Question

Companion cells are associated with
A. Tracheids
B. Vessels
C. Sieve tubes of angiosperms
D. Sieve tubes of gymnosperms

Answer 1

Hint: Companion cells are living parenchymatous cells found inside the phloem of flowering plants. Each companion cell is generally in close association with a sieve element. Its function is to regulate the activity of the nearby sieve element and to help in loading of phloem sieve cells with sugars through active transport.

Complete solution:
Option A. Tracheids: Tracheids are enlarged cells found inside the xylem of vascular plants. They help to conduct water and mineral salts. Unlike vessel elements, tracheids do not possess perforation plates. The presence of tracheary elements differentiates vascular plants from nonvascular plants.
Option A is not correct.
Option B. Vessels: Vessels form the major part of the water transporting system. The building blocks of the vessel are known as vessel elements. Vessel elements are generally present in angiosperms (flowering plants) but are absent in majority of the gymnosperms
Option B is not correct.
Option C. Sieve tubes of angiosperms: Companion cells are characteristic components of phloem tissue, which are closely associated with the sieve tubes (sieve elements) in the angiosperms. Both are linked ontogenically, as they originate from the same mother cell. The sieve tubes and companion cells maintain close cytoplasmic connections via plasmodesmata.
Option C is correct.
Option D. Sieve tubes of gymnosperms: In gymnosperms, phloem lacks both sieve tubes and companion cells. Instead, they possess sieve cells for the conduction of food material. Sieve cells of gymnosperm lack a sieve layer, and in place of that have sieve pores that allow flow between adjacent cells.
Option D is not correct.

Hence, Option C is the correct answer.

Note:
Plasmodesmata (singular, plasmodesma) are minute channels that directly link the cytoplasm of neighbouring plant cells together, thus forming living bridges between cells. It perforates both the primary and secondary cell walls, and permits specific molecules to pass through one cell to another. Thus, it plays an important role in cellular communication.