Abscisic acid hormone levels can mean the difference between life and death for many plants.
Under adverse condition such as drought or salinity, phytohormone, abscisic acid (ABA) is accumulated in plant cells. ABA induces the expression of genes that are required for stress tolerance and close stomata in order to reduce the loss of water; thereby plants become tolerant to stressful conditions.
Abscisic acid or ABA, generally inhibits other hormones, such as IIA. ABA helps to bring about dormancy in a plant's buds and maintains dormancy in seeds.
It was originally thought to promote abscission, hence its name. ABA helps to bring about dormancy in a plant's buds and maintains dormancy in its seeds.
ABA is normally produced in the leaves of plants, originating from chloroplasts, especially when plants are under stress. In general, it acts as an inhibitory chemical compound that affects bud growth, seed and bud dormancy. It mediates changes within the apical meristem causing bud dormancy and the alteration of the last set of leaves into protective bud covers. In other plants, as ABA levels decrease, growth then commences as gibberellin levels increase. Without ABA, buds and seeds would start to grow during warm periods in winter and be killed when it froze again. Since ABA dissipates slowly from the tissues and its effects take time to be offset by other plant hormones, there is a delay in physiological pathways that provide some protection from premature growth. It accumulates within seeds during fruit maturation, preventing seed germination within the fruit, or seed germination before winter. Abscisic acid's effects are degraded within plant tissues during cold temperatures or by its removal by water washing in out of the tissues, releasing the seeds and buds from dormancy.