FRUIT QUALITY DEVELOPMENT OF `GRANNY SMITH' APPLES IN RESPONSE TO TREE CANOPY LIGHT MICROCLIMATE.

Abstract

A preliminary study suggested light distribution (400-700nm) did not change from terminal bud set (July) to harvest (9/9/88). Therefore, limbs of 5-year-old trees were shaded the last 90 days of the season in 1988 and 7-year-old trees were shaded the last 60 days in 1989 with 30, 63, 95% or no shadecloth. Medium (63%) and heavy (95%) shade decreased fruit weight both years. Fruit soluble solids (SSC) decreased with increasing shade in 1988 but not in 1989 until after 60 days of storage. Fruit peel chlorophyll (chl) declined with time for all treatments. Apples from full sun and heavy shade treatments had the lowest chl and visually appeared the lightest. Evidence from both years suggested there was an optimal light level between 37-70% full sun for maximum fruit color and chl. Link of 7-year-old trees were shaded at intervals, light all season, mid-season and late season. Fruit weight and firmness were not affected by time of shading. SSC was liner for mid-season shaded fruit. Chl was highest for late season shaded fruit but differences evaporated by 90 days of storage.