ABA (Abscisic Acid) is called a stress hormone.
1. How does this hormone overcome stress conditions?

2. From where does this hormone get released in leaves?

 A. Stress hormone ABA (Abscisic Acid) gives signals to stomata to get closed, whenever; there is scarcity of availability of water to the plant. This prevents the loss of water through transpiration by leaves. It also increases the tolerance of plants to various kinds of stresses.
B. It (ABA) is released or transported from stem apices to leaves.