VIGOR AND NONSTRUCTURAL CARBOHYDRATES IN YOUNG PRUNE TREES

To determine if differences in vegetative vigour are related to carbon partitioning in trees, three rootstock clones (i.e. Marianna GF8.1, Ishtara(R) and St. Julien Pixy 2879), inducing vigorous or dwarfing graft combinations with two Prunus domestica L. scion genotypes, were studied. Three years after planting in the orchard, just before bud burst, partitioning of dry matter and carbohydrate content were determined in the different paris of the tree. Dry matter, starch and soluble carbohydrate distribution in Spring were slightly affected by the rootstock. During Year 4 after planting, sorbitol, soluble sugar and starch content were determined monthly in the trunk wood. The relationship between vegetative vigour and carbohydrate content depended on the type of carbohydrate examined and on the season. The kinetics of starch mobilization were modified with the dwarfing rootstock when compared with the other rootstocks. Differences in the kinetics of starch accumulation were observed between the two cultivars which showed the same vigour. The level of carbohydrate reserves in perennial parts did not appear to be related to rootstock-induced modification of vegetative vigour.