CHANGES IN THE LEVELS OF ENDOGENOUS CYTOKININS AND INDOLE‐3‐ACETIC ACID DURING EPIPHYLLOUS BUD FORMATION IN BRYOPHYLLUM DAIGREMONTIANUM

Abstract

Levels of endogenous cytokinins and indole‐3‐acetic acid (IAA) in mature leaves and shoot tips of Bryophyllum daigremontianum (R. Hamet and Perr.) Berg, were determined at various times following transfer of the plants from short to long photoperiods, a treatment which results in release of the epiphyllous buds from correlative inhibition. There were transient increases in levels of both cytokinins and IAA following transfer to long days. The increase in IAA levels occurred prior to the increase in cytokinins. Maximum IAA levels were present in shoot tips 5 to 10 days after transfer, while maximum cytokinin activity was not detected until after 20 long days in the case of shoot tips, and 10 to 20 long days with mature leaves. Growth of epiphyllous buds, which was restricted to the shoot tips, became apparent only after 20 long days. Levels of both cytokinins and IAA were higher in shoot tips of plants grown throughout in short days than in plants raised entirely in long days. The types of cytokinins present in the two sets of plants did not, however, appear to differ. Copyright © 1977, Wiley Blackwell. All rights reserved