Question

ABA-mediated stomatal closure occurs due to:

• A. Influx of K+ into guard cells
• B. Efflux of K+ from guard cells
• C. Increase in turgor of guard cells
• D. Blue-light activation

Answer 1

Answer:

B. Efflux of K+ from guard cells

• Abscisic acid (ABA) mediates stomatal closure primarily by triggering the efflux of potassium ions (K⁺) from guard cells through activation of anion channels and outward-rectifying K⁺ channels. This ion loss reduces osmotic potential, causing water efflux and decreased turgor pressure that collapses the guard cells.