Question

The translocation of organic solutes in sieve tube members is supported by:

• A. Root pressure and transpiration pull
• B. P-proteins
• C. Mass flow involving a carrier and ATP
• D. Cytoplasmic streaming

Answer 1

The correct option is C Mass flow involving a carrier and ATP

Organic solutes are transported from the source to the sink (destination) in a plant by the mass flow process. Glucose synthesized in the leaves is converted to sucrose. The sucrose is then moved to the sieve tube cells by active transport. This causes an inflow of water from the xylem, thus increasing the hydrostatic pressure. The solution in the phloem then moves to the sink which has lower hydrostatic pressure. At the sink, the sucrose is actively transported out from the phloem.