Why is abscisic acid also known as stress hormone?

Abscisic acid (ABA) is termed the “stress hormone” in plants because its synthesis increases markedly under environmental stress conditions such as drought, salinity, cold, or waterlogging

ABA accumulates in roots and leaves, then translocates via xylem and phloem to guard cells and other tissues

• Physiological functions under stress

  • Induces stomatal closure by triggering ion efflux from guard cells, reducing turgor and conserving water

  • Promotes synthesis of dehydrins, osmoprotectants, antioxidant proteins, aiding in osmotic adjustment and cell protectionRegulates root growth and architecture, enhancing water and nutrient uptake under stress

  • Induces seed and bud dormancy or delay germination to survive unfavorable conditions

• Role in stress signal transduction

  • Acts as a central signaling molecule coordinating stress-response genes via ABA-dependent pathways and transcription factors like AREB/ABF, DREB, MYB/MYC

  • Interacts with other hormones (jasmonates, salicylates, nitric oxide) to balance growth-defense trade-offs under multiple simultaneous stresses

Summary

ABA’s stress-induced accumulation, rapid physiological responses (e.g., stomatal closure), gene regulatory roles, and cross‑talk with other hormones justify its title as the plant “stress hormone”

It enables adaptive adjustments at molecular, cellular, and whole‑plant levels, improving survival during abiotic and biotic challenges