MOBILIZABLE CARBON RESERVES IN YOUNG PEACH-TREES AS EVIDENCED BY TRUNK GIRDLING EXPERIMENTS

The seasonal patterns in concentrations of both soluble (NSC-S) and in soluble (NSC-I) non-structural carbohydrates, in 3-year-old peach tree s (Prunus persica L. Batsch) grown in sand culture are described. The ability of trees to mobilize their carbohydrate reserves in response t o scion-trunk girdling, which prevents photosynthate transport toward the roots, was tested at four phenological stages, Girdling induces a NSC-I depletion in roots and rootstock-trunk bark and a NSC-I accumula tion in leaves and shoots, On the contrary, the NSC-S concentrations o f the organs located both above and below girdling were not significan tly affected by the treatment, Consequently, when phloem transport bre aks down, trees, whatever their growing stage, mobilize carbohydrate r eserves below the girdle to maintain the soluble sugar contents at the same level as in control trees.