The diagram shows a cross-section of part of a leaf. Which cell controls the rate of gas exchange?
▶️ Answer/Explanation
Ans: B
The guard cells (B) regulate the opening and closing of stomata, controlling gas exchange (CO2 intake and O2 release) during photosynthesis.
Palisade mesophyll (A) and spongy mesophyll (C) are involved in photosynthesis, while the upper epidermis (D) protects the leaf. Since guard cells directly adjust stomatal aperture, B is the correct answer.
The diagram shows a plant cell. Which type of cell is shown?
A) cuticle cell
B) epidermal cell
C) palisade mesophyll cell
D) spongy mesophyll cell
▶️ Answer/Explanation
Ans: C
The diagram depicts a palisade mesophyll cell (C), identifiable by its dense arrangement of chloroplasts, which maximize photosynthesis. These cells are located just below the epidermis in leaves.
Why not others? Cuticle (A) is a waxy layer, not a cell. Epidermal cells (B) lack abundant chloroplasts. Spongy mesophyll (D) has loosely packed chloroplasts for gas exchange, not primary photosynthesis.