PLANT TISSUES

A tissue is formed by a group of cells which are similar in structure and perform similar functions. There are two different types of tissues present in plants ;   the simple tissue and the complex tissues. The meristematic tissue, the ground tissue, the dermal tissue are simple tissues whereas the vascular tissue is a complex tissue .

THE TYPES OF SIMPLE TISSUES:

I.  MERISTEMATIC TISSUE

These are called as the growing tissue in plants. They help in bringing about the  growth in length and diameter in plants. The cells in these tissue are small ,with prominent nucleus and abundant cytoplasm. The cells are continuously dividing ,compactly arranged without any intercellular spaces. Depending upon the regions where these tissues are present, they can be classified as :

APICAL MERISTEMATIC TISSUE

These are present at the growing regions of shoot tip and root tip. They bring out the growth in length of plants.

LATERAL MERISTEMATIC TISSUE

These are present at the lateral sides of stem and root. They bring out the growth in width or diameter of plants.

INTERCALARY MERISTEMATIC TISSUE

These are present at the internodes or at the buds. They are present at the places from where the branches,leaves,flowers or fruits arises.

II.  THE DERMAL TISSUES

The group of cells which forms the outer covering of the plants and provides protection to them together forms dermal tissue . They can be of three different types; the epidermis,the  

mesodermis and the endodermis.

The epidermis gives rise to structures such as the stomata which helps in loss of water through transpiration and exchange of gases,the roothair for absorption of water and nutrients from the soil,the bark or cork which substitute the epidermis in old and mature stems and roots . Cork cells are lifeless and lack intercellular spaces. Their cellwalls are are coagulated by suberin, which makes them impervious to gas and  water molecules.

III . THE GROUND TISSUES

These tissues occupies the major portion of plant body and add bulk to the plants . They store food and nutrients. They are of three different types depending on the functions they perform .

A.The  parenchyma : The cells are large with big vacoules and intercellular spaces. The parenchyma consisting of chloroplasts are called as chlorenchyma . They help in photosynthesis.

The parenchyma which has large air cavities in them are called as aerenchyma . They help the aquatic plants to float and maintain buoyancy.

Aerenchyma tissue

The parenchyma which stores food and water are called storage tissue.

B.The collenchyma: These have living  cells with few intercellular spaces. Their cellwalls are made of pectin and cellulose and they give the mechanical support to the plants .

C.The scelerenchyma: These have long cells with many intercellular spaces. The cells are dead with legnin in their cellwalls. They provide strength to the plants.

 THE COMPLEX TISSUE:

I . VASCULAR TISSUES /PERMANENT TISSUES/ TRANSPORTING TISSUES

The cells which have lost the ability to divide and produce new cells form permanent tissues. But they still give Elasticity, flexibility and strength to the plants. They are further categoried into

XYLEM and PHLOEM.

a. XYLEM:

It helps in the transport of dissolved substances and water all through the plant. The diverse components of the xylem include vessels, tracheids, xylem fibres and xylem parenchyma. Xylem fibres and Tracheids are made up of lignin, which provides structural support to the plant.

b. PHLOEM: 

This tissue helps in the transportation of food all through the plant. The diverse elements of phloem include phloem fibres, sieve tubes, phloem parenchyma and companion cells.