NEET BIOLOGY

Detailed explanation-1: -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-2: -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.

Detailed explanation-3: -Through complex signaling mechanisms ABA triggers efflux of anions and potassium via guard cell plasma membrane ion channels, resulting in decrease of turgor pressure in guard cells and stomatal closure (Figure 1).

Detailed explanation-4: -Abscisic acid (ABA) regulates various aspects of plant physiology, including promoting seed dormancy and adaptive responses to abiotic and biotic stresses. In addition, ABA plays an im-portant role in growth and development under non-stressed conditions.

Detailed explanation-5: -Abscisic acid-induced stomatal closure is mediated by ion efflux from guard cells. Ion efflux in turn leads to osmotic water efflux and a reduction in the turgor and volume of the guard cells, resulting in stomatal closure.