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

Abstract

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.