Which statement about translocation in the phloem is correct?
Answer and explanation
Correct answer: C. Sucrose is moved from sources to sinks, and the direction can vary with the season
- Step 1: Sucrose is loaded into the phloem at sources such as mature leaves using active transport.
- Step 2: It flows by mass flow to sinks such as roots, fruits and growing tips, so the direction varies.
Answer
Sucrose is moved from sources to sinks, and the direction can vary with the season.
Why not the others: Water and minerals move only upwards from the roots: describes transport in the xylem. Sucrose moves only from the leaves to the roots by diffusion: phloem transport is by mass flow, and sinks include fruits and growing shoots. Sucrose moves passively because phloem cells are dead: phloem sieve tubes are living cells, and loading uses energy.
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