Factors Affecting the Water-sensitive Phase of Flowering in the Short Day Plant Lemna perpusilla.

The flowering of Lemna perpusilla strain 6746 is inhibited by daily transfers to water for short periods during a sensitive phase. Supplementing the water with Ca(NO(3))(2) partially reverses the inhibition of flowering while MgSO(4) increases the inhibition. The inhibition by MgSO(4) is overcome by low concentrations of Ca(NO(3))(2). Flower-promoting activity was detected in water and in MgSO(4) solutions that had been incubated with plants under dark but not light conditions. The prevention of this effect by light appears to be photosynthetic rather than to depend on phytochrome. The activity is destroyed by autoclaving but not by brief boiling. This loss of a flower-promoting material may explain the inhibiting effect on flowering by transfers to water.