permanent tissues

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Structure and Functions of Permanent Tissues:

Structure and Functions of Permanent Tissues Prepared by- Arjun.T IX-A 9

Permanent Tissues:

Permanent Tissues These tissues derived from the meristematic tissues but their cells have lost the power of division & have attained their definite forms. Permanent tissues are classified into two-simple & complex. The meristematic tissues that take up a specific role lose the ability to divide. This process of taking up a permanent shape, size and a function is called cellular differentiation .

Simple permanent tissues:

Simple permanent tissues Simple permanent tissue -these tissues are composed of cells which are structurally & functionally similar.Thus,these tissues are all made of one type of cells. They are of three types- Parenchyma Collenchyma Sclerenchyma


Parenchyma Parenchyma is a term used to describe a bulk of a substance. It is used in different ways in animals and in plants. It consists of relatively unspecialized cells with thin cell walls. They are live cells. They are usually loosely packed, so that large spaces between cells(intercellular spaces)are found in this tissue. This tissue provides support to plants and also stores food. In some situations, it contains chlorophyll and performs photosynthesis, and then it is called chlorenchyma.


Collenchyma Cells are thin-walled but possess thickeningof cellulose and pectin substances at the corners where number of cells join together. This tissue gives a tensile strength to the plant and the cells are compactly arranged and do not have inter-cellular spaces. It occurs chiefly in hypodermis of stems and leaves. It is absent and in roots.


Sclrenchyma Sclerenchyma is Greek word where "Sclrenes" means hard and "enchyma" means infusion. This tissue consists of thick-walled, dead cells. These cells have hard and extremely thick secondary walls due to uniform distribution of lignin . Lignin deposition is so thick that the cell walls become strong, rigid and impermeable to water. Sclerenchymatous cells are closely packed without inter-cellular spaces between them. Thus, they appear as hexagonal net in transverse section .

Complex permanent tissues:

Complex permanent tissues The complex tissue consists of more than one type of cells which work together as a unit. Complex tissues help in the transportation of organic material, water and mineral up and down the plants. That is why it is also known as conducting and vascular tissue. The common types of complex permanent tissue are: Xylem or wood Phloem or bast


xylem Xylem is a very important plant tissue as it is part of the ‘plumbing’ of a plant. Think of bundles of pipes running along the main axis of stems and roots. It carries water and dissolved substances throughout and consists of a combination of parenchyma cells, fibers, vessels, tracheids and ray cells. Long tubes made up of individual cells are the vessels, while vessel members are open at each end. Internally, there may be bars of wall material extending across the open space.


phloem Phloem is an equally important plant tissue as it also is part of the ‘plumbing’ of a plant. Primarily, phloem carries dissolved food substances throughout the plant. This conduction system is composed of sieve-tube member and companion cells, that are without secondary walls. The parent cells of the vascular cambium produce both xylem and phloem. This usually also includes fibers, parenchyma and ray cells. Sieve tubes are formed from sieve-tube members laid end to end.

Protective Tissues:

Protective Tissues These tissues are usually present in the outermost layer of the plant body such as leaves, stem and roots. It is one cell thick and covered with cetin and protects the underlying tissues present in the plant body. Protective tissues are of 2 types Epidermis Cork


epidermis The main function of epidermis is to protect the plant from desiccation & infection. In fact, cuticle of epidermis helps to reduce water loss by evaporation from the plant surface as well as helping in preventing the entry of pathogens.


COrk As plants grow older,the outer protective tissue undergoes certain changes.A strip of secondary meristem, called phellogen or cork cambium replaces epidermis of stem. Cork cambium is a simple tissue having only one type of cells. The cells of cork cambium are rectangular & their protoplasrs are vacuolated & contain tannins & chloroplasrs.

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