Influence of Crop Load on Photosynthesis and Dry Matter Partitioning of Seyval Grapevines. III. Seasonal Changes in Dry Matter Partitioning, Vine Morphology, Yield, and Fruit Composition

Abstract

Single leaf photosynthesis, whole vine photosynthesis measured in a whole plant chamber, dry matter partitioning, and several morphological indices were measured at four phenological stages of development on two-year-old, own-rooted Seyval grapevines adjusted to five different crop loads. Crop loads were 0, 1, 2, 4, or 6 clusters/vine with all laterals removed to eliminate intra-vine shading. Leaf area was inversely related to crop load, with differences evident as early as fruit set. Differences in dry weight partitioning did not become evident until mid-season. Leaf and shoot dry weight were inversely correlated, and fruit dry weight positively correlated with crop load, respectively. Root dry weight was inversely related to crop load only at harvest. Leaf area per vine, leaf size, shoot length, node number, and internode length were inversely related to crop load. Berries per cluster and cluster weight were inversely correlated with clusters per vine. Yield and berries per vine were correlated with clusters per vine. Sugar accumulation and shoot maturation were delayed by high crop loads. Implications of the crop load treatments on vine photosynthesis are discussed.