Induction of flowering in Lemna paucicostata, a short-day plant, by chelating agents and iron

Lemna paucicostata is a short-day plant which normally flowers only in a medium supplemented with EDTA or EDDHA. On a molar basis EDDHA is more effective for induction of flowering. The chelating agent can be replaced by high concentrations of ferric citrate in the medium. Simultaneous supply of both EDDHA and a high level of ferric citrate results in flowering even under long days

Induction of flowering by cytokinins in a short-day plant, Lemna paucicostata

Lemna paucicostata, normally a short-day plant, can be induced to flower under long-day conditions by providing a cytokinin in a medium containing a high level of ferric citrate (5 × 10-4M). Interestingly, when a cytokinin and EDDHA are present together in the medium, flowering is induced even at low levels of iron (10-5 and 5 × 10-5M ferric citrate). However, in the absence of a cytokinin, flowering takes place only under short days

Growth and flowering of Lemna paucicostata I. General aspects and role of chelating agents in flowering

Lemna paucicostata HEGELM. is normally a short-day plant and flowers only in the presence of a chelating agent (EDTA or EDDHA) in the medium. The plant can be induced to flower even by a single long night treatment; the flowering percentage, however, increases with further inductive cycles. The length of the critical dark period depends upon the chelating agent employed in the medium. It is between 10 and 12 hr in the medium containing EDTA and about 8 hr in the EDDHA-supplemented medium. Red light interruption in the middle of the dark period-even for a minute-is inhibitory for flowering. Attempts to identify the metal ion(s) chelated reveal that the chelating agents affect flowering by facilitating iron uptake. This is also supported by the fact that the requirement of a chelating agent for flowering can be overcome with an excess of iron in the medium. Interestingly, provision of EDDHA and excess of ferric citrate, together, can bring about flowering even under long days

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

Lemna paucicostata HEGELM., a short-day plant, can be induced to flower under long days by provision of cytokinins in the medium. Of several cytokinins tested, zeatin and 6-benzylaminopurine are the most potent. They are effective when added in a medium containing excess of iron and thus can bring about the same affect as EDDHA. Interestingly, when both EDDHA and a cytokinin are provided together, flowering occurs even in the medium containing normal level of iron. Other cytokinins such as SD 8339, kinetin and 6-(δ,δ-dimethylallylamino)-purine are also effective in medium containing a slightly higher level of ferric citrate. In contrast to cytokinins, indole-3-acetic acid and gibberellic acid are not only ineffective by themselves, but even nullify the inductive effect of cytokinins on flowering. Growth retardants such as CCC and abscisic acid have been found to inhibit flowering at high levels