Abstract
Partial defoliation of grapevines often increases fruit phenolic content; however, improved light interception by fruit and possible improved photosynthetic efficiency of leaves are confounding factors. In this study, potted De Chaunac grapevines were partially defoliated at three phenological stages, but cluster light environment was unaffected. Partial defoliation at berry set significantly reduced glucose and fructose concentrations in the leaf/shoot tissue, and also reduced total flavonols and total phenolics in the fruit. Vines partially defoliated pre-harvest had increased sucrose concentration in the leaves and roots, increased glucose in the roots, and produced fruit with improved total anthocyanins compared to the control. Key words: Grapevines (French hybrid), carbohydrates, phenolics