Involvement of Norepinephrine in the Production of a Flower-Inducing Substance in the Water Extract of Lemna

A flower-inducing substance (FIS) is produced by incubationof the pellet of centrifuged ho-mogenates of Lemna paucicostata441 (P441) with commercial enzyme preparations such as catalase,cellulase, lipase and proteinase K. The active component inthese preparations was identified as tyrosine. The tyrosinemetabolites, dopa, dopamine, norepinephrine (NE) and epinephrine,were also effective for the production of FIS, and NE the mosteffective. Addition of only 1 µg NE to the pellet obtainedfrom 100 mg fresh weight of P441 produced FIS without incubation.NE added to the pellet heated after resuspension also producedFIS but that added to the pellet resuspended in boiling waterimmediately after separation did not. A heat-stable substance(s)produced by a heat-unstable reaction in the pellet may reactwith NE to produce FIS or interact with NE to induce flowering.About 400 ng per g fresh weight of NE was detected in the waterextract of P441 plants, but only about 0.5 ng in the hot-acidicwater extract of the plants, which suggests that most of theNE was produced after homogenization. (Received October 17, 1990; Accepted December 28, 1990)