14C-Assimilate partitioning in grapevine shoots: effects of shoot pinching, girdling of shoot, and leaf-halving on assimilates partitioning from leaves into clusters

Motomura, Y.

American Journal of Enology and Viticulture 44(1): 1-7


ISSN/ISBN: 0002-9254
Accession: 002280874

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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 the cultivar Delaware (Vitis labrusca X V. aestivalis X V. vinifera). 14C-labelling was performed weekly from full bloom until 3 weeks after full bloom. In untreated shoots, 83-89% 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 7 and 10 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 with shoot girdling.