Phloem · Botany

Which statement best explains why phloem transport is considered an energy-dependent process?

  1. Water moves through sieve tubes only by evaporation
  2. Lignin synthesis directly pumps sucrose
  3. Dead sieve tube elements use mitochondria to create pressure
  4. Active loading and unloading of sugars often require ATP
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Correct answer: Active loading and unloading of sugars often require ATP

Sugar loading and unloading in phloem may involve active transport, which requires ATP. This energy use helps establish the concentration gradients that drive pressure flow.

Difficulty: Medium Question 20 of 20

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