Describe Abscisic Acid $(ABA)$ and its effects.

(N/A) Abscisic Acid $(ABA)$ is a plant growth inhibitor that acts as a stress hormone. Its key effects include:
$1$. Stomatal Closure: It induces the closure of stomata in response to water stress,thereby reducing transpiration.
$2$. Seed Dormancy: It promotes seed dormancy,which helps seeds withstand desiccation and other unfavorable environmental conditions.
$3$. Growth Inhibition: It acts as a general inhibitor of plant metabolism and growth.
$4$. Abscission: It promotes the abscission of leaves,flowers,and fruits.
$5$. Stress Tolerance: It increases the tolerance of plants to various types of stress,such as drought and salinity.