Question

Sucrose is transported throughout plants in phloem tissue, as shown in the model. The varying concentrations of water and sucrose allow for the movement of both of these molecules through the plant. Which explanation best describes the transport of sucrose in the plant? A) Sucrose is moved into the companion cells and sieve tubes against its concentration by active transport. B) Sucrose is moved into the companion cells along its concentration gradient by facilitated diffusion and then into the sieve tubes by osmosis. C) Sucrose is moved into the companion cells against its concentration via active transport and then into the sieve tubes by facilitated diffusion. D) Sucrose is moved into the companion cells along its concentration gradient by facilitated diffusion and then into the sieve tubes by simple diffusion.

Answer 1

Answer:

A

Explanation:

Sucrose is actively transported AGAINST a concentration gradient into sieve-tube elements. Technically, the sieve-tube elements LACK (have no) NUCLEI but the adjacent companion cells do. Companion cells are CLOSELY ASSOCIATED with sieve tubes and ALSO CARRY OUT ALL THE CELLULAR FUNCTIONS of the sieve tubes as well.