Question

Sieve tubes are the constituent of
A) Wood
B) Vascular Cambium
C) Phellem
D) Bast

Answer 1

Hint: Sieve tubes are the perforated areas in the end walls which help in transport of food to the different parts of the plant. They do not have nuclei.

Complete Answer:
- Sieve tubes are the specialised cells which transport the food synthesised during photosynthesis. They originate at the meristem.
- Its major function is to transport sugars over large distances by acting as a channel.
- The porous cells help in establishing cytoplasmic connection between the neighbouring cells and thus result in movement to molecules. They lack nucleus but contain a few ribosomes. They are the major conducting cells in the phloem.

A) Vascular cambium- It is the major growth tissue in the stem and roots. It contains meristem cells.
B) Phellem- Phellem is also known as cork. It is composed of dead cells.
C) Wood- It is the structural tissue found in the roots and stem of the plants.
D) Bast- Phloem fibres are also called bast fibres. They are present in the inner bark and are fibrous in nature. Jute, flax, hemp etc are obtained from the fibrous phloem tissue.

Thus the correct answer is (D). Sieve tubes are constituent of bast or phloem.

Note: Sieve tube cells are elongated cells placed vertically with perforations. Sieve tube cells along with the companion cells play a major role in conduction of food in the plants.