[Campbell Biology P.846] Which of the following is the primary mechanism by which guard cell... | Practice Question

Which of the following is the primary mechanism by which guard cells become turgid and cause stomatal opening?

  • A: Active transport of water into the guard cells.
  • B: Passive diffusion of CO2 into the guard cells, increasing internal pressure.
  • C: Active uptake of K+ ions into the guard cells, followed by water entry via osmosis.
  • D: Release of H+ ions from the guard cells, increasing their internal pH.

Explanation

The text explains that stomata open when guard cells actively accumulate K+ from neighboring epidermal cells. This K+ uptake causes the water potential to become more negative, leading to water entry by osmosis and increased turgor.