- A Stomatal opening to fix more CO2
- B Stomatal closure to reduce water loss
- C Increased transpiration
- D Stomatal neutral response
Correct answer: B. Stomatal closure to reduce water loss
Explanation: ABA (drought hormone): binds to receptors on guard cells, triggers Ca2+ signaling, K+ and water efflux, turgor decreases, stomata close.
Concept context
Water and mineral absorption, the ascent of sap, transpiration, and phloem transport via the pressure flow hypothesis.