Growth and flowering of Lemna paucicostata II. Role of growth regulators

Lemna paucicostata HEGELM., a short-day plant, can be inducedto flower under long days by provision of cytokinins in themedium. Of several cytokinins tested, zeatin and 6-benzylaminopurineare the most potent. They are effective when added in a mediumcontaining excess of iron and thus can bring about the sameaffect as EDDHA. Interestingly, when both EDDHA and a cytokininare provided together, flowering occurs even in the medium containingnormal level of iron. Other cytokinins such as SD 8339, kinetinand 6-(,-dimethylallylamino)-purine are also effective in mediumcontaining a slightly higher level of ferric citrate. In contrastto cytokinins, indole-3-acetic acid and gibberellic acid arenot only ineffective by themselves, but even nullify the inductiveeffect of cytokinins on flowering. Growth retardants such asCCC and abscisic acid have been found to inhibit flowering athigh levels. (Received September 8, 1969; )