1. Abscissic acid (ABA) is a natural growth inhibiting hormone.
2. It was observed by Carns and Addicott that shedding of cotton balls occur due to chemical substance abscission I and II.
3. From the buds of Acer, Wareing isolated substance that causes bud dormancy and named it as dormin.
4. These two chemical substances were identical and now known as abscissic acid.
5. ABA is synthesized in leaves, fruits and seeds from mevalonic acid.
