Complex permanent tissue -1) xylem
2) phloem
Mention the different parts and its functions
Answers
Xylem
Xylem originates from the Greek word “xylon” that means wood. Carl Nägeli coined the word xylem. Xylem is a type of vascular tissue present in plants, which primarily transports water and nutrients from roots to stem and leaves. They also provide mechanical strength to the plants.
On the basis of origin, there are two types of xylem cells:
Primary xylem: originating from procambium, further divided into protoxylem and metaxylem
Secondary xylem: originating from the vascular cambium
Xylem is composed of four different kinds of elements:
Tracheids: Dead, tube-like cells with a tapering end. 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.
Vessels: They are present in angiosperms. These are a long cylindrical structure having tube-like appearance. The walls are lignified and have a large central cavity. 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.
Xylem Fibre: Dead cell with lignified walls and a central lumen. Involved in water transportation and providing mechanical support.
Xylem Parenchyma: Only living cells of xylem and store starch and fat. They assist in the short distance transportation of water.
Phloem- It consists of four of elements: sieve tubes, companion cells, phloem fibres and the phloem parenchyma. Unlike the xylem, phloem conducts in both directions. It is responsible for transporting food from the leaves to the other parts of the plant. Phloem contains living tissues except for fibres that are dead tissues.