Whole-plant transpiration efficiency of Sultana grapevine grown under saline conditions is increased through the use of a Cl--excluding rootstock

The aim of this study was to test the influence of salinity (1, 20, 40 and 80 mol m(-3)) on the transpiration efficiency (W = biomass/water transpired), lamina gas exchange and carbon isotope discrimination (Delta) of grapevine (Vitis vinifera L. cv. Sultana) grown on own roots or grafted to a Cl-- excluding rootstock (Ramsey; Vitis champini L.). Growth of own-rooted and Ramsey-rooted vines irrigated with a salinity of 40 mol m(-3) was reduced by 55 and 12%, respectively, compared with vines irrigated with 1 mol m(-3). At 1 mol m(-3) W of Ramsey-rooted vines was 1.3-fold higher than own-rooted vines (3.9 and 3.0 g L-1, respectively). Salinity resulted in a decrease in W of own-rooted vines (31% reduction at both 40 and 80 mol m(-3)). In contrast, W of Ramsey-rooted vines increased by up to 1.25-fold under saline conditions. Consequently, at 80 mol m(-3) W of Ramsey-rooted vines was 2-fold higher than own-rooted vines. To our knowledge this is the first demonstration of the potential of a rootstock to increase W of a crop species under saline conditions. The rootstock-dependent differences in grapevine W under saline conditions were not determined by differences in lamina gas exchange. Differences in W associated with rootstock may be attributed to differences in ion uptake and the energy requirements associated with ion partitioning and the formation of compatible solutes.