TISSUE

                      
                         TISSUE
                                          (By: Ghanshyam kr. chaudhary)

Tissue: A group of specialised cell having a common origin, similar shape and specific or common generalised function is known as tissue.
Types of tissues:
Their are mainly two types of tissues

Qus: Write/ discuss the importance of tissues?
Ans:Tissues are very important due to the following reasons:

• They are organised to form different organs and organ system.
• They divide the work labour in multicellular organisms.

classfy the plant tissue:
Plant tissues is broadly classified into two groups
1. Meristematic tissue,
2. permanent tissue.
( Note: meristematic and permanent tissues is further classifed into the following categories as shown in block
diageram. )

Explanation

A. Meristematic tissue:

• It consists of simple living tissues having thin cellulose cell walled compactly arranged immature cells which are capable of division and posses totipotency i.e. capability to divide and form new types of cells.
• They found in growing regions of the plants.
• They are responsible for the formation of new cells of the plants.
• These cell divides rapidly and help in increasing the length and girth of the plant.

Meristematic tissues are classified into the following groups which are as follows:

1. Apical meristems:

• They are present at the tip of the stems i.e shoot apex and roots i.e root apex.
• It help in elongation of root and stems which cause the length of the plant will increase.
• It is responsible of primary growth.

2. Lateral meristems:

• It present along the sides of longitudional axis of the plant.
• It help in the formation of vascular bundles.
• It help to increase the diameter and girth of stems or root.
• It is also called as secondary meristems and responsible for secondary growth of the plant.

3. Intercalary meristems:

• They are located at the base of the leaves or internodes.
• They increase the length of the leaves and internodes.
• ( Note: Intercalary Meristems is a part of apical Meristems which is left behind during the growth period.)

B. Permanent tissues:

• The division and differentiation of the cells of meristematic tissue give rise to permanent tissues.
• These are the group of those meristematic tissues which have lost their division capability.
• Permanent tissue have definite shape, size and thickness.
• (Note: meristematic tissues are living while the permanent tissue may be dead or living.)

On the basis of structure composition and function permanent tissue are classified into two groups:

1. Simple permanent tissues &
2. Complex permanent tissues.

Explanation:
1. Simple permanent tissues are made up of one kind of cells which are similar structurally and functionally.
Simple permanent tissue are three types,

• Parenchyma,
• Collenchyma &
• Sclerenchyma.

Parenchyma

• It is the fundamental tissue because, it is widely distributed in plant body such as stems, roots, leaves, flowers and fruits.
• It cells are isodiametric and it contain live Protoplasm.
• It serve as a food storage and packing tissue.
• It also store waste products of the plant.

Collenchyma

• It is located below the epidermis of Dicot stem and petiole.
• It consist of living cells.
• The characteristics property of the these cells are it contain extra depositions of the cellulose at the corner of each cell.
• It is mechanical tissue in young plant.
• It provide mechanical support and elasticity in young stems of dicotyledonous plant.
• They manufacture sugar and starch if their cells processes chloroplast.

Sclerenchyma

• It consist of dead lignified cells.
• It occur in abundance or in patches in definite layers, in stems, roots, veins or leaves, hard covering of seeds and nut It provide mechanical support to the plant.
• Sclerenchyma contains two types of cell:
• fibres &
• sclereids (stone cell).

Some conceptual Question:


Qus. Defined the term idioblast?
Ans. Secretory cells of the plant is known as idioblast.
It store and secret resin, tannins, guns & oil.
Qus. Why parenchyma cells are called idioblast?
Ans. Some parenchyma tissueand their cells involved in storage of excretory substance, so it is called as idioblast.
Qus. Write the primary function of parenchyma?
Ans. The primary function of parenchyma is storing the food.
Qus. (a) Write the name of parenchyma tissue when it contain chlorophyll?
(b) Write the function of this tissues?
Ans. Chloroplast (chlorophyll) containing parenchyma tissues are known as chlorenchyma.
(b) Function:
(i.) Normal parenchyma ( i.e  parenchyma) without chloroplast is involved in storing the food material inside the plant cell.
(ii.) Parenchyma containing chloroplast ( i.e chlorenchyma) perform photosynthesis.
Eg. mesophyll cells (tissue) of the leaves.
Qus. Why the hydrolytic or water plant floating on the surface of water?
Ans. In hydroelectric plant aerenchyma (a type of parenchyma containing large air space) provide a force of buoyancy which is responsible for floating the hydrolytic plant in surface of water.

Complex permanent tissue

• Complex tissue consists of more than one kind of cells having a common origin.
• Complex tissue are involved in transportation of organic materials, water and Minerals.
• It is also known as conducting or vascular tissue.
• (Note: xylem and phloem arrange together to form vascular bundle or vascular tissue or bundle sheeth.)

xylem
It is a conducting tissue composed of four different types of cells that is:
1. Tracheids,
2. Vessels,
3. Xylem parenchyma &
4. Xylem fibre.
( Note: except xylem parenchyma, all other component of the xylem are dead and lignified cells.)
Function

• Tracheids and vessels are involved in the conduction of water.
• Xylem parenchyma store food and help in lateral conduction of water.

Phloem
It is also conducting tissue composed of four different types of cells that is:
1. Sieve tubes,
2. companion cell,
3. Phloem parenchyma &
4. Phloem fibre.
( Note: except phloem fibre, all other component of the phloem are living.)

Function

• Sieve tube and companion cells work together as a single unit.
• Phloem transport photosynthetically prepared food materials from the leaves to the storage organs and later from storage organ to the growing region of the plant body.

Qus. write the difference between xylem and phloem?
Ans. Xylem

• It conduct water and Minerals.
• Conduction is unidirectional i.e form route to apical part  re of the plant.
• Conducting cells of xylem are tracheids and vessels.
• It provide mechanical strength to the plant.
• Except xylem parenchyma, it is composed of dead cell 

Phloem

• It conduct organic solute or food materials.
• Conduction is bidirectional.
• Conducting cells of phloem are sieve tubes.
• It has no mechanical function in the plant.
• Except phloem fibre it is composed of living cells.

 Animal Tussue
It is Divided into four groups, these are as follows:
Epithelial tissue it is it is the simplest animal tissue and it is also known as protective tissue in animal body they are tightly packed and contain very little or no matrix it cover most of the organs and cavities  within the body.
Make it forms barrier and separate different body systems the skin and lining of buccal cavity blood vessels alveoli and kidney tubules are made up of the epithelial tissue note epithelial tissue maybe simple that is composed of single layers of cells or stratified that means made up of several layer of cells epithelial tissue is classified into four different group depending upon the shape and function first squamous epithelium cuboidal epithelium nominal glandular epithelium ciliated epithelium.
Function the main function of epithelial tissue are as follow it forms the outer layer of skin and protects the underlining underline underlying lying cells from drying injury and chemical effect it forms the lining of mouth and alimentary canal and protects these organ it helps in elimination of waste product it helps in absorption of water and nutrients.