Molecular requirements for abscisic acid activity in two bioassay systems.

Twenty-two analogues of ABA have been tested in the Avena coleoptile and lettuce germination bioassays. Ten of these analogues were considerably more active than ABA itself as inhibitors of lettuce germination, but in the Avena coleoptile assay their activity never significantly exceeded that of ABA. The molecular requirements for activity also differ in the two assay systems, although the presence of the ring double bond is a requirement of both.