Question

Abscissic acid is the common name given to two identical substances isolated separately. Name them. Give the chemical features of abscissic acid.

Hint:

ABA’s role in stress responses (e.g., stomatal closure) depends on its chemical stability and receptor binding.

Answer 1

Step 1: Abscissic acid (ABA) was independently isolated as two substances: - Abscisin II: Isolated from cotton bolls, linked to abscission. - Dormin: Isolated from sycamore leaves, associated with dormancy. Step 2: Chemical features of ABA: - A sesquiterpenoid with a 15-carbon skeleton (C15H20O4). - Contains a carboxylic acid group, contributing to its acidity. - Features a cyclohexene ring with a keto group and conjugated double bonds. - Has a side chain with a double bond and methyl groups, conferring stereospecificity (S-(+)-ABA is the active form).