Effect of salinity and Ramsey rootstock on ion concentrations and carbon dioxide assimilation in leaves of drip-irrigated, field-grown grapevines (Vitis vinifera L. cv. Sultana)

Salinity treatments of 0.43, 1.7 and 3.4 dS/m were applied through a drip-irrigation system to four-year-old vines of own-rooted Sultana (SO) and Sultana on Ramsey rootstock (Sr) The vines were planted in spring 1987 and established for two years under irrigation with low salinity (0.43 dS/m) water before commencing the range of salinity treatments in spring 1989. The effects of salinity and rootstock on yield, size and composition of berries, canopy size, lamina CO2 assimilation, leaf water relations and lamina ion concentrations were studied between veraison and harvest during the second season of salinity treatments. Mature leaves of SR had higher rates of CO2 assimilation (leaf area basis) and stomatal conductance than comparable leaves of SO. The high salinity treatment (3.4 dS/m) reduced CO2 assimilation rate of SO but not of SR. Medium salinity (1.7 dS/m) had no significant effect on CO2 assimilation rate of either type. Laminae of SO accumulated significantly higher concentrations of chloride than SR vines at all salinity levels. There was a significant negative correlation (r2= 0.44) between CO2 assimilation rate and laminae chloride of SO. Leaf sodium concentrations increased with increasing salinity, but concentrations in laminae at high salinity were similar in SO and SR, with SR showing no reduction in CO2 assimilation. Leaf potassium concentrations were higher in SR, but decreased with increasing salinity, whereas magnesium concentrations were similar in SO and SR vines but increased in both at high salinity. Leaf water potential and relative water content were not significantly affected by salinity in either SO or SR vines. Both vine types had reduced total leaf area and pruning wood weights as salinity increased, but they were greater in SR at all salinity levels because of the higher inherent capacity for biomass production in SR vines. The bigger canopies, lower lamina chloride concentrations and ‘normal’ photosynthesis rates of SR vines at 3.4 dS/m enabled these vines to mature crops with similar berry weights, sugar contents and fruit yield compared with those of SO vines at 0.43 dS/m. The research demonstrated the benefit of using Ramsey rootstock for Sultana under saline field conditions and provided a physiological explanation for their higher salt tolerance