Partial drying of the rootzone of grape. II. Changes in the pattern of root development

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 gas exchange and root growth of 110 Richter (Vitis berlandieri x Vitis rupestris). The initial decrease in 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 gas exchange of half-dried grapevines occurred without any further change in soil water content of the dried half of the root system, and coincided with the point at which there was no further decrease in soil water content. For half-dried plants, there was a relative increase in root development in moist soil layers, both in the ‘wet’ container as a whole or in the lower part of the ‘dry’ container. Recovery of gas exchange of half-dried plants occurred at the time when there were no more roots dried in the ‘dry’ container. We propose that, for half-dried plants, the part of the root system in dry soil can survive because water moves from ‘wet’ roots to ‘dry’ roots.