BIOMOLECULES AND ENZYMES

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: -In response to such dehydration signals, the hormone abscisic acid (ABA) accumulates in plant leaves where it regulates stomatal movement to prevent water loss by transpiration.

Detailed explanation-3: -It has an essential role in multiple physiological processes of plants, such as stomatal closure, cuticular wax accumulation, leaf senescence, bud dormancy, seed germination, osmotic regulation, and growth inhibition among many others.

Detailed explanation-4: -Leaves are covered by a waxy cuticle on the outer surface that prevents the loss of water. Plants that grow in dry environments and plants that grow on other plants (epiphytes) have a much thicker waxy cuticle than those growing in more moderate, well-watered environments (Figure 17.1. 2.1. 1).

Detailed explanation-5: -On a hot day when a plant needs to conserve water they will close their stomata which are the small openings on the underside of the leaves. The stomata are closed when the guard cells on both sides of the opening take in more water and swell closing off the opening and thus preventing excess water loss.