Development and survival of leaves in Magnolia obovata in a deciduous broad-leaved forest in Hokkaido, northern Japan

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Abstract
Seasonal changes were determined for leaf numbers on shoots and primordial and embryonic leaf numbers in terminal buds of Magnolia obovata growing in a deciduous broad-leaved forest in Hokkaido, northern Japan. Leaf-emergence pattern was "flush and succeeding type," i.e., many of the preformed leaves in a bud emerged at one time and after that several leaves appeared one by one successively. The lamina of the basal leaf was abortive in the bud and fell immediately after budbreak. The laminae of the shoot-tip leaves aborted after leaf emergence stopped, leaving stipules of the same leaves enclosing the bud. Such abortive laminae indicate that the shoot structure of M. obovata was evolved from homonomous to heteronomous structure. Magnolia obovata was consistently found in many types of forest but did not become dominant in number or in volume. This species was usually found in forest gaps and occasionally attained the canopy of the stand. Shoot structure of M. obovata was assumed to have changed in accordance with the leaf-emergence pattern, which is an adaptation of this species to its habitat.