STUDIES ON CELL-DIFFERENTIATION: THE ROLE OF AUXIN IN ALGAE, WITH PARTICULAR REFERENCE TO RHIZOID-FORMATION IN BRYOPSIS

Abstract

Young plants of Bryopsis plumosa were inverted, the tips buried in sand, and a diffusion-gradient of indoleacetic acid established along the long axis of the plants with the highest concn. at the formerly basal end. This treatment resulted in the differentiation of rhizoids at the proximal end of most of the exposed "branches." Control plants formed no rhizoids. Similar results were obtained in regard to rhizoid formation on secondary "branches" when the primary branches were excised from the original main stem and exposed to an auxin gradient. The response was not so strong in such material. Considered with the fact that auxin is present in large amts. in Bryopsis (van Overbeek), with most of the auxin being in the lower (i.e., rhizoid forming) half of the plant (Darsie), these expts. verify the hypothesis that the formation and distr. of auxin control rhizoid formation in Bryopsis in a closely analogous way to auxin''s effect on root initiation in many seed plants.