Question

Functions of companion cells is :

• A. Providing energy to sieve elements for active transport
• B. Loading of sucrose into sieve elements
• C. Providing water to phloem
• D. Loading of sucrose into sieve elements by passive transport

Answer 1

The correct option is B Loading of sucrose into sieve elements

Companion cell is a type of cell found within the phloem of flowering plants. Each companion cell is usually closely associated with a sieve element.

Companion cells are closely linked with sieve elements. These cells are found in the phloem of flowering plants. They shift sugar and amino acids in and out of the sieve elements. In the leaf (source tissue), the companion cells make use of the transmembrane proteins for the uptake of sugar and amino acids by active transport.

It is at the source that the movement of sugars in the phloem is initiated, wherein the sugars are loaded into the sieve tube (active transport). The movement of sugar is promoted by loading, which establishes a water potential gradient.

So, the correct answer is "option D"