysimeters to measure how three short (six days) droughts affected vines’ seasonal transpiration. Then, we calculated the vines’ stress coefficient (KS) and compared it with the vines’ stem water potential and gs.
Repeated droughts reduced vines’ cumulative evapotranspiration by 848 L vine-1 (11% of the seasonal uptake). Approximately half of the transpiration losses were directly attributed to water deficits, while the other half were driven by stomatal limitations during the first days of rehydration, and to permanent restrictions to the vines’ leaf area. KS was reliably predicted from SWP, but the relation largely depended on phenology.
The findings highlight the drought’s limitation on water uptake could be much larger than its instantaneous effect.
