Total leaf area per spur and individual spur leaf area were measured for various apple cultivars (Malus domestica Borkh), and removal of spur leaves was conducted from the mid-May to late August in order to investigate the role of spur leaves on spur bud development and flower bud formation.
The results were as follows:
1. Well flower bud differentiated cultivars had larger spur leaf and greater total spur leaf area than `Fuji´. Size of spur leaf area was smallest when sampled during the period of flower bud formation.
2. Spur leaf area of Fuji cultivar increased continuously during the period of flower bud formation.
3. In `Spur EarliBlaze´ the spur leaf area was smallest, but the leaf number per spur was greatest, and thus by the end of August the spur leaf area became to be as large as other cultivars.
4. No specific tendency was found in seasonal changes of a shoot leaf area, but total leaf area per shoot was largest in `Spur EarliBlaze´ and smallest in `Fuji.´ There was no difference in leaf numbers per shoot between the cultivars.
5. Spur bud development was significantly reduced by the removal of spur leaves.
6. Flower bud differentiation of spur buds on spurs by the removal of spur leaves was greatly inhibited in both `Fuji´ and `Starkrimson´, particularly by early defoliation, whereas removal of spur leaves in `Mutsu´, `Jonagold´ and `Spur EarliBlaze´ did not greatly reduce Sower bud differentiation.
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