Water transport in leaves via osmosis, evaporation, and diffusion

Steps:

• Stage 1-2: Water moves from xylem into mesophyll cells across semi-permeable membranes due to water potential gradient.
• Stage 3-4: Water in cell walls changes from liquid to vapor in air spaces, driven by heat.
• Stage 4-5: Water vapor moves from high concentration in leaf to low in atmosphere through stomata.
• Match processes: Osmosis for 1-2 (membrane transport), evaporation for 3-4 (phase change), diffusion for 4-5 (concentration gradient).

Why D is correct:

• Osmosis defines water movement across membranes (1-2), evaporation as liquid-to-gas transition (3-4), and diffusion as passive spread down gradients (4-5), aligning with leaf physiology.

Why the others are wrong:

• A: Diffusion unfit for 1-2 (requires no membrane); evaporation misplaced for 3-4.
• B: Evaporation unfit for 1-2 (no phase change); diffusion unfit for 3-4 (not gaseous spread).
• C: Evaporation unfit for 4-5 (not exit mechanism); diffusion misplaced for 3-4.

Final answer: D