Control and Coordination

Science
CLASS - 10th
 About Your Teacher

● Cleared JEE Mains + advanced

● Mentored 1 Lakh+ Students

● Author of Two Books for Class 10th

Prashant Kirad
 What We’ll Provide!

● Lectures

● Top 25 Questions

● Sample Papers
(NCERT Exercises Included)
 Topics We’ll Cover!
● Human Nervous System
● Peripheral Nervous System
● Neurons
● Brain
● Spinal Cord
● Three types of Responses
● Glands
● Pancreas
● Control and Coordination in Plants
 Human Nervous System

Central Nervous Peripheral Nervous

System (CNS) System (PNS)
 Human Nervous System

Central Nervous Peripheral Nervous

System (CNS) System (PNS)

Brain Spinal Cord

Peripheral Nervous System
Reflex Action:
It is quick, sudden and immediate response of
the body to a stimulus.
Example - Knee jerk, withdrawal of hand on
touching an object.
 Peripheral Nervous System
Three types of Nerves:
● Spinal nerves arise from the spinal cord along most to the length of the spinal
cord and spread throughout the body (except the head).
● Cranial nerves arise from the brain and spread throughout the head. They
carry both sensory and motor neurons.
● The visceral nerves arise from the spinal cord. They are connected to the
internal organs of the body. They carry both sensory and motor neurons.
STIMULI
The factors which bring response or change in the environment.
Example : Light, Heat, Cold, Sound, Smell, Touch etc.
Receptor and Effector

● A receptor is a cell (or a group of cells) in a sense organ which is sensitive to a

particular type of stimulus. Example: Nose and ears.

● An effector is a part of the body which can respond to a stimulus according to

the instructions sent from the nervous system (spinal cord and brain). Example:
Glands and muscles.
Receptors
These are special tips of some nerve cells that detect information from the
environment. These are located in our sense organs.
Receptors
1. Ear
● It acts as phono receptors
● It helps in hearing and maintaining the
balance of the body.
Receptors
2. Eyes
● It acts as photoreceptors
● It helps in seeing.
Receptors
3. Nose
● It acts as olfactory receptors. It helps in detection of the smell.
Receptors
4. Tongue
It acts as Gustatory receptors. It helps in
detection of taste.
Receptors
5. Skin
It acts as thermoreceptors. It helps in feeling heat or cold and touch.
Important Questions
Q. How to we detect the smell of agarbatti?
Neuron
● Structural and functional unit of Nervous System.
● Neuron is a highly specialized cell.
● Responsible for the transmission of signals to and
from the different parts of the body.
● Structural and functional unit of nervous system.
● Longest cell in human body.
 Neuron
Parts of Neuron:
1. Dendrite :
It acquires information and receive impulse from other neurons.

2. Cell Body:
The information acquired by it
travels as an electric impulse.
Neuron
Parts of Neuron:
3. Axon:
● Longest fiber on the cell body is called axon.
● It transmits electrical impulse from cell body to dendrite of next neuron.
● It may be myelinated or unmyelinated Impulse transmission is faster in
myelinated neurons.
Functions of Neuron
● The information or signals from receptors is acquired at the end of the
dendritic tip of a nerve cell as chemical reaction that creates an electric
impulse.
● This impulse travels from the dendrite to the cell body and then at the end
of the axon.
● There is a gap between two neurons called (Synapse ). These chemicals
cross the gap and transfers the same signal to next neuron.
● Chemicals are released at the end of the the axon by the effect of electrical
impulse.
 How exactly do these
signals pass through and
between neurons?
Nerve Impulse
● Nerve impulses are wave of electrical and chemical signals carried along
nerves or neurons.
● Nerve impulses are initiated at receptor cells as a result of stimuli from the
environment.
 Types of Neuron

Sensory neurons Motor neurons Interneurons

(afferent neuron) (efferent neurons) (relay or associated
neuron)
They help in transmitting They help in transmitting
nerve impulse from nerve impulse from They connect sensory
receptor to central central nervous system to and motor neuron.
nervous system. a muscle or gland.
Neuromuscular Junction
The neuromuscular junction (NMJ) is a synaptic connection between the
terminal end of a motor nerve and a muscle.
 Voluntary actions Involuntary actions Reflex actions
● These actions can be ● These actions cannot be ● These actions can not be
controlled by our own will. controlled by our own will. controlled by our own will.
● Thinking involved. ● Thinking not involved. ● Thinking is not involved.
● Brain involved. ● Brain is involved. ● Spinal Cord is involved.

eg. Walking eg. Pumping of Blood eg. Withdrawal of hand

Writing Peristaltic movements when touch an hot object.
Dancing Contraction relaxation of
Jumping blood vessels
Brain
● Highest coordinating centre in the body.
● Located inside the skull.
● Protected by a box called Cranium.
● The brain is surrounded by 3 membranes called
meninges.
● The space between the membranes is filled with
Cerebrospinal fluid.
● The fluid protects the brain from mechanical shocks.
Three regions of Brain
1. Fore Brain

2. Mid brain

3. Hind brain
Fore Brain
● It mainly consists of Cerebrum.
● Cerebrum is the main thinking part of the brain.
● Site of learning, reasoning, intelligence,
personality and memory.
● It also controls thoughts, sensations, actions and
movements.
● Information from sense organs like (eyes, ears,
nose, tongue or skin) is received in cerebrum.
● It also has motor areas from which instructions
are sent to muscles to do voluntary actions.
Fore Brain
Forebrain consists of :
1. Cerebrum (largest part)
2. Thalamus
3. Hypothalamus (Diencephalon)
Fore Brain
Cerebrum
● Seat of mental abilities, controls thinking, memory, reasoning, perception,
emotions, and speech.
● Interprets sensations and responds to pain, cold, heat, and pressure.
Mid Brain
It is composed of the hypothalamus.
Hypothalamus
● It lies at the base of the cerebrum.
● It controls sleep and wake cycle of the body.
● It also controls the urges for eating and drinking.
Hind Brain
It is composed of three parts:
● Cerebellum
● Medulla
● Pons
Cerebellum
● It lies below cerebrum.
● It coordinates the motor functions.
● It controls posture and balance.
● It controls voluntary activities
Medulla
● It forms the brain stem.
● It lies at the base of the brain and continues
into the spinal cord.
● It controls involuntary functions like hearing,
heart beating and Respiration, salivation,
vomiting.
Pons
● It also controls involuntary actions.
● It regulates respiration.
Spinal Cord
● A cylindrical structure
● Begins in continuation with medulla
● It is enclosed in a bony case called vertebral
column.
● It is surrounded by membranes called meninges
● 31 pairs of nerves arise from the Spinal Cord.
● It is concerned with spinal reflections.
● It helps in conduction of nerve impulses to and
from the brain.
Q. How are nervous organs protected?

1. Protection of Brain:
● The brain is placed in a bony box called cranium and is a part of the skull.
● Brain is wrapped in three separate membranes called meninges.
● The space present between these layers is filled with cerebro-spinal fluid(CSF).
● This fluid-filled balloon acts as a shock absorber/ spring/ cushion and protects
the brain from injuries and shocks.
2. Protection of Spinal Cord :
● Like brain, spinal cord is also wrapped in spinal meninges and consist of
Cerebrospinal fluid.
● The spinal cord is protected by the vertebral column or backbone.
● The vertebral column is formed by 33 individual bones called vertebrae.
 Reflex Arc
The pathway through which nerve impulses pass during reflex action is
called Reflex Arc.
Heat Receptors Spinal organs Effector Organ Response
(Stimulus) (Skin) (Muscles) (Hand withdrawal)

Response : It is final reaction after

the reflex action.
Important Questions
Q. “Reflex arcs continue to be more efficient for quick responses”. Justify this
statement giving reason.

Reflex action is an automatic and spontaneous response to a stimulus. The pathway

taken by nerve impulses and responses in a reflex action is called a reflex arc. It
consists of receptor, sensory nerve (afferent), spinal cord, motor nerve (efferent) and
effector (muscles or glands). Reflex arc is evolved in animals because the thinking
process of the brain is not fast enough. Reflex arc enables the body to give quick
responses to harmful stimuli so that chances of damage to body are decreased. It
also prevents overloading of brain, so prevents its fatigue. Many animals have very
little or none of the complex neuron network needed for thinking. So, it is likely that
reflex arc has evolved as an efficient way of functioning in the absence of true
thought processes. However, even after complex neuron networks have came into
existence, reflex arcs continue to be more efficient for quick responses.
Q. How does process of reflex action take place in human body?

The process of reflex action is like

● The stimuli is sensed by the sensory receptors and sensory neurons generate
impulses.
● These impulses reach the spinal cord
● The relay neuron in the spinal cord passes signals between neurons.
● The motor neurons pass the signals for response to the organ that needs to
respond to stimulus.
The information input also goes on to reach the brain. But it is not involved in
reflex action.
Q. What is the role of the brain in reflex action?

There is no direct involvement of brain in reflex actions.

When Reflex actions are generated in spinal cord the information also
reaches brain. This helps the brain to record this event and remember it for
future use.

Brain helps the person to get awareness of the stimulus and prevent himself from
that situation again in the future.
Q. Which of the following does not involve thinking?

A. Peristaltic movement
B. Dancing
C. Withdrawing hand after touching hot surface
D. Both A and C
Q. Brain is a part of?

A. CNS
B. PNS
C. Reflex Action
D. All of these
Q. Which neuron links sensory and motor neurons?

A. NMJ
B. Neurotransmitter
C. Relay neuron
D. None of these
 THREE TYPES OF RESPONSES
1. Voluntary
Controlled by forebrain. Example – talking, writing etc
 THREE TYPES OF RESPONSES
2. Involuntary
Controlled by mid & hind brain. Example – heat beat, vomiting, respiration
 THREE TYPES OF RESPONSES
3. Reflex action
Controlled by spinal cord. Example – withdrawal of hand on touching hot object.

NEED FOR REFLEX ACTIONS

● In situations like touching a hot object,
pinching etc. a sudden response is
required.
● Reflex action is generated from SPINAL
CORD instead of brain.
● So that time taken for action is reduced.
Glands
A gland is a structure which secretes a specific substance (or substances) in
the body. A gland is made up of a group of cells or tissue.

There are two types of glands in the body:

1) exocrine glands 2) endocrine glands
Glands
1. Exocrine Glands
● Secretes its product into a duct (or tube).
● For example, the salivary gland secrets the
saliva into a duct called salivary duct.
Glands
2. Endocrine Glands
● A group of endocrine glands which produces
various hormones are called endocrine glands.
● The endocrine glands present in the human
body are : Pineal gland; Hypothalamus gland;
Pituitary gland; Thyroid gland; Parathyroid
glands; Thymus; Pancreas; Adrenal glands;
Testes (only in males) and Ovaries (only in
females).
Hypothalamus
Hypothalamus gland is present in the brain. Hypothalamus produces ‘releasing
hormones’ and ‘inhibitory hormones’. The function of hypothalamus is to regulate
the secretions of hormones from pituitary gland. That is how, hypothalamus
controls the pituitary hormones.
Pituitary Gland
● Pituitary gland is present just below the brain.
● The pituitary gland secretes a number of
hormones.
● One of the hormones secreted by pituitary gland
is growth hormone (or human growth hormone).
● The growth hormone controls the growth of the
human body.
● For example, growth hormone controls the
development of bones and muscles.
Pituitary Gland
A person having a deficiency of growth hormone in childhood remains very
short and becomes a dwarf.
On the other hand, a person having too much growth hormone becomes very
tall (or a giant).
Thyroid Gland
● Thyroid gland is attached to the windpipe in
our body.
● Thyroid gland makes a hormone called
thyroxine (which contains iodine).
● The function of thyroxine hormone is to
control the rate of metabolism of
carbohydrates, fats and proteins in the body.
GOITRE
● Iodine is necessary for the making of thyroxine hormone in the body.
● The deficiency of iodine in the diet of a person produces less thyroxine
hormone and causes a disease known as goitre.
Sources of Iodine
Seaweed, Fish, shellfish, Table salts
labeled “iodized”, Dairy (milk, cheese,
yogurt), Eggs, Beef liver, Chicken.
Hormones
Hormones are chemical substances that act like messenger molecules in the body.

Hormones are secreted in small quantities by ENDOCRINE GLANDS.

Parathyroid Glands
● There are four small parathyroid glands
which are embedded in the thyroid gland.
● Parathyroid glands secrete a hormone called
parathormone.
● The function of parathormone hormone is to
regulate calcium and phosphate levels in the
blood.
Thymus Gland
● Thymus gland lies in the lower part of the
neck and upper part of chest. Thymus gland
secretes thymus hormone which plays a role
in the development of the immune system of
the body.
● Thymus gland is large in young children but
shrinks after puberty (or sexual maturity).
 Pancreas
(Dual gland/ mixed gland/ heterocrine gland)
Function as both:

Exocrine gland Endocrine gland

Pancreatic Juice - Hormones

Trypsin, lipase, etc.
Pancreas
● The pancreas is just below the stomach in
the body.
● Pancreas secretes the hormone called
insulin.
● The function of insulin hormone is to lower
the blood sugar level (or blood glucose
level).
 Pancreas

Alpha Cells Beta Cells

Glucagon Insulin
Increase level of blood Decrease blood glucose
glucose (sugar) (sugar) level in our blood
level in blood
DIABETES
● Deficiency of insulin hormone in the body causes a disease known as diabetes.
● Diabetes is characterized by large quantities of sugar in the blood (and even urine)
● The insulin hormone controls the metabolism of sugar.
Adrenal Glands
● There are two adrenal glands which are located
on the top of two kidneys.
● The adrenal glands secrete adrenaline hormone.
● The function of adrenaline hormone is to
regulate heart rate, breathing rate, blood
pressure and carbohydrate metabolism.
Adrenal Glands
● Adrenaline hormone is secreted in small amounts all the time but in large
amounts when a person is frightened or excited.
● When adrenaline is secreted in large amounts it prepares our body for
action.
● It speeds up heartbeat and breathing, raises blood pressure and allows
more glucose (carbohydrate) to go into the blood to give us a lot of
energy quickly to fight or flight (run away).
● Adrenal glands are often called ‘glands of emergency’.
Testes
● Testes are the glands which are present only in males (men).
● Testes make male sex hormones called testosterone.
● The testes also make the male gametes called sperms.
Testes
● The function of testosterone hormone is to control the development of
male sex organs and male features such as deeper voice, moustache,
beard, and more body hair (than females).
● All these changes caused by testosterone are associated with male puberty
which the boys attain at an age of 13 to 14 years.
Ovaries
● Ovaries are the glands which are present only in females (women).
● Ovaries make two female sex hormones called oestrogen and progesterone.
● The function of oestrogen hormone is to control the development of female
sex organs, and female features such as feminine voice, soft skin and
mammary glands (breasts).
Ovaries
● All these changes caused by oestrogen are associated with female puberty
which the girls attain at an age of 10 to 12 years.
● The functions of progesterone hormone is to control the uterus changes in
menstrual cycle.
● It also helps in the maintenance of pregnancy. The ovaries also make the
female gametes called ova (or eggs).
Feedback Mechanism
● The excess or deficiency of hormones
has a harmful effect on our body.
● For example, the deficiency of insulin
hormone results in a disease called
diabetes whereas excess of insulin in
the body can lead to coma.
Feedback Mechanism
● The timing and amount of hormones released by various glands are
controlled by the ‘feedback mechanism’ which is in-built in our body.
For example, if the sugar level in the blood rises too much, they are
detected by the cells of pancreas which respond by producing and
secreting more insulin into blood. And as the blood sugar falls to a
certain level, the secretion of insulin is reduced automatically.
Important Questions
Q. Why is it advised to use iodised salt in our diet ?

Iodine stimulates the thyroid gland to produce thyroxine hormone. Deficiency

of this hormone results in the enlargement of the thyroid gland. This can lead
to goitre.

Feedback Mechanism - The timing and amount of hormone released in our

body is controlled by a mechanism called the feedback mechanism. It keeps
the secretion of hormones from glands in appropriate quantity. Eg- if sugar
levels in the blood rise, the insulin hormone is secreted by the pancreas and if
it falls then glycogen is broken down.
Q. How does our body respond when adrenaline is secreted into the blood?

It is secreted by the adrenal gland. At the time of emergency or stress, it is

released in large quantities. As a result, the heartbeat increases which result in
more supply of oxygen in muscles. All these responses together help the
animal to deal with an emergency.
Q. Why is it advised to use iodised salt in our diet ?

All hormones secreted in our body are required in the appropriate amount. Slightly
more or less can lead to diff disorders.

Dwarfism- Growth hormone is responsible for regular growth and development of

the body. A deficiency of this leads to dwarfism.
Gigantism- Excess secretion of growth hormone leads to an abnormal condition
known as gigantism.
Goiter- Iodine is essential for releasing thyroxine hormone. In case, iodine is
deficient in the body, there occurs the possibility of goiter. One of the major
symptoms is a swollen neck.
Diabetes- It occurs when less amount of insulin is secreted by the pancreas. In this
condition, sugar is accumulated in the body causing harmful effects.
Control and Coordination in Plants

Movements Hormones

● The plants do not have a nervous system and sense organs like eyes, ears, or
nose, etc., like the animals, but they can still sense things.
● The plants coordinate their behaviour against environmental changes by using
hormones.
Control and Coordination in Plants
● The plants do not have a nervous system and sense organs like eyes, ears, or
nose, etc., like the animals, but they can still sense things.
● The plants coordinate their behaviour against environmental changes by using
hormones.
 RESPONSE IN PLANTS

Root and Shoot growing

Leaves of touch - me - not plant
downward and upward
drooping on touching
respectively

Not related to Growth Related to Growth

Comparing Response to stimulus in
Animals and Plants
Plant Hormones (Phytohormones)
● The control and coordination in plants is done by plant hormones (or
phytohormones).
● The growth of a plant can be divided into three stages:
1. Cell division
2. Cell enlargement
3. Cell differentiation (or cell specialization)
Plant Hormones (Phytohormones)
● There are four major types of plant hormones (or phytohormones) which are
involved in the control and coordination in plants.
● 1) Auxins 2) Gibberellins 3) Cytokinins 4) Abscisic acid (ABA)
Plant Hormones (Phytohormones)
1. Auxins
● Auxins are the plant hormones which promote cell enlargement and cell
differentiation in plants. Auxins also promote fruit growth.
● Auxin hormone controls a plant’s response to light and gravity.
● Auxin is made by cells at the tip of stems and roots.
● Auxin moves away from light, and towards gravity.
● Auxin speeds up growth in stem but it slows down growth in roots.
● Synthetic auxins are applied in agriculture and horticulture.
Plant Hormones (Phytohormones)
2. Gibberellins
● Gibberellins are plant hormones which
promote cell enlargement and cell
differentiation in the presence of auxins.
● Gibberellins help in breaking the
dormancy in seeds and buds. They also
promote growth in fruits.
● Gibberellin hormone is involved mainly in shoot extensions. Gibberellin
stimulates elongation of shoots of various plants.
Plant Hormones (Phytohormones)
3. Cytokinins
● Cytokinins are the plant hormones which
promote cell division in plants.
● Cytokinins also help in breaking the
dormancy of seeds and buds. They delay
the ageing in leaves.
● Cytokinins promote the opening of
stomata. They also promote fruit growth.
Plant Hormones (Phytohormones)
4. Abscisic Acid (ABA)
● Abscisic acid is a plant hormone which functions mainly as a growth
inhibitor.
● It promotes the dormancy in seeds and buds (this is the opposite of
breaking of dormancy). It also promotes the closing of stomata.
● It promotes the wilting and falling of leaves (which is called abscission).
It also causes the detachment of flowers and fruits from the plants.
Plant Hormones (Phytohormones)
4. Abscisic Acid (ABA)
TROPISMS (OR TROPIC MOVEMENTS)
● A growth movement of a plant part in response to an
external stimulus in which the direction of stimulus
determines the direction of response is called
tropism.
● Thus, tropism is a directional movement of the part of
a plant caused by its growth.
● If the growth (or movement) of a plant part is towards
the stimulus, it is called positive tropism.
● If the growth (or movement) of a plant part is away
from the stimulus, then it is called negative tropism.
 TYPES OF TROPISMS
1. Phototropism:
● The movement of a plant part in response to light is called phototropism
● If the plant part moves towards light, it is called positive phototropism.
Types of Tropisms
1. Phototropism:
● On the other hand, if the plant part moves away from
light, then it is called negative phototropism.
● The stem (or shoot) of a growing plant bends towards
light, so the stem (or shoot) of a plant shows positive
phototropism.
● On the other hand, the roots of a plant move away from
light, so the roots of a plant show negative
phototropism.
Types of Tropisms
2. Geotropism
● The movement of a plant part in response to
gravity is called geotropism.
● If the plant part moves in the direction of
gravity, it is called positive geotropism.
● On the other hand, if the plant part moves
against the direction of gravity, it is negative
geotropism.
Types of Tropisms
3. Chemotropism
● The movement of a plant part in response to a
chemical stimulus is called chemotropism.
● If the plant part shows plant part shows movement (or
growth) towards the chemical, it is called positive
chemotropism.
● If the plant part shows movement (or growth) away
from the chemical, then it is called negative
chemotropism.
Types of Tropisms
4. Hydrotropism
● The movement of a plant part in response to water is called hydrotropism.
● If the plant part moves towards water, it is called positive hydrotropism.
● If the plant part moves away from water, then it is called negative hydrotropism.
Types of Tropisms
5. Thigmotropism
● The directional growth movement of a plant
part in response to the touch of an object is
called thigmotropism.
● The climbing parts of the plants such as tendrils
grow towards any support which they happen to
touch and wind around that support. So, tendrils
of plants are positively thigmotropism.
Response of Plants to Light : Phototropism
● Plants need sunlight, so the stems (or shoots)
respond to sunlight by growing towards it.
● This observation shows that the stem of plant
responds to light and bends towards it.
● The plant stem responds to light and bends
towards it due to the action of ‘auxin hormone.
Response of Plants to Light : Phototropism
● When sunlight comes from above, then the auxin hormone present in the
tip of the stem spreads uniformly down the stem. Due to the equal
presence of auxin, both the sides of the stem grow equally rapidly. And
the stem grows straight up.
● When the light falls only on the right side
of the stem, then the auxin hormone
collects in the left side of the stem,
away from light. This is because auxin
hormone prefers to stay in shade.
Response of Plants to Light : Chemotropism
● The growth (or movement) of a plant part due to
chemical stimulus is known as chemotropism.
● The growth (or movement) of a pollen tube
towards the ovule induced by a sugary
substance as stimulus, is an example of
chemotropism.
● The ripe stigma in the carpel of flower secretes a
chemical substance (which is a sugary
substance) into the style towards the ovary.
Response of Plants to Light : Chemotropism
● This sugary substance acts as a stimulus for the pollen grains which fall on the
stigma of the carpel.
● The pollen grain responds to this stimulus by growing a pollen tube in the
downward direction into the style of the carpel and reaches the ovule in the
ovary of the flower for carrying out fertilization.
● This growth of the pollen tube in response to a chemical substance secreted by
the stigma of a flower is an example of Chemotropism.
Response of Plants to Light : Hydrotropism
● The roots of plants always go towards water, even if it means going against the
pull of gravity.
Thigmotropism
● Tendrils are the thin, thread-like growth on
the stems or leaves of climbing plants.
● Thus, there are two types of tendrils : stem
tendrils and leaf tendrils.
● Tendrils are sensitive to the touch (or
contact) of other objects.
● Tendrils are positive thigmotrophic which
means that they grow towards things they
happen to touch.
Nasties (OR Nastic Movements)
● The movement of a plant part in response to an external stimulus in which the
direction of response is not determined by the direction of stimulus is called
nastic movement.
● The folding up of the leaves of a sensitive plant (Mimosa pudica) on touching is
an example of nastic movement. Here the stimulus is touch.
Nasties (OR Nastic Movements)
● The opening up of the petals of dandelion flowers in morning in bright light
and closing in the evening when the light fades is an example of nastic
movement. In this case the stimulus is light.
● The closing of the petals of moonflower
in the morning in bright light and opening
at dark when the light fades is also an
example of nastic movement. In this case
also the stimulus is light.
Thigmonasty
● The non-directional movement of a plant part in response to the touch of an
object is called thigmonasty.
● The nastic movement in plants caused by touch (or thigmonasty) is provided
by the sensitive plant (Mimosa pudica) which is also known as touch-me-not
plant. It is called chhui-mui in Hindi.
● If we touch the leaves (or rather leaflets)
of the sensitive plant with our fingers, then
its leaves fold up and droop almost
immediately.
Thigmonasty
● The folding up of the leaves of a sensitive plant on touching is due to the sudden
loss of water from pad-like swellings called ‘pulvini’ present at the base of all
leaves of the sensitive plant which make the pulvini lose their firmness causing
the leaves to drop and fall.
Photonasty
● The non-directional movement of a plant part
(usually petals of flowers) in response to light is
called photonasty.
● The opening and closing of flowers in response to
light (or photonasty) are growth movements.
● Petals open when their inner surfaces grow more
than their outer surfaces. On the other hand, petals
close when their outer surfaces grow more than
their inner surfaces.
Functions of Plant Hormone (OR Phytohormones)
● Germination of seeds (or ● Growth of root, stem and leaves.
Breaking the dormancy of
seeds).
 Functions of Plant Hormone (OR Phytohormones)

● Movement of stomata (or ● Flowering of plants ● Ripening of fruits

stomatal movement) in leaves
Thankyou!!