Which one of the following statements about transport of nutrients in phloem is correct?

Question

Quizplus · Accepted Answer

Differences in osmotic concentration between the source (where nutrients are produced in the leaves through photosynthesis) and sink (where nutrients are used or stored) areas create a pressure gradient that drives the flow of phloem sap from source to sink. The companion cells help load and unload the solutes into and out of the phloem, but they do not control the rate and direction of movement of phloem sap. Solute particles do not move from phloem to xylem as the two vascular tissues have different functions - xylem is responsible for water and mineral transport, while phloem transports organic solutes. A sink can be any part of a plant where nutrients are utilized, such as roots or fruits, but it is not necessarily where a solute is produced.

Which One of the Following Statements About Transport of Nutrients