Class 11th

Class 11 Biology Revision Notes for Plant Growth and Development of Chapter 15

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• Root, stem, leaves, flowers, fruits and seeds arise in orderly manner in plants. The sequence of growth is as follows-
• Plants complete their vegetative phase to move into reproductive phase in which flower and fruits are formed for continuation of life cycle of plant.
• Development is the sum of two processes growth and differentiation. Intrinsic and extrinsic factors control the process of growth and development in plants.

• Growth is a permanent or irreversible increase in dry weight, size, mass or volume of cell, organ or organism. It is internal or intrinsic in living beings.
• In plants growth is accomplished by cell division, increase in cell number and cell enlargement. So, growth is a quantitative phenomenon which can be measured in relation to time.
• Plant growth is generally indeterminate due to capacity of unlimited growth throughout the life. Meristem tissues are present at the certain locality of plant body.
• The plant growth in which new cells are always being added to plant body due to meristem is called open form of growth.
• Root apical meristem and shoot apical meristem are responsible for primary growth and elongation of plant body along the axis.
• Intercalary meristem located at nodes produce buds and new branches in plants.

• Secondary growth in plants is the function of lateral meristem that is vascular cambium and cork cambium.

Growth is measurable

• At cellular level, growth is the increase in amount of protoplasm. It is difficult to measure the increase in amount of protoplasm but increase in cell, cell number and cell size can be measured.
• The parameter used to measure growth is increase in fresh weight, dry weight, length, area, and volume and cell number. All parameters are not used for every kind of growth.
• Formative phase is also called as the phase of cell formation or cell division. It occurs at root apex, shoot apex and other region having meristematic tissue. The rate of respiration is very high in the cells undergoing mitosis division in formative phase.
• Phase of Enlargement- newly formed cells produced in formative phase undergo enlargement. Enlarging cells also develops vacuoles that further increase the volume of cell.
• Cell enlargement occurs in all direction with maximum elongation in conducting tissues and fibres.

• Phase of maturation- the enlarged cells develops into special or particular type of cells by undergoing structural and physiological differentiation.
• Growth Rate- increase in growth per unit time is called growth rate. Growth rate may be arithmetic or geometrical.
• Arithmetic Growth- the rate of growth is constant and increase in growth occurs in arithmetic progression- 2,4,6,8 ……. It is found in root and shoot elongation.

L_t = L₀ + rt
Length after time = length at beginning + growth rate x time.

• Geometric Growth- here initial growth is slow and increase rapidly thereafter. Every cell divides. The daughter cells grow and divide and the granddaughter cells that result into exponential growth.
• Geometrical growth is common in unicellular organisms when growing in nutrient rich medium.

• Sigmoid growth curve consists of fast dividing exponential phase and stationary phase. It is typical of most living organisms in their natural environment.

Exponential growth can be represented as follows-
W₁ =W₀e^rt. W1 = final size, W0 = initial size, r = growth rate, t = time of growth and e is the base of natural logarithms (2.71828).

• Quantitative comparison between the growth of living system can be made by

1. Measurement and comparison of total growth per unit time is called the absolute rate.
2. The growth of given system per unit time expressed on a common basis is called relative growth rate.

Condition for growth

• Necessary condition for growth includes water, oxygen and essential elements. Water is required for cell enlargement and maintaining turgidity. Water also provide medium for enzymatic conditions.
• Protoplasm formation requires water and micro and macronutrients and act as source of energy.
• Optimal temperature and other environmental conditions are also essential for growth of the plant.
• Cells produced by apical meristem become specialized to perform specific function. This act of maturation is called differentiation.
• The living differentiated cells that have lost ability of division can regain the capacity of division. This phenomenon is called dedifferentiation. For example interfascicular cambium and cork cambium.
• Dedifferentiated cells mature and lose the capacity of cell division again to perform specific functions. This process is called redifferentiation.

Development
It is the sequence of events that occur in the life history of cell, organ or organism which includes seed germination, growth, differentiation, maturation, flowering, seed formation and senescence.

Sequence of development process in plant cell

• Different structures develop in different phases of growth as well as in response to environment. The ability to change under the influence of internal or external stimuli is called plasticity. Heterophylly in cotton plant is the example of plasticity.

Plant Growth Regulators are simple molecules of diverse chemical composition which may be indole compounds, adenine derivatives or derivatives of carotenoids.

• Auxin was isolated by F.W. Went from tips of coleoptiles of oat seedlings.
• The ‘bakane disease’ of rice seedlings is caused by fungal pathogen Gibberella fujikuroi. E. Kurosawa found that this disease is caused due to presence of Gibberellin.
• Skoog and Miller identified and crystallized the cytokinesis, promoting active substance called kinetin.

Auxin- was first isolated from human urine. It is commonly indole-3-acetic acid (IAA). It is generally produced at stem and root apex and migrate to site of action.
Functions-

1. Cell enlargement.
2. Apical dominance
3. Cell division
4. Inhibition of abscission
5. Induce Parthenocarpy

Gibberellins- are promotery PGR found in more than 100 forms named as GA1GA1, GA2GA2, GA3GA3…. GA100GA100. The most common one is GA3GA3 (Gibberellic Acid).
Functions-

1. Cell elongation.
2. Breaking of dormancy.
3. Early maturity
4. Seed germination.

Cytokinins- the plant growth hormone is basic in nature. Most common forms include kinetin, zeatin, etc. They are mainly synthesized in roots.
Functions-

1. Cell division and cell differentiation.
2. Essential for tissue culture.
3. Overcome apical dominance.
4. Promote nutrient mobilisation.

Ethylene – it is a gaseous hormone which stimulates transverse or isodiametric growth but retards the longitudinal one.
Functions–

1. Inhibition of longitudinal growth.
2. Fruit ripening
3. Senescence
4. Promote apical dominance

Abscisic Acid – it is also called stress hormone or dormin. It acts as a general plant growth inhibitor. Abscisic acid is produced in the roots of the plant and terminal buds at the top of plant.
Function-

1. Bud dormancy
2. Leaf senescence
3. Induce Parthenocarpy
4. Seed development and maturation.

Photoperiodism- the effect of photoperiods or day duration of light hours on the growth and development of plant, especially flowering is called Photoperiodism. On the basis of photoperiodic response, flowering plants have been divided into the following categories-

1. Short Day Plants– they flower when photoperiod is below a critical period (continuous duration of light which must not be exceeded in short day plants and should always be exceeded in long day plants in order to bring them flower). Example- Xanthium, Rice, Sugarcane, Potato etc.
2. Long Day Plants– these plants flower when they receive long photoperiod of light, greater than critical period. Example- Radish, Barley, Lettuce.
3. Day Neutral Plants – the plant can blossom throughout the year. Example- Bean, Wild Kidney.

Vernalisation– is the process of shortening of the juvenile or vegetative phase and hastening of flowering by cold treatment. The stimulus of Vernalisation is perceived by meristematic cells.

• Vernalisation helps in shortening of vegetative period of plant and brings about early flowering.
• It is applicable to temperate plants like Wheat, Rice, Millets, etc.

Class 11 Biology Revision Notes for Respiration in Plants of Chapter 14

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Respiration is an energy releasing, enzymatically controlled catabolic process which involves a step-wise oxidative breakdown of food substance inside living cells.
C6H12O6+6O2→6CO2+6H2O+EnergyC6H12O6+6O2→6CO2+6H2O+Energy

• Living organism require energy for all activities like absorption, movement, reproduction or even breathing. Energy required is obtained from oxidation of food during respiration.
• Cellular respiration is the mechanism of breaking down of food materials within the cell to release energy for synthesis of ATP.
• Breaking down of complex molecules takes place to produce energy in cytoplasm and in the mitochondria.
• Breaking down of C-C bond of complex compounds through oxidation within the cells leading to release of energy is called respiration. The compounds that get oxidized are called respiratory substrates.
• Energy released during oxidation is not used directly but utilized in synthesis of ATP, which is broken down when energy is required. Therefore, ATP is called energy currency of cells.
• The process of respiration requires oxygen. In plants oxygen is taken in by stomata, lenticels and root hairs.
• Plants can get along without respiratory organs because:
  1. Each plant part takes care of its own gas-exchange needs.
  2. Plants do not present great demands for gas exchange.
  3. Distance that gases must diffuse in large plant is not great.
  4. During photosynthesis O2 is released in leaves and diffuse to other part of leaves.

• During process of respiration oxygen is utilized and carbon dioxide and water is released along with energy molecules in form of ATP.
• Respiratory Quotient is the ratio of the volume of carbon dioxide produced to the volume of oxygen consumed in respiration over a period of time. RQ is equal to one for carbohydrate and less than one for protein and peptones.

 
Aerobic Respiration is an enzymatically controlled release of energy in a stepwise catabolic process of complete oxidation of organic food into carbon dioxide and water with oxygen acting as terminal oxidant.

Glycolysis

• The scheme of glycolysis is given by Gustav Embden, Otto Meyerhof, and J. Parnas. It is also called as EMP pathway.
• Glycolysis is the partial oxidation of glucose or similar hexose sugar into two molecules of pyruvic acid through a series of enzyme mediated reaction releasing some ATP and NADH2. It occurs in cytoplasm.
• In plants glucose is derived from sucrose or from storage carbohydrates. Sucrose is converted into glucose and fructose by enzyme invertase.
• Glycolysis starts with phosphorylation of glucose in presence of enzyme hexokinase to form Glucose-6-phosphate. One molecules of ATP is used in this process.
• In next steps Glucose-6-phosphate is converted into fructose-6-phosphate, catalysed by enzyme phosphohexose isomerase.
• Fructose-6-phosphate uses another molecule of ATP to form Fructose-1-6 biphospahte in presence of enzyme phosphfructokinase.

• In glycolysis two molecules of ATP are consumed during double phosphorylation of glucose to fructose 1,6 biphosphate. Two molecules of NADPH2 are formed at the time of oxidation of glyceraldehyde 3-phosphate to 1,3 biphosphoglycerate. Each NADH is equivalent to 3ATP, so that net gain in glycolysis is 8 ATP.
• Pyruvic acid is the key product of glycolysis, further breakdown of pyruvic acid depends upon the need of the cell.
• In animal cells, like muscles during exercise, when oxygen is insufficient for aerobic respiration, pyruvic acid is reduced to Lactic acid by enzyme lactate dehydrogenase due to reduction by NADH2.

• In fermentation by yeast, pyruvic acid is converted to ethanol and CO2. The enzyme involved is pyruvic acid decarboxylase and alcohol dehydrogenase catalyse this reaction.
• In both lactic acid fermentation and alcohol fermentation very less amount of energy is released.
• Yeasts poison themselves to death if concentration of alcohol reaches above 13%.
• Final product of glycolysis, pyruvate is transported from the cytoplasm into mitochondria for further breakdown.
• Oxidation of Pyruvate to Acetyl-CoA is done to produce CO2 and NADH. The reaction catalyzed by pyruvic dehydrogenase requires the participation of several Coenzymes including NAD+ .

Pyruvicacid+CoA+NAD+Pyruvicacid+CoA+NAD+−→−−−−−−−−−−−−−PyruvatedehydrogenaseMg2+AcetylCoA+CO2→PyruvatedehydrogenaseMg2+AcetylCoA+CO2+NADH+H++NADH+H+

• The Acetyl CoA enters a cyclic pathway called TCA cycle or Kreb’s cycle.

Tricarboxylic Acid Cycle/Krebs Cycle

• TCA cycle was discovered by Hans Krebs in 1940. This cycle is called TCA cycle because initial product is citric acid.
• Acetyl CoA combine with OAA ( Oxaloacetic acid) and water to yield citric acid in presence of enzyme citrate synthase to release CoA.
• Citrate is then isomerised to isocitrate. It is followed by two successive
  steps of decarboxylation, leading to the formation of α-ketoglutaric acid and then succinyl-CoA.
• In the remaining steps, succinyl-CoA is oxidised to OAA allowing the cycle to continue.
• There are three points in the cycle where NAD + is reduced to NADH2 and one point where FAD + is reduced to FADH2 .
• A molecule of glucose produces two molecules of NADH2NADH2, 2ATP and two pyruvate while undergoing glycolysis. The two molecules of pyruvate are completely degraded in Krebs cycle to form two molecules of ATP, 8NADH28NADH2 and 2FADH22FADH2.

pyruvic + 4NAD⁺ + FAD⁺ + 2H₂O + ADP + Pi −→−−−−−−−−−−−−MitochondrialMatrix→MitochondrialMatrix 3CO₂ +4NADH+4H+FADH2ATP+4NADH+4H+FADH2ATP
Terminal Oxidation is the name of oxidation found in aerobic respiration that occurs towards end of catabolic process and involves the passage of both electrons and protons of reduced coenzyme to oxygen to produce water.

Electron Transport Chain

• The metabolic pathway through which the electron passes from one carrier to another inside the inner mitochondrial membrane is called ETC or mitochondrial respiratory chain.
• Electrons from NADH produced during citric acid cycle are oxidized by NADH dehydrogenase and electrons are transferred to ubiquinone located within the inner membrane. Ubiquinone also receives electrons from FADH2 which is transferred to cytochrome c via cytochrome bc₁ complex.
• When the electrons pass from one carrier to another via electron transport chain, they produce ATP from ADP and inorganic phosphate. The number of ATP molecules synthesized depends upon electron donor.
• Oxidation of one molecule of NADH gives rise to 3 molecules of ATP, while oxidation of one molecule of FAD2FAD2 produce two molecules of ATP.

Oxidative phosphorylation	Photophosphorylation
a) It occurs in respiration process.  b) Energy of oxidation-reduction is used for production of proton gradient required for phosphorylation.	a) It occurs in photosynthesis.  b) Light energy is utilized for production of proton gradient for phosphorylation.

• The energy released during ETC is used to make ATP with the help of ATP synthase, which consists of two major parts F1 and F0.
• F1 is a peripheral membrane protein complex having site for synthesis of ATP from ADP and inorganic phosphate. F0 is integral membrane protein that form channel for proton.
• For each ATP produced 2H+ passes through F0 from the intermembrane space to the matrix down the electrochemical proton gradient.

Fermentation	Aerobic Respiration
a. It accounts for incomplete oxidation of glucose.  b. In fermentation, there is net gain of only two molecules of ATP. c. NADH is oxidized to NAD+ very slowly.	a. It accounts for complete oxidation of glucose.  b. In aerobic respiration, there is more net gain of ATP. c. NADH is oxidized to NAD+ very fast.

Amphibolic Pathway

• Glucose is the favored substrate for respiration. All carbohydrates are usually converted into glucose before used for respiration.
• Fats needs to be broken down into glycerol and fatty acid, which is further broken converted into Acetyl CoA and enter the respiratory pathway.
• Proteins are broken into amino acids and further enter into Krebs cycle.
• Breaking down process within living organism is called catabolism and synthesis process is called anabolism process. So, respiration is an Amphibolic pathway.

Class 11 Biology Revision Notes for Photosynthesis in Higher Plants of Chapter 13

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Photosynthesis is a physico-chemical process by which green plants use light energy to drive the synthesis of organic compounds. It is an enzyme regulated anabolic process.
6CO2+12H2O−→−−LightC6H12O6+6H2O+6O26CO2+12H2O→LightC6H12O6+6H2O+6O2

• Photosynthesis is the basis of life on earth because it is the primary source of all food on earth and it is responsible for release of O2O2 in the atmosphere.
• Chlorophyll, light and CO2CO2 is required for photosynthesis. It occurs only in green part of leaves and in presence of light.

Early Experiments

• Joseph Priestley in 1770, on the basis of his experiments showed the essential role of air in growth of green plants. A mouse kept in closed space could get suffocated and die but if a mint plant is kept in bell jar neither candle will extinguish nor will the mouse die. He concluded that foul air produced by animal is converted into pure air by plants. Priestley discovered Oxygen gas in 1774.

• Julius Von Sachs in 1854 shows that green part in plants produces glucose which is stored as starch. Starch is the first visible product of photosynthesis.
• T.W.Engelmann (1843-1909) used prism to split light into its components and then illuminated Cladophora (an algae) placed in a suspension of aerobic bacteria. He found that bacteria accumulated in blue and red light of the split spectrum. He thus discovered the effect of different wavelength of light on photosynthesis (action spectrum).
• Cornelius Van Neil (1897-1985) on the basis of studies with purple and green sulphur bacteria showed that photosynthesis is a light dependent reaction in which hydrogen from an oxidisable compound reduces CO2CO2 to form sugar.

2H2A+CO2−→−−Light2A+CH2O+H2O2H2A+CO2→Light2A+CH2O+H2O
In green sulphur bacteria, when H2SH2S , instead of H2OH2O was used as hydrogen donor, no O2O2 was evolved. He inferred that O2O2 evolved by green plants comes from H2OH2O but not from CO2CO2 as thought earlier.
Where Does Photosynthesis Takes Place?

• Chloroplasts are green plastids which function as the site of photosynthesis in eukaryotic photoautotrophs. Inside the leaves, chloroplast is generally present in mesophyll cells along their walls.
• Within the chloroplast there is a membranous system consisting of grana, the stroma lamellae and the fluid stroma.

• The membrane system is responsible for synthesizing light energy for the synthesis of ATP and NADPH. In stroma enzymatic reactions incorporate CO2CO2 in plants leading to synthesis of sugar.
• The reaction in which light energy is absorbed by grana to synthesis ATP and NADPH is called light reaction. The later part of photosynthesis in which CO2CO2 is reduced to sugar, light is not necessary and is called dark reaction.

Pigments involved in Photosynthesis – Chromatographic separation of leaf pigments are as follows-
 
Maximum absorption by chlorophyll a occurs in blue and red regions having higher rate of photosynthesis. So, chlorophyll a is the chief pigment.

• Other thylakoid pigments like chlorophyll b, xanthophyll and carotenoids are called accessary pigments that absorb light and transfer energy to chlorophyll a and protect them from photo-oxidation.

Light reaction

• Light reaction(photochemical phase) includes:

1. Light absorption
2. Water splitting
3. Oxygen release
4. Formation of high energy chemical intermediates (ATP and NADPH).

• The pigments are organized into two discrete LHC( light harvesting complex) within photosystem I and photosystem II.
• LHC are made up of hundreds of pigments molecules containing all pigments except single chlorophyll a molecules in each PS.

• The pigments in photosystem I and photosystem II absorbs the lights of different wavelength. Single chlorophyll a molecule makes the reaction centre. In PS I reaction centre has highest peak at 700nm, hence called P700. And PS II reaction centre has highest peak at 680 nm, so called P680.

The Electron Transport System

• Reaction centre of photosystem II absorbs light of 680 nm in red region and causing electron to become excited. These electrons are picked by an electron acceptor which passes to electron transport system consisting of cytochromes.

• Electrons are passed down the electron transport chain and then to the pigment of PS I.
• Electron in the PSI also get excited due to light of wavelength 700nm and are transferred to another accepter molecule having a greater redox potential.
• When electron passes in downhill direction, energy is released. This is used to reduce the ADP to ATP and NADP+ to NADPH. The whole scheme of transfer of electron is called Z-scheme due to its shape.
• Photolysis of water release electrons that provide electron to PS II. Oxygen is also released during this process.

2H2O→4H++O2+4e−2H2O→4H++O2+4e−

• Difference between cyclic and non-cyclic photophosphorylation

Cyclic photophosphorylation	Non-cyclic photophosphorylation
It is performed by photosystem I independently.An external source of electron is not required.It synthesizes only ATP.It occurs only in stromal or intergranal thylakoids.	It is performed by collaboration of both PS I and PS II.The process requires an external electron donor.It synthesizes ATP and NADH both.It occurs in the granal thylakoids only.

 
Chemiosmotic Hypothesis of ATP FORMATION
This hypothesis was proposed by Mitchell in 1961. ATP synthesis is linked to development of proton gradient across the membrane of thylakoid and mitochondria.
The process that causes development of proton gradient across the membrane is-

1. Splitting of water molecules occurs inside the thylakoid to produce hydrogen ion or proton.
2. As electron passes through the photosystems, protons are transported across the membrane because primary acceptor of electron is located towards the outer side the membrane.
3. The NADP reductase enzyme is located in the stroma side of membrane. Electrons come out from the acceptor of electron of PSI, protons are necessary for reduction of NADP+ to NADP + H+. These protons are also removed from the stroma. This creates proton gradient across the thylakoids membrane along with pH in the lumen.
4. Gradient is broken down due to movement of proton across the membrane to the stroma through trans-membrane channel of F0 of ATPase. One part of this enzyme is embedded in membrane to form trans-membrane channel. The other portion is called F1that protrudes on the outer surface of thylakoid membrane which makes the energy packed ATP.
5. ATP and NADPH produced due to movement of electron is used immediately to fix CO2 to form sugar.

• The product of light reaction used to drive the process leading to synthesis of sugar are called biosynthetic phase of photosynthesis.

Calvin Cycle/C3 cycle/Reductive Pentose Sugar Phosphate Pathway
Malvin Calvin, Benson and their colleagues used radioactive 14C and Chlorealla and Scenedesmus algae to discover that first CO2CO2 fixation product is 3-carbon organic compound (3-phosphoglyceric acid) or PGA. Later on a new compound was discovered which contain 4-carbon called Oxaloacetic Acid (AAO). On the basis of number of carbon atoms in first stable product they are named C3 and C4 pathway.
Calvin cycle can be described under three stages: carboxylation, reduction and regeneration.

• Carboxylation is the fixation of CO2CO2 into 3-phosphoglyceric acid (3-PGA). Carboxylation of RuBP occurs in presence of enzyme RuBP carboxylase (RuBisCO) which results in the formation of two molecules of 3-PGA.
• Reduction is series of reaction that leads to formation of glucose. Two molecules of ATP and two molecules of NADPH are required for reduction of one molecules of CO2CO2. Six turn of this cycle are required for removal of one molecule of Glucose molecules from pathway.
• Regeneration is the generation of RuBP molecules for the continuation of cycle. This process require one molecules of ATP.

Fig-Calvin Cycle/ C3 Cycle

• For every molecules of CO2CO2 entering the Calvin Cycle, 3 molecules of ATP and 2 molecules of NADPH is required. To make one molecules of glucose 6 turns of cycle is completed so total energy molecule required is

In	Out
Six CO2CO2  18 ATP 12 NADPH	One glucose  18 ADP 12 NADP

C4 pathway/Hatch Slack Pathway

• This pathway was worked out by Hatch and Slack (1965, 1967), mainly operational in plants growing in dry tropical region like Maize, Sugarcane, Sorghum etc.
• In this pathway first stable product is a 4-carbon compound Oxaloacetic acid (AAO) so called as C4C4 pathway. C4C4 plants have Kranz Anatomy (vascular bundles are surrounded by bundle sheath cells arranged in wreath like manner), characterized by large no of chloroplast, thick wall impervious to gases and absence of intercellular spaces.
• The primary CO2CO2 acceptor is a 3-carbon molecule Phosphoenol Pyruvate present in mesophyll cells and enzyme involved is PEP carboxylase.
• OAA formed in mesophyll cell forms 4-carbon compound like malic acid or aspartic acid which is transported to bundle sheath cells.
• In bundle sheath cell, it is broken into CO2CO2 and a 3-carbon molecule. The 3-carbon molecule is returned back to mesophyll cells to form PEP.
• The CO2CO2 molecules released in bundle sheath cells enters the Calvin cycle, where enzyme RuBisCO is present that forms sugar.

Photorespiration

• It is a the light dependent process of oxygenation of RuBP and release of carbon dioxide by photosynthetic organs of plants.
• Photorespiration decreases the rate of photosynthesis when oxygen concentration is increased from 2-3% to 21%.
• Presence of light and higher concentration of Oxygen results in the binding of RuBisCO enzyme with O2 to form.

RuBisCO + O2→O2→ PGA + phosphoglycolate
This pathway involves Chloroplast, Peroxisome and Mitochondria. Photorespiration do not occurs in C4C4 plants.

C3 plants	C4 plants
The leaves do not have Kranz anatomy.Photorespiration occurs.RuBisCO is the first acceptor of CO2.PGA is the first stable product.Plants are adapted to all climates.Mesophyll cells perform complete photosynthesis.	The leaves show Kranz anatomy in leaves.Photorespiration does not occur.PEP is the first acceptor of CO2.OAA is the first stable product.Plants are adapted to tropical climate.Mesophyll cells perform only initial fixation.

Factors affecting photosynthesis

1. Light- as light intensity increases, the rate of photosynthesis also increases until light saturation point.
2. Carbon dioxide concentration– with increase in concentration of CO2CO2 rate of photosynthesis increase till the compensation point.
3. Temperature- it does not influence the rate of photosynthesis directly but at higher temperature enzyme activity is inhibited due to denaturation of enzymes which affect the dark reaction.
4. Water– due to increase in amount of water, rate of photosynthesis does not increase proportionally as after saturation no more water is required during photosynthesis.

Blackman’s Law of Limiting Factors states:
If a chemical process is affected by more than one factor, then its rate will be determined by the factor which is nearest to its minimal value: it is the factor which directly affects the process if its quantity is changed.

Class 11 Biology Revision Notes for Mineral Nutrition of Chapter 12

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Mineral nutrition is the study of source, mode of absorption, distribution and metabolism of various inorganic substances (minerals) by plants for their growth, development, structure, physiology and reproduction.
Methods to study the Mineral Requirement of Plants

• Hydroponics is the technique of growing plants in nutrient solution in complete absence of soil. This method is used to determine the nutrients essential for plants.
• In this method plant is cultured in soil-free, defined mineral solution. These methods require purified water and mineral nutrients.
• Essential elements are identified and their deficiency symptoms are discovered by hydroponics methods. It is also used for commercial production of vegetables, like tomato and cucumber.

Essential mineral nutrients- About 65 elements are found in different plants. Following criteria is used to determine the essentiality of an element.

1. Element must be absolutely necessary for the normal growth and reproduction to complete their life cycle.
2. The requirement of element must be specific and not replaceable.
3. Element must be directly involved in the metabolism of plants.

• Macronutrients are present in plants tissues in larger quantity. C, H and O is obtained from water and rest are absorbed from soil.
• Micronutrients or trace nutrients are required in very small quantity.

On the basis of diverse functions, essential elements are divided into following categories-

Role of Macro and Micro nutrients-

1. Essential elements participate in various metabolic processes in plants such as permeability of cell membrane, maintenance of osmotic potential, ETS. Etc.
2. Act as major constituents of macromolecules and co-enzymes.

Various forms and function of essential nutrients-

1. Nitrogen- required by plants in greatest amount, it is absorbed by plants as NO₂^–, NO₃^– and NH₄⁺ . It is one of the major constituent of proteins, nucleic acids and vitamins.
2. Phosphorus- Absorbed by plants from soil in the form of phosphate ions. It is the constituent of cell membrane. All nucleic acids and nucleotides require phosphorus.
3. Potassium – absorbed as potassium ions (K⁺). Help to maintain cation-anion balance in cells. It is involved in protein synthesis, opening and closing of stomata.
4. Calcium – absorbed by plants from soil in form of Calcium ions (Ca²⁺). Used in synthesis of cell wall. It activates certain enzymes.
5. Magnesium- absorbed by plants in form of Mg²⁺ ions. It activates the enzymes for respiration, photosynthesis, and involved in synthesis of DNA and RNA. It is constituent of chlorophyll.
6. Sulphur- plants obtain sulphur in form of sulphate (SO₄^2-). Present in amino acids (cysteine, methionine) and is main constituent of coenzymes and vitamins.
7. Iron- obtained in the form of ferric iron (Fe³⁺). It is important constituent of protein involved in transport system.
8. Manganese-absorbed in form of Mn²⁺ ions. Main function is splitting of water to liberate Hydrogen and Oxygen during photosynthesis.
9. Zinc-obtained as Zn²⁺ ions. Activate enzymes like carboxylases. Needed in formation of Auxin.
10. Copper –absorbed as cupric ions(Cu²⁺). Involved in various metabolic activities and redox reactions.
11. Boron-absorbed as BO₃^3- or B₄O₇^2- ions. Required for uptake of calcium, cell elongation and pollen germination.
12. Chlorine – it is absorbed in form of Cl^– ions. Determine the solute concentration and splitting of water during photosynthesis.

Deficiency Symptoms of Essential elements

• When supply of essential elements becomes limited, plant growth is retarded. The concentration of essential elements below which plant growth is retarded is called critical concentration.
• In absence of any particular element, plant shows certain morphological changes. These morphological changes are called deficiency symptoms.
• The parts of plant that show deficiency symptoms depend upon mobility of elements in the plants. Elements that are actively mobilized (N,Mg,K) show deficiency in older regions. On the other hand, symptoms appear first in young region if the elements are relatively immobile (Ca) and not transported out of mature tissues.
• Kinds of deficiency syndrome are as follows-

Deficiency Disease	Symptoms	Deficient elements
Chlorosis	Loss of chlorophyll leading to yellowing of leaves.	N, K, Mg, S, Fe, MN, Zn, Mo
Necrosis	Death of tissue (leaf).	Ca, Mg, Cu, K.
Stunted plant growth	Less height of plant	Fe, K.
Premature fall of leaves and buds.	Falling of leaves and buds.	P, Mg, Cu
Inhibition of cell division	Less elongation in stem.	Low level of N, K, S, Mo.

• Deficiency of any element may cause many symptoms or same symptoms may be caused by different elements. To identify the deficient elements various symptoms are compared with standard chart.Toxicity of micronutrients- in higher doses, micronutrients become toxic. Any tissue concentration which reduces dry weight of tissue by 10% is called toxic concentration. Critical toxic concentration is different for different elements.
  Mechanism of absorption of elements
• It takes place in two phases. In first phase, rapid intake of ions occurs in free space or outer space of the cells, apoplast. In second phase, ions are taken slowly into inner space, the symplast of the cells.
• Passive movement of ions in apoplast occurs through ion channels and trans-membrane protein. On the other hand, movement of ions into symplast occurs by expenditure of energy by active process.
• The movement of ion is called flux. The inward movement is called influx and outward movement is called efflux.

• Translocation of solutes occur through xylem along with ascending stream of water

Soil as reservoir of essential elements- most of the nutrients required for growth and development is obtained from soil by roots. These minerals are formed by weathering of rocks. Soil also harbours nitrogen fixing bacteria and other microbes, holds water and supplies air to roots. Deficiency of essential elements affects the crop yield. So, fertilisers are used to supplement these elements.
Metabolism of Nitrogen

• Nitrogen is the most prevalent element in living world along with C, H and O. It is the main constituent of proteins, nucleic acids, fats, hormones, enzymes etc.
• The process of conversion of nitrogen to ammonia is called nitrogen fixation. In nature lightening and ultraviolet radiation provide energy to convert atmospheric nitrogen into nitrogen oxide ( No, NO₂ and N₂O).
• Industrial combustion, forest fire and automobiles along with thermal power plants produce nitrogen oxides.
• The decomposition of organic nitrogen of dead plants and animals into ammonia is called ammonification.
• Ammonia is first oxidized to nitrite by bacteria Nitrosomonas or Nitrococcus which is further oxidized to nitrate with help of bacteria Nitrobactor. These processes are called nitrification.

2HN3+3O2→2NO−2+2H++2H2O2NO−2+O2→2NO−32HN3+3O2→2NO2−+2H++2H2O2NO2−+O2→2NO3−

• Nitrates formed is absorbed by plants and transported to leaves. Nitrates is converted into free nitrogen by the process called denitrificaion by bacteria Pseudomonas and Thiobacillus.
• Reduction of nitrogen to ammonia by living organism is called Biological Nitrogen Fixation. The enzyme nitrogenase is present in prokaryotic organism called nitrogen fixer.

N≡N−→−−−−−−NitrogenaseNH3N≡N→NitrogenaseNH3

• Nitrogen fixing microbes may be symbiotic (Rhizobium) or free living (Nostoc, Azotobactor, Anabaena).
• Symbiotic biological nitrogen fixation includes legume-bacteria relationship in which rod shaped Rhizobium lives with symbiotic relation with nodules of Leguminous plants.
• Central portion of nodule is pink or red due to presence of leguminous haemoglobin or leg-haemoglobin.

Nodule formation involves sequence of interaction between root and Rhizobium as follows-

• Rhizobia increase in number and attach with epidermis of roots. Root hairs curls and bacteria invade it. An infection thread is formed that carries the bacteria into cortex of root.
• Nodule formation starts in cortex of root. Bacteria is released from thread to cells which leads to formation of specialized nitrogen fixing cells.
• Nodules establish direct vascular connection with host for exchange of nutrients.
• Nodule contains all necessary biochemical components like enzyme nitrogenase and leg-haemoglobin.

• Enzyme nitrogenase is a Mo-Fe protein and catalyses the conversion of atmospheric nitrogen into ammonia.

The reaction is as follows-
N2+8e−+8H++16ATPN2+8e−+8H++16ATP→2NH3+H2+16ADP+16P1→2NH3+H2+16ADP+16P1

• The enzyme nitrogenase is highly sensitive to molecular oxygen and needs anaerobic condition. To protect this enzyme from oxygen, the nodules contain an oxygen scavenger called leg-haemoglobin.
• The ammonia synthesized by nitrogenase enzyme require large amount of energy (18ATP) for each NH3 produced.

Fate of ammonia- at physiological pH, ammonia is converted into ammonium ions (NH₄⁺).It is toxic for plants in larger concentration and ammonium ion is converted into amino acids by two methods-

1. Reductive amination– in this process ammonia reacts with α-ketoglutaric acid to form glutamic acid.

α−ketoglutaricacid+NH+4+NADPHα−ketoglutaricacid+NH4++NADPH−→−−−−−−−DehydrogenaseGlutamateglutamate+H2O+NADP→DehydrogenaseGlutamateglutamate+H2O+NADP

1. Transamination– it involves the transfer of amino group from amino acids to keto group of keto acid. Glutamic acid is the main amino acid from which transfer of NH3 takes place and other amino acids are formed by transamination. The enzyme transaminase catalyses all such reactions.

Two important amides asparagine and glutamine found in plants as structural part of proteins. They are formed from aspartic acid and glutamic acid by addition of another amino group to it.

Class 11 Biology Revision Notes for Transport in Plants of Chapter 11

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Plant transport various substances like gases, minerals, water, hormone and organic solutes to short distance (one cell to another) or long distance as water from roots to tips of stem.

• Long distance transport occurs through vascular system, xylem and phloem called translocation through mass flow.
• The direction of translocation may be unidirectional as in case of water and multidirectional as in minerals and organic solutes.

Simple Diffusion-

• Movement by diffusion is passive and slow along the concentration gradient through permeable membrane.
• No energy expenditure takes place. It occurs in liquid and gases.
• Rate of diffusion are affected by gradient of concentration, permeability of membrane, temperature and pressure.

Facilitated Diffusion-

• Lipid soluble particles easily pass through cell membrane but the hydrophilic solutes movement is facilitated.
• For facilitated diffusion, membrane possesses aquaporins or water channels. Aquaporins are membrane proteins for passive transport of water soluble substances without utilization of energy.
• The protein forms channels in membrane for molecules to pass through. The porins are proteins that forms huge pores in the outer membrane of the plastids, mitochondria etc.
• Water channels are made up of eight different types of aquaporins.

Symport, Antiport and Uniport-

• In Symport, both molecules cross the membrane in the same direction.
• In Antiport, both molecule moves in opposite direction.
• When a molecule moves across a membrane independent of other molecules, the process is called uniport.

Active Transport

• Uses energy to pump molecules against the concentration gradient. It is carried out by membrane proteins.
• In active transport movable carrier proteins are called pumps.
• The pumps can transport substance from low concentration to high concentration. The carrier proteins are very specific in what it carries across the membrane.

Comparison between Transport mechanisms-

Simple diffusion	Facilitated diffusion	Active transport
Special membrane protein is not required.	Special membrane protein is required.	Special membrane protein is required.
Not selective	Highly selective	Highly selective
Transport do not saturate	Transport saturate	Transport saturate
No uphill transport	Uphill transport	Uphill transport
No ATP energy is required.	No ATP energy is required.	ATP energy is required.

Plant Water Relationship

• Water is essential for all physiological activities of plants along with all living organisms. It provide medium for most substances to dissolve in it.
• Protoplasm of cells contains water in which different molecules are dissolved and suspended.
• Terrestrial plants take lot of water and release most of it in form of water vapour by the process of transpiration.
• Water is the limiting factor for plant growth and productivity in both agricultural and natural environments.

Water Potential (ΨwΨw)- is a concept fundamental to the understanding of water movement. Water potential is determined by solute potential (ΨsΨs) and pressure potential (ΨpΨp).

• Water molecules possess kinetic energy. The greater the concentration of water in the system, the greater is its kinetic energy or water potential. So pure water has greatest water potential.
• Water potential is denoted by Greek symbol Psi (ΨΨ) and is expressed in pressure unit Pascal (Pa).
• Water pressure of pure water is taken as zero at standard temperature and pressure. A solution has less water potential due to less water concentration.
• The magnitude of lowering of water potential due to dissolution of solute is called solute potential (ΨsΨs). Solute potential is always negative. More the solute molecules in the solution lesser the solute potential.
• If a pressure greater than atmospheric pressure is applied to pure water or solution, its water potential decreases. Pressure potential is usually positive. Pressure potential is denoted by (ΨpΨp).
• Water potential of a cell is affected by both solute and pressure potential. The relationship is as follows.

ΨwΨw = ΨsΨs + ΨpΨp
Ψw=Ψs+ΨpΨw=Ψs+Ψp
Osmosis is the diffusion of water across a semi-permeable membrane. The net direction and rate of osmosis depends upon the pressure gradient and concentration gradient. Water will move from its region of higher concentration to region of lower concentration until equilibrium is reached.

• Solute A has more water and less solutes so high water potential in comparison to the solution in B container.
• Osmotic potential is the pressure required to prevent water from diffusing. More the solute concentration greater will be the pressure required to prevent water from diffusing it.
• Numerically osmotic pressure is equal to osmotic potential but sign is opposite. Osmotic pressure is the positive pressure while osmotic potential is negative.
• If the surrounding solution balances the osmotic pressure of cytoplasm, the solution is called isotonic.
• If the external solution is more dilute than cytoplasm, it is hypotonic. The cells swell up when placed in hypotonic solution.
• If the external solution is more concentrated than cytoplasm, it is hypertonic. Cell will shrink in hypertonic solution.
• Plasmolysis is the shrinkage of the cytoplasm of the cell away from its cell wall under the influence of hypertonic solution. The pressure of plasmolysis is usually reversible when the cell is placed in hypotonic solution.
• The pressure build up against the wall due to movement of water inside is called turgor pressure. It is responsible for enlargement and extension growth of cells.
• Imbibition is a special type of diffusion when water is absorbed by solid colloids causing them to increase in volume. For example absorption of water by seeds and dry woods. Imbibition is also a kind of diffusion because movement of water is from higher concentration to lower concentration.
• Water potential gradient between the absorbent and liquid imbibed is essential for imbibition.

• Long distance transport of water in plants takes place by mass or bulk flow system. It is the movement of substance in bulk from one point to another as a result of pressure difference between two points.
• The bulk movement of substances through the conducting or vascular tissue of plants is called Translocation. Xylem is associated with translocation of water and mineral salts, some organic nitrogen and hormone from roots to aerial parts of plants.
• Phloem transport organic and inorganic solutes from leaves to other part of plants.

Absorption of water by plants

• Water is absorbed along with mineral solutes by root hairs by diffusion. The absorbed water passes to deeper layer by two pathways.

Apoplast pathway	Symplast pathway
It consists of nonliving parts of plants body such as cell wall and intercellular spaces.There is little resistance in movement of water.It is faster.Metabolic state of root does not affect apoplast pathway.	It consists of living parts of plant body such as protoplast connected to plasmodesmata.Some resistance occurs in the movement of water.It is slightly slower.Metabolic state of root directly affect symplast pathway.

• Most of the water flows in roots via apoplast pathway because cortical cells are loosely packed and offers no resistance to water movement.

• The inner boundary of cortex, endodermis is impervious to water due to suberised matrix called Casperian strip. Water molecules are directed through wall regions that are not suberised.
• Water flows through the different layers of roots to reach the xylem tissues as follows-

• A mycorrhiza is the symbiotic association between a fungus and angiospermic roots. The fungal filaments forms a network around the young root to have large surface area that help to absorb mineral ions and water from the soil. The fungus provide minerals and waters and roots in turn provide organic and nitrogen containing compounds.

Ascent of saps (Translocation of water)
The upward movement of water from roots towards the tips of stem, branches and their leaves is called ascent of sap.

• Vital force theory was forwarded by J.C.Bose in 1923. This theory believes that the innermost cortical cells of the root absorb water from the outer side and pump the same into xylem channels.
• Root pressure theory was forwarded by Priestley in 1916. Root pressure is positive pressure that develops in the xylem sap of the root of plants. It can be responsible for pushing up water to small heights in plants.
• Loss of water in liquid phase by herbaceous plants from the tips of leaf blades is known as guttation.
• Water rises in tubes of small diameters, kept in vessels having water due to force of surface tension. Similarly water rises up in the walls of xylem channels due to adhesion and cohesion. This theory is called Theory of Capillarity.
• Cohesion Tension theory was put forwarded by Dixon and Joly in 1894. According to this theory water is mostly pulled due to driving force of transpiration from the leaves. The water molecules remain attached with one another by cohesion force. The water molecule does not breaks in vessels and tracheid due to adhesive force between their walls and water molecules. On account of tension created by transpiration, the water column of plant is pulled up passively from roots to great heights.
• Transpiration is the loss of water in the form of water vapour from aerial parts of plants. The following purpose is fulfilled by transpiration-

1. Creates transpirational pull for absorption and transport in plants.
2. Supplies water for photosynthesis.
3. Transport minerals and salts from soil to other parts of plant.
4. Cool the leaves and maintain their shape and size.

• Photosynthesis is limited by available water. C4C4 plants are twice as efficient as C3C3 plants in term of fixing carbon. Although C4C4 plants uses half as much water as C3C3 plants for the same amount of CO2CO2 fixed.

Uptake and transport of mineral nutrients

• Most of the minerals enter the roots by active absorption into the cytoplasm of epidermal cells because-

1. Minerals are present in the soil as charged particles (ions) which cannot move across cell membranes.
2. The concentration of ions in soil is usually lower than concentration in roots.

• Active absorption needs energy in form of ATP. Active uptake of ions is also responsible for water potential gradient in roots.
• Transport proteins of epidermal cells are control point where quantity and type of solutes that reach the xylem is adjusted.
• The ions that reaches to xylem by active or passive transport moves further upward along with transpirational pull.
• The chief sink of mineral elements are growing region of plants like apical meristem, young leaves, growing flower and fruit, and the storage organs.
• Minerals are frequently remobilized from older senescing part of the plants to young growing parts of plant.
• The elements most readily mobilized include phosphorus, sulphur, nitrogen and potassium. The element like calcium is not mobilized as it is the structural components of plant body.

Phloem transport: Flow from Source to Sink

• Food (sucrose) is transported by phloem from source to sink. The part of plant that synthesize the food is called source and part where food is used or stored is called sink.
• The source and sink can be reversed by the plants depending upon the season or plant’s need. So, the direction of movement in the phloem is bi-directional.
• Phloem sap is mainly water and sucrose but other sugars, hormones and amino acids are also translocated through it.

Pressure flow or Mass flow hypothesis

• It is the most accepted theory for the translocation of sugar from source to sink. Glucose is prepared at source by photosynthesis which is converted into disaccharides (sucrose). Sucrose moves into companion cells and then into sieve tube cells by active transport.
• Loading of phloem at source creates a water potential gradient that facilitates the mass movement in the phloem.
• Sieve tube cells of phloem forms a long column with holes in their wall called sieve plates. Cytoplasmic strands pass through the hole in the sieve plates to form continuous filament. Hydrostatic pressure developed in sieve tube cells moves the sap in the phloem.
• At sink, incoming sugar is actively moved out of the phloem as complex carbohydrates. The loss of solute produces a high water potential in the phloem and water passes out and returning into xylem.

Class 11 Biology Revision Notes for Cell Cycle and Cell Division of Chapter 10

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• The sequence of events by which a cell duplicates its genome, synthesizes the other constituents of cells and eventually divides into two daughter cells is called cell cycle.
• DNA synthesis occurs in one specific stage of cell division but distribution of chromosome in cells occurs in complex series of events during cell division.

Phases of Cell cycle
Human cell divides once in approximately 24 hours, which may vary in different organisms. In yeasts it takes about 90 minutes to complete the cell division process.
Cell cycle is divided into two basic phases-

1. Interphase– it is the phase between two successive M phases. Interphase lasts for 95% of a cell cycle. This phase is called as resting phase but during this period the cells prepare itself for nuclear division by cell growth.
2. M Phase– when the actual cell division or mitosis occurs. It starts with karyokinesis (nuclear division) or duplication of chromosome and end with cytokinesis or division of cell matrix (cytoplasm division).The interphase is divided into three further phases:

• G1 phase represents the interval between mitosis and initiation of DNA replication. Cell is continuously active and grows in size.

• During synthesis phase, replication or synthesis of DNA takes place and amount of DNA get doubles per cell.
• During G2 phase protein is synthesized in preparation for mitosis.
• In adult animals, some cells do not divide or may divide occasionally. These cells do not divide further and exits the G1 phase to enter an inactive stage called Quiescent Stage (G0) of cell cycle.
• In animals mitotic division is present in only somatic diploid cells but in plants it is seen in both haploid and diploid cells.
• Mitosis cell division is also known as equational division because the numbers of chromosome remain same in parental and progeny cells.

• Prophase is the first phase of mitosis followed by G2 phase. It involves following events-

1. Initiation of condensation of chromosomal materials.
2. Movement of centrioles towards opposite poles of the cell.
3. At the end of prophase, endoplasmic reticulum, nuclear membrane, Golgi complex disappears.

• Metaphase starts with complete disappearance of nuclear membrane. The most suitable stage for study of morphology of chromosomes. It involves

1. Condensation of chromosomal materials in to compact and distinct chromosomes made up of two sister chromatids attached with spindle fibres with kinetochores.
2. Chromosomes arrange at centre of cell called metaphase plate.

• Anaphase involves following steps:

1. Splitting of each chromosome at centromere into two sister chromatids.
2. Two chromatids start moving towards opposite poles.

• Telophase is the last stage of mitosis which involves

1. Chromosomes reach at opposite poles and loose its identity as discrete unit.
2. Nuclear membrane reassembles around the chromosome clusters.
3. Nucleolus, Golgi complex and ER reappear.

• Cytokinesis is the division of cytoplasm of a cell after karyokinesis (division of chromosome) into two daughter cells. In animal cells, appearance of furrows in plasma membrane that deepens gradually and joins to divide cytoplasm into two parts.
• In plant cells, wall formation starts at the centre and grows outwards to meet lateral walls. The formation of cell wall begins with formation of cell plate.

Significance of Mitosis

1. Mitosis produces diploid daughter cells with identical genetic complement.
2. It helps in repair of cells, especially in lining of gut and blood cells.
3. Meristematic division in apical and lateral cambium results in continuous growth of plants.

Meiosis- The cell division that reduces the number of chromosome into half and results in the production of haploid daughter cells is called meiosis. It helps in production of haploid phase in the life cycle of sexually reproducing organism. It involves following events.

1. Two sequential cycles of nuclear and cell division called meiosis I and meiosis II but single cycle of DNA replication.
2. It involves pairing of homologous chromosome and recombination of them.
3. Four haploid cells are formed at the end of meiosis II.

Meiosis I	Meiosis II
Prophase I	Prophase II
Metaphase I	Metaphase II
Anaphase I	Anaphase II
Telophase I	Telophase II

• During Leptotene, the chromosome becomes distinct and visible under microscope. Compaction of chromosome continues throughout the leptotene phase.
• During Zygotene stage, chromosomes start pairing together (synapsis). The paired chromosomes are called homologous chromosome. Synaptonemal complex formed by a pair of homologous chromosome is called bivalent or a tetrad.
• During Pachytene stage, crossing over between non-sister chromatids of homologous chromosome occurs for exchange of genetic materials. The crossing over is enzyme –mediated process which involves enzyme recombinase.
• Diplotene is recognized by dissolution of synaptonemal complex and tendency to separation of bivalent except at the site of crossing over. This forms an X like structure called chiasmata.
• Diakenesis is marked by terminalisation of chiasmata. The nuclear membrane breaks and nucleolus disappear.
• In metaphase I the bivalent chromosome align at equatorial plate and microtubules from the opposite poles of the spindle get attached to the pair of homologous chromosomes.
• Anaphase I – homologous chromosome separate but sister chromatids remain attached at centromere.

• During Telophase I, nuclear membrane and nucleolus reappears and cytokinesis follows. This is called as diad of the cells.
• The stage between two meiotic divisions is called interkinesis and it is short lived that follows Prophase II.

Meiosis II

• It is initiated immediately after cytokinesis before chromosome gets elongated.
• In prophase II, nuclear membrane disappears and chromosome becomes compact.
• At metaphase II stage, the chromosomes align at equator and microtubules attach with kinetochores of sister chromatids.
• Anaphase II start with splitting of centromere of each chromosome to move towards opposite poles.

• Meiosis ends with Telophase II in which two groups of chromosomes get enclosed by nuclear membrane followed by cytokinesis to form tetrad of cells (four haploid daughter cells).

Significance of meiosis–

1. Meiosis forms the gametes that are essential for sexual reproduction.
2. Crossing over introduces new recombination of traits.
3. Helps in maintenance of chromosome number of sexually reproducing organism.
4. Provides evidence of basic relationship of organisms.

Difference between Mitosis and meiosis

Mitosis	Meiosis
Takes place in the somatic cells.It is a single division which produces two cells.Haploid and diploid both kind of cells may undergo mitosis.Crossing over absent.Pairing of chromosome does not occur.	Takes place in reproductive cells.It is a double division which produces four cells.Only diploid cells undergo meiosis cell division.Crossing over takes place.Pairing of homologous chromosome occurs.

Class 11 Biology Revision Notes for Biomolecules of Chapter 9

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• Chemicals or molecules present in the living organism are known as biomolecules. Biomolecules are divided into two types- inorganic and organic.
• Inorganic biomolecules includes minerals, gases and water and organic biomolecules includes carbohydrates, fats, proteins, nucleic acids, vitamins, etc.
• Different biomolecules can be classified as aldehyde, ketones and aromatic compounds as chemical forms. The amino acids, nucleotides and fatty acids can be classified as biochemical forms.

• Except lipids, macromolecules are formed by polymerization of sub-units called monomers.
• Proteins are polymers of amino acids. Amino acids are linked by peptide bond formed by dehydration between COOH group of one amino acids and NH3 group of next with the removal of H2O.

• In nucleic acids, the phosphate molecules links 3’ C of sugar of one nucleoside to the 5’ C of sugar of next nucleosides releasing two water molecules to form 3’-5’ phosphodiester bond.
• In polysaccharides, the mono-saccharides are linked by glycosidic bonds formed by dehydration between two carbon atoms of two adjacent monosaccharides.

Carbohydrates (Polysaccharides)

• Polysaccharides are long chain of sugar containing different monosaccharaides as a building block.

• Starch is present in plants as store house of energy. It forms helical secondary structure. It can hold the I₂ molecules in the helical structure.
• Cellulose molecules contain glucose molecules joined together by 1-4 β linkage. It is the most abundant organic molecules on earth.
• Glycogen is called animal starch as it is the reserve food materials for animals, bacteria and fungi. In this, glucose molecules are arranged in highly branched bush like chain having two types of linkage 1-4 α in straight chain and 1-6 linkage in branching.

Proteins are polypeptide chains made up of amino acids. There are 20 types of amino acids joined together by peptide bond between amino and carboxylic group. There are two kinds of amino acids-

1. Essential amino acids are obtained by living organism along with food.
2. Non-essential amino acids can be prepared by our body from raw materials.

• The main functions of protein in living cell are

1. Transport of nutrient across the membrane.
2. Fight infectious organisms.
3. Produce enzyme and proteins.

• Collagen is the most abundant protein in animal world.

• Primary structure of protein is the basic structure of protein in which a number of polypeptides are involved having sequence of amino acids. The first amino acid of sequence is called N-terminal amino acid and last amino acid of peptide chain is called C-terminal amino acid.

• Secondary structure protein threads forms helix. There are three types of secondary structure- α helix, β pleated and collagen. In α helix, the polypeptide chain is coiled spirally in right handed manner.
• In β pleated secondary proteins two or more polypeptide chains are interconnected by hydrogen bonds. In collagen there are three strands or polypeptides coiled around one another by hydrogen bonds.
• In Tertiary structure long protein chain is folded upon itself like a hollow woollen ball to give three dimensional view of protein.

(a) secondary structure (b) Tertiary structure

• In Quaternary structure each polypeptide develops its own tertiary structure and function as subunit of protein. Eg. Hemoglobin. In adult human hemoglobin 4 sub-units are involved. The two subunits are of α type and two subunits of β types.

Nucleic Acid: Nucleic acids are polynucleotides. A nucleic acid has three chemically distinct components- heterocyclic compound ( nitrogenous base), polysaccharides ( ribose/ deoxy-ribose sugar) and phosphate or phosphoric acid.

• The sugar found in nucleic acid is either ribose or deoxyribose. Nucleic acid containing deoxyribose sugar is called DNA (Deoxyribonucleic Acid) and those containing ribose sugars are called RNA (Ribonucleic acid).
• Biomolecules are constantly being changed into some other biomolecules and also made from other biomolecules. This breaking and making is through chemical process called metabolism.
• In living organism, all the metabolic reactions are enzyme catalyzed. Catalysts are those substances that alter the rate of reaction. The protein with catalytic power is called enzyme.

Metabolic Basis for living organism

• The metabolic pathways that lead to more complex structure from simpler structure are called biosynthetic or anabolic pathways and those pathways that lead to simpler structure from complex structure are called catabolic pathways.
• Photosynthesis and protein synthesis are example of anabolic pathway. Respiration and digestion are examples of catabolic pathway.
• ATP (adenosine triphosphate) is the most important form of energy currency in living world.
• All living organism exist in steady state characterized by concentration of each of the metabolites. The living state is a non-equilibrium steady state to be able to perform work.

Enzymes

• Enzymes are commonly proteinaceous substances which are capable of catalysing chemical reactions of biological origin without themselves undergoing any change. They are commonly called as biocatalysts.
• The nucleic acids that behave like enzymes are called ribozymes.

• The tertiary structure of protein/Enzyme has pockets or crevice into which substrate fit to form ES complex.
• The formation of the ES complex is essential for catalysis.
  E + S       ES →EP →E + P
• The structure of substrate gets transformed into the structure of product through formation of transient state structure.
• The major difference between inorganic and organic catalyst is inorganic catalyst works effectively at high temperature and pressure but enzyme get damaged at high temperature.
• The external energy required to start a chemical reaction is called activation energy.

Factors influencing Enzyme Activity

1. Temperature- An enzyme is active within a narrow range of temperature. Temperature ate which enzyme is most active is called optimum temperature. The enzyme activity decrease above and below this temperature.

2. pH – every enzymes has an optimum pH at which it is maximum active. Most of the
intracellular enzymes work at neutral pH.
3. Concentration of Substrate– increase in substrate concentration increases the rate of
reaction due to occupation of more active sites by substrate.

Competitive Inhibitor- when the molecular structure of inhibitor resembles the substrate, it inhibits the function of enzymes.
Enzymes are classified as
1.  Oxidoreductases/Dehydrogenases–
S reduced + S’ oxidised →→ S oxidised + S’ reduced
2.  Transferases
S – G + S’ →→ S + S’ – G
3. Hydrolases catalyses the hydrolysis of peptide, ester, glycosidic bonds et
4. Lyases remove the groups from substrate.

5. Isomerases-inter conversion of optical, geometrical or positional isomers.
6. Ligases – catalyses the linking together of two compounds.
Co-factors are the non-protein constituent of an enzyme which make the enzyme more catalytically active. The protein portions of enzyme are called apoenzyme.

Prosthetic groups are organic compounds and are tightly bound to the apoenzyme. For
example, in peroxidase and catalase, which catalyze the breakdown of hydrogen peroxide, haem is the prosthetic group
The essential chemical components of any coenzymes are vitamins. Example, coenzyme NAD and NADP contain the vitamin niacin

Class 11 Biology Revision Notes for Cell: The Unit of Life of Chapter 8

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• Study of form, structure, and composition of cell is called cytology.
• Cell is the structural and functional unit of life. In unicellular organism (amoeba, paramecium, yeast, bacteria) single cell performs all the essential functions of life.
• In multicellular organism, different kinds of tissues perform different function and have division of labour.
• Anton Von Leeuwenhoek first saw and described a live cell. Robert Brown later discovered the nucleus.
• Metthias Schleiden and Theodore Schwann( 1938) proposed the cell theory which was later modified by Rudolf Virchow(1855)-

1. All living organisms are composed of cells and products of cells.
2. All cells arise from pre-existing cells.

Prokaryotic cells	Eukaryotic cells
Membrane bound nucleus is absent.Cells are smaller in size.Single chromosome is present.Membrane bound organelles are absent.	Membrane bound nucleus is present.Cells are larger in size.More than one chromosome is present.Membrane bound organelles are present.

Shape and size of cells varies greatly according to their position and function. Mycoplasma is the smallest cell and largest isolated cell is the ostrich egg. The shape of cell may be cuboid, columnar, polygonal, thread like or irregular.
Prokaryotic Cells

• Prokaryotic cells are represented by Bacteria, Blue green algae, Mycoplasma and PPLO. They multiply rapidly and vary in size greatly.
• Bacterial cells may be Bacillus (rod shaped), Coccus (spherical), Vibrio (comma-shaped) and Spirillum (spiral).
• All prokaryotic cells have cell wall surrounding the cell membrane except in Mycoplasma. Genetic material is naked.
• The plasmid DNA, in some bacteria provides some special features like resistance to antibiotics.
• Cell organelles like Mitochondria, Golgi bodies etc. are absent in prokaryotes. A specialized differentiated cell membrane called Mesosome is the characteristic of prokaryotes.

• In bacterial cell a chemically complex cell envelope is present, which consist of three layers. The outermost is Glycocalyx, middle one cell wall and inner innermost is the cell membrane.
• Glycocalyax may be as loose sheath in some bacteria called slime layer. In some other bacteria Glycocalyx may be thick and tough called capsule.
• Plasma membrane is semi-permeable having mesosome in the form of vesicles, tubules and lamellae. They help in cell wall formation, DNA replication and distribution to daughter cells.
• Motile bacterial cell contain flagella, which is composed of filament, hook and basal body. Pili and fimbriae are the other surface structures that help the bacteria to attach with host and other substances.
• In prokaryotes, ribosome are attached with cell membrane having two sub-units – 50S and 30S to form together 70S prokaryotic ribosomes.
• Ribosomes are site of protein synthesis. Ribosomes attached with mRNA to form a chain are called polyribosomes.
• Reserved materials in prokaryotic cells are present in cytoplasm as cell inclusion bodies, which may contain phosphate, granules, glycogen granules etc.
• Gas vacuoles are found in blue green algae and purple and green photosynthetic bacteria.

Eukaryotic Cell

• Eukaryotic cells are present in Protista, plants, Animals and Fungi. Cytoplasm is divided into compartments due to presence of membrane bounded organelles.
• The cells contain well organized nucleus with nuclear membrane. The genetic materials are arranged in chromosomes.
• Plants cells differ in having cell wall, plastids and large central vacuole as compared to animal cells. Animal cells have centrioles, which are absent in plant cells.

Plant cell

Animal cell

• Cell membrane is composed of lipids that are arranged in bilayer. The lipid component is mainly composed of phosphoglycerides. Later it was found that protein is also present in cell membrane. Ratio of protein and lipids varies in different cells.
• Membrane protein may be integral or peripheral. Integral protein remains buried in membrane but peripheral protein lies on the surface.
• Singer and Nicholson (1972) proposed fluid mosaic model. According to this model the quasi-fluid nature of lipid enables lateral movement of protein within the bilayer of lipids.

• The main function of plasma membrane is the transport of molecules across it.

Active Transport	Passive Transport
The transport involves an expenditure of energy by the cells.It occurs against the concentration gradient.It is a rapid process.	The cells do not spend energy in passive transport.This transport is always along the concentration gradient.It is comparatively slow process.

• The movement of water from higher concentration to lower concentration by diffusion is called osmosis.
• Cell wall is present in plant cells and fungi. Algae have cell wall made up of cellulose, galactans and minerals like calcium carbonate. In other plants it consists of cellulose, hemicellulose, pectin and proteins.
• Primary cell wall of young plant is capable of growth, which diminish in mature cells. Secondary cell wall is formed on inner side of the cells.
• Plasmodesmata connects the cytoplasm of neighboring cells.
• Endomembrane system of cell includes endoplasmic reticulum, golgi complex, lysosomes and vacuoles.

• Endoplasmic Reticulum are the tubular structure scattered in the cytoplasm.

1. Rough endoplasmic reticulum bears ribosomes on its surface. RER is involved in protein synthesis and secretion.
2. Smooth endoplasmic reticulum does not bear ribosomes on its surface. SER is involved in lipid synthesis and steroidal hormones.

• Golgi apparatus was first observed by Camillo Golgi in 1898 near nucleus. They consist of many flat, disc-shaped sacs or cisternae stacked parallel to each other.
• Golgi apparatus performs the function of packaging of materials and its transportation. A number of protein synthesized by ribosomes are modified in cisternae of golgi apparatus. Golgi apparatus is the site for synthesis of Glycoprotiens and glycolipids.

• Lysosomes are membrane bound vesicular structures formed by the process of packaging in the Golgi apparatus. They are rich in hydrolytic enzymes- lipase, protease, carbohydrases active at acidic PH. These enzymes are capable of digesting carbohydrates, proteins, lipids and nucleic acids.
• Vacuoles are membrane bound space found in cytoplasm containing water, sap and excretory product. They are bound by single membrane. They form contractile vacuole and food vacuole in many organisms.
• Mitochondria is double membrane bound structure with the outer membrane and inner membrane dividing its lumen in two compartments. The inner membrane forms a number of infoldings called cristae towards the matrix.

• Two membranes have their own specific enzyme.
• Mitochondria are sites for aerobic respiration. They produce cellular energy in form of ATP so, they are called power house of the cells. The matrix of mitochondria also contain circular DNA molecules, a few RNA molecules, ribosomes and components of protein synthesis.
• Plastids are found in plant cells and in Euglenoids.

• Chloroplast contains chlorophyll that traps solar energy for photosynthesis. Chromoplast provides yellow, orange and red colours to different parts of plants.
• Leucoplasts are colourless plastids that store food, amyloplasts (carbohydrates), elaioplasts (oils) and aleuroplasts (proteins).
• Chloroplasts are double membrane structures. The space limited by inner membrane is called stroma. Thylakoids are present in stroma as stacks like the piles of coins called grana.

• Stroma contain enzymes for synthesis of protein and carbohydrates. Double strand circular DNA and ribosomes are also present in stroma.
• Eukaryotic cells have 80S ribosomes. They have granuler structure with two subunits.
• Centrosome is an organelles containing two cylindrical structures called centrioles. Each centrioles is made up of 9 fibrils of tubulin protein. Central part of centriole is called hub and peripheral fibrils are called spokes .
• Nucleus has highly extended, elaborate nucleoprotein fibres called chromatin, nuclear matrix and nucleoli. The outer membrane is continuous with endoplasmic reticulum and bears ribosomes.
• The chromatin materials change into chromosome during active cell division. It consists of DNA and histone proteins.
• Every chromosome has a primary constriction or the centromere, on the sides of which disc shaped kinetochores are present.

• On the basis of position of centromere chromosomes are of following types-

Some chromosomes have non-staining secondary constriction at certain location. This gives a small fragment called satellite.

Class 11 Biology Revision Notes for Structural Organisation in Animals of Chapter 7

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In multicellular organism a group of similar cells along with intercellular substances perform a specific function. Such organization is called tissue.

Epithelial Tissue: This tissue provides covering or lining for some part of the body. Cells are compactly packed without intercellular space.

• Simple epithelium is composed of single layer of cells and function as lining of body cavities, ducts and tubes.
• The compound epithelium consists of two or more than two layers of cells and has protective function.
• The squamous epithelium is made up of single layer of flattened cells with irregular boundaries. They are present in lining of blood vessels, air sacs of lungs.
• Cuboidal epithelium is made up of single layered cube-like cells and found in ducts of glands and tubular part of nephron of kidney for absorption and secretion.
• Columnar epitheliums are made up of tall and slender cells. The nuclei are located at the base. Free surface may have microvilli found in lining of stomach and intestine. The ciliated one are called as ciliated epithelium.
• Columnar and cuboidal epithelium specialized for secretion are known as glandular epithelium, which may be unicellular as in goblet cells of alimentary canal or multicellular as in salivary gland.

Endocrine glands	Exocrine glands
Endocrine gland secretes hormones.Products are directly released at target sites through blood.	Secretes enzymes, milk, mucus, saliva etc.Products are released through ducts.

• Main function of compound epithelium tissue is to provide protection against chemical and mechanical stress. They cover the dry surface of skin, moist surface of buccal cavity, etc.
• Epithelial cells are held together by intercellular material to form specialized junction.

Connective Tissues: They are most abundant and widely distributed tissues which link and support the other tissues. All connective tissues except blood cells, secrete fibres of structural protein called collagen or elastin to provide elasticity and flexibility.

• Loose Connective Tissues contain cells and fibres loosely arranged in semi-fluid ground substance. It includes areolar tissue and adipose tissue.

Areolar Connective Tissue	Adipose Connective Tissue
It contains fibroblast, macrophages and mast cells.It acts as support framework for epithelium.	Fibroblast, macrophages and mast cells are absent.The cells are specialized to store fats beneath the skin.

• Dense connective Tissue contains fibres and fibroblast compactly packed. The orientation of fibres may be regular or irregular pattern.
• In dense regular connective tissues collagen fibres are present in rows between parallel bundles of fibres as in tendons and ligaments.

Tendon	Ligament
Tendon connects bones to skeletal muscles.It is made up of white fibrous tough tissue.	Ligament connects one bone to another bone.It is made up of yellow elastic tissue with collagen fibres.

• Cartilage, bones and blood are specialized connective tissue.

Cartilage	Bone
They are soft skeletal tissue.Chondriocyctes are enclosed in small cavities with matrix.They are present in tips of nose, outer ear, between vertebral bones.	Bones are hard skeletal tissue.They are rich in Calcium salt and collagen fibres.They form the skeletal framework of vertebrates like limbs, legs, etc.

• Blood is fluid connective tissue containing plasma, red blood cells, white blood cells and platelets. It helps in transportation of various substances between organs.

Muscle Tissue

• Each muscle is made up of long cylindrical fibres arranged parallel to each other. Fibres are composed of fine fibrils called myofibrils. Muscle fibres contract and relax in response to stimulation.

Skeletal	Smooth	Cardiac
They are also known as striated, voluntary muscles.Multinucleated with light and dark bands.They are attached with bones.They are fibrous and un-branched, cylindrical in shape.	They are known as unstriated or involuntary muscles.They are uninucleate without bands.They are present in vessels, oesophagus.They are fibrous and un-branched, spindle shaped.	They are known as heart muscles and involuntary in nature.Uninucleate with faint light and dark bands.They are present in wall of heart.They are fibrous and branched, cylindrical in shape.

Neural Tissue

• The unit of neural system is neuron. Neuroglial cell protects and supports the neuron.
• When neuron get stimulated, electrical impulses are generated that travel along the plasma membrane (axon).

The tissues organize to form organs which in turn associate to form organ system in multicellular organisms.
Earthworm

• Earthworm is reddish brown terrestrial invertebrate that lives in upper layer of moist soil. The common Indian earthworms are Pheretima and Lumbricus.
• Earthworms have long cylindrical body divided into segments called metameres. The ventral surface contain genital pore and dorsal surface contain mid dorsal line.
• First body segment is called peristomium which contain mouth. 14-16 segments are covered by dark band called clitellum.

• Single genital pore is present on mid ventral line of 14th segments. A pair of male genital pore is present on 18th segment on ventro-lateral side.
• All the segment except 1st , last and clitellum contain S-shaped setae for locomotion.
• Alimentary canal is straight tube from 1st to last segment having, buccal cavity, muscular pharynx, oesophagus that leads to gizzards, which help in grinding the soil particles and decaying leaves. Stomach and small intestine leads to anus.
• Between 26-35 segments, the intestine has an internal median fold called typhlosole. This increases the effective area of absorption in the intestine.
• Closed vascular system consists of heart, blood vessels and capillaries. Blood glands are present on the 4th, 5th and 6th segments. They produce blood
  cells and haemoglobin which is dissolved in blood plasma.
• Earthworms lack respiratory organs and respire through moist skin.
• Excretory organs is coiled segmental tubules called nephridia. There are three types of nephridia: Septal nephridia, integumentary nephridia and pharyngeal nephridia.
• Nervous system is represented by ganglia arranged segmentwise on the ventral
  paired nerve cord. The nerve cord in the anterior region (3rd and 4th segments) bifurcates and joins the cerebral ganglia dorsally to form a nerve ring.
• Earthworm is hermaphrodite. Two pairs of testis is present in 10th and 11th segment. Prostrate and spermatic duct open to surface as male genital pore on 18th segment.
• One pair of ovaries is attached to the intersegmental septum of 12th and 13th segments. Female genital pore open on ventral side of 14th segment. Mutual exchange of sperms takes place during mating.

• Mature sperms and egg cells along with nutritive materials are deposited in cocoon in the soil where fertilisation takes place.
• Earthworms are known as friends of farmer because they make burrows in soil to make it porous for respiration and root penetration. Earth worms are also used for vermicomposting and as bait in game fishing.

Cockroach(Periplaneta americana)

• Cockroaches are nocturnal omnivorous organisms that lives in damp places everywhere. The body of cockroach is segmented and divisible into head, thorax and abdomen. The body is covered by hard chitinous exoskeleton.

• Head is triangular in shape formed by fusion of six segments to show flexibility. Head bears compound eyes. Antenna attached on head help in monitoring the environment.
• Thorax consists of three parts- prothorax, mesothorax and metathorax. Forewings and hind wings are attached with thorax. Abdomen consists of 10 segments.

Male Cockroach	Female Cockroach
The abdomen is long and narrow.Brood pouch is absent.Male have longer antenna.Anal styles are present.	The abdomen is short and broad.Brood pouch is present.Female have shorter antennae.Anal styles are absent.

Digestive System of Cockroach-

• Alimentary canal is divided into foregut, midgut and hindgut. Food is stored in crop. Gizzard help in grinding the food particles.

• At the junction of midgut and hindgut yellow coloured filamentous Malpighian tubules are present which help in excretion.
• Blood vascular system is open type having poorly developed blood vessels. The haemolymph is made of colourless plasma and haemocytes.
• Respiratory system consists of network of trachea which open through 10 pairs of spiracles on lateral side.
• The nervous system of cockroach consists of a series of fused, segmentally arranged ganglia joined by paired longitudinal connectives on the ventral side. Three ganglia lie in the thorax, and six in the abdomen. The nervous system of cockroach is spread throughout the body.
• Each compound eye of cockroach consists of about 2000 hexagonal ommatidia.
  With the help of several ommatidia, a cockroach can receive several images of an object. This kind of vision is known as mosaic vision with more sensitivity but less resolution,
• Cockroaches are dioecious. Male reproductive system consists of a pair of testes one lying on each lateral side in 4th-6th abdominal segments. The female reproductive system consists of two large ovaries situated on 2nd -6th abdominal segments.

 
Male reproductive system / Female reproductive system

• The fertilized eggs are encased in capsule called ootheacea. 9 to 10 ootheace are produced by each female.
• Cockroaches are pests and destroys the food, contaminate with smelly excreta.

Frog (Rana tigrina)
Frogs are cold-blooded organism having ability to change colours to hide from enemies. Body is divisible into head and trunk, bulged eyes covered by nictitating membrane. Male frog is different from female having vocal sacs and copulatory pad on first digit of forelimb.

• Digestive system consists of alimentary canal and digestive glands.

• Digestion starts in stomach and final digestion occurs in small intestine. Digested food is absorbed by villi and microvilli present in the inner wall of small intestine.
• Skin acts as aquatic respiratory organs (cutaneous respiration). On lands skin, buccal cavity and lungs acts as respiratory organs.
• The vascular system of frog is well-developed closed type. Heart is 3-chambered. Blood consist of plasma, RBC, WBC and Platelets.
• Frogs have a lymphatic system consisting of lymph, lymph channels and lymph nodes.
• The elimination of nitrogenous wastes is carried out by a well developed excretory system. The excretory system consists of a pair of kidneys, ureters, cloaca and urinary bladder. The frog excretes urea and thus is a ureotelic animal.
• The system for control and coordination is highly evolved in the frog. It
  includes both neural system and endocrine glands
• Frogs have well organised male and female reproductive systems. Male reproductive organs consist of a pair of yellowish ovoid testes, which are found adhered to the upper part of kidneys by mesorchium.
  The female reproductive organs include a pair of ovaries which are situated
  near kidneys.
• Fertilisation is external and takes place in water. Development involves a larval stage called tadpole. Tadpole undergoes metamorphosis to form the adult.

Reproductive systems of frog-
 
Male / Female

Class 11 Biology Revision Notes for Anatomy of Flowering Plants of Chapter 6

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Anatomy is the study of internal structure of organism. Study of plant anatomy includes histology- study of organization and structure of tissues. Anatomy helps in knowing the structural peculiarities of different group of plants and indicates the structural adaptation to diverse environments.
The tissue
A group of cells having a common origin and usually performing common function are called tissues.

• Meristematic tissue is a simple tissue composed of group of similar and immature cells which can divide and form new cells. The meristem which occurs at tips of roots and shoots are called apical meristem.
• Intercalary meristem occurs between mature tissues especially in grasses.Both apical meristems and intercalary meristems are primary meristems because they appear early in life of a plant and help to form the primary plant body.
• The meristem which occurs on the sides and takes part in increasing girth of the plants are called Lateral meristem. Intrafascicular cambium in the primary lateral meristem. Vascular cambium, cork cambium are secondary meristem.
• The cells that have become structurally and functionally specialized and lose the ability to divide are called permanent tissue. Permanent tissues having all cells similar in structure and function are called simple permanent tissues and those having different kinds of cells are called complex tissue.
• Parenchyma is a simple permanent living tissue which is made up of thin-walled  isodiametric cells. Each cell encloses a large central vacuole and peripheral cytoplasm containing nucleus. They are found in non-woody and soft areas of stem, root, leaves, fruits and flowers. They store the food and provide turgidity to softer parts of plant.

• Collenchyma consists of cells which are much thickened at corner due to cellulose, hemicellulose and pectin. Oval, spherical or polygonal often contain chlorophyll. They provide mechanical support to the growing parts of the plants like young stem.

• Sclerenchymas are supportive tissue having highly thick walled cells with little or no protoplasm due to deposition of cellulose or lignin. They are of two types: fibres and sclereids. They provide mechanical support to mature plant organs to tolerate bending, shearing, compression etc.

Complex Tissues– Xylem and phloem constitute the complex tissues in plants and work together as a unit.

Xylem	Phloem
It conducts water or sap.Xylem is found deep in the plant.Xylem provides mechanical strength.Xylem is made up of vessels, tracheid, xylem fibre and xylem parenchyma.	Phloem conducts organic food.It is situated towards the outer side.It has no mechanical functions.Phloem is made up of sieve tube, companion cells, phloem parenchyma and phloem fibres.

• Primary xylem is of two types- protoxylem and metaxylem. In stem, protoxylem lies in centre and metaxylem towards periphery. This type of primary xylem is called endarch.
• In roots, protoxylem lies in periphery and metaxylem lies towards the centre. This type of primary xylem is called exarch.
• In gymnosperms, albuminous cells and sieve cells lack sieve tube and companion cells.

Epidermal Tissue System

• It forms the outermost covering of whole plant body, which consists of epidermal cells, stomata, epidermal appendages (trichomes and hairs).
• Epidermis is single layered, parenchymatous with waxy thick layers of cuticle to prevent water loss.
• Stomata is present in epidermis of leaves. It regulates the transpiration and gaseous exchange. In dicots, stomata are bean-shaped having two guard cells closing the stomatal pore. In monocots, stoma is dumbbell-shaped. Guard cells contain chloroplasts and help in opening and closing of stomata.
• Guard cells are surrounded by subsidiary cells. The stomatal aperture, guard
  cells and the surrounding subsidiary cells are together called stomatal apparatus

Dicots (Bean shaped) Monocots (Dumb-bell shaped)

• Epidermis also contains a number of hairs. Root hairs are unicellular elongation of epidermal cells. Trichomes are present on stems, which are multicellular, branched or un-branched preventing water loss due to transpiration.

The ground Tissue System

• All the tissue between epidermis and vascular bundle forms the ground tissues. It consists of simple permanent tissues. Parenchyma is present in pericycle, cortex, pith and medullary rays in stem and roots.
• In leaves the mesophyll, chloroplast containing cell, forms the ground tissues.

The Vascular Tissue System

• The vascular system consists of complex tissues, xylem and phloem that together form vascular bundles.

• When xylem and phloem within a vascular bundle are arranged in alternate manner on different radii, the arrangement are called radial as in roots. When xylem and phloem are situated at the same radius of vascular bundle, it is called conjoint as in stem and leaves.

Radial
Dicotyledonous Root

• The outermost layer of dicot root is epidermis containing unicellular root hairs.
• The cortex consists of several layers of thin-walled parenchyma cells.
• The innermost layer of cortex is called endodermis having waxy material suberin as casparian strips, which is impermeable to water.

Monocotyledonous Root

• The anatomy of the monocot root is similar to the dicot root in many respects.
  It has epidermis, cortex, endodermis, pericycle, vascular bundles and pith. As
  compared to the dicot root which have fewer xylem bundles

Dicotyledonous Stem

• Epidermis: is covered with a thin layer of cuticle and may have Trichomes and stomata.
• Cortex: The cortex is made up of the multiple layers of cells including hypodermis, middle layer of parenchyma cells and innermost layer called endodermis.
• Endodermis cells are rich in starch grains and are called the starch sheath. Pericycle is present on the inner side of endodermis. Layers of radially placed parenchyma between the vascular bundles are called medullary rays.
• A large number of vascular bundles are arranged in a ring. Each vascular bundle is conjoint, open. Protoxylem is endarch

Monocotyledonous Stem

• The hypodermis is made up of sclerenchyma. Vascular bundles are conjoint, closed and  scattered. Each vascular bundle is surrounded by a sclerenchymatous bundle sheath.
• Phloem parenchyma is absent. Water-containing cavities are present within the vascular bundles.

Dorsiventral (Dicotyledonous) Leaf

• The leaf lamina of a dorsiventral leaf has 3 parts:  epidermis, mesophyll and vascular system.
• The upper epidermis is called adaxial epidermis and lower one is called abaxial epidermis. More number of stomata are present on the abaxial epidermis.
• There are two types of cells in the mesophyll: palisade parenchyma and spongy parenchyma. The palisade parenchyma is placed adaxially.
• The spongy parenchyma is situated below the palisade parenchyma and extends to the lower epidermis. There are numerous large spaces and air cavities between the cells of spongy parenchyma.
•  Vascular bundles are surrounded by a layer of thick-walled bundle sheath cells.

Isobilateral (Monocotyledonous) Leaf

• Stomata are present on both the surfaces of an isobilateral leaf. The mesophyll is not differentiated into palisade and spongy parenchyma.
• Some adaxial epidermal cells in grasses are modified into large, empty cells called bulliform cells. When the bulliform cells absorb water, they become turgid. So the leaf surface is exposed. During water stress, when the bulliform cells become flaccid, the leaves curl inwards to minimize water loss.

SECONDARY GROWTH
The increase in girth of a plant body is called secondary growth. The tissues involved in secondary growth are: vascular cambium and cork cambium.
Vascular Cambium:
In case of young stem vascular cambium is present in patches as a single layer between the xylem and phloem. It forms a complete ring at a later stage.
Activity of the Cambial Ring:

• The cambial ring becomes active and begins to cut off new cells, both towards the inner and the outer sides.
• The cells which are cut off towards pith mature into secondary xylem. The  cells which are cut off towards periphery mature into secondary phloem.
• The cambium is more active on the inner side than on the outer. As a result, the amount of secondary xylem produced is more than secondary phloem. The primary and secondary phloems get gradually crushed due to the continued formation and accumulation of secondary xylem.
• At some places, the cambium forms a narrow band of parenchyma, which passes through the secondary xylem and the secondary phloem in the radial directions. These are the secondary medullary rays

Spring wood and autumn wood:

•  Cambium is very active during the spring season, but less active during the winters. Hence, during spring; a large number of xylem elements are formed having wider vessels. During winter, less xylem elements are formed having narrow vessels.
• The wood formed during summer is called spring wood. The wood formed during winter is called autumn wood.
•  The two kinds of wood appear as alternate concentric rings in transverse section of a trunk of a tree. These are called annual rings and provide information about age of the tree.

Heartwood and sapwood:

• In old trees, the greater part of secondary xylem is dark in colour, hard, and resistant to attacks by microorganisms and insect. This region is made of dead elements with highly lignified walls. This wood is called heartwood. The heartwood gives mechanical support but does not conduct water.
• The peripheral part of the secondary xylem is lightly coloured. This is known as sapwood. It helps in conduction of water and minerals.

Cork Cambium

• Mmeristematic tissue which develops in the cortex region is called cork cambium or phellogen.
• The phellogen cuts off cells on both sides. The outer cells differentiate to form cork or phellem while the inner cells differentiate into secondary cortex or phelloderm.
•  Phellogen, phellem and phelloderm are collectively called periderm.
• Due to activity of the cork cambium, pressure builds up on the remaining layers peripheral to phellogen. These layers gradually die and fall off.

Lenticels

• At certain regions, the phellogen cuts  off  closely  arranged parenchymatous cells on the outer side instead of cork cells. These parenchymatous cells soon rupture the epidermis, forming a lens-shaped openings called lenticels.
• Lenticels permit the exchange of gases between the outer atmosphere and the internal tissue of the stem.

Secondary Growth in Roots

• The vascular cambium of the dicot root originates from the tissue located just below the phloem bundles. A portion of pericycle tissue present above the protoxylem forms a continuous wavy ring. It gradually becomes circular. Rest of the steps are similar as in dicot stem.
• Secondary growth takes place in stems and roots of gymnosperms. No secondary growth occurs in monocots.