Light Level Influences Spur Quality and Canopy Development and Light Interception Influence Fruit Production in Apple

Abstract

To model canopy growth and fruiting of apple trees, a thorough understanding of the interaction of light levels and leaf and fruit growth is required. Light distribution within a tree canopy is determined by spatial aspects of leaf development, which is usually influenced by horticultural practices such as pruning and tree training. However, individual leaf growth is itself directly influenced by light penetration to the site of leaf development. In this paper we discuss the influence of light levels on the development of individual vegetative and fruiting spurs of apple and the relationships of light interception, leaf development, and fruit production for whole trees. Apple tree canopy development within a season and over the life of an orchard is crucial to the production of high quality fruit each season and to the early and sustained productivity of the orchard. Canopy development within a season and, in many cases, its development the following season can be influenced by cropping level, mineral nutrition, moisture level, plant growth regulators, pruning and training, scoring, light distribution, rootstock, and cultivar. The effect of these factors on canopy development was recently reviewed by Forshey and Elfving (1989). However, few studies have examined the influence of these factors on the development of individual spurs, the site of fruiting on apple trees. Spur leaves develop before shoot leaves (Cain, 1973; Forshey et