AP BIOLOGY

Detailed explanation-1: -ABA is produced under drought-stress conditions de novo, which requires protein biosynthesis. As mentioned above, this process is important for drought-inducible gene expression.

Detailed explanation-2: -Abscisic acid (ABA) is a hormone involved in pivotal physiological functions in higher plants, such as response to abiotic stress and control of seed dormancy and germination.

Detailed explanation-3: -ABA also prevents the precocious germination of premature embryos. Stomatal closure under drought conditions prevents the intracellular water loss and thus ABA is aptly called as a stress hormone. Main function of ABA seems to be the regulation of plant water balance and osmotic stress tolerance.

Detailed explanation-4: -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.