- A Functions as a receptor tyrosine kinase embedded directly in the plasma membrane structure under most conditions encountered
- B Is a calcium sensor that, when Ca2+ bound, activates multiple target enzymes (kinases, phosphatases, NOSs)
- C Operates mainly within guard cells, largely absent from other plant tissues studied as frequently observed in practice
- D Is itself a diffusible plant hormone synthesized within the shoot apex region in many documented cases
Correct answer: B. Is a calcium sensor that, when Ca2+ bound, activates multiple target enzymes (kinases, phosphatases, NOSs)
Explanation: Calmodulin: ubiquitous Ca2+-binding protein. Ca2+ binding changes its conformation, enabling it to activate/inhibit target proteins, transducing Ca2+ signals to diverse cellular responses.
Concept context
Phases of plant growth, the five classical plant hormones plus newer ones, photoperiodism, vernalization, and seed dormancy.