Effect of Crop Level and Leaf Area on Growth, Composition, and Coloration of `Tokay' Grapes

Abstract

The effect of leaf area per unit weight of fruits on growth, composition, and coloration of `Tokay' grapes was investigated on vines in which the crop level was adjusted by pruning or by pruning and cluster thinning. Significant (P<0.001) curvilinear equations were obtained for relationships between leaf area per unit weight of fruits and fruit maturity (°Brix), berry weight, fruit coloration, and level of proline in berry juice. Correlation coefficients ranged from 0.76 to 0.92. Regression analysis indicated that fruit maturity, berry weight, fruit coloration, and proline concentration in berry juice were maximum when the ratio of square centimeters of leaf surface to gram of fruits was between 11 and 14. Severe overcropping occurred on unpruned and unthinned vines, and on vines pruned but not cluster thinned (3.8 and 5.0 cm² leaf area per g fruits, respectively). This was reflected in significant reductions in pruning weights, total leaf area per vine, berry and cluster weights, total soluble solids, fruit coloration, and concentrations of proline and arginine in berry juice, compared with those for vines that were pruned and thinned to 18 clusters per vine (12.6 cm² leaf area/g fruits).