Which hormone is known as a plant stress hormone due to its role in inhibiting growth?

Abscisic Acid is recognized as a plant stress hormone because it plays a crucial role in helping plants manage stress conditions, such as drought and salinity. When plants experience environmental stress, abscisic acid is synthesized and accumulates, leading to various physiological responses that enhance the plant’s ability to survive.

One of the key functions of abscisic acid is its ability to inhibit growth. This is particularly important during periods of stress, as it directs the plant’s resources toward survival rather than growth. For instance, under drought conditions, abscisic acid signaling prompts the closure of stomata to reduce water loss, effectively prioritizing water conservation over growth.

In contrast, hormones like ethylene, auxins, and cytokinins promote growth or developmental processes. Ethylene is involved in fruit ripening and responses to stress, auxins are critical for cell elongation and growth direction, and cytokinins promote cell division and shoot development. Hence, abscisic acid uniquely stands out as the hormone that specifically inhibits growth in response to stress, defining its role as a plant stress hormone.