during-active-phloem-loading-sucrose-enters-companion-cells-through-a-symporter-

Question

During active phloem loading, sucrose enters companion cells through a symporter coupled to proton movement. What provides the immediate energy source that drives sucrose uptake against its concentration gradient?

Accepted Answer

Energy stored in the proton gradient across the membrane

Answer

Water potential differences between xylem and phloem

Answer

Kinetic energy from bulk flow in sieve tubes

Answer

Passive transport of sucrose through membrane channels