Root-Shoot Interactions in Peach: The Function of the Root

Abstract

Peach seedlings were grown in aerated nutrient solution in small (15 cm³) or large (500 cm³) containers. Subsequently, some plants were removed from the small containers to the large, or were stressed by root pruning. Half the plants received a foliar spray of synthetic cytokinin 6-benzylaminopurine (BAP) every 4 days. Analysis of all the results enabled correlations between function and growth measurements to be made. Irrespective of the treatment the total water and the total nutrient uptake by the roots was directly related to the total dry weight increment. This suggests that for both water and nutrient uptake a functional equilibrium existed between the root and the shoot. Where BAP treatment increased the top: root ratio there was a corresponding increase in the rate of water uptake per unit length of root. The relationship between root number and leaf number and the complementary action of BAP suggests that the root tip and its production of cytokinins exerts considerable control over top growth.