The polarity of endogenous regulatory substances inBryophyllum crenatum leaves and stems

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Abstract
In isolated leaves ofBryophylluni crenatum the intensity of marginal bud formation decreases from the apex towards the blade base, which is associated with the decreasing content of enioganous gibberallins. As proved by Dostál (1930), the formation of marginal buds on transversely divided blade of the isolated leaf increases in comparison with the non-divided control leaf. The results of our experiments have revealed that the increase in the formation of marginal buds in the blade transversely divided into the apical, middle and basal parts is connected with the increasing level of endogenous gibberellins, especially in the apical part. This rising level appears as early as 7 days following blade division,i.e. at the time preceding the formation of marginal bud bases. InBryophyllum crenatum plants the level of endogenous cytokinins was estimated in apical, middle and basal leaves, as well as in adjacent internodia. Maximum content was found out in the leaves from the middle stem part, which is probably associated with the capacity of this part to form marginal buds spontaneously also in intact plants. However, prior to flowering the maximum of cytokinin activity is shifted to the apical stem part.