Which one of the following pairs, is not correctly matched ? [2007] (a) Gibberellic acid - Leaf fall (b) Cytokinin - Cell wall elongation (c) IAA - Cell wall elongation (d) Abscisic acid - Stomatal closure.
Option A. Stomata open in response to light. In response to drought stress, plants synthesize the hormone abscisic acid (ABA), which triggers closing of stomatal pores. Therefore it is a correct match. Gibberellic acid promotes growth and does not have any effect on leaf fall. Therefore it is not a correct match. Cytokinins (CK) are a class of plant growth substances (phytohormones) that promotecell division or cytokinesis, in plant roots and shoots. Therefore it is a correct match. Auxin induces rapid elongation growth of higher plants. The mechanism of auxinaction in the elongation growth acts on the cell walls.
