Question

Name the different types of cells that form xylem.

Answer 1

Hint: The complex tissues are made up of more than one type of cells. These cells differ from one another in their form and structure; however, these cells work together as a unit. The two types of complex tissues are found in the plants: the Xylem and the Phloem.

Complete step-by-step answer:
The xylem is the chief water-conducting tissue of the plants. The xylem functions as a conducting tissue for the water and the minerals from the roots to the top of plants, i.e., to the stems and leaves. It is made up of the following elements.
Tracheids:
Structure: These are the elongated cells with the tapering ends. These are the tube-like cells with both ends taper slowly to give an appearance of pointed ends.
The tracheids have thick and lignified walls.
These are the dead cells and are without protoplasm.
Occurrence: The tracheids are found in all categories of vascular plants, i.e., the Pteridophytes,
Gymnosperms and the Angiosperms.
Functions: The main purpose of the tracheids is to transport the water and minerals from roots to stems and leaves. Due to the presence of thickened and hard walls, they also provide the mechanical support to the plant body.
Vessel:
Structure: The vessels are also called the tracheae. The vessel is a long cylindrical tube-like structure made up of many cells. These cells which constitute the vessel are called the vessel members or the vessel elements.
Occurrence: The presence of vessels is a characteristic feature of the angiosperms. The gymnosperms and the pteridophytes lack vessels in their xylem, although other xylary elements are present in them to permit the conduction of the water and minerals.
Functions: The longitudinal water and mineral transport mechanical support.
Xylem fibres :
They are the sclerenchymatous fibres. They are long, narrow and tapering at both ends. They are also the dead elements like the vessels and tracheids. They have highly thickened lignified walls. The xylem fibres have obliterated central lumens. They are obliterated due to very thick walls which leaves no space inside them.
Occurrence: The xylem fibres are the components of the xylem in all categories of the vascular plants.
Functions: They are mechanical in function and provide support to the plant organs.
  Xylem parenchyma :
The cells of the xylem parenchyma are living and thin-walled. Their cell walls are made up of cellulose. They have a prominent nucleus and the dense cytoplasm.
Occurrence: The xylem parenchyma is present in the xylem of all vascular plants.
Functions: The xylem parenchyma cells, as usual, store food materials in the form of reserve foods like starch or fat. They also store other substances like tannins.

Note: The xylem parenchymatous cells help in the radial conduction of the water, i.e., in the radial directions. It is also called the lateral conduction. The parenchymatous cells which help in the radial conduction of the water are called the ray parenchyma cells.