Effect of High Temperature on Grapevines (Vitis vinifera L.). II. Distribution of Soluble Sugars

Abstract

Chenin blanc and Chardonnay grapevines were subjected to zero, four, eight, or 12 days of heat stress (40°/20°C day/night temperatures) in a phytotron room. The distribution and relative amounts of soluble sugars present in 13 different plant fractions 24 hours after administrating ¹⁴C to a fully-expanded leaf were determined. Sucrose, glucose, and fructose were found in all vegetative and woody tissues of both cultivars, however, no free sucrose was detected in Chardonnay berries. Exposure of grapevines to heat stress significantly increased the concentration of sucrose in most of the plant fractions of both cultivars. Relatively higher concentrations of sucrose were found in leaf tissues than woody tissues. Heat stress significantly reduced the concentrations of glucose and fructose in Chardonnay berries and increased the glucose to fructose ratio compared to control vines (no heat stress). Heat stress generally increased glucose and fructose accumulation in trunks and roots of both cultivars but had the opposite effect on all other above-ground fractions.