Leaf Area and Fruit Size on Girdled Grapefruit Branches1

Abstract

Abstract The dependence of fruit growth of grapefruit ( Citrus paradisi Macf.) upon leaf area was investigated on girdled branches by manipulating leaf and fruit numbers. Leaf areas of 2.0 ± 0.5 m 2 per fruit were found to be saturating with regard to fruit growth rate and size. Fruit on internal, shaded branches required larger leaf areas. Fruit on girdled branches weighed 44 to 119% more than fruit in ungirdled branches, which had leaf areas of 0.35 to 0.55 m 2 per fruit. This indicates that leaf area is one of the factors limiting fruit growth. Starch accumulated in thin twigs during the fruit growth season, forming a saturation curve similar to those obtained for fruit size when plotted against leaf area per fruit. Increasing leaf area per fruit could involve a decrease in photosynthetic activity, a possibility which now is being investigated further.