Phytohormones assignment Plant Hormones

Phytohormones assignment

Plant Hormones: (Phytohormone)

Definition

Certain chemical produced by plants have profound effect on their subsequent growth and development. Such chemicals are called Plant Hormones or Phytohormone.
Phytohormone are synthesized by plants in minute concentration and exert their effect by activating gene expression or inhibiting enzyme or changing properties of membrane.

Types of Phytohormone

There are five kinds of plant hormones
1. Auxins
2. Gibberellins
3. Cytokinins
4. Abscisic Acid
5. Ethene

1. Auxins 

Discovery 

the first auxin was discovered by Fret Went in 1926.

Chemical Nature 

Indol Acetic Acid (I.A.A)
Indol Acetic Acid (I.B.A)
Nephthalene Acetic Acid (N.A.A)
Site of Synthesis
It is synthesize at the apices of stem and foot, young leaves and young embryo.

Role of Auxin 

i. Cell division and cell enlargement
It stimulate teh cell division and cell enlargement and plant in increase the length of plant.
ii. Initiation of Root
Auxins also initiates development of adventitious roots when applied at the cut base of stem.
iii. Abscission
In mature leaves and fruits when auxin production diminishes, a layer of thin walled cells is formed at the base of petiole and stake of fruit. This layer is called Abscission layer and causes fall of leaves and fruit with slight jerk. 

iv. Growth of FruitAuxins produced in young embryo promotes the growth of fruit.
v. ParthenocarpyUse of auxin helps in producing parthenocarpic or seedless fruits. 
vi. Apical DominanceBesides growth promoting function on Auxin, also has inhibitory effect on growth. Growth of apical bud inhibits growth of lateral buds beneath the stem. This phenomenon is termed as apical dominance removal of apical buds initiates growth of lateral buds with more leaves and axillary bud.
vii. WeedicideAuxins are selective weed killer 2-4 dichlorophenoxy acetic acid (-2-4-D) is used to kill weeds in lawn's and cereal crops.

2. Gibberellins 

DiscoveryGibberellins was discovered by T.Yabuta and I.Hayashu in a fungus called Gibberellins funjikuroi. This fungus causes foolish seedling (Bakanae) disease in rice. In this disease the infected rice seedling elongated and ultimately fallover without producing grains.
Chemical NatureThe chemical nature of Gibberellins is Gibberellins acid 70 types of gibberellins have been discovered.

Role of Gibberellins
i. Cell division and cell enlargementLike auxins Gibberellin also promotes cell division and elongation.
ii. Control of DwarfismGibberellins can control genetic and physiological dwartism plants.
iii. Seed GerminationThey promote the synthesis of a-amylase enzyme is dorman seeds due to the production of this enzyme, the seed starts germination.
iv. ParthenocarpyThese hormones help in the formation of seedless fruit which are called Parthenocarpic fruits.
v. Increase of Crop YieldThe crop yield of sugar can can be increased by the application of gibberellin about 50 tons/ acre.
vi. Formation of Flower and Growth of Pollen TubeThey stimulate flowering and the growth of pollen tubes during fertilization

3. Cytokinins 

DiscoveryCytokinins are discovered by Miller in coconut milk.
Chemical NatureChemically there are two types of cytokinins. 
Kinetin It is found in coconut milk etc.
Zeatin It is found in maize.

Role of Cytokinins
i. Cell DivisionThey initiate rapid cell division only in the presence of auxin.
ii. Delay in SenescenceThey also caused delayed senescence (old age).
iii. Breaking of Seed DormancyThey break seed dormancy and promote fruit development some species.

4. Abscisic Acid (A.B.A) 

In contrast to growth promoting hormones, abscisic acid is growth inhibitor, produced by plants during adverse environment conditions such as drought conditions.

Role of Abscisic Acid 

• It increases dormancy in buds and seeds.

• It causes stomata to close.

• It turn leaf primordia into scale.

5. Ethene 

It is a gas which also acts as a growth inhibitor.

Role of Ethene 

• It triggers ripening of fruits.

• It contributes in leaf abscission and also breaks the dormancy of seeds and buds.

It also initiates flowering in plants e.g. pineapple.

Brain notes for class for students

BRAIN-NOTES

                                          BRAIN

Definition 

The most important part of Central Nervous System develops from dorsal, hollow nerve cord well protected in the cranium of skull and composed of inter neurons and is the seat of our intelligence, learning and memory is called Brain.

Part of Brain

The brain consists of three parts
1. Fore Brain
2. Mid Brain
3. Hind Brain

1. Fore Brain 

Fore brain can be divided into two regions
i. Telencephalon
ii. Diencephalon

i. Telencephalon 

The largest part of fore-brain which is differentiated into two cerebral hemisphere or cerebrum is called Telencephalon.

Cerebrum 

Cerebrum is the largest part of the brain and is divided into two halves called Cerebral Hemispheres.

Cerebral Hemisphere 

Each hemisphere consist of an outer grey matter or cerebral cortex and an inner white matter.
Cerebral Cortex 
• Cerebral cortex is the largest and the most complex part of human brain.
• It is highly convulated to occupy the greater number of inter neurons.

Corpus Callosum 

The two cerebral hemisphere communicate with each other by means of large band of axons called Corpus Callosum.

Part of Cerebrum 

Functionally, the cerebrum is differentiated into four lobes.
• Anterior Frontal Lobe
• Lower Central Temporal Lobe
• Parietal Lobe
• Dorsal Occipital Lobe

Function of Cerebrum 

• Cerebrum is concerned with intelligence memory, learning, resoning and overall control of all voluntary actions.
• It involved in all conscious activities.
• It co-ordinated different senses together.

2. Diencephalon 

The diencephalons consists of two parts
i. Thalamus
ii. Limbic System

i. Thalamus 

The clearing house for sensory impulses is called Thalamus.
Functions 
• It receives them from different parts of brain and relays them to the appropriate part of the motor cortex.
• It also involves in the perception of pleasure and pain.

ii. Limbic System 

The limbic system is located in an are between the thalamus and cerebrum.
Parts of Limbic System
The limbic system consists of
i. Hypothalamus
ii. Amygdala
iii. Hippocampus

i. Hypothalamus 

Hypothalamus is the part of limbic system which is called Thermostal of the body.
Functions
• The hypothalamus is important in regulation of homeostasis.
• It regulates pituitary gland.
• It also regulate body temperature, blood pressure, hunger, thirst, aggression, pleasure and pain.

ii. Amygdala 

The amygdala produces sensation of pleasure, punishment or sexual arousal stimulation.
It also involve in the feelings of fear.

iii. Hippoc Ampus 

Hippocampus is involved in long term memory.

Mid Brain

In mammals mid brain is relatively very small. It consists of the optic lobes which are represented by four small bodies.

Functions 
It receives sensory information like vision, odour etc. It receives sensory information from spinal cord and sends them to the fore brain.

Hind Brain

Hind brain consists of
1. Medulla Oblongata
2. Cerebellum
3. Pons
4. Reticular Formation

1. Medulla Oblongata 
Medulla oblongata lies on the top of spinal cord.
Function
• It controls involuntary actions like blood pressure, heart beat, sneezing, coughing, breathing rate, hicupping, swallowing etc.

2. Cerebellum 
The cerebellum lies dorsally behind the optic lobes. It is highly convoluted. It is large in mammals than other animal.
Functions
• The cerebellum plays an important part in controlling muscular co-ordination.
• It specially maintains balance and also position of the body in space.

3. Pons 
Pons regulates activities like muscular co-ordination, facial expressions, breathing and sleeping.

4. Reticular Formation 
Reticular formation lies in pons, medulla and mid brain.
Functions
• It monitors the messages to the brain which should be ignored or should be realized.

Brain Stem

The oldest tissues formed by the combination of medulla oblongata, pons and mid brain is called as Brain Stem.
Functions
• It involved in the control of sleep and wakening.

Spiral Cord

Definition 

A thick whitish nerve cord that lies below the medulla oblongata and extends down through the neural canal of vertebrate upto the hips is called Spinal Cord.

Cross Section of Spinal Cord

In cross section, the spinal cord is differentiated into two areas.
• White Matter
• Gray Matter
Unlike brain, spinal cord has grey matter inside surrounded by white matter on the outside. They grey matter has the shape of an "H". The first synapse of each sensory neuron is located in the grey matter.

Central Canal 

The narrow central containing cerebrospinal fluid runs through the middle of the spinal cord. This fluid brings nutrients to the spinal cord.

Spinal Nerves

The nerve arises from spinal cord is called Spinal Nerves.
• Each spinal nerve divides into two roots just before it joins spinal cord.
1. Dorsal Root
2. Ventral Root

1. Dorsal Root 

The dorsal root joints the dorsal part of the spinal cord and it contains axons of sensory neurons.
Dorsal Root Ganglion
The cell bodies of these neurons aggregate in a small swelling known as the dorsal root ganglion.

2. Ventral Root 

The ventral root which is attached to the ventral part of the spinal cord carrying axons of motors neurons, arised from the spinal cord.
Functions of Spinal Cord 
• Spinal cord serves as an express way for signals between autonomic nervous system.
• It is also the control centre for many reflexes.

Receptors 

Definition 

The single or group of either modified neurons or epithelial cells which receive stimuli either from external environments and relaying them in the form of impulses to the CNS are called Receptors.

Receptionists 

The receptors are acts as receptionist of nervous system because they receive any kind of change, which is then transferred to the brain and spinal cord.

Sensation 

Receptor converts stimuli into nerve impulses, this stage awareness of stimulus is called Sensation.

Perception 

In the control centre of the nervous system, the impulses are converted into perception.

Types of Receptors

Receptors are classified according to type of stimulus which they can detect and give response. Following are some types of receptor.

1. Thermoreceptor 

The receptors which detect and respond to temperature fluctuations (heat and cold) are called Thermoreceptor.

2. Chemoreceptor 

The receptors which can detect and respond to presence of certain chemicals in their surrounding are called Chemoreceptor.

3. Mechanoreceptor 

The receptors which can detect the stimuli of sound, motion, touch, pressure gravity and movement are called Mechanoreceptor.

4. Photoreceptor 

The receptors which respond to the stimulus of light and ultraviolet rays are called Photoreceptor.

5. Pain Receptor 

The receptors which produced sensation of pain or damage tissues are called the Pain Receptor.


Working of Sensory Receptors in Skin

In human, the receptors in skin are concerned with at least five different senses i.e., touch, pressure, cold, warm and pain.

Types of Sensory Receptor in Skin
There are two types of sensory receptors in the skin.
i. Free Nerve Ending Receptors
ii. Encapsulated Receptors

i. Free Nerve Ending Receptors
The simplest types of receptor which contain free end without any protective capsule and are located just beneath the epidermis are called Free Nerve Ending Receptors.
Functions
Free nerve ending receptors adapt very slowly to stimulation.
Types
They are of different types

a. Mechanoreceptors Receive touch and pressure.
b. Nociceptors Feel pain
c. Thermoreceptors Feel change in temperature

ii. Encapsulated Receptors
The type of receptor contain a protective capsule of connective tissues at their ends and lie in skin are called Encapsulated Receptors.
Types
Encapsulated receptor are of following two types
i. Meissner's Corpuscles
ii. Pacinian Corpuscles

i. Meissner's Corpuscles
The encapsulated receptors that are found in those parts which do not have hairs such as finger tips, eyelids, lips palms, soles, nipples etc are called Meissner's Corpuscles.
Structure of Capsule
Their capsules consists of thick collagen fibers with spiral and highly coiled nerve endings.
Function
There are touch receptors means very sensitive to touch.

ii. Pacinian Corpuscles 

The encapsulated receptors which are found in dermis layer and also in some internal organs and moveable joints are called Pacinian Corpuscles.

Structure 

Their nerve endings are surrounded by an onion like capsule made of concentric layers of membrane. Between the membranes fluid filled spaces are present.

Functions 

They are pressure receptor and detect rapid and deep pressure changes produced by vibration and touch.

Sensory Receptors with Reference to Arteries 

The aortic arch and the carotid artery contain many receptor which are
Mechanoreceptor 
They detect the pressure changes in arteries.
Baroreceptor 
They detect the pulse pressure

Function
These receptors transfer these changes to the medulla oblongata which controls blood pressure.

Aortic Body and Carotid Body 

The aortic arch and the carotid sinus also contain chemoreceptor called Aortic body and carotid body.

Function 

They are sensitive to CO2 concentration and hydrogen ion concentration of the blood.

Chapter 2 notes biology-class 9th

Chapter 2  notes biology-class 9th

Give an example of solving biological problem keeping in view the study of malaria.

 Introduction: 

Malaria is a disease of chills and fevers with recurring attacks. Scientists observed that this disease was common in low, marshy areas.

The word “Malaria” was derived from two Latin words: i) Mala means bad. ii) Aria means air. 

So, the meaning of malaria becomes bad air. Quinine from cinchona bark was an effective remedy for malaria.

Observations: 

i) In 1878, a French army physician Laveran began to search for the cause of malaria.
ii) He observed the blood of malarial patients under microscope and found some tiny creatures in it.
iii) His discovery was not believed by other biologists.
iv) Two year later same results were drawn by another physician and three years later same observations were found third time.
v) The organism was given the name Plasmodium.

Hypothesis: 

Regarding malaria the hypothesis made was: “Plasmodium is the cause of malaria”

Deduction:

 Regarding malaria deduction was made from above hypothesis is: “If plasmodium is the cause of malaria, then all person ill with malaria should have plasmodium in their blood.”
Experiments:
• Then blood of 100 malarial patients was examined under microscope.
 • The results showed that all malarial patients had plasmodium in their blood. While 7 out of 100 healthy persons also had plasmodium in their blood.
• In the healthy people plasmodium was in incubation period (The period between the entry of parasite in host and the appearance of symptoms.)
• The result was convincing and proved the hypothesis.

 How Plasmodium enter in Man:

 Now next step was that how plasmodium gets into the blood of man? In this regard biologists were having following observations:
i) Malaria is associated with marshes
ii)  Drinking water of marshes does not cause malaria.

In this regard, A.F.A King made his observations in 1883. His observations were: 

i) People who slept outdoors in open spaces suffered more from malaria than www.allonlinefree.com those who slept indoors.
ii) People who slept under mosquito nets did not suffer from malaria. iii) Person who slept near smoky fire also did not suffer from malaria.
On the basis of these observations King suggested a hypothesis:
“Mosquitoes transmit Plasmodium and so are involved in the spread of malaria.” For this hypothesis, following deductions were made:
i) “Plasmodium should be present in mosquitoes”
ii) “A mosquito can get Plasmodium by biting a malarial patient”

Experiment of Ronald Ross: 

To test these deductions Ronald Ross, a British army physician performed his experiments in 1880’s in India.
• He allowed a female Anopheles mosquito to bite a malarial patient. He killed the mosquito some days later and found Plasmodium multiplying in mosquito’s stomach.
• Next step was to allow the infected mosquito to bite a healthy person. But this was a risky work as that healthy person can be suffered from malaria. So he selected sparrows for his experiment.
• He allowed a female Culex mosquito to bite a malarial sparrow.
• Then he allowed those mosquitoes to bite a healthy sparrow.
• The healthy sparrow also suffered from malaria.
• In this way he proves that plasmodium is the real cause of malaria and they are transmitted by mosquitoes.
In 1898, an Italian biologists performed same experiments on human beings and find the same results. This confirmed that mosquitoes are involved in the spread of this disease.

Theory:

 When a hypothesis has been proved by consistent results it becomes a theory.

Scientific Principle or Law: 

When a theory can explain many natural phenomena and consistently supported by experiments, and also universally accepted by scientists it becomes a scientific principal or Law.