This is a very important chapter from examination point of view. In this section containing Class 10 Science chapter 7 notes pdf, we have discussed various concepts like “control and coordination, structure and functioning of human nervous system, reflex action, plant movements and their types, plant hormones and their types, and other related concepts”.
Notes For Control and Coordination Class 10 Science
In the forthcoming section, you will get control and coordination class 10 notes. These notes have been prepared by a group of experienced teachers, and we are very sure that you will find them very suitable for your preparation. At the end of this section, we have also provided text questions and their answers. Check them out.
Some Basic Terms
(1) Coordination:- The working of various organs of the body of an organism in a proper manner to produce proper reaction to a stimulus is called coordination.
(2) Stimulus :- The changes in the environment to which the organisms responds and react are called stimuli (Sing-stimulus)
(3) Receptor : It is a nerve cell or group of nerve cells which is sensitive to a specific stimulus or to specific change in the environment.
(4) Effector: An effector is some muscle or gland in specific part of the body which produces suitable response.
(5) Dormancy :- It refers to a resting, inactive condition of the seed when it fails to germinate even though the environmental conditions usually considered favorable for active growth are present.
(6) Parthenocarpy :- Development of seedless fruits with the act of fertilization e.g in Grapes
(7) Homeostasis:- The mechanism of maintaining constancy of internal environment in the living organisms.
(8) Apical dominance :- The terminal bud at the apex of a shoot, suppresses the growth of lateral buds into branches. This phenomenon is called apical dominance.
(9) Synapse:- The loose connection between the axon endings of one nerve cell and Cyton of next nerve cell is called synapse.
(10) Synaptic cleft:- The space between adjacent neurons is called the synaptic left.
(11) Synaptic bulb:- The synaptic cleft is about 20mm in width. The axon terminal of a presynaptic neuron has a bulb-like appearance known as synaptic bulb.
What do you mean by control and coordination?
The working together of various organs (parts) of the body of an organism in a proper manner to produce response to a stimulus is called coordination.
For proper control and coordination, higher organisms have evolved two systems – nervous system and endocrine system.
The nervous system is composed of nerves which control and coordinate the body by sending electrical signals called nerve impulses.
The endocrine system, composed of endocrine glands, controls and coordinates the body by sending chemical messengers called hormones.
Higher multicellular animals have both nervous and chemical control and coordination, whereas plants posses only chemical coordination and lack nervous coordination. It is to be noted that nervous control is speedy and spontaneous but its effect is localized, where as chemical control (hormonal control) is usually slow acting but its effect is specific.
Write a short note on nervous system of man?
The nervous system of man is divisible into three main parts. (1) Central nervous system (2) Peripheral nervous system (3) Autonomic nervous system.
(1) Central nervous system: All the parts of the nervous system which are present along the main longitudinal axis of the body constitute the central nervous system. It consists of brain and spinal cord.
(A) Brain (Encephalon): The human brain is soft, whitish highly developed organ situated in the cranium or cranial cavity of the skull. It weighs about 1200 – 1400 gms.
Covering and protection of brain: The brain is surrounded by three membranes called meninges. These are Piamater membrane (inner layer), Arachnoid membrane (middle layer) and duramater (outer layer). The space between these meninges is filled with a fluid called Cerebro Spinal Fluid (CSF) which protects the brain from mechanical shocks.
Structure of brain: The adult human brain has three sub-divisions.
- Fore – brain or prosencephalon
- Mid-brain or mesencephalon
- Hind brain or rhombencephalon
(a)Fore brain: It is the anterior region and the largest part of the brain. It has three parts.(i) Olfactory lobes (ii) Cerebrum (iii) Diencephalon
- Olfactory lobes: The olfactory lobes of brain of human beings are a pair of poorly developed, club shaped, widely separated bodies, which are visible from the ventral surface only. The olfactory lobes are concerned with sense of smell.
- Cerebrum: Cerebrum makes bulk of human brain. It constitutes 4/5th weight of the brain. It consists of two lobes called cerebral hemispheres. The two cerebral hemispheres are separated from each other by a very deep groove known as cerebral fissure. The two hemispheres are held together by a transverse band of nerve fibres called corpus callosum. The outer layer of cerebrum is the cerebral cortex which is made up of grey matter. The surface of cerebrum shows many folds and grooves called gyri and sulci, which increases the surface area (2000 sq.cm)of cerebrum to accommodate more nerve cells. There are three sulci present in on the surface of each cerebral hemisphere which are very prominent as a result of which it is divided into four lobe.
- Frontal lobe: It controls facial muscular activities as well as higher mental activities.
- Parietal lobe: It has areas for touch, taste, smell, temperature and conscious association.
- Occipital lobe: It is the region for sight.
- Temporal lobe: It is the region for auditory reception (hearing).Besides above the cerebrum governs reasoning, learning, memorizing and intelligence. It also controls feelings of love, admiration and hatred. It also perceives the sensory impulse such as pain, touch, taste, smell, hearing etc.
- Diencephalon: It is a small rhomboidal lobe completely covered superiorly by large cerebrum but visible from inferior surface. The roof of diencephalon is called epithalmus, floor hypothalamus and lateral walls called thalmi. Diencephalon contains reflex centres for muscular and glandular activities. It has also centres of emotion, hunger and thirst. It also helps in maintaining body temperature and water salt balance of the body.
(B) Mid brain (Mesencephalon: It is the thick walled structure and small part of the brain. The mid brain or mesencephalon connects the anterior region of the brain to the posterior region of the brain. The mid brain is differentiated into corpora quardrigemina on the upper side and the crura cerebri on the lower side. Corpora quardrigemina consists of four lobes, i.e. upper lobes called superior colliculi and the lower lobes called interior colliculi.
Write down the types of Neurons?
The neurons are of three types:(i) Sensory neurons (ii)Motor neurons, (iii) Inter neurons.
(1)Sensory neurons: The neurons which conduct impulses from the peripheral tissues to the central nervous system are called sensory neurons. These are also called afferent neurons as they carry impulses towards the CNS. Sensory neurons perceive sensations from receptors through their dendrites and dendrons attached with receptors and conduct and transmit sensations in the form of nerve impulses through successive sensory neurons towards CNS. As the nerve impulses always travel from cell body to Axons, thus sensory neurons have cell body directed towards the receptors and axons and synaptic knobs towards CNS (Brain and spinal card). (ii)
(2) Motor neurons: The neurons which conduct impulses from the central Nervous system to the peripheral tissues (effectors) are called motor neurons. These are also called efferent neurons as they carry impulses away from the CNS. Motor neurons have their cell bodies and dendrites directed towards the CNS and, axons and synaptic knobs directed towards the effectors i.e, muscles and glands. The motor neurons at the terminal part of the motor nerve at effectors possess motor end plate which is formed by the branching of the terminal part of axon.
(iii) Inter neurons: The neurons which conduct nerve impulses between sensory neurons and motor neurons, are called inter-neurons. Thus inter-neurons connect sensory neurons with motor neurons and are also called connectors or intermediate neurons or relay neurons. These neurons are mostly present in the spinal cord and brain where they transmit impulses between sensory neuron and motor neurons. Inter Neurons play very important role in reflex actions. Inter neurons posses some what different structure. They have cell body almost at middle between length of dendron and axon.
What are synapses?
Synapses are the junctions between the two neurons, across which the nerve impulses transmit from one neuron to another one. A synapse consists of synaptic knob of one neuron and the dendrite of another neurons with a very minute gap between their two membranes called synaptic cleft which is usually filled with synaptic fluid.
The membrane of the synaptic knob facing towards synaptic cleft is thickened and is called pre-synaptic membrane, and similarly the membrane of dendrite facing the synaptic cleft is thickened and is called post synaptic membrane.
The function of synapses are to transmit the nerve impulses from synaptic knobs to dendrites. When the nerve impulse reach the synaptic knob, the synaptic vesicles get stimulated to release the neuron transmitter in the synaptic cleft. The neurotransmitter molecules diffuse across the synaptic cleft to the post synaptic membrane of the dendrite and activates the other neuron.
Thus the nerve impulse is transmitted from one neuron to another through synapse and the time taken by the neurotransmitter molecules to diffuse from pre-synaptic membrane to post-synaptic membrane is about 0.5ms called as synaptic delay. The nerve impulses always travel from synaptic knobs to dendrites in reverse direction.
The neurons releasing acetylcholine as neurotransmitter are termed as cholinergic neurons. The neurons releasing noradrenaline as neurotransmitter at synaptic knobs are termed as adrenergic neurons.
Describe the functioning of nervous system?
The nervous system receives a stimulus through a receptor organ, which coordinates it and responses through the effector organ. Thus a coordinated behaviour has five main components; stimulus, receptor, coordinator, effector and response. The stimulus of sound, sight, touch, etc. is perceived by receptor organs like ears, eyes, skin, etc. The brain and spinal cord are the coordinators which receive information in the form of message called nerve impulses, from receptor organs via neurons. The information flows to the effector organs, i.e. muscles, and the response occurs.
Communication through the nerve.
Nerve impulses pass along a neuron in one direction only. At one end, the neuron is connected to a sensory receptor that receives the message of stimulus and converts it into electro-chemical waves which are carried by the neuron.
In a given neuron, the dendrites are the receptors, the cell body is the integrator and the ends of the axons are the transmitters. This means that the stimulus from the receptor organ is received by the dendrites, conducted to the cell body of the neuron and passed on through the axon to another neuron and finally to the effector organ. The axon endings of one nerve cell are loosely placed on the cell body or cyton of another nerve cell called Synapse. Signals travel from one neuron to another neuron across this junction (Synapse).
Discuss reflex action with suitable examples?
There are certain body responses which are immediate and spontaneous do not require any processing by the brain. These responses or actions are controlled by spinal cord and are called reflex actions.
Thus Reflex action may also be defined as a spontaneous, automatic and mechanical response to a stimulus without the will of the individual. Some examples of reflex actions are:
- Immediate withdrawal of hand if a person touches hot object unknowingly.
- Blinking of eyes.
- Sneezing, laughing, yawning etc.
- Watering of mouth on seeing food.
- Withdrawal of the leg by a man walking barefoot if he steps on nail.
What happens in reflex action (Mechanism of reflex action) ?
In reflex action, whenever there is any stimulus perceived by any receptor, it sets up sensory impulse that is carried to the central nervous system mainly spinal cord through sensory or afferent nerve. In the spinal cord, the sensory impulse is converted into a motor impulse and is then carried to effectors (muscles or glands) via motor nerves.
The effector organ responds according to the message received. The path taken by nerve impulse in reflex action is called reflex arc. So the components involved in reflex are are:
(a) Receptor or sensory organ. (b) Sensory or Afferent nerve (c) Intermediate or internuncial neuron (d) Motor or Efferent nerve. (e) Effector organs.
e.g. When our hand accidentally touches a hot object the heat is sensed by the thermoreceptors present in the skin and, the receptor triggers nerve impulse in sensory neuron. It transmits message to spinal cord. In the spinal cord impulse is passed to connector neuron, which in turn. passes it to the motor neuron. The motor neuron transmits the instruction to a muscle of our arm.
The arm muscle contracts and pulls our hand away from hot object.
Types of reflex action.
On the basis of origin, reflex actions are of two types:(i) Unconditioned reflexes (ii) Conditioned reflexes.
(i) Unconditioned reflexes: The inborn reflexes are unconditioned reflexes. It is present from the birth and is hereditary; e.g. respiratory reflexes, micturition reflexes, sexual reflexes, anckle jerk, bicep jerk etc are some of the examples of unconditioned reflexes.
(ii) Conditioned reflexes: These are learned automatic reflex actions carried out by the body. These are acquired by an organism during his life time through experience and learning.
Crying and jerking hands by a child on seeing a burning candle. Salivation of mouth on hearing the bell for lunch break are conditioned reflexes.
On the basis of involvement of brain, the reflex actions are of two types (a) Cerebral actions (b)Spinal actions.
(a) Cerebral actions: The reflex actions in which brain is involved are called cerebral actions e.g. contraction of pupil of human eye in presence of bright light.
(b) Spinal actions: The reflex actions in which only spinal cord is involved e.g. withdrawal of hand on touching a hot object.
What are plant movements? Discuss different types of movements in plants?
Movements in plants are in the form of bending, twisting or elongation of certain parts. It is characteristic of plants that do not show locomotion. However, movements of individual plant organs are possible and are modified by the sensitivity of the plant to stimuli. Plants show two main types of movements: (i) Autonomic or spontaneous movements.(ii) Paratonic or induced movements.
(i) Autonomic or spontaneous movements: They are independent of any external stimulus; i.e. they are self controlled and are not induced by external stimulus.
(ii) Paratonic or induced movement: They are caused by the result of application of external stimulus.
Classification of induced or paratonic plant movements.
Induced plant movements can be broadly classified into two types; (a) Nastic movements (b) Tropic movements
(a) Nastic movements: These are non-directional induced variation movements that occur due to the turgor changes induced by external stimulus such as light, temperature, touch etc. In nastic movements the part of the plant do not respond towards or away from the stimulus. These reveal quick responses to stimulus but does not involve growth.
Nastic movements include:-
- Nyctinastic movements: Variations in the position of flowers and leaves of many plants in day and night are called nyctinastic movements or sleep movements. Nyctinastic movements include;
- Photonastic movements: These are variations in non-directional position of plant parts (like petals of flowers) caused by the light stimulus, e.g. photonastic movements in the leaf of oxalis.
- Thermonastic movements: These are the variations in the position of plant parts caused by the change in temperature of surroundings.
- Seismonastic movements or Thigmonastic movements: These are the non-directional movements which occurs in response to touch or shock. These movements are very quick and are best seen in mimosapudica (touch me not) also called chhui-mui or sensitive plant or Lajwanti.
Mechanism of folding up and droping of leaves.
The sensitive plant has pad like swellings called pulvini at the base of each leaf. These pulvini contain lot of water in their cells.
Due to the internal water pressure in them, all the pulvini are very firm and hold the leaves above them upright. The pulvini also contains large intercellular spaces between their cells. The folding up of leaves of chui-mui plant on touching is due to the sudden loss of water from pulvini present
at the base of all the leaves of the sensitive plant which make the pulvini lose their firmness causing the leaves drop to fall. This happens as follows.
When the leaves of sensitive plant are touched with a finger, then an electrical impulse is generated which travels through ordinary cells. This electrical impulse acts on a plant hormone.
The plant hormone makes the water migrate from the cells of one half of a pulvinus to the intercellular spaces in the other half of pulvinus. This loss of water from half of pulvinus causes the pulvinus to lose its firmness and become limp due to which all the leaves above them collapse and fold up.
(b) Tropic movements or Tropism: The movement of a plant in the direction of stimulus is known as tropism. The stimulus may be light, force, gravity, chemicals, water etc. Tropic movements are induced growth movements of curvature that occur due to differential growth.
Tropic movements are very slow and the movement of plant part can be either towards the stimulus or away from the stimulus. Depending upon the stimulus, it is categorized as:
- Phototropism: It is the directional movement or orientation of the plant part in response to light stimulus. If the plant moves towards light, it is called positive phototropism. If the plant moves away from light, it is called negative phototropism. Example. The shoot of a plant moves towards light and hence shows positive phototropism.
- Geotropism: It is the directional movement or orientation of the plant part in response to gravity. If the plant part moves in the direction of gravity, it is called positive geotropism. Alternatively, if the plant moves against the direction of gravity, it is termed as negative geotropism eg. roots are positively geotropic.
- Chemotropism: It is the directional movement or orientation of the plant part in response to chemical stimulus. If the plant part moves towards the chemical stimulus, it is called positive chemotropism and if the plant moves away from the chemical stimulus it is called negative chemotropism, e.g. during fertilization, growth of pollen tube towards the ovule in the ovary is an example of positive chemotropism.
- Hydrotropism: If the plant part moves towards the water stimulus, it is called positive hydrotropism and if the plant part moves away from water stimulus it is called negative hydrotropism, e.g. the roots of the plants always grow towards the water are thus positively hydrotropic.
- Thermotropism: It is directional movement or orientation of the plant part in response to stimulus of temperature. e.g. shoot is positively thermotropic..
- Thigmotropism: It is directional movement or orientation of the plant part in response to the stimulus of contact or friction. This is common in tendril climbers, e.g. 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 thigmotropic.
Important Terms Related To Endocrinology
- Endocrinology: (Greek: endon = within, krienien = to separate) the study of endocrine glands and role of their secretions is called endocrinology.
- Gland: A cell, tissue or an organ which secretes useful chemical compound required for particular function.
- Endocrine gland: The glands which lack ducts and pass their secretion into the surrounding blood to transport to the site of action are called endocrine glands. They are also called ductless glands and their secretions are known as hormones.
- Endocrine system: It is the system of endocrine glands which secretes hormones.
What are hormones? What are the characteristics of a hormone?
Hormone: (Greek: hormoein = excite). The term hormone for the first time was coined by Starling in 1905. Hormones are informational molecules secreted by the endocrine cells in one part of the body and carried by blood to another part to stimulate or inhibit specific physiological process for the proper functioning of the body as a whole.
Characteristics of hormone:
- Hormones are secreted by endocrine cells which act as chemical messengers.
- They are carried by blood stream to target organs.
- They are produced in trace amounts.
- They act away from the site of production.
- They are soluble in water.
- They are destroyed or inactivated as soon as their functions are over.
- They are not species specific because hormones extracted from animals are found to be effective in man.
- The hormones are generally slow in action.
Names different endocrine glands?
- Pituitary gland
- Thyroid gland
- Para thyroid gland
- Adrenal gland
- Islets of langerhans (pancreas)
- Testes/ovary (glands)
Discuss the thyroid gland? What are hormones released by thyroid gland and write their functions?
Location of thyroid gland: The thyroid gland surrounds the front part of the larynx and upper part of the trachea in the neck.
Structure of Thyroid gland: Thyroid gland consists of two lobes connected by narrow band called isthmus. Each lobe is composed of numerous spherical masses called follicles. Each follicle is covered by basement membrane. In the centre of each follicle contains a cavity filled with collidal material. Thyroid gland is composed of two types of cells i.e. Follicular cells and Para follicular cells or C cells.
Functions of thyroid Hormones: The thyroid gland releases three hormones (a) Thyroxine (T4) (b) Tri-iodo thyronine (T3) (c) Calcitonin.
Functions of T4 & T3
- Both T3 & T4 control general metabolism by regulating the rate of oxidation & production of energy.
- They maintain Basal metabolic rate of body.
- They stimulate protein synthesis and hence improve growth.
- Thyroxine also controls the working of kidneys.
Functions of Calcitonin
It is secreted by “C” cells. It regulates the concentration of calcium and phosphorus in the blood. Calcitonin decreases blood calcium ion concentration.
Improper Secretion of T3 & T4 Causes following disorder:
(1) Under secretion of Thyroid Hormone (Iodine deficiencies Goiter):- It is caused by the deficiency of iodine in the diet. The disease is common in hilly areas. It causes enlargement of thyroid gland. Swollen neck is one of its symptoms of the disorder. It may lead to Cretenism or myxodema (Gulls disease).
- Cretinism :- It is caused by hyposecretion of thyroid hormones in infants. Affected child is called cretin. The symptoms appear after 6 months of birth which are as follows:
- Cretins are short and fingers are club shaped.
- Bones and teeth are deformed.
- Tongue are protruding and saliva is dribbling.
- Cretins are idiots.
- Appetite is reduced.
- BMR and body temperature is also low.
- Myxodema or Gulls diseases:- It is the disorder produced in adults as a result of hyposecretion of thyroid. Some of the symptoms are:
- Face is swollen.
- Sex degenerates and appetite is reduced.
- BMR is lowered
- Respiratory rates are reduced.
- Heart rate and cardaic out put is also low.
(11) Oversecretion of Thyroid Hormone leads to Grave’s disease or Exothalmic Goiter:
- Grave’s disease or Exothalmic Goiter:- It is caused by hyper secretion of the thyroid hormones due to enlargement of thyroid gland. Some of the symptoms of Grave’s diseases are:
- Eye balls are protruded with a staring look
- Body temperature is raised.
- Patients are emotional and restless.
- The skin becomes soft, moist, flushed.
- Blood sugar level and iodine level are raised.
The disorder can be rectified by the removal of part of the gland.
Location of pancreas:- Pancreas lies below the stomach. The pancreas is an elongated, yellowish gland. It consists of large lobules (acni, alveoli). In between the acni, there are some cells which constitute the endocrine part of the gland. The endocrine part of the pancreas is called islets of langerhans.
The isiets of langerhans is composed of 3 types of cells.(1) A Cells (b) B Cells (c) C Cells.
Hormones produced by islets of Langerhans
Islets of langerhan’s secrets two hormones.
(1)insulin:- Insulin is secreted by ‘B’ cells of islets of langerhans.
Role of insulin :- The main role of insulin is to lower the blood sugar level. It acts in following ways to bring down sugar level of blood:
- It makes cells more permeable to glucose.
- It enhances glucose oxidation in the cells.
- It increases rate of conversion of blood glucose into liver glycogen.
- It promotes the conversion of glucose into fat deposits.
Deficiencies of insulin:- Deficiency of insulin causes a disease called diabetes mellitus. The symptoms of diabetes mellitus are as follow:
- Hyperglycaemia:- Pronounced increase in blood sugar level.
- Glycosuria:- Appearance of sugar in urine.
- Polyueria:- large volume of urine about 10 lit/day.
- Frequent urination.
- Delayed healing of wounds.
- The diabetic has blured vision and is weak, tired, irritable and under weight.
(2) Glucogon:- It is secreted by A Cells of islets of langerhans.
Role of glucogon: Its main role is to raise blood sugar level. It has opposite effect of insulin. It promotes process of glycogenolysis, gluconeogenesis.
Both insulin and glucagon act antagonistically and by virtue of it maintains proper blood glucose concentration.
Control and Coordination Class 10 Textual Questions and Answers pdf
In this section you will find Control and Coordination Class 10 Textual Questions and Answers pdf. These answers have been prepared by teachers who have an experience of more than 10 years of teaching at secondary level. These answers are best for your exam preparation.
What is the difference between reflex action and walking?
|It is spontaneous action.||It is non spontaneous action.|
|It is an automatic action.||It is not an automatic action.|
|It occurs without a person’s will and is involuntary action.||It occurs with the person’s will and is voluntary action.|
|Here brain is not involved immediately. i.e, it takes place without consultation of brain.||Here cerebellum (part of brain) is controlled.|
What happens in synapse between two neurons?
The closeness between nerve end-plate of one neuron and the dendrite of another neuron is called synapse. The nerve end-plate has bulb like structure called synaptic bulb, in which secretary vesicles secrete a chemical substance called acetylcholine (neuro transmitter).
When a nerve impulse arises at the axon terminal, it causes synaptic bulbs to release neuro transmitter. Neuro transmitter diffuses easily and carries impulse across the synapse and passes it to the dendron of the neuron. Thus a nerve impulse passes from axon of one neuron to dendron of other neuron through a synapse.
Which part of brain controls equilibrium of body?
Cerebellum (part of hind brain) maintains posture and equilibrium of the body.
How do we detect the smell of an Agarbatti (incense stick)?
We have olfactory receptors in our nose. These receptors detect the smell of agarbati and transmits this information in the form of nerve impulse to the olfactory lobes of the forebrain via nerve. The message of smell is analyzed and interpreted there (in the brain).
What is the role of the brain in reflex action?
Reflex actions generally involve spinal cord for quick response to specific stimulus.
However, the information input also goes on, to reach the brain where thinking process occurs in case of cranial reflections e.g. Reduction of pupil size of eye due to bright light focused on it.
What are plant hormones or phytohormones or plant growth regulators. Discuss their functions?
Phytohormones are defined as chemical substances which are produced naturally in plants and are capable of translocation and bring about control and coordination of various activities in plants. They are present in low concentration. There are five main types of naturally occurring phytohormones or plant growth regulators: (a) Auxins (b) Gibberilins (c) Cyto kinins (d) Ethylene (e) Abscisic acid (ABA).
(a) Auxins: Auxins (Greek-auxin means to increase) are a group of growth regulators discovered by F.W Went in 1928. Auxins are synthesized in the shoot apex and young leaves of the plant. These chemicals move from cell to cell by the process of diffusion.
Functions of Auxin:
- The root of the plant is positively geotrophic i.e. grows downwards and the shoot is negatively geotropic; i.e. grows upwards. Auxins help to control the geotropic behaviour of the shoot and root of plant.
- Auxins stimulate tissues at the tips of the root and shoot to undergo rapid cell division.
- Auxins cause considerable cell enlargement and cell elongation during the growth of plants
- Auxins have been found to increase the rate of formation of root initials.
- Auxins play an important role in the development of seedless fruits withput pollination and fertilization. This phenomenon is known as parthinocarpy.
- Auxins promote apical dominance in plants.
- Auxins play an important role in the prevention of fall of leaves and pre-harvest fruit drop in plants.
- Auxins promote various processes associated with reproduction like flowering, pollen grain germination, fertilization and fruit development.
(b) Gibberellins: Gibberellins are phyto hormones which are synthesized in the chloroplasts of young apical leaves, buds,seeds and root tips. They move to all parts of the plant through xylem and phloem vassels. Till now more than 100 gibberellins have been identified e.g. GA3, etc
Functions of Gibberellins:
- They promote cell enlargement and cell differentiation in plants in présence of auxins.
- Gibberellins induce parthenocarpy in many plants.
- Gibberellins enhance the phenomenon of apical dominance induced by auxins.
- Gibberellins increase the size of fruits. flowers, stem and roots.
- Gibberellins induce flowering in long day plants but inhibit flowering in short day plants
These were Control and Coordination Class 10 science chapter 7 Notes Pdf in the form of questions and answers. We are sure that you will find them very useful for your 10th class exam preparation.
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