MOVEMENT OF BORON OUT OF TREE FRUIT LEAVES

Foliar B sprays (500 mg.liter-1) had increased the B content of apple (Malus domestica Borkh), pear (Pyrus communis L.), plum (Prunus domestica L.), and cherry (Prunus cerasus L.) leaves 90% to 185% 3 days after treatment. Boron levels in treated apple, pear, and plum leaves decreased to levels similar to nontreated leaves by 9 days after application, whereas cherry leaves required 33 days to approach levels in nontreated leaves. Movement of applied B was also studied by treating cherry leaves with B solutions enriched in the stable isotope, B-10. Isotope analysis indicated that applied B moved out of leaves and into subtending tissues. The highest concentrations of applied B were found in buds, followed by bark and wood.