Which hormone is primarily responsible for inducing stomatal closure in vascular plants under severe water stress conditions, earning it the common name of stress hormone?

💡 Solution & Explanation

Abscisic acid accumulates rapidly in plant tissues during water stress, triggering rapid efflux of potassium ions from guard cells and causing stomata to close to prevent transpirational water loss. Auxin promotes cell elongation, gibberellins stimulate stem growth, and cytokinins promote cell division. Plant hormones regulate developmental responses.