INFLUENCE OF CROP LOAD ON PHOTOSYNTHESIS AND DRY-MATTER PARTITIONING OF SEYVAL GRAPEVINES .3. SEASONAL-CHANGES IN DRY-MATTER PARTITIONING, VINE MORPHOLOGY, YIELD, AND FRUIT COMPOSITION

Single leaf photosynthesis, whole vine photosynthesis measured in a wh ole plant chamber, dry matter partitioning, and several morphological indices were measured at four phenological stages of development on tw o-year-old, own-rooted Seyval grapevines adjusted to five different cr op loads. Crop loads were 0, 1, 2, 4, or 6 clusters/vine with all late rals 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 mi d-season. Leaf and shoot dry weight were inversely correlated, and fru it dry weight positively correlated with crop load, respectively. Root dry weight was inversely related to crop load only at harvest. Leaf a rea per vine, leaf size, shoot length, node number, and intemode lengt h were inversely related to crop load. Berries per cluster and cluster weight were inversely correlated with clusters per vine. Yield and be rries per vine were correlated with clusters per vine. Sugar accumulat ion and shoot maturation were delayed by high crop loads. Implications of the crop load treatments on vine photosynthesis are discussed.