AP BIOLOGY

Detailed explanation-1: -Abscisic acid (ABA) is a plant hormone involved in the response of plants to reduced water availability. Reduction of guard cell turgor by ABA diminishes the aperture of the stomatal pore and thereby contributes to the ability of the plant to conserve water during periods of drought.

Detailed explanation-2: -Abscisic acid (ABA) is a stress hormone that accumulates under different abiotic and biotic stresses. A typical effect of ABA on leaves is to reduce transpirational water loss by closing stomata and parallelly defend against microbes by restricting their entry through stomatal pores.

Detailed explanation-3: -Abscisic acid (ABA) is a plant hormone that regulates numerous aspects of plant growth, development, and stress responses. ABA-deficient mutants from various plant species display reduced seed dormancy and wilty phenotypes, highlighting that these crucial ABA functions are conserved in the plant kingdom.

Detailed explanation-4: -The turgor pressure in the guard cells controls the opening and closing of the guard cells. Stomatal pores open when guard cells enlarge as a result of water absorption and close when guard cells shrink.

Detailed explanation-5: -Among these, abscisic acid (ABA), is the best-known stress hormone that closes the stomata, although other phytohormones, such as jasmonic acid, brassinosteroids, cytokinins, or ethylene are also involved in the stomatal response to stresses.