Involvement of Native Abscisic Acid in the Regulation of Onset of Dormancy in Spirodela polyrrhiza

The medium in which an old culture of S. polyvrhiza was growing aseptically decelerated frond multiplication and promoted turion (= dormant propagule) formation in a young culture of this plant. The effect is attributed to abscisic acid (ABA) which had been released by the old culture into the medium. The time of appearance of the released ABA in the solution was correlated with the beginning of turion formation in the old culture. Native ABA is probably involved in the regulation of onset of dormancy in S. polyrvhiza.