Purity >98%. Abscisic acid (ABA) is a plant hormone with diverse roles in disease resistance, plant development, and response to stresses (water, salt, temperature, and pathogens). It is also produced by some plant pathogenic fungi. In addition to key roles in regulating stomatal closing, seed dormancy, and cell division, 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.