Question

Companion cells cannot be traced in

• A. Primitive dicots
• B. Gymnosperms
• C. Both of the above
• D. Monocots

Answer 1

The correct option is C Both of the above

In plant anatomy, sieve tube elements, also called sieve tube members, are a specialised type of elongated cell in the phloem tissue of flowering plants. The ends of these cells are connected with other sieve tube members and together they constitute the sieve tube. The main function of the sieve tube is transport of carbohydrates, primarily sucrose, in the plant e.g., from the leaves to the fruits and roots. Each sieve tube element is normally associated with one or more nucleated companion cells, to which they are connected by plasmodesmata.

Each companion cell is derived from the same mother cell as its associated sieve tube member. Sieve tube members have no cell nucleus, ribosomes or vacuoles. Companion cells are present only in angeosperms and absent in gymnosperms, primitive dicots and monocots. Thus, option C is correct.