Abstract

Lemna paucicostata 151, a weakly responsive short-day plant, flowers even under continuous illumination when cultured on nitrogen-free medium for more than 72 hours with subsequent culture on nitrogen-rich medium. During the nitrogen-free culture, the protease activity and protein content of the plant increased and decreased, respectively. The plant contained a protein(s) that induced flowering of the plant when added to the medium. The level of this protein(s) also decreased during the nitrogen-free culture. The total amount of free amino acids in plants cultured on nitrogen-free medium for 96 hours decreased to about 15% of that in plants at the start of nitrogen-free culture, but levels of some amino acids increased. These amino acids were examined for their effects on flowering of plants cultured on nitrogen-deficient or nitrogen-free medium. Most of the amino acids had no effect on flowering. However, profuse flowering was induced when lysine was added to the medium. Lysine promoted the flower-inductive process(es) rather than the development of flower buds.

These results suggest that nitrogen deficiency-induced flowering of the plants is induced by lysine, which is generated from a specific protein(s) by proteolysis.

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