Partial drying of the rootzone of grape. I. Transient changes in shoot growth and gas exchange

Split-root plants, where the root system was divided between two containers, were used to study the effect of partial drying of the root system on shoot growth and gas exchange of Shiraz (syn. Syrah) (Vitis vinifera), Kober 5 BB (Vitis berlandieri x Vitis riparia) and 110 Richter (Vitis berlandieri x Vitis rupestris). The initial decrease in both shoot growth rate and gas exchange in response to half-drying coincided with the decrease in soil water content of the dried half of the root system. Recovery of shoot function of half-dried grapevines occurred without rewatering of the dried half of the root system, and commenced when there was no further decrease in soil water content. There was no effect of half-drying on leaf water potential at the times of greatest inhibition of shoot growth rate and stomatal conductance relative to control; this suggests the involvement of a non-hydraulic signal originating from the roots in drying soil. Changes in stomatal conductance in response to half-drying were strongly correlated with shoot growth rate.