Hormone which helps in the closing of stomata is: (a) Auxin (b) Ethylene (c) Cytokinin (d) Abscisic acid.
Hormone which helps in the closing of stomata is: (a) Auxin (b) Ethylene (c) Cytokinin (d) Abscisic acid.

Solution: Hormone which helps in the closing of stomata is abscisic acid.

Explanation:

  • Efflux of water and potassium ion and halt in efflux of hydrogen ion result into closing of stomata.
  • The influx of calcium ion also leads to closure of the stomatal pore.
  • The halt in efflux of hydrogen builds up alkaline environment.
  • The abscisic acid induces efflux of potassium that in turn initiates closure of stomata.