Flower-inducing activity of lysine in Lemna paucicostata 6746

Flowering of Lemna paucicostata 6746, a typical short-day plant, was induced by culture for 96 or 120 h in nitrogen-free medium under continuous illumination. To examine the effects of lysine, we homogenized entire plants of L. paucicostata 151 in a solution of lysine and the supernatant obtained after centrifugation of the homogenate was added to the medium to give various concentrations of lysine in the medium. Flowering of strain 6746 in nitrogen-free or nitrogen-deficient culture medium was effectively promoted by the addition of a lysine-containing supernatant to the medium. The suppressive effect of elastatinal, a protease inhibitor, on the induction of flowering was almost completely reversed by the simultaneous application of a lysine-containing supernatant to the medium. During nitrogen-free culture, the level of endogenous free lysine, expressed on the basis of the amount of total free amino acids, increased. Lysine-containing supernatants also induced flowering of plants in nitrogen-rich medium under continuous illumination. These findings suggest that endogenons lysine is involved in the induction of flowering in L. paucicostata 6746 on nitrogen-free or nitrogen-deficient medium, as it is in the induction of flowering in L. paucicostata 151.