Studies on the Flowering Mechanism in Lemna

The dark reaction of the short day plant Lemna perpusilla was investigated. It was found that 3‐phosphoglycerate and pyruvate (10−6M) increased the flowering rate in the presence of nitrates. Pyruvate‐2‐14C was added to the culture solution during two hours of the dark reaction and 14C was incorporated into serine, aspartate and glutamate. It was postulated that pyruvate reacted with a nitrogen source forming an intermediate, possibly aspartate, which was further converted into serine. L. perpusilla failed to flower when the dark period was interrupted with red light and as a result endogenous serine accumulated in a high concentration. The dark reaction of L. perpusilla, in which serine was involved, required (1) oxygen, (2) ATP, (3) moderate temperature, and (4) an enzyme system.