MW: 264.32. Purity ≥98%. Background: Abscisic acid is a plant hormone and growth regulator that is involved in several physiological mechanisms including seed dormancy, leaf abscission, stomatal movement, and plant stress responses. In addition, ABA regulates gene expression and may contribute to epigenetic changes at the chromatin level. The (+)-enantiomer is the naturally occurring and more active form of ABA.