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.