Plant Tissue NCERT Notes | Tissue NCERT | The Cbse Solver

 

Tissue:

A group of cells which are similar in structure, function & origin and together they perform a particular function is called a tissue. 

Tissue is divided into two groups on the basis of cell wall- Plant Tissue & Animal Tissue.

Plant Tissue:

Plants are made up of various types of cell which come together to form Tissue. Further plant tissues ate divided in two groups on the basis of their dividing capability i.e. Meristematic Tissue ( Dividing tissue ) & Permanent Tissue ( Non-dividing tissue ). Meristematic tissues convert to Permanent Tissue by the process of Differentiation. Differentiation is the process of taking fixed shape, size, function of cells.

Meristematic Tissue:

The growing or dividing tissues are called Meristematic tissue. This tissue is very active, dense cytoplasm, thin cell wall, prominent nuclei and they lack vacoules due to fast division purpose.

 This tissue is also divided into three types on the basis of their location. 

• Apical Meristem: Apical is present at the tip of stem, branches and roots. It involved in the increase in plant height or length.

• Intercalary Meristem: Intercalary Meristeme is present at the internodes (space between two adjacent branches). It involved in the growth of leaves & internodes.

• Lateral Meristem: It is present at the girth of the stem and roots. It increases the diameter or thickness of the plant blody.

Permanent Tissue:

Earlier these tissues were Meristematic tissue but they lose the ability to divide and have taken a fixed shape, size and function to perform. There are two divisions of these tissues i.e. Simple Permanent Tissue & Complex Permanent Tissue.

1.  Simple Permanent Tissue: A few layers of cells which are found beneath epidermis are generally Simple Permanent Tissue. It includes Simple Protective Tissue and Simple Supporting Tissue.

Simple Protective Tissue: These are the outermost layers of plants. It includes Epidermis and Cork.

Epidermis:

•   It is the outermost living layer of all soft parts of the plants like young stems, roots, leaves, etc. 
• It is single layer of cells.
•  In desert plants, covered with waxy coating of cutin and have minute openings called stomata.
•  It acts as a protective tissue & allows exchange of gases.

Cork:

• It is made up of dead cells.
• It is the outermost protective tissue of old stems and roots.
• It is impervious to water and gasses due to the presence of SUBERIN.
• Prevents the entry of micro-organisms.

Simple Supportive Tissue:

Parenchyma: 

• It is the soft parts of the plants such as cortex and pith.
• Cells are thin walled, living cells, oval or round in shape and have lage vacuole.
• It stores the food.
• Acts as packing tissue.
• Privides mechanical support.

Parenchyma tissue is of two types-

Chlorenchyma: It the form of Parenchyma that contains the food producing pigment "chlorophyll" in plants.

Aerenchyma: It is another type of Parenchyma tissue that possess large air cavities and it is present in aquatic plants. It provides bouyancy to aquatic plants in water.

Collenchyma:

• It is present in the leaf stalks, and below the epidermis, etc.
• Collection of living cells.
• Elongated in shape.
• Have thickenings at the corners of the cell wall.
• Very little inter-cellular spaces are present.
• It provides flexibility and support to the plants.

Sclerenchyma:

• It is made up of dead cells.
• No inter-cellular spaces.
• Thick cell walls due to deposit of LIGNIN.
• It surrounds the the vascular bundles in stems.
• It present in leaf veins, makes covering of seeds.

        2. Complex Permanent Tissue: 

It is made up of more than one type of simple permanent cells that coordinate to perform a common function. Xylem and Phloem are examples of such complex tissues. They are both conducting tissues and constitute a vascular bundle. Vascular tissue is a distinctive feature of the complex plants.

Xylem: 

• Xylem consists of tracheids, vessels, xylem parenchyma and xylem fibres. 
• The cells have thick walls, and many of them are dead cells. 
• Tracheids and vessels are tubular structures. This allows them to transport water and minerals vertically.
• The parenchyma stores food and helps in the sideways conduction of water. 
• Fibres are mainly supportive in function.

 

Phloem:

• Phloem is made up of four types of elements: sieve tubes, companion cells, phloem fibres and the phloem parenchyma. 
• Sieve tubes are tubular cells with perforated walls. 
• Phloem is unlike xylem in that materials can move in both directions in it. 
• Phloem transports food from leaves to other parts of the plant. 
• Except for phloem fibres, phloem cells are living cells.