Photosynthesis in Salt-Stressed Grapevines

Abstract

Rooted cuttings of grapevine (Vitis vinifera L. cv. Sultana syn. Thompson Seedless) were grown in sand culture irrigated with nutrient solution containing 1-125 mM NaCl. The effect of salinity on vine growth and photosynthesis is described. Salinity led to reduced growth where foliar symptoms of salt toxicity were absent. Rates of CO₂ fixation decreased with increasing levels of chloride in leaves. This decrease in photosynthesis could be largely attributed to increased residual (mesophyll) resistance to CO₂ fixation. Radiotracer studies showed that salt stress led to the accumulation of label in intermediates of the glycollate pathway. Salt-stressed leaves contained decreased amounts of sucrose and starch, but increased levels of reducing sugars.