© 1992 Heron Publishing—Victoria, Canada
Effects of varying crop load on photosynthesis, dry matter production and partitioning of Crispin/M.27 apple trees
J. W. Palmer (1, 2)
1. Horticulture Research International, East Malling, West Malling, Kent ME19 6BJ, UK / 2. DSIR, Riwaka Research Station, Old Mill Road, Brooklyn, R.D. 3, Motueka, New Zealand / Received May 24, 1991
Summary
Fruit load was altered by flower thinning on three- and four-year-old, field-grown apple trees. Increasing fruit load led
to increases in dry matter production per unit leaf area and partitioning to fruit and to decreases in fruit size, percentage
fruit dry matter, dry matter partitioning to new shoot growth, thickening of existing woody tissue and root growth. Flower
bud production for the following spring was also negatively affected by an increase in fruit load. Leaf photosynthesis was
increased in cropping trees in July and August at the time of maximum fruit dry weight increase. Calculated light interception
was linearly related to leaf area. The efficiency of conversion of intercepted photosynthetic active radiation to dry matter
energy equivalents was 3.3% in heavily cropping trees and 1.8% in non-cropping trees. Total dry matter production was linearly
related to both leaf area and light interception, but the variance accounted for by the regression was more than doubled if
fruit dry matter or fruit number was included in the regression.
