What is the Driving Force for the Movement of Solutes

Question

What is the driving force for the movement of solutes in the phloem of plants?
A) gravity
B) a difference in water potential (Ψ) between the source and the sink
C) root pressure
D) transpiration of water through the stomata
E) adhesion of water to phloem sieve tubes

Accepted Answer

The driving force for the movement of solutes in the phloem of plants is a difference in water potential (Ψ) between the source, where sugars are produced, and the sink, where sugars are used or stored. This creates a pressure gradient that drives the movement of solutes from high pressure at the source to low pressure at the sink. Gravity, root pressure, transpiration of water through the stomata, and adhesion of water to phloem sieve tubes are not the primary driving forces for phloem transport.