Abstract
In a previous experiment, dry matter production per unit dry weight leaf (DM/L) increased more than twofold with the increment in the fruit load on apple trees. Fruits on three 10-year-old 'Tsugaru' and 'Fuji' trees/M. 9 were enveloped in bags, and the dry matter production rate of the trees (DM) were compared with the control trees with non-bagged fruits during the 1990 growing season. The purpose of this experiment was to assess the effect of fruit photosynthesis on the total dry matter production rate of the trees.
1. There were significant correlations between the trunk girth measured early in the growing season and a) the total leaf area (r=0.89) and b) the total leaf numbers (r=0.90), independent of cultivars and the treatments.
2. Total dry matter production per tree (DM) was highly correlated with the fruit dry weight (F), whose regression lines were Y=1.21X +5441.0 (r=0.87) for the bagging treatment and Y=1.50X +5164.6 (r =0.99) for the non-bagging treatment (control), respectively. The gradient of the regression lines did not differ significantly between both treatments.
3. A highly significant correlation (r=0.87) existed between the fruit/leaf dry weight ratio (F/L) and the dry matter production per unit dry weight leaf (DM/L) of the trees, even if the bagging and the non-bagging treatments were combined. A smaller but significant negative correlation was also found between the leaf area per fruit and DM/L (r= -0.49). The fact that the bagging treatment did not alter these correlations also suggests that the dry matter production by the fruit was not so large as to enhance the total dry matter production rate of the tree significantly.
4. The total dry matter production rate per leaf area was higher in 'Tsugaru' than in 'Fuji'.
