Metabolism of 2-14C-(±)-Abscisic Acid in Excised Bean Axes

Excised embryonic bean axes (Phaseolus vulgaris, var. White Marrowfat) rapidly metabolize 2-(14)C-(+/-)-abscisic acid to two compounds, M-1 and M-2, which have very low growth-inhibitory activity. Chemical tests indicate the M-1 and M-2 are not previously described abscisic acid metabolites. M-2 accumulates in the axes and evidence is presented for the hypothesis that abscisic acid --> M-1 --> M-2. Zeatin, which partially reverses the abscisic acid-mediated growth inhibition of axes, neither decreases abscisic acid uptake nor causes any major changes in its metabolism. It was observed that axes transferred from abscisic acid-containing solutions to buffer resume control rates of fresh weight increase while still containing considerable quantities of abscisic acid.