Biology Revision Notes Of Plants Physiology and Reproduction For NDA


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• The materials produced in plants or absorbed through roots are transported to each and every part of the plant.
• Xylem conducts water and minerals from root to leaves, while phloem distributes food upto roots. Thus, xylem and phloem constitute the transport system of plants.

• The process of transport of soluble products, i.e. sugar produced in photosynthesis from leaves to other parts of plant via phloem tissue is termed as translocation. Translocation is mainly achieved by use of energy.

• Loss of water in the form of vapours from aerial parts of the plant is called transpiration.
• Transpiration can occur in stems and leaves.
• Curtis ( 1926) called it a necessary evil.
• Potometer is used to measure transpiration.
• Transpiration is of three types, i.e. cuticular transpiration, lenticular transpiration and stomatal transpiration.
• Stomatal transpiration occurs through stomata. These are pores guarded by guard cells (possess chloroplast), which arc in turn surrounded by subsidiary cells. In dicot, the guard celh are kidney-shaped, while in monocot they are dumb-bell-shaped.
• Stomata open when the guard cells take up K+ ions from the surroundir g cells, which leads to osmotic entry of water in th:o guard cells and they close when K+ ions exit the guard cells.
• The rate of transpiration increases due to increase in the temperature, while it decreases in high humidity.
• Transpiration is called a necessary evil as it aids in water movement. Stomata arc usually open during day and close at night.
• Rate of transpiration can be reduced by antitranspirants such as Abscissic Acid (ABA) and Phenyl Mercuric Acetate (PMA). Process of transportation of water absorbed by roots against the gravity i: known as ascent of sap.
• Imbibition is water absorption by solid particles without forming a liquid, e.g. dry piece of wooden absorbs water.
• Plasmolysis is the shrinkage of plant cytoplasm due to exosmosis, e.g. if excess fertiliser applied to plant without water, plant dies due to plasmolysis. Guttation is loss of water from the small pores called hydathodes, e.g. in rose, strawberry, tomato, etc.


• De Saussure (1804) first of all demonstrated that plants obtain mineral from soil through root system.
• Analysis of plant ash shows that about 92 mineral elements are present in different plants.
• Out of these 16 elements are necessary for plants and are called essential elements.
• Essential elements are of three types.
(i) Macroelements required in large amounts, e.g. C, E, O, N, S, P, K, Ca, Mg.
(ii) Microelements required in very small amounts, ·e.g. Fe, Cu, B, Zn, Mn, Mo, Cl.
(iii) Trace elements used to detect various metabolic pathways 1· n p I ants, e.g `C^!4, N^15, P^32`

Specific Role and Effect of Deficiency of Minerals for Plants

• A complete fertiliser should have N, P and K in adequate amounts.


• Green plants prepare their food using C02 and H 20 as
raw materials in the presence of sunlight and chloropbyll
by a process called photosynthesis. About 90% of total
photosynthesis in world is done by algae occurring in
oceans and in freshwater. Chloroplast is the site of
photosynthesis, which is present in green leaves.
• Photosynthesis is an anabolic process that requires energy (endothermic).
• All green plants carry out the process of photosynthesis because of the presence of green pigment in leaf. These are chlorophyll-a and b mainly along with some other accessory pigments. These pigments have the ability to use light energy and convert it into the chemical energy in the form of organic compounds (carbohydrates). Starch is the visible product of photosynthesis.
• The equation of photosynthesis is.
`6CO_2 + 12H_2O underset(Green plant)overset(Light)(->)`
• Factors influencing the rate of photosynthesis arc `CO_2` ,. light, water and temperature.
• Photosynthesis mainly includes two types of reasons, i.e. light reaction and dark reaction.

Light Reeaction or Hill Reaction

• Light reactior. of photosynthesis occurs in grana part of chloroplast. It involves photolysis of water and production of NADPH and ATP in phosphorylation (production of ATP in the presence of light).
• Rate of photosynthesis is measured in quantum.
•· Quantum requirement in photosynthesis is 8.
• There are two photosystems involve in the process of light reaction.
(i) `P_700` is the reaction centre of PS-I.
(ii) `P680 _690` is the reaction centre of PS-II.

Dark Reaction or Blackman's Reaction

• Dark reaction of photosynthesis occurs in stroma (matrix) part of chloroplast.
• It is also known as Calvin cycle or `C_3` cycle.
• In this cycle, one mole of hexose sugar (glucose) is formed by `18 ATP + 12 NADPH_2`
• This process of `CO(_2-)` fixation occurs in the presence of RuBisCO enzyme (most abundant enzyme).
• In some plant~: instead of C, cycle, `C_4` cycle is observed. In this cycle, first stable product of `CO_2`-fixation is a four carbon compound unlike `C_3` plants in which it is a `3` carbon compound.
• This `4_C` compound produced in `C_4` cycle is Oxaloacetic Acid (OAA). Which is the first product of !watch and Slack pathway. In `C_1` plants a special type of leaf anatomy, i.e. Kranz anatomy is seen.
• Examples of C.1 plants that are monocots are sugarcane, maize, Cyprus, etc., and dicots arc Amaranthus. Artiplex can show both C, and `C_4` cycle. In plants such as Opuntia, Bryophyllum, Agave, etc.
`CO_2`-fixation occurs at night. These plants are known as CAM plants and this process is known as Crassulaceac Acid Metabolism (CAM).

Bacterial Photosynthesis

• Like green plants, some purple and green sulphur bacteria arc capable of synthesising their organic food in the presence of light and in the absence of `O_2`, which is known as bacterial photosynthesis, e.g. Green sulphur bacteria (Chlorobium), purple sulphur bacteria ( ChronuJ..tium) and non-sulphur bacteria (Rhodospirillium ).


• Chemosynthesis is the formation of organic food, utilising chemical energy by some aerobic bacteria. These bacteria arc
(i) Nitrifying bacteria, e.g. Nitrosomonas, N itrosococcus, N itrobacter.
(ii) Sulphur bacteria, e.g. Beggiatoa, Thiothrix, Thiobacillus.
(iii) Iron bacteria, e.g. Ferrobacillus, Leptothrix, Cladothrix.
(iv) Hydrogen bacteria, e.g. Bacillus pentotrophus.
(v) Carbon bacteria, e.g. Bacillus oligocarbophilus.


• Respiration is a catabolic, i.e. breaking up and cxergonic, i.e. energy releasing process of cell that involves oxidation of complex carbonic substances such as carbohydrates, proteins, fats, etc., into `CO_2,` water and energy without utilising `O_2` This process occurs in every living cell, so called cellular respiration.
• The equation of respiration is shown by following equation.
`C_6H_12O_6+12-> 6CO_2+6H_2O+E(686 kcal)`
• The process of respiration involves glycolysis, Krebs' cycle, electron transport chain and oxidative phosphorylation of ATP.
• In glycolysis, 1 molecule of glucose is converted into 2 molecules of pyruvic acid, 2 A TP and 2 NADH molecules.
Krebs' cycle occurs in mitochondria and it involves complete oxidation of pyruvic acid.
• One molecule of glucose may yield 38 ATP molecules.
• In yeasts and bacteria, J.naerobic respiration occurs outside
the protoplasm. This is known as fermentation.
• In our muscles, during vigorous physical exercise, glucose is metabolised to form lactic acid. Due to the lactic acid, muscle cramps and fatig:ue occurs after heavy exercises.
• Respiratory Quotient (RQ) is the ratio of `CO_2` and `O_2` released in respiration.
• RQ is less than one for proteins and fats, more than one for carbonic acids and one for carbohydrates.


Plant:; have the capacity of changing their position in response to external or internal stimuli. These are known as plant movements.
• This specific site that receives the stimuli is known as perception site.
• The minimum time, required for a response to occur against a stimuli is known as presentation time.
Movements are basically of four types.

`text(1. Movements of Locomotion)`
These arc further of two types
(i) Autonomic
Due to internal stimuli, these are of following types
(a) Ciliary movement Move from one place to another with the help of cilia, e.g. Chlamydomonas.
(b) Amoeboid movement Locomotion with the help of pseudopodia, e.g. slime moulds.
(c) Cyclosis movement Autonomic movement of protoplasm, e.g. Hydrilla.
`text((ii) Induced)`
Due to external stimuli, these are of following types
(a) Chemotactic Movements of bacteria towards chemicals.
(b) Phototactic Many algae move from weak and high light to medium light intensity.
(c) Thermotactic Some algae move from cold water to warmer water.

Movements of Curvature

These are of two types
(i) Mechanical Movement These are shown by dead organs.
(a) Xerochasy by loss of `H_2O`, e.g. capsules.
(b) Hydrochasy by absorption of `H_2O`, e.g. peristomial teeth of moss capsule.

`text((ii) Viital Movement)`

These are shown by living organs. They are of two types
(a) Autonomic Response to internal stimulus, e.g. leaf opening by hyponasty.
(b) Induce This is also called tropic or nastic movement.

Tropic Movement

Response to unidirectional external stimulus. These are of following types
(a) Phototropism Response to light stimulus, e.g. root is negatively phototropic.
(b) Geotropism Response to gravity stimulus, e.g. stem is negatively geotropism.
(c) Hydrotropism Response to water stimulus, e.g. young roots are positive hydrotropic.
(d) Thigmotropism Movements shown by tendrils due to contact stimulus.

Nastic movement

Response to diffused external stimulus.
(a) Sleeping movement Leaves of some legume plants show horizontal position during daytime and become vertical (sleep) during night, e.g. leaves of Oxalis.
(b) Seismonastie movement These are due to shock or touch stimulus, e.g. Mimosa pudica (touch-me-not).
(c) Thigmonastic movement Shown by some insectivorous plants, e.g. Dionaea and Drosera.


Plant growth is a complex, stable and irreversible process. For complete regulation of plant growth and development, certain growth regulatory substances are utilised.


• All living organisms show various positive changes in their weight, shape, size and volume during their entire life cycle (birth to death). All these changes are\ collectively known as growth.
• Growth means an increase in size (usually an increase in length and volume) and an increase in the dry weight of the growing parts of the organism.
• In plants, growth is confined only to meristems and associated with both anabolic and catabolic means.
• The growth of cells of plants is divided into three phases, i.e. formative phase, cell enlargement and cell maturation.
• If the growth rate is plotted against time, a sigmoid or S-shaped curve is obtained, which is called growth curve.
• The growth curve can be differentiated into three phases,
i.e. lag phase, log phase (exponential phase), steady phase
(stationary phase).
• The rate of growth is called efficiency index.
• Growth can be measured by auxanometer horizontal microscope and crescograph. Growth is affected by many external and internal factors. Some external facwrs are light, temperature, water, oxygen, `CO_2` , pollutants, etc.
• The optimum temperature for growth is 20-30°C.
• The internal faction include genetic factors and growth regulators.

Plant Growth Hormones

Plant growth hormores also called phytohormones. These are the chemical substances that are naturally produced in plants and are capable of regulating the important processes of plants. Different plant hormones help to coordinate growth, development and response to the environment.
• Term 'phytohormcne' was first utilised by Thimann.
• Plant harmones arc of five types. Auxin, gibberellin and cytokinin (growth promotory), abscisic acid and ethylene (growth inhibitory) hormones.


• Auxins were first collected by Went in 1928 from colcoptile of Avena. Auxins were first isolated from urine.
• The auxins in apical bud inhibit the development of lateral buds and the phenomenon is called apical dominance.
• Auxin is produced from tryptophan.
• IAA (Indole-3-acetic acid) is natural, while NAA (Naphthaleneacetic acid) and 2, 4-D (2,4 Dichloro phenoxyacetic acid) are synthetic auxins.
• Indole-3-Acetic Acid (IAA) is the best known and universal natural auxin found in all plants and fungi.
• Auxin test is known as auxin bioassay, which is the quantitative test and is famous by the name of Avena curvature test.
• 2, 4-D and 2, 4, 5-T are used as herbicides.
• Auxin causes parthenocarpic fruit development.
• It controls phototropism and geotropism.
• Auxin helps a plait in bending towards light in phototropism.
• Auxins promote cell division and cell elongation. Femaleness in plats is caused by auxins.
• It induces rooting in stem cuttings.

• It is isolated by Kurosawa from a fungus Gibbrella fujikuroi (a causative agent of bakanae or foolish seedling disease in rice plants).
• Gibberellins cause cell elongation and increase in internodal length (bolting).
• Gibberellins are produced in embryos, roots and young leaves near the shoot tip.
• It is a hormone, which stimulates the plant cells to grow in a manner such that the plant appear to be bent towards light.
• It is helpful in flowering, enzyme synthesis and fruit growth.
• Gibberellin induces parthenocarpy in some cases, e.g. pome fruits, so gibberellins are more potent parthenocarpic agents than auxins.
• Antigibberellins are those compounds, which supress and reduce the effect of gibberellins, e.g. phosphon-D, malaic hydrazide, Chlorocholine Chloride (CCC).

• Cytokinins are known to promote cytokinesis (cell division).
• Kinetin was first isolated from degraded sample of DNA.
• Zeatin is the first natural cytokinin isolated from maize endosperm.
• Cytokinins are synthesised in roots as well as stems.
• It is responsible for cell division, cell enlargement, prevention of senescence (Richmond Lang effect) and enzyme synthesis.
• Auxin-cytokinin ratio causes root-shoot initiation.
• Cytokinins also promote flowering in short day plant.

• Only gaseous hormone, which promotes transverse growth. It is a ripening hormone that mainly acts as a natural growth inhibitor.
• Ethylene hastens ripening of fruits and promotes aging of plant organs.

`text(Abscisic Acid (ABA))`
• It acts as a growth inhibitor by counteracting other hormones.
• It is responsible for dormancy in buds and seeds, aging in leaves, inhibition of mitosis, abscission of leaves, flowers and fruits.
• It supresses the growth of dormant lateral buds. Florigens, caline and traumatin are some other plant hormones.


The process of producing new organisms from the existing organisms of the same species is known as reproduction. There are two modes of reproduction, i.e. asexual and sexual.

Asexual Reproduction

Asexual reproduction is a rapid mode of multiplication in which
single parent is involved. The cells divide either mitotic ally or asymptotically. The new individuals produced in asexual reproduction are exactly similar to their parent (i.e. clone). Asexual reproduction is of following types
(i) Fission Found in unicellular organisms. Fission leads to equal division of the cell, e.g. Amoeba.
(ii) fragmentation By simple breaking of body part and generation of whole body by fragmented part, e.g. Spirogyra, bryophytes, etc.
(iii) Regeneration Any part of body has the ability to form the new part, e.g. Hydra.
(iv) Budding Any bud comes out the body and capable to grow into full length body of main organism, e.g. Hydra, yeast, etc.
(v) Vegetative propagation Any part of plant body cyclops into new plant. vegetative propagation is of following types
(a) Cuttings It is of three types
• Stem cuttings, e.g. sugarcane, rose, Bougainvillea.
• Root cuttings, e.g. apple, lemon.
• Leaf cuttings, e.g. Begonia, etc.
(J) Grafting, e.g. mango, guava, rubber, etc.
(c) Layering, e.g. jasmine.
(d) Leaves When the leaves fall down in soil, from their edges, new plants arc formed. e.g. Bryophyllum and Begonia, etc.
(vi) Spore formation in many multi cellular organisms, spore is the reproductive cell, which has the ability to Crminate and give rise to a new colony. Algae, ferns, mosses and fungi reproduce through spore formation. Different types of spores produced in different organisms are as follows
(a) Zoospores (motile), e.g. Algae-Ulotlnix, Oedogonium, Fungi-Pythium and Achlya.
(J) Sporangiospores non-motile), e.g. Mucor and Rhizopus.
(c) Conidia (non-mo:ile), e.g. Penicillium, Aspergillus, Fusarium.
(d) Cysts (thick coverings), e.g. Vaucheria and Botrydium.

Sexual Reproduction

Sexual reproduction is an adaptation for adverse conditions. R Camararius was the fir~;t one to describe sexual reproduction in plants. It is the process of producing new individuals by two parents. It involves production of gametes by meiosis and fusion of fametes. In plants, all the events related to sexual reproducrion, takes place in flower.
• Flower is the reproductive organ of plants. When flower cor tains both male and female reproductive organs, it is called bisexual flower and when it contains only one either ma e or female reproductive part it is called unisexual flower.
• Stamens and carpels are the male and female reproductive parts of plants respectively present in flower.
• Stamen comprises of two parts, i.e. anther and filament.
• Anther is the microsporangium in which microspores (pollen grains) are formed. Within pollen grains male gametes are formed.
• Anthers are usually bithecous and tetrasporangiate. Carpel consists of three parts, i.e. stigma, style and ovary.
• Stigma is the receptive surface where pollen grains are received. Style connects stigma to ovary.
• Ovary consists of ovules. Ovules act as the megaspores, i.e. female gamete bearing structures. They remain connected to the ovary by means of placent

Types of Ovules

An ovule consists of micropyle (opening), chalaza (part opposite to micropyle) and funicle (stalk). It is always 7 -celled and 8-nucleated. One of the cell is female gamete. There are following types of ovules
(i) Orthotropous The micropyle, chalaza, and funicle are in straight line. This is the most primitive type of ovule, e.g. piper, polygonum and Cycas.
(ii) Anatropous The ovule turns at 180° angle. Thus, it is inverted ovule. It is found in 82% angiosperm families.
(iii) Hemianatropous The ovule turns at 90° angle upon the funicle or the body of ovule and is at right angle to the funicle, e.g. Ranunculus.
(iv) Campylotropous The ovule is curved more or less at right angle to the funicle, e.g. in the members of Leguminosae and Cruciferae.
(v) Amphitropous The ovule as well as embryo sac is curved like horseshoe, e.g. Lemna, poppy and Alisma.
(vi) Circinotropous The ovule turns at more than 360° angle, e.g. Opuntia (Cactacea).

Shapes of ovule (a) Orthotropous,
(b) anatropous,
(c) hemianatropous,
(d) campylotropous,
(e) amphitropous,
(f) circinotropous


The process of transfer of pollen grains from the anther to the stigma is called pollination. Pollination is of two types, i.e. self-pollination and cross-pollination.
• Self-pollination involves the transfer of pollen grains from the anthers to the stigma of the same flower or of another flower borne by the same plant.
• Self-pollination occurs only in bisexual or hermaphrodite flower/plant.
• Cross-pollination involves the transfer of pollen grains from the flower of one plant to the stigma of the flower of another genetically different plant.
• Pollination may occur by means of abiotic or biotic agents.
• Abiotic agents arc wind and water.
• Biotic agents arc living organisms.
• Based on type of agent, pollination can be
Pollination by wind - Ancmophily
Pollination by insect - Entomophily
Pollination by bats - Chiroptcrophily
Pollination by ants - Myrmecophily
Pollination by water - Hydrophily
Pollination by birds - Ornithophily
Pollination by snails - Malacophily

• Since cross-pollination ensures more variable seeds self-pollination is generally prevented by means of some mechanisms. Th,s mechanism is known as self-sterility or self-incompatibility.
• Dichogamy is one of the mechanism of self-incompatibility in which either anthers (protandry) or carpels (protogyny) mature earlier than the other.


• Process of male and female gamete fusion is known as fertilisation. It involves the following steps.
• The pollen grains after pollination absorb water and swell on stigma.
These germinate and form a pollen tube.
• By means of pollen tube the male gametes are transferred from pollen grains to ovary and finally ovule.
• Now, fertilisation occurs in following manner
• Since, process of fertilisation in plants includes two fusions, i.e. syngamy and triple fusion, it is known as double fertilisation. The changes taking place in flower after fertilisation.
• Ovary changes to fruit and ovule changes to seed after fertilisation.
• Endosperm in angiosperms is triploid (3n), but in gymnosperms, it is haploid (n).
• Polyembryony is the phenomenon of production of multiple embryos, e.g. Citrus.
• Fruits develop from ovary after fertilisation, but when a fruit is formed without fertilisation, process is called part henocarpy.
• Parthenogensis is the development of embryo/seed from an egg without fertilisation
• Sometimes, dormant seeds are exposed to low temperature to induce germination in them. This process is known as internationalist.
• Vivipary is germination of seed within the fruit, while still attached to mother plant.