Physiological and biochemical responses to partial root-zone drying of three grape cultivars

Physiological and biochemical responses of three grapevine cultivars (Vitis Vinifera L., 'Pinot Noir', Vitis Labrusca Bailey, 'Concord' and French American hybrid (JS 23.416 9 Gewurztraminer, 'Traminette') to partial root-zone drying (PRD) were investigated in potted plants under controlled environmental conditions. The treatments were either full irrigation (FI) where both sides of the root system were irrigated daily to pot capacity (the controls), or PRD where irrigation was withheld on the dried side for 14 days while the wet side was irrigated as FI. PRD and FI treatments did not exhibit any significant differences in leaf water potential (WL) or photosynthetic rate (A). Stomatal conductance (gs) was more sensitive to PRD than photosynthesis. PRD reduced stomatal conductance by 41, 28 and 47 % in Concord, Pinot Noir, and Traminette, respectively, compared to the controls. This resulted in increased water use efficiency (WUE) by 14, 76 and 67 % in Concord, Pinot Noir, and Traminette, respectively. ABA concentration in the PRD-dry side treatment was higher (P > 0.001) than both PRD-wet side and the full irrigation treatment. Shoot growth rate of PRD-treated vines was reduced by 36, 26 and 51 % in Concord, Pinot Noir, and Traminette, respectively, compared to fully irrigated vines. The inhibition of gs and shoot growth that occurred independently of changes in leaf water status could be due to enhanced accumulation of ABA in roots and shoots, which probably maintained a high water status by reducing water loss under PRD conditions.