Abstract

The main constrain that reduces growth and development processes in plants is the stressful conditions, affecting crop yield. Under stress conditions, plants have developed mechanisms to cope with stresses, being insufficient depending on plant species. Phytohormones as abscisic acid (ABA) is a key-regulator mediating environmental stress-responses, being a potential candidate for improving stress tolerance in plants. ABA is an isoprenoid that regulates physiological, biochemical, and molecular processes like stomatal closure and protein storage, providing adaptation to many stresses such as drought, salt, and heavy metals. ABA is also an important messenger, acting as a signaling mediator, regulating adaptive responses of plants to different environmental stresses. The chapter attempts to underline the biosynthesis, signaling, and transport of ABA and its role in different physiological, biochemical, and molecular responses of plants under adverse environmental conditions.