Respiration's Role in Magnesium Ion Absorption

Steps:

• Poison inhibits respiration, halting ATP production needed for active transport.
• Graph shows poisoned plant (point N) absorbs ions steadily, indicating no energy requirement.
• Normal plant (point P) shows similar uptake rate, suggesting passive carrier-mediated process.
• Both points reflect facilitated diffusion, termed "active diffusion" in context.

Why B is correct:

• Active diffusion describes carrier-assisted passive movement without ATP, matching continued uptake in poisoned plant per Fick's law of diffusion.

Why the others are wrong:

• A: Assumes energy-dependent transport at both, but poisoned plant lacks ATP.
• C: Implies passive at N but active at P, contradicting similar rates.
• D: Suggests simple diffusion only, ignoring potential carrier involvement.

Final answer: B