Effect of Girdling on Leaf Gas Exchange, Water Status, and Non-structural Carbohydrates of Field-grown Vitis vinifera L. (cv. Flame Seedless)

Abstract

Flame Seedless grapevines were girdled at fruit set to determine the effect of this practice on leaf net CO₂ assimilation rate (A), carbohydrate partitioning, and water potential. The treatments consisted of vines that were trunk girdled, cordon girdled (one of a vine's cordons were girdled), the non-girdled cordon from vines of the previous treatment, and a non-girdled control vine. Girdling reduced midday A and stomatal conductance (g_s) by approximately 50% for a period of four weeks after treatment imposition when compared to vines or cordons that were not girdled. Midday leaf water potential values were more negative for the two control treatments than those of the two girdled treatments during the same time period. Diurnal measurements of leaf non-structural carbohydrates did not differ among treatments. Both girdling treatments increased berry size compared to the controls. The data indicate that the reduction in g_s due to girdling resulted in less leaf transpiration and, therefore, a more favorable vine water status (as measured by leaf water potential) for those vines. In addition the reduction in A after girdling was probably due to a reduction in g_s and not to an accumulation of carbohydrates in the leaf.