Structural Adaptations in Phloem and Xylem for Transport

Steps:

• Recall phloem transports sugars via sieve tubes with perforated end walls (sieve plates) for solute flow.
• Recall xylem transports water via vessels with lignified walls for strength and perforated end walls for continuous flow.
• Evaluate each option for accurate structure-function links without errors.
• Select option matching both: perforated phloem ends for solutes and lignified xylem walls for water column support.

Why C is correct:

• Phloem sieve plates (perforated end walls) allow mass flow of solutes; xylem lignification provides tensile strength per Hooke's law for upward water transport against gravity.

Why the others are wrong:

• A: Phloem mitochondria aid loading but not tube structure; xylem lignin is correct but incomplete pairing.
• B: Phloem tubes have nuclei in companion cells, not absent; xylem perforation is accurate but phloem part wrong.
• D: Phloem has sieve plates, not no end walls; xylem lacks cytoplasm but transport relies on cohesion-tension, not just that.

Final answer: C