CANOPY EFFICIENCY OF APPLE AS AFFECTED BY MICROCLIMATIC FACTORS AND TREE STRUCTURE

In several trials conducted at the Univ. of Bologna there has emerged a fairly constant equivalence in cropping and fruit quality of trees trained to different shapes and planted at varying densities and according to different orchard designs. Fruit quality, on the other hand, is more responsive to density, declining at densities lower than those yielding maximum productivity. This outlines a generally high capacity for light interception and use by the trees, but it also points to differences in the trees' efficiency in light use. In fact, despite comparable 4-year-cumulated total leaf areas and comparable cumulative yields, the data relative to the leaf area components of trees from different orchard designs reported in this paper indicate how in thin, well-exposed canopies (i.e., the palmette and bed systems) the ratio between spur and shoot leaf area (including both bourse and extension shoots) varied from 1:2.5 to 1:4, in comparison with a value up to 1:7 for the bushy-type spindle-based systems. This difference is due to a larger spur leaf area in the thinner canopies, compared with the spindle types. The ratio of cumulated yield per hectare to cumulated leaf area per hectare over the fourth to the seventh seasons shows that greater yields were obtained per unit leaf area from the thin canopies, as opposed to those based on spindle, indicating a difference in their efficiency of light use.