Flower-promoting effect of some amino acids and amides in <italic>Lemna paucicostata</italic> 6746

Abstract

Cultures of Lemna paucicostata 6746 were exposed to a single 96-hr dark period followed by continuous illumination at 24±1°C. Flowering percentage increased to a maximum 3 days after the end of the dark period and then fell off to 0% on the 5th day. Among 20 amino acids and 2 amides tested, addition of asparagine, aspartate, glutamate, α-alanine, glycine and serine clearly increased the flowering percentages and retarded the regression of floral buds by 2–3 days. These substances given after the end of the long dark period were more effective than those given during the dark period, suggesting that they favored the flower-producing process following the inductive dark process. On the other hand, if the above amino acids or amide were applied under repeated light-dark cycles, they shortened the critical dark period by 1–2 hr and almost completely nullified the light-break effect. They seem to promote the flower-inductive dark process, too. Glutamate, for instance, was effective even at 5 μm, while this amino acid is found in the plant body in large quantities. The mechanism of flower promotion by these amino acids and amide remains unknown.