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Control and Coordination in Plants: Role of Phytohormones, Lecture notes of Nursing
An overview of the control and coordination mechanisms in plants, focusing on the role of phytohormones. It discusses tropism, nastic movements, and the major types of plant hormones, including auxins, gibberellins, cytokinins, abscisic acid, and ethylene. It also compares the nervous and endocrine systems in plants and animals.
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Class 10
BIOLOGY
BEST
FOUNDATION MATERIAL
Revised as per CBSE & NCERT
Effective content to build a strong foundation
Covers complete theory, Practice, and Assessment
Special focus on New Pattern Objective Questions
INTRODUCTION
Living organisms respond and react to their external environment. The linking together of various activities in the living organism is known as coordination. The process of co-ordination must be carefully controlled.
- Plants do not have any special structure for perception of stimuli. In plants control and coordination is performed by chemical substances known as plant hormones or phytohormone. Phytohormones are of five types namely Auxins, Gibberellins, Cytokinins, Abscissic Acid (ABA) and Ethylene.
- Multicellular animals except sponge have specialized cells called neurons for responding to stimuli. Neuron or nerve cell is the structural and functional unit of the nervous system. Nervous system includes brain, spinal cord and nerves. Nervous system and Endocrine or hormonal system control and coordinate body functions in animals.
CONTROL AND COORDINATION IN PLANTS
- Plants lack nervous system and muscles so they relay on chemical or hormonal control.
Stimulus and Response:
- Stimulus is the change in the external or internal environment of an organism that provokes a physiological and behavioral change in the organism. The changes thus caused are termed as response.
- Tropism : Movement of plant towards the direction of stimulus is called tropism. Eg. Bending of shoot towards light is called positive phototropism. Root of plants show negative phototropism. Downward movement is in response to gravitational force is called geotropism. Roots of plants shows positive geotropisms, stems show negative geotropism.
- Other movements in plants which are caused by external stimuli but are not directional are called nastic movements (such as in touch-me-not plant).
Type of Plant Movements
- Plants show two types of movements – one dependent on growth and other independent of growth.
Nastic (Non-directional) Tropic (Directional) Rapid response to non directional stimuli (eg temperature)
Slow response to directional stimuli.
It is reversible as independent of growth Related to growth so irrevesible eg. Movement in Mimosa pudica on touching (thigmonastic)
eg. Bending of shoot towards light (phototropic)
Plant Movement
C O N T R O L
A N D
C O O R D I N A T I O N
(ii) Geotropism is the upward growth of shoots (Negative) and downward growth of roots (Positive) in response to the pull of earth or gravity. It is due to accumulation of Auxin in lower half.
(iii) Hydrotropism is the movement of a part of the plant in response to water. It is stronger as compared to geotropism as shown in the figure that root denies gravity to ensure water availability.
(iv) Chemotropism is the movement of a part of the plant in response to a chemical stimulus. If the plant part shows movement or growth towards the chemical, it is called positive chemotropism and if the plant part shows movement or growth away from the chemical, it is called negative chemotropism. For example, the growth the pollen tube towards a chemical which is produced by cells of ovule during the process of fertilization in a flower.
PLANT HORMONE
- Plant Hormones or Phytohormones can be defined as chemical substances which are produced naturally in plants and are capable of translocation and regulate one or more physiological processes when present in low concentration.
- Plant hormones help to coordinate growth, development and responses to the environment.
- They are synthesized at places away from where they act and simply diffuse to the area of action.
Types of Phytohormones
- The major types of plant hormones that are involved in the control and coordination are as follows :
(1) Auxins : Indole Acetic Acid (IAA) is major Auxin in plants. Important function : (i) Responsible for tropic movement. Plants bend towards sunlight (Positive Phototropism). (ii) Help in increasing length of plant as these are synthesized at the tip of roots and shoots. Cell elongation is the primary and chief function of auxin in plants. By removing tips we can make the plants bushy. As apical bud suppresses growth of lateral buds in plants. It is called apical dominance. (iii) These induce parthenocarpy to obtain seedless fruits eg. seed less grapes, papaya etc. (iv) Prevent falling of unripen fruits. (v) Help in removal of weeds eg. 2, 4–D.
(2) Gibberellins : (i) These stimulate the elongation of stem particularly at the internodal region. (ii) These induce germination of dormant seeds. (iii) Help in removing genetic dwarfism. (iv) Help in flowering and development of fruits.
(3) Cytokinins : (i) These compounds are synthesized in the seeds and the roots of the plants. (ii) These promote cell division by activating DNA synthesis and protein synthesis. (iii) They are present in large concentration in areas of rapid cell division (such as fruits and seeds). (iv) Break dormancy. (v) Delay senescence.
(4) Abscisic acid (ABA) : (i) Commonly known as stress hormone because the production of hormone is stimulated by drought, water logging and other adverse environmental conditions. (ii) It reverses the promotory effects of Auxins and gibberellins. (iii) Abscisic acid is primarily a growth Inhibitor responsible for wilting of leaves. It is found in leaves, dormant seeds, buds and other parts of the plant. (iv) ABA promotes abscission of leaves, flowers and fruits. (v) It also promotes the senescence of leaves. (vi) Helps in reducing transpiration rates by closing stomata.
(5) Ethylene (i) Ethylene is a gaseous plant hormone that stimulates transverse growth but retards the longitudinal one. (ii) It is formed in almost all plant parts – roots, leaves, flowers and seeds. (iii) Ethylene promotes fruit growth and its ripening. (iv) Normally reduces flowering in plants except pineapple. (v) It behaves as growth inhibitor.
CONTROL AND COORDINATION IN ANIMALS
Animals receive external information through specialized structure called sense organs (receptors). These are photoreceptors for light, phonoreceptors for sound and olfactoreceptors for smell. Control and coordination is achieved by two systems (a) nervous system (b) endocrine system.
A. NERVOUS SYSTEM AND SENSE ORGANS OF ANIMALS
- In animals, control and co-ordination is achieved with the help of nervous and muscular tissues. Nervous system is made up of specialized cells called neurons. Structure of neuron
- A neuron (nerve cell) consists of cyton and processes : (a) Cell body / Cyton / Soma
- Cyton or cell body has a central nucleus and surrounding cytoplasm.
- Around the nucleus there are granules called Nissles granules, which are made up of RNA and Protein (exact function unknown, they are believed to convert a nerve impulse into an electrical impluse). It transfers impulse to axon. (b) Two types of processes namely dendrites and axon. Dendrites:
- These are hair like processes connected to the Cyton through dendrone.
- They receive sensation or stimulus, which may be physical, chemical, mechanical or electrical.
- The information received at dendrite tip sets up a chemical reaction that creates an electric impulse.
- This impulse travels from dendrite to cell body Axon
- It is the longer part of the neuron.
- It transmits the impulse from Cyton to the tip of the axon called axon bulb.
- The plasma membrane of an axon may be covered by a sheath of lipid and protein called the myelin sheath.
- The sheath is formed by the Schwann cells, and is broken into constrictions called the nodes of Ranvier.
- The ending of axon is called synaptic terminals or nerve endings.
- The impulse on reaching terminal releases some chemicals or neuro-hormones i.e. Acetyl Choline (Ach) or glutamic acid which crosses the synapse (The physical gap between a synaptic terminal and the dendrite of another neuron or an effector cell) and transfer impulses to next neurons.
- These chemicals start a similar electrical impulse in dendrite of next neuron and in same manner impulses are transmitted to effectors, such as muscles (Neuromuscular junction) and/or glands.
Knowledge Enhancer : Synapse is the point of contact between the terminal branches of the axon of a neuron with one dendrites of another neuron. Here the nerve impules "jumps" into the next neuron. This is a chemical process. As the impulse reaches the terminal end of an axon, a chemical acetylcholine
or glutamic acid is released. This chemical sets a new impulse in the dentrites of the adjacent (next) neuron. The chemical is soon broken down by an enzyme to make the synapse ready for the next tranmission.
Do you Know : Impulse is an electrical disturbance received by the dendrite and passed through the cyton to the axon. Messages are transmitted in the form of electrical impulses along the fibre of the neurons. It flows only unidirectionally.
- A nerve may terminate in one of the given three ways : (i) Synapse (ii) Neuromates junction / Neuroglandular junction (iii) Sensory nerve ending
Types of Nervous System in Animals
- In all vertebrates including humans the nervous system may be divided into the Central nervous system and peripheral nervous system. Peripheral nervous system may be somatic or autonomous. (A) Central nervous system (CNS) consisting of brain and spinal cord.There are 12 pairs of cranial and 31 pairs of spinal nerves in humans. (B) Peripheral nervous system (PNS) consisting of cranial nerves and spinal nerves. It connects CNS to the body organs.PNS may be somatic and autonomic as defined below:
- PNS that connects CNS and voluntary muscles is Somatic and that connects CNS to involuntary muscles is Autonomic Nervous System (ANS).
Autonomic Nervous System (ANS) may be further of two types (A) Sympathetic:The sympathetic division typically functions when quick responses to stimulus is require. It dialates pupil, Inhibits flow of saliva and contract bladder but acclerates heart beat. (B) Parasympathetic:The parasympathetic division functions with actions that do not require immediate reaction.It constricts pupil, increases flow of saliva, relaxes bladder but slows down heart beat.
- Sympathetic and parasympathetic divisions are typically antagonistic to each other. The sympathetic division work as the accelerator and the parasympathetic division works as a brake.
- A useful acronym to summarize the functions of the autonomous nervous system is STUDD (salivation, tear, urination, digestion and defecation).
FUNCTIONS OF AUTONOMIC NERVOUS SYSTEM
Organ (^) sympathetic systemFunction of parasympathetic systemFunction of
Heart Accelerates heart beat Slows heart beat
Arteries (^) & raises blood pressureConstricts arteries & lowers blood pressureDilates arteries
Urinary bladder Relaxes bladder Constricts bladder Muscles of iris Dilate pupil Constricts pupil
Stimulus ReceptororganSensorynervesspinalcordMotornerveEffectororgan Response
Significance of Reflex Action (i) It enables the body to give quick responses to threatening stimuli and thus protects our body. (ii) It helps to minimize the overloading of brain. (iii) Thinking process of brain is not fast enough. (iv) Many lower groups of animals have very little or none of the complex neuron network needed for thinking. In them the reflex arcs have evolved as efficient ways of functioning in the absence of true thought processes.
Do you know?
- As per definition reflex actions are purely instinctive. Such reflex are unconditioned reflex.
- Ian Pavlon however demonstrated that some reflex can be learnt by training. Such reflexes are termed as Conditioned reflex.
HUMAN BRAIN
- It is the highest coordinating centre in the body. Complex processes like thinking, memory etc. are concerned to brain.
The brain is broadly divided into three regions : Fore-brain, mid-brain and hind-brain.
Fore Brain Hind Brain
Thalamus Hypothalamus
Cerebrum Cerebellum
Medulla
(Voluntary activities, Memory etc)
(Master of Pituitary, Thermostat)
(Involuntary activities)
(Respiratory Center, transfers messages between various parts of the brain and the spinal cord.)
(Maintaining Body Posture)
(Breathing reflexes and Swallowing reflexes)
Diencephalon
Pons Optic lobes Crura cerebri Anterior vision
Posterior hearing
Superior vision
Inferior vision
(Emotions,regulating states of sleep and wakefulness)
Mid Brain
Brain
I. FORE-BRAIN
Its includes Cerebrum and Diencephalon (Thalamus and hypothalamus).
A. Cerebrum
- The cerebrum is the largest part of the human brain, associated with higher brain function such as thought and action.
- The cerebrum is divided into four sections, called “lobes”: the frontal lobe, parietal lobe, occipital lobe, and temporal lobe. (a) Occipital lobe is the regions for sight, i.e., visual reception. (b) Temporal lobe is the region for hearing, i.e. auditory reception. (c) Frontal lobe is the region for speech, facial muscular activities and higher mental activities. (d) Parietal lobe is the region for taste, smell, touch and conscious association.
- The cerebrum has sensory areas where information is received from the sense organs called receptors.
- Similarly, cerebrum has motor areas from where instructions are sent to the various muscles of the body called effectors to do the various jobs.
- Areas of association are present in cerebral cortex.
- They are neither sensory nor motor.
- They receive information from sensory areas and is involved in “higher” functions such as perception, thoughts and decision-making, etc.
B. Diencephalon : Smallest part of brain Epithalamus : roof of brain
- Thalamus It is essentially a relay station that receives sensory information and passes it on to the cerebral cortex. It is related to emotions and controlling state of wakefulness and sleep.
- Hypothalamus It is master of master endocrine gland which is mainly responsible for maintaining body temperature (Thermostat). It also regulates desires, Food and Water Intake, Sleep & Wake Cycle etc.
Knowledge Enhancer : (i) Electroencephalogram : It is graph made by an instrument called encephalograph that records the waves of the brain. The minute electrical waves produced by the nerve cells of the brain are transmitted to the instrument, which amplifies and records them on strip of paper. (ii) Spinal Cord : It lies in the mid-dorsal region along the longitudial axis of the body. It is a slender, cylindrical structure, about 45 cm long, originating from medulla oblongata and extending downwards upto the lumber region. It then extends to the end of vetebral column as fibrous connective called filum terminals. Spinal cord is enclosed in the vertebral column, which protects it. Internally, the spinal cord possesses a narrow fluid- filled cavity called central canal. Spinal cord is also covered by three meninges, like the brain, in between which is the cerebrospinal fluid. Spinal cord acts as a centre for reflex actions, thus, reduces brain's work. It also conducts sensory and motor impulses to and from the brain. Thirty–one pairs of spinal nerves arise from the spinal cord and twelve pairs of nerves arise from the brain.
Protection of Central Nervous System (Brain and Spinal Cord)
- Owing to function and importance of Central Nervous System it is well protected inside the body.
- Brain is protected inside brain box or cranium.
- Brain is covered by layers known as meninges (Outer Dura-mater, Arachnoid, and Pia-mater)
- Spinal cord is protected by Vertebral column & meninges.
- Brain has grey matter on the outer side and white matter in the centre while the spinal cord has the reverse i.e., grey matter in the central core and white matter on the outer side.
How does the Nervous Tissue cause Action on Effector (Muscles).
- The nervous tissue collects information from receptors and sends it to the brain (CNS), brain processes information and makes decision.
- Decision is conveyed to muscles for action.
- When a nerve impulse reaches the muscles, the muscle fibers move by changing the shape of the muscle cells with the help of special proteins (actin and myosin).
- This process require certain chemical massenger (Neuro-hormones) to transmit impulses to muscles and also ATP and Ca++^ ions. Impulse is transmitted in electrochemical form.
- The overall pathway is: Ner vous ti ssue Collect information Transfer information Brain Process information Interpretation Action (By muscle & glands)
B. HORMONES IN ANIMALS
Chemical Messengers
- Hormones are the chemical substances which coordinate and control the activities of living organisms and also their growth.
- The term hormone was introduced by Bayliss and Starling. Hormones are chemically made up of proteins or lipids.
Characteristics and Functions of Hormones (i) Hormones are the secretions of endocrine (ductless) glands. (ii) They are poured directly into the blood and carried through out the body by blood circulatory system. (iii) Hormones have their effect at the sites different from the sites of there origin. So, they are also called ‘chemical messengers’. (iv) They act on specific tissues or organs called ‘target organs’ or ‘target site’. (v) They coordinate the activities of the body and also its growth. (vi) They are secreted in extremely minute quantities. (vii) Hormones are non-nutrient chemical which act as inter-cellular messengers.
S.NO. EXOCRINE GLANDS ENDOCRINE GLANDS
- Exocrine glands have ducts. Endocrine glands are ductles s.
- Thes e glands dis charge their s ecretions into the ducts.
Thes e glands dis charge their s ecretions directly into the blood.
- Thes e glands are pres ent near the s ite of action. Exam ples : Sweat and oil glands of s kin, s alivary glands , etc.
Thes e glands are pres ent far away from the s ite of action.e.g.Pituitary, thyroid, hypothalam us , etc.
DIFFERENCES BETW EEN EXOCRINE & ENDOCRINE GLANDS.
ENDOCRINE GLANDS
- These are the structures or group of cells or tissue which manufacture hormones and secrete them directly into the bloodstream to act at distant sites in the body known as target organs or cells.
Male Female
- They lack ducts and pour their secretion in blood.
- Thus, are also known as ductless glands.
- The following are the major endocrine glands in human body:
(vi) Thymus
- It is paired structure present in chest.
- It secretes the hormone thymosin which activates immune responses and helps in the production of antibodies.
- This gland degenerates when sexual maturity is attained.
(vii) Adrenal glands
- These are two in number, they are located one on top of each kidney. So are also called supra- renal glands.
- Internally these consist of two parts outer cortex and inner medulla which secretes corticoids and adrenaline hormone respectively.
- Corticoide hormones regulate carbohydrate metabolism, mineral balance and sexual development in the body.
- Adrenaline hormone is secreted in emergency or stress condition and regulate heart beat, breathing rate, blood pressure etc. in the body. It works on the principle of flight, fright and fight. So the gland is also known as 3F gland.
- This gland is related with sex, sugar, salt, stress, so also called as 4S gland.
(viii) Pancreas
- It is present just below the stomach in between both limbs of duodenum in the body.
- Pancreas is mixed gland (exocrine as well as endocrine gland). The endocrine parts are called islets of langerhans.
- It secretes two hormones-insulin and glucagon.
- The function of insulin hormone is to lower the blood glucose as it converts sugar into glycogen.
- The function of glucagon hormone is to increase the blood glucose as it converts glycogen into sugar.
Sugar Glycogen
Insulin Glucagons
(ix) Testes
- In males, testes are present outside the abdomen cavity in scrotum. These produce male hormone and male gametes.
- They secrete male sex hormone called testosterone.
- The function of testosterone is to regulate development of male accessory sex organs and secondary sexual characters of male like moustache, beard and voice.
(x) Ovaries
- In female, ovaries are present in the lower abdomen. These perform dual function of producing female gametes as well as female sex hormones.
- They secrete two female sex hormones called estrogen and progesterone.
- The function of estrogen hormone is to regulate the development of female accessory sex organs and secondary sexual characters of female such as mammary glands, soft skin, hair pattern and feminine voice.
- The function of progesterone hormone is to control the changes in uterus during menstrual cycle. It also helps in the maintenance of pregnancy.
DIFFERENT ENDOCRINE GLANDS
S.NO. LOCATION HORMONES SECRETED
(A) Pituitary Located below Hypothalamus
Somatotropic hormone(SH/GH) (Growth Hormone) Follicle stimulating hormone(FSH) Leutinizing hormone(LH) Adrenocorticotropic hormone(ACTH) Thyroid stimulating hormone(TSH)
Anterior lobe
Middle Melanocyte stimulating hormone (MSH) Posterior lobe
Vasopressin/Anti Diuretic Hormone Oxytocin (ADH)
Prolactin
DIFFERENT ENDOCRINE GLANDS, THEIR LOCATION IN THE BODY & THE HORMONES SECRETED BY THEM.
(B)
Thyroid Thyroxine Calcitonin
(C)
Parathyroid Situated on thyroid gland.
(D) lobes of the Parathormone
Adrenal gland
Located on the top of kidneys. Adrenal cortex
Adrenal medulla
Adrenaline Noradrenaline
(E)
(F)
Thymus gland
Located in the upper part of the thorax near heart.
Thymosin
(G)
Pancreas
Pancreas lies below the stomach in a bend of the duodenum.
Insulin,Glucagon and Somatostatin (Islets of Langerhans)
(H) Gonads Ovaries (Female) - Located in pelvic cavity in abdomen.
Estrogen Progesterone Relaxin Testes (Male) extra- abdominal in position
Testosterone
Mineralo corticoids
Gluco corticoids
Pineal gland Located betweencerebral hemispheres. Melatonin Serotonin
Sex hormones
TRY YOURSELF
- Olfactory reception is related to sense of : (A) Smelling (B) Tasting (C) Hearing (D) Vision
- Axon are : (A) Impulse (B) Cytoplasmic extension (C) Part of muscles (D) All are correct
- Receptor for stimulus are present in : (A) Stomach (B) Response (C) Sense organ (D) Hot objects
- Impulse is generated when (A) Response is over (B) Response is going to be over (C) Stimulus is gained (D) Stimulus is over
- CNS consists of : (A) Brain (B) Spinal Cord (C) Both (A) and (B) (D) None of these
- Which among them is not a voluntary action of body : (A) Writing (B) Talking (C) Walking (D) Breathing
- Cranium is related to : (A) Head (B) Thorax (C) Abdomen (D) Limbs
- Response in plant are regulated by : (A) Sunlight (B) Gravity (C) Air (D) Phytohormone
- Animals have specialized protein that helps in movement. Plant show movement due to change in : (A) nature of plasma membrane (B) amount of water (C) amount of enzyme (D) none of these
- Movement of pollen tubes towards ovule is an example of : (A) Geotropism (B) Hydrotropism (C) Chemotropism (D) Phototropic
- Unlike tropisms, nastic movements are in response to : (A) Darkness (B) Wind (C) Non-directional stimuli (D) Directional stimuli
- Roots grow downward as a ________ response. (A) Positive phototropic (B) Negative phototropic (C) Negative geotropic (D) All of these
- Ripening of fruits, such as bananas, is hastened by : (A) Gibberellins (B) Abscisic acid (C) Cytokinin (D) Ethylene
- A human hormone reducing blood flow to the digestive system and skin during stress is : (A) Thyroxin (B) Adrenaline (C) Growth hormone (D) Insulin
- Hormone associated with gonads : (A) Testosterone (B) Estrogen (C) Auxin (D) Both (A) and (B)
- Name the hormone which controls the basal metabolic rate in animals. (A) Adrenaline (B) Thyroxine (C) Aldosterone (D) Oxytocin
- ________is responsible for maintaining biological clock of body : (A) Pineal (B) Kidney (C) Thyroid (D) Adrenal
- Deficiency of ______cause dwarfism (A) GH (B) FSH (C) LH (D) All of these
- A person consuming sea food is least likely to develop : (A) Diabetes (B) Goiter (C) Both A and B (D) Heart Diseases
20 A patient of diabetes is not producing : (A) Insulin (B) Thyroxin (C) Oestrogen (D) Adrenaline
- Growth hormone is produced by : (A) Adrenal (B) Pituitary (C) Pancreas (D) Thyroid