Which plant hormone is known as the "stress hormone"?

Abscisic acid is referred to as the "stress hormone" because it plays a crucial role in plant responses to environmental stress conditions. This hormone is primarily involved in regulating processes that help plants cope with drought, salinity, and other stressors. For instance, during water scarcity, abscisic acid promotes stomatal closure, reducing water loss through transpiration and helping the plant conserve water.

Additionally, it helps in the regulation of seed dormancy and maturation, ensuring that seeds do not germinate until conditions are favorable. This capability to mediate stress responses is what solidifies its reputation as the "stress hormone" in plants. The other hormones listed, while important for various growth and developmental processes, do not have the same direct association with stress responses as abscisic acid does.