Effectiveness of gibberellins and 6‐benzyladenine on flowering of Arabidopsis thaliana

Abstract

The different phases of development of the apical meristem in two ecotypes of Arabidopsis thaliana (L.) Heynh. [one French (a quantitative long‐day plant), the other one Swedish (an absolutely cond‐requiring plant)] were established, under conditions either inductive or not inductive of flowering. Then the effects of gibberellins (GA3, GA4/7) and cytokinin (6‐BA) on these ecotypes were studied at different stages of their ontogenic development. The rate of plant growth was estimated by measuring the plastochron duration. The activities of the different apical zones were determined with cytochemical methods and by histoautoradiography after incorporation of 3H‐thymidine into DNA. When treated during the vegetative stage, i.e. at a young age (French ecotype) or in absence of cold treatment (Swedish ecotype) flowering was not induced. The tested chemicals had similar effects: at first a stimulation of the phylogenetic activity of the cells of the lateral zone and of the rib meristem and, after extended treatments, a differentiation of the axial cells of the meristem and, as a result, an inhibition of flowering. On the other hand, the different hormonal applications on meristems which have reached the intermediate stage, were effective in inducing the reproductive state. The activity of the central cells already in the process of dedifferentiation was increased and, by this, flowering was promoted.