Distribution of14C-Assimilates from Individual Leaves on Clusters in Grape Shoots

Using Delaware grape shoots with one or two clusters on the same or opposite side of the shoot, the distribution of 14 C-assimilates from ten basal leaves into the clusters was investigated weekly from one week before full bloom through three weeks after. By increasing the number of the clusters on a shoot, both the percentage of export from the leaves and the percentage of distribution of 14 C into the clusters increased. All clusters obtained 14 C-assimilates mostly from the leaves on its own side of the shoot and only a little from the leaves on the opposite side. Based on the percentage distribution of 14 C-assimilates into clusters from individual leaves on the shoot, percentage contribution of leaves at either side of the shoot to the cluster growth was calculated. Each of the clusters obtained 69% to 98% (84% average) of 14 C-assimilates from the leaves on its own side of the shoot, regardless of the relative position of the cluster(s) on the shoot.