Branch orientation as a factor determining fruit set in apple trees

Abstract

Shoot growth, flower production and fruit set were examined in branches of Cox’s Orange Pippin trained to either the horizontal or vertical axis. Branches orientated to the horizontal in August during flower bud development showed a decline in shoot extension growth and an increase in fruit set in the following year. This increase in fruit set was also evident in branches which had been trained to a vertical position in August and then re-orientated to the horizontal in the following April during flowering. A decline in fruit set was equally obvious when the reverse treatment was undertaken. The failure of vertical branches, without their shoot tips, to show an increase in fruit set would suggest that shoot extension and flower production were not antagonistic. Studies of flower and cluster leaf development showed that branch orientation had no influence on their mineral content, or the ability of cluster leaves to acquire carbon. Morphologically, the flowers from different branch orientations were simila...