Tissues Class 9 Short Notes | Chapter 6

Class 9 Science Notes on Tissues

Introduction

Think about the different organisms we have read about.
Now let us list a few:
1.      Amoeba
2.      Rose plant
3.      Cockroach
4.      Crow
5.      Dog
6.      Mango tree
7.      Elephant
8.      Human Being

Note- What is common between all these organisms?

They are all living

What is a common factor in all living organisms?

They are composed of cells.

 

In organisms like Amoeba, Paramecium, Euglena etc. a single cell is responsible for all the life supporting processes like respiration, digestion, movement, excretion etc. They are single celled or unicellular organisms.

On the other side, organisms like animals, plants and human beings are made up of multiple cells and are called multicellular organisms.

Millions of cells work is responsible for the life supporting processes in multicellular organisms

They are grouped to perform specialised functions

For Example:

In animals –

1.      Muscle cells contract and relax to cause movement.

2.      Nerve cells carry messages

3.      Blood flows to transport oxygen, food, hormones and waste material.

In plants –

1.      Vascular tissues conduct food and water from one part of the plant to other parts.

Cells that are responsible for a particular function are grouped together.

A group of cells that are similar in structure and work together to achieve a particular function forms a tissue.

Example – Blood, Phloem, Muscles

This means, there is division of labour in multicellular organisms, as a group of cells called tissues are specialised for different activities.

So the levels of organisation in organisms are:

Plants and animals are multicellular organisms

They are thus composed of cells

Cells perform function together forming tissues

 

Notes – plants and animals have the same type of tissues?

Answer is NO

 

Difference Between Plant and Animal Tissues

Plant Tissues	Animal Tissues
Plants do not move from one place to another. They require structural strength and support.	Animals move from  one space to another for food, shelter, mating etc. and require tissues to support that
Plant growth is limited to only certain regions	Animals have overall growth patterns
The tissues are distinguished as meristematic (capable of dividing) and permanent (do not divide)	There is no such difference in animal tissues
Plant tissues have a simple organization	Animal tissues are further organized into more specialized and localized organs and organ systems
They have mostly dead tissues as dead cells provide strength and support	They have mostly living tissues
These tissues do not require much maintenance	These tissues require more maintenance
Thus plant tissues are targeted towards sedentary or stationary existence of plants	Thus animal tissues are targeted towards locomotory and highly mobile nature of animals.
Examples – Xylem, Phloem, Apical, Meristems	Examples – Muscles, Blood, Bone

 

 

Plant Tissues

Plant tissues are two types

1.      Meristematic Tissues

They are further divided into 3 types

1.      Apical Tissues

2.      Lateral Tissues

3.      Intercalary Tissues

 

2.      Permanent Tissues

Permanent tissues are divided into 2 types

1.      Simple Tissues- which are of 3 other types

Parenchyma, Collenchyma, Sclrenchyma

 

2.      Complex Tissues- which are of 2 types

Phloem, Xylem

 

 

3.      Meristematic Tissues

Take 2 onions and put them in 2 separate jars as shwn below

Observe how the roots grow each day for 3 days

Now, cut the root tips of the onion in both the jars and observe the growth for another 3 days.

What do you observe?

We observe that plant growth is restricted to certain regions. In this case the roots.

This is because the dividing tissues responsible for growth is present only in these regions

These dividing tissues are called meristematic tissues.

Characteristic of meristematic tissues

Characteristics	Remarks
Structure	All cells are similar with thin cell wall made of cellulose
Shape	Spherical, oval, polygonal, rectangular
Cellular arrangement	Compact without intercellular space (no space between cells)
Cellular content	They have dense cytoplasm and single large nucleus few or no vacuoles at all
Position	Tips of roots and shoot, bark or stem, base of leave etc.

 

Types of Meristematic tissues (based on position)

Apical Meristem

1.      They are present at the growing apices (tips) of stems and roots and sometimes leaves as well

2.      They increase the length of the roots and shoot.

3.      This results in increase in height of the plant

4.      This is called primary growth

Lateral Meristem

1.      They are also called cambium

2.      They increase the girth or thickness of the root or bark/stem

3.      This is called secondary growth

Intercalary Meristem

1.      It is present at the base of the leaves or internodes (on either side of the node_ on twigs

2.      It increases the length of an organ like internode or leaves

 

Permanent Tissues

The meristematic tissues are capable of dividing but at a point these cells take up a specific role and lose the ability to divide. So, when the cells attain permanent shape, size and function it is called differentiation.

The cells of meristematic tissues undergo differentiation to form permanent tissues.

Permanent tissues are further divided into-

1.      Simple permanent tissues

2.      Complex permanent tissues

Simple permanent tissues

Parenchyma Tissues

1.