Growth-Inhibiting and Growth-Promoting Substances in Relation to the Dormancy and After-Ripening of Apple Seeds

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Abstract
Recent work has suggested that the dormancy shown by the seeds and buds of many temperate zone plants may be due to the action of specific growth-inhibiting substances The experiments described were designed to test this hypothesis, with particular reference to apple seeds which will not germinate until they have been after-ripened at a temperature just above freezing point for 60-70 days. Extracts made from different parts of the seed were tested by observing their effects on the growth of isolated sections of young oat coleoptiles under standardized conditions. These tests showed that the outer layers of freshly harvested apple seed do, in fact, contain relatively high concentrations of a growth-inhibiting substance, which disappears during the after-ripening process. Low temperature treatment, however, does not appear to be essential for the disappearance of the inhibitor, though it may be essential for the production of growth-promoting substances which appear in the embryo towards the end of the after-ripening process. In addition, it is suggested that moist conditions are necessary for the leaching out of growth-inhibiting substance from the seed coat.

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