Abscisic Acid (ABA), also known as abscisin II and dormin, is a plant hormone. ABA functions in many plant developmental processes, including bud dormancy. It is degraded by the enzyme (+)-Abscisic Acid 8'-hydroxylase. ABA is an isoprenoid plant hormone, which is synthesized in the plastidal 2-C-Methyl-D-Erythritol-4-Phosphate (MEP) pathway; unlike the structurally related sesquiterpenes, which are formed from the Mevalonic Acid-derived precursor farnesyl diphosphate (FDP), the C15 backbone of A