A-LevelBiologyTransport in plants9700/12 · May/June 2012 · Q251 Mark
Which statement explains why the circumference (girth) of a tree is less in the middle of the day than at night?
AMineral uptake by the root hair cells decreases during the night because root pressure has decreased.
BStomata close during the night and there is a build-up of water in the vascular tissue within the stem.
CThe phloem sieve tubes fill with dissolved solutes because the translocation rate is reduced at night.
DThere is less tension in the xylem vessels at night because the rate of transpiration is at a minimum.
✓ Correct answer
D: There is less tension in the xylem vessels at night because the rate of transpiration is at a minimum.
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