Question

What is xylem? Explain the structure of various kinds of components of xylem.

Answer 1

Hint: Plants have transport tissues which help in transportation of water, minerals and nutrients. Xylem is a type of transport tissue in vascular plants. The other type of transport tissue is phloem.

Complete Answer:
Xylem is a type of vascular tissue present in plants. Its primary function is to transport water and nutrients from roots to stem and leaves. They also provide mechanical strength to the plants. Xylem helps in the conduction of water in plants in uni-direction.

The xylem is composed of four different kinds of elements:
1. Tracheids: These are elongated, tube-like cells with a tapering end and are dead. They are present mostly in gymnosperm and lower angiosperm. They have a thick lignified wall and lack protoplasm. Their main function is water and mineral transportation.
2. Vessels: These are a long cylindrical structure having a tube-like structure. They have lignified walls and have a large central cavity. They are present in angiosperms. They are also dead and lack protoplasm. They have many cells called vessel members which are interconnected through a perforation in common walls. Mostly involved in the conduction of water, minerals and give mechanical strength to the plant.
3. Xylem Fibre: Dead cell with lignified, thick walls, and an obliterated central lumen. They help in the transportation of water and provide mechanical support.
4. Xylem Parenchyma: It is the only living cells of xylem and stores starch and fat. They assist in the short distance transportation of water.

Note: It is to be noted that on the basis of origin, there are two types of xylem cells:
i. Primary xylem: It originates from procambium and further divides into protoxylem and metaxylem.
ii. Secondary xylems: It originates from the vascular cambium.