Q27 / 180 · NEET 2020 (Phase 2) · Botany

Select the incorrect statement.

  • A
    Transport of molecules in phloem can be bidirectional.
  • B
    Movement of minerals in xylem is unidirectional.
  • Correct answer
    C
    Unloading of sucrose at sink does not involve the utilization of ATP.
  • D
    Elements most easily mobilized in plants from one region to another are phosphorus, sulphur, nitrogen and potassium.

Solution

The long-distance movement of organic substances from the source or storage end (region of manufacture or leaf) to the region of utilization or sink. The sink and source can be reversed depending on the need of the plant or the seasonal changes. Sugar mainly in form of sucrose that is stored in roots is mobilized to become a source of food in the early spring when the buds act as sink and require energy in form of ATP for their unloading. Since the source-sink relationship is highly variable, the direction of movement of organic solutes in phloem is bi-directional, i.e. can be upwards or downwards. It is in contrast to the unidirectional movement of water in the xylem. 

Hence, the correct answer is option: 'C'.

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