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Which statement about phloem conducting cells is correct?
AThey are dead at maturity, unlike xylem cells
BThey are alive at maturity, unlike xylem cells
CThey are dead at maturity, exactly as xylem is
DThey are alive at maturity, exactly as xylem is
Answer & Solution
Correct answer: B. They are alive at maturity, unlike xylem cells
1. Vascular tissue holds two conducting tissues, xylem and phloem, and they differ in whether the conducting cells survive.
2. Xylem cells that conduct water, meaning tracheids and vessel elements, are dead at functional maturity.
3. Phloem conducting cells are alive at maturity, which is the stated contrast with xylem.
4. So the pairing must be alive for phloem and dead for xylem, which rules out both options that call them the same.
5. The option calling phloem dead reverses the two tissues and is the trap for a reader who remembers only the word maturity.
6. Living phloem cells matter because sugar loading needs metabolic work, which a dead cell could not do.
_Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 30 "Plant Form and Physiology", section 30.1 The Plant Body_
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