¹⁴C-Assimilate Partitioning in Grapevine Shoots: Effects of Shoot Pinching, Girdling of Shoot, and Leaf-Halving on Assimilates Partitioning from Leaves into Clusters

¹ Department of Agronomy, Faculty of Agriculture, Tohoku University, 1-1 Tsutsumidori Amamiyamachi, Aoba-ku, Sendai, 981, Japan.

The distribution of ¹⁴C-assimilates into the cluster from individual leaves fed with ¹⁴CO₂ and the effects of pinching and leaf-halving on such distribution were investigated in Delaware (Vitis labrusca x V. aestivalis x V. vinifera). ¹⁴C-labeling was performed weekly from full bloom through three weeks after full bloom. In untreated shoots, 83% to 89% of the ¹⁴C-assimilates incorporated by the cluster originated from the leaves on the same side as the cluster. The percentage of ¹⁴C distribution into the cluster from the leaves on the same side of the stem as the cluster were higher than those on the opposite side, regardless of pinching, leaf-halving and feeding times. The effect of girdling on the distribution of ¹⁴C from individual leaves into the cluster was studied weekly between seven and ten weeks after full bloom. In the shoots girdled at the basal node, no effect of phyllotaxis on the percentage export and percentage distribution of ¹⁴C was observed. These results indicate that the partitioning of assimilates from leaves to cluster is greatly affected by the relative position of the source leaves and clusters. The influence of phyllotaxis on the distribution of assimilates was less altered by shoot-pinching and leaf-halving, but vanished by girdling of shoots.

Key words: ¹⁴C-assimilate partitioning, grape shoot, phyllotaxis, pinching, leaf-halving, girdling

Submitted on July 30, 1991

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