Two experiments were carried out with young apple trees (Fuji/Malus pruni folic Borkh. var. ringo) to examine the effect on the next season's shoot growth of summer and dormant thinning-out pruning, leaving short stubs. In Experiment 1 with 1-yearold trees, 4 lateral shoots which had been allowed to grow were cut, leaving 1.2 cm stubs on 8 occasions in the period between early July and late May in the next spring, while the terminal shoot was kept unpruned. The next season's shoot growth was weaker on the trees pruned in late August or earlier as compared with those pruned between late September and late March. In Experiment 2 with 2-year-old trees, which consisted of the central leader and 2 side branches, pruning was applied on 6 occasions in the period between late June and late November. All the shoots longer than 20 cm were cut, leaving 2-3 cm stubs except the terminal ones of the central leader and of two side branches. The next season's shoot growth was weaker on the trees pruned in late July or earlier than on the trees pruned between late August and late November. It was concluded that summer pruning does not invigorate the next season's shoot growth if it is applied early enough in the season for a balanced root : shoot ratio to be restored by the resultant regrowth.

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Light and fruit distributions within foliar canopies were measured on three 27-yearold 'Fuji'/Marubakaido (Malus prunifolia Borkh. var. ringo Asami) apple trees trained to a traditional flat open-center system developed in Japan. The canopies extended more horizontally than in depth and were interspersed with many open spaces. The percent instantaneous incident photosynthetic photon flux density (%INPPFD) was measured with quantum sensors on overcast days in mid-September and early November. Measurements were taken on four vertical plane grids placed through the center of each tree with an angle of 45 degrees made by two neighboring grids. Because of the canopy conformation, the imaginary lines connecting points of equal %INPPFD (contour lines) extended along the horizontal plane, suggesting a prevailing influence of the light from above on the withintree environment. The canopy area receiving less than 20% INPPFD was fairly limited in depth. The depth of the main cropping zone was estimated from the contour maps at a mean height of 1.7m. More than 50% of the fruits were distributed in the canopy area receiving 40% or less INPPFD. Relatively large fruits were found in the zones receiving 20% or less INPPFD. Light measurements in early November revealed that the leaf removal practice to obtain better fruit coloration significantly improved light environment within the canopy, almost eliminating the areas receiving 20% or less INPPFD.

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