Chapter: 7 Control and Coordination
Stimuli
The changes in the environment to which the organism respond & react are called stimuli. For
example: heat, light, cold, sound, smell etc.
Coordination
The working together of various organs of an organism in a systematic manner so as to produce a
proper response to the stimulus is called coordination.
Ques: What is the difference in the way plants and animal response towards stimulus?
Plants Animals
Plants respond to of stimulus in a very limited Animals respond toward stimulus in many
way because they don't have nervous system different way because they have nervous system
They use only hormones for reproducing They use both nervous system as well as
reaction endocrine system (hormonal system) for
producing reactions
These responses release very slowly these respond to stimulus quickly
Ques: What is the need for a system of control and coordination in an organism?
i) This system is necessary for survival of an organism in the world.
ii) This system allows the stomata in the leaves to open for CO2 gas the roots to bend towards
water and the shoot to bend towards sunlight.
iii) In human beings this system is needs for all actions, thinking and behaviour
Control and coordination in plants
The plants coordinate their behaviour against stimuli by using hormones. The hormones coordinate
their behaviour by affecting their growth. The plants respond to various stimuli very quickly by
growing.
Metabolism
The chemical reaction which takes place in the body of living organism to maintain their life is called
metabolism.
Dormancy
A resting inactive condition in which metabolism almost stop is called dormancy. For example:
1. The seed of a plant is dormant and requires condition like water, warmth, air and hormones
to break it dormancy.
2. A bud is a young undeveloped shoot of the plant which requires certain plant hormones to
break dormancy
Phytohormones
, The plant hormones are known as phytohormones. They coordinates the activities of plants by
controlling one or more aspects of growth. The growth of a plant can be divided in three stages:
i) cell division ii) cell enlargement iii) cell differentiation
Types of Phytohormones
The major types of plant hormones are:
1. Auxin
2. Gibberellins
3. Cytokinin
4. Abscisic acid (ABA)
5. Ethylene
Functions of plant hormones
Phytohormones helps in:
1. Promotion of dormancy
2. Breaking of dormancy
3. Opening and closing of stomata
4. Falling of leaves
5. Growth of plants
6. Ripening of fruits
7. Phototropism, geotropism, chemotropism, thigmotropism and nastic movements
Auxin:
1. It promotes cell enlargement and all differentiation
2. It promotes food growth
3. It is made by the cells at the tips of stems and roots
4. It moves away from light, gravity and support
5. It speeds up growth in stem but it slows down growth in roots
6. This hormones is made and secreted by meristematic tissue at the tip of the stem
Gibberellins:
1. It promotes an enlargement and cell differentiation in presence of oxygen
2. It helps in breaking dormancy of seeds and birds
3. It promotes growth in food
Cytokinin:
1. It promotes cell division
2. It helps in breaking of dormancy of seeds and buds
3. It delivers the ageing in leaves
4. It promotes opening of stomata
5. It promotes fruits growth
Abscisic acid (ABA):
1. It acts as growth inhibitor
2. It promotes the dormancy in seeds and buds
, 3. It promotes closing of stomata
4. It promotes witting and falling of leaves
5. It is responsible for detachment of flowers and fruits from the plants.
Ethylene:
1. It helps in ripening of fruits
Ques: How auxin causes the stem to bend?
If one side of stem has more auxin then the other side having more auxin will grow faster which
causes the stem to bend
Plant movement
There are two major types of plant movements,
i) Tropic movement (Tropism) ii) Nastic movement (Nasties)
All the tropic movements are the growth moments but all the nastic movements are not necessary
the growth movements
Tropic movements
A growth movement of plant in response to an external stimuli in which the direction of stimuli
determines the direction of response is called a tropic movement. It is a directional movement.
1. If the growth of plant part is towards the stimuli, it is called positive tropism
2. If the growth of plant part is away from stimuli, it is called negative tropism
Types of tropism
There are five common types of tropism,
Stimulus Tropic Movement
Light Phototropism
Water Hydrotropism
Chemical Chemotropism
Gravity Geotropism
Touch Thigmotropism
Phototropism
The movement of a plant part in response to light is called phototropism.
1. If the plant part moves towards the light it is called positive phototropism
2. If the plant part moves away from the light it is called negative phototropism
Experiment
Take a potted plant and kept it in an open space such that sunlight flows from above we will notice
that:
1. The stem of plant grows straight upwards towards the sun while roots of the plant
grows straight downwards
Stimuli
The changes in the environment to which the organism respond & react are called stimuli. For
example: heat, light, cold, sound, smell etc.
Coordination
The working together of various organs of an organism in a systematic manner so as to produce a
proper response to the stimulus is called coordination.
Ques: What is the difference in the way plants and animal response towards stimulus?
Plants Animals
Plants respond to of stimulus in a very limited Animals respond toward stimulus in many
way because they don't have nervous system different way because they have nervous system
They use only hormones for reproducing They use both nervous system as well as
reaction endocrine system (hormonal system) for
producing reactions
These responses release very slowly these respond to stimulus quickly
Ques: What is the need for a system of control and coordination in an organism?
i) This system is necessary for survival of an organism in the world.
ii) This system allows the stomata in the leaves to open for CO2 gas the roots to bend towards
water and the shoot to bend towards sunlight.
iii) In human beings this system is needs for all actions, thinking and behaviour
Control and coordination in plants
The plants coordinate their behaviour against stimuli by using hormones. The hormones coordinate
their behaviour by affecting their growth. The plants respond to various stimuli very quickly by
growing.
Metabolism
The chemical reaction which takes place in the body of living organism to maintain their life is called
metabolism.
Dormancy
A resting inactive condition in which metabolism almost stop is called dormancy. For example:
1. The seed of a plant is dormant and requires condition like water, warmth, air and hormones
to break it dormancy.
2. A bud is a young undeveloped shoot of the plant which requires certain plant hormones to
break dormancy
Phytohormones
, The plant hormones are known as phytohormones. They coordinates the activities of plants by
controlling one or more aspects of growth. The growth of a plant can be divided in three stages:
i) cell division ii) cell enlargement iii) cell differentiation
Types of Phytohormones
The major types of plant hormones are:
1. Auxin
2. Gibberellins
3. Cytokinin
4. Abscisic acid (ABA)
5. Ethylene
Functions of plant hormones
Phytohormones helps in:
1. Promotion of dormancy
2. Breaking of dormancy
3. Opening and closing of stomata
4. Falling of leaves
5. Growth of plants
6. Ripening of fruits
7. Phototropism, geotropism, chemotropism, thigmotropism and nastic movements
Auxin:
1. It promotes cell enlargement and all differentiation
2. It promotes food growth
3. It is made by the cells at the tips of stems and roots
4. It moves away from light, gravity and support
5. It speeds up growth in stem but it slows down growth in roots
6. This hormones is made and secreted by meristematic tissue at the tip of the stem
Gibberellins:
1. It promotes an enlargement and cell differentiation in presence of oxygen
2. It helps in breaking dormancy of seeds and birds
3. It promotes growth in food
Cytokinin:
1. It promotes cell division
2. It helps in breaking of dormancy of seeds and buds
3. It delivers the ageing in leaves
4. It promotes opening of stomata
5. It promotes fruits growth
Abscisic acid (ABA):
1. It acts as growth inhibitor
2. It promotes the dormancy in seeds and buds
, 3. It promotes closing of stomata
4. It promotes witting and falling of leaves
5. It is responsible for detachment of flowers and fruits from the plants.
Ethylene:
1. It helps in ripening of fruits
Ques: How auxin causes the stem to bend?
If one side of stem has more auxin then the other side having more auxin will grow faster which
causes the stem to bend
Plant movement
There are two major types of plant movements,
i) Tropic movement (Tropism) ii) Nastic movement (Nasties)
All the tropic movements are the growth moments but all the nastic movements are not necessary
the growth movements
Tropic movements
A growth movement of plant in response to an external stimuli in which the direction of stimuli
determines the direction of response is called a tropic movement. It is a directional movement.
1. If the growth of plant part is towards the stimuli, it is called positive tropism
2. If the growth of plant part is away from stimuli, it is called negative tropism
Types of tropism
There are five common types of tropism,
Stimulus Tropic Movement
Light Phototropism
Water Hydrotropism
Chemical Chemotropism
Gravity Geotropism
Touch Thigmotropism
Phototropism
The movement of a plant part in response to light is called phototropism.
1. If the plant part moves towards the light it is called positive phototropism
2. If the plant part moves away from the light it is called negative phototropism
Experiment
Take a potted plant and kept it in an open space such that sunlight flows from above we will notice
that:
1. The stem of plant grows straight upwards towards the sun while roots of the plant
grows straight downwards
