QUANTITATIVE-ANALYSIS OF THE VEGETATIVE DEVELOPMENT OF THE SHOOT SYSTEM OF YOUNG PEACH-TREES

The growth and branching processes occurring during the first growing season of Flavorcrest and Royal Glory peach (Prunus persica L Batsch) trees have been described quantitatively. The axis level and the metamer (set of internode, node, leaf and associated bud) level were considered. Axes elongated continuously throughout the growing season, but with growth rate variations (figs 2A, B). These variations tended to be synchronous within a tree and between trees. On the contrary, the number of leaves at each axis increased at a constant rate (figs 2C, D). This rate depended on the branching order of the axis. The study of growth and branching at the metamer level showed how these 2 processes were related. Leaves and internodes of metamers tended to be longer if the axis they composed grew fast while they were being formed. Their axillary bud was also less likely to remain dormant in such a case. On first-order axes, buds grew most frequently into a short branch with 1-5 leaves if the growth rate of the axis was intermediate, and into a long shoot if the growth rate was high (fig 4). On second-order axes, the probability for a bud to grow into a shoot was lower and was significantly influenced by the position of the leaf around the axis (fig 5). The later growth of an axillary shoot was only slightly influenced by the growth rate of the father axis during the formation of the metamer bearing this shoot.