What is meant by permanent tissue ? Give its types.

$\rightarrow$ Following divisions of cells in both primary and as well as secondary meristems, the newly formed cells become structurally and functionally specialised and lose the ability to divide. Such cells are termed permanent or mature cells and constitute the permanent tissues.

$\rightarrow$ There are two types of permanent tissues : $(A)$ Simple Tissues $(B)$ Complex Tissues.

$(A)$ Simple Tissues : The cells of the permanent tissues do not generally divide further. Permanent tissues having all cells similar in structure and function are called simple tissues. There are 3 types of simple tissues : $(a)$ Parenchyma $(b)$ Collenchyma $(c)$ Sclerenchyma. $(a)$ Parenchyma Tissues : Parenchyma forms the major component within organs.

$\rightarrow$ The cells of the parenchyma are generally isodiametric.

$\rightarrow$ They may be spherical, oval, round, polygonal or elongated in shape.

$\rightarrow$ Their walls are thin and made up of cellulose.

$\rightarrow$ They may either be closely packed or have small intercellular spaces.

$\rightarrow$ Importance : The parenchyma performs various functions like photosynthesis, storage, secretion.

$(b)$ Collenchyma Tissues: The collenchyma occurs in layers below the epidermis in dicotyledonous plants. It lacks in monocotyledonous and under ground parts of the plant.

$\rightarrow$ It is found either as a homogeneous layer or in patches.

$\rightarrow$ It consists of cells which are much thickened at the corners due to a deposition of cellulose, hemicellulose and pectin.

$\rightarrow$ Collenchymatous cells may be oval, spherical or polygonal and often contain chloroplasts.

$\rightarrow$ These cells assimilate food when they contain chloroplasts.

$\rightarrow$ Following divisions of cells in both primary and as well as secondary meristems, the newly formed cells become structurally and functionally specialised and lose the ability to divide. Such cells are termed permenent or mature cells and constitue the permenant tissues.