Chemical Changes Associated with the Breaking of the Rest Period in Vegetative Buds of Pyrus communis

Buds of heat and cold treated shoots were examined for their soluble and insoluble nitrogen, lipid‐P, ester‐P, RNA‐P, DNA‐P, phosphoprotein‐P, inorgnnic‐P. and total‐P contents. Results indicated a direct relationship of bud growth with insoluble‐N, ester‐P and RNA‐P concentrations. Decrease in phosphoprotein‐P was found to be concomitant with increase in RNA‐P. Various postulates have been considered in the light of the present results and those of others. A pathway of action in budrest break has been proposed which assumes that rest‐breaking treatments cause liberation of DNA from a DNA‐phosphoprotein‐complex, which latter determines the resting slate. The freed DNA then acts as a template for RNA synthesis. This increased RNA synthesis coupled with increased ATP content (inferred from ester‐P levels) induce protein synthesis (inferred from insoluble‐N) and bud rest is broken.