Find the incorrect match in the following

The correct answer is Gibberellic acid - Leaf abscission.

To understand why this is the incorrect match, let us examine the functions of the plant hormones (phytohormones) mentioned in the options:
1. Abscisic acid - Stomatal closure: This is a correct match. Abscisic acid (ABA) is a stress hormone that stimulates the closure of stomata in the epidermis of leaves to prevent excessive water loss during drought conditions.
2. IAA (Indole-3-acetic acid) - Cell wall elongation: This is a correct match. IAA is a major naturally occurring auxin. Auxins promote cell elongation by increasing the plasticity of the cell wall (acid growth hypothesis).
3. Cytokinin - Cell division: This is a correct match. Cytokinins are plant hormones that promote active cell division (cytokinesis) in plants, especially in root and shoot meristems.
4. Gibberellic acid - Leaf abscission: This is an incorrect match. Gibberellic acid (GA) is primarily responsible for promoting stem elongation, seed germination, and flowering. It does not cause leaf abscission (leaf fall). Instead, leaf abscission and senescence are promoted by hormones like abscisic acid and ethylene, while gibberellins generally help delay senescence in leaves.