Botany वनस्पतिशास्त्र

Quick summary

Microorganisms (microbes) are living things too small to be seen clearly without a microscope – viruses, bacteria, cyanobacteria, many algae, fungi and protozoa. This topic covers what microorganisms are, how they were discovered, how they were classified over time (two kingdoms to five kingdoms to three domains) and why they matter to botany.

Key points

• Microbiology is the study of microorganisms. Microbes are found in soil, water, air, inside plants and animals, and even in hot springs and salt pans.
• Antonie van Leeuwenhoek (1670s) first saw bacteria ("animalcules") with his simple microscope. Louis Pasteur disproved spontaneous generation and gave pasteurisation. Robert Koch proved that a specific microbe causes a specific disease (Koch's postulates).
• Two-kingdom system (Linnaeus, 1758): Plantae and Animalia. Bacteria and fungi were wrongly placed in plants.
• Three-kingdom system (Haeckel, 1866): added Protista for simple organisms.
• Five-kingdom system (R. H. Whittaker, 1969): Monera, Protista, Fungi, Plantae, Animalia. Based on cell type, body organisation, mode of nutrition and phylogeny.
• Three-domain system (Carl Woese, 1990): based on 16S rRNA sequences. Domains: Bacteria, Archaea and Eukarya.
• Archaea look like bacteria but differ in cell wall (no peptidoglycan), membrane lipids (ether-linked) and rRNA. Examples: methanogens, halophiles, thermoacidophiles.
• Mycoplasma (PPLO) are the smallest free-living cells; they have no cell wall, so they are resistant to penicillin. They cause little-leaf of brinjal.
• Actinomycetes are filamentous, Gram-positive bacteria; Streptomyces gives antibiotics such as streptomycin.
• Viruses are not cells; they are kept outside all kingdoms in Whittaker's system.

Important terms

• Prokaryote – cell without a true nucleus or membrane-bound organelles (bacteria, archaea).
• Eukaryote – cell with a true nucleus and membrane-bound organelles.
• 16S rRNA – RNA of the small ribosome subunit; used to compare and classify prokaryotes.
• Extremophile – organism living in extreme heat, salt or acidity.
• Mycoplasma – wall-less, pleomorphic prokaryote.

Key facts

5 important questions

Q1. What are archaebacteria? Give two examples.

Archaebacteria (Archaea) are prokaryotes that live in extreme habitats. Their wall lacks peptidoglycan and their membrane lipids are ether-linked. Examples: methanogens (Methanobacterium) and halophiles (Halobacterium).

Q2. What is Mycoplasma?

Mycoplasma are the smallest known free-living prokaryotes. They have no cell wall, so their shape changes (pleomorphic). They cause diseases such as little leaf of brinjal and are not affected by penicillin.

Q3. Explain Whittaker's five-kingdom classification.

• Proposed in 1969; criteria: cell type, body organisation, nutrition, reproduction, phylogeny.
• Monera – prokaryotes (bacteria, cyanobacteria).
• Protista – unicellular eukaryotes (diatoms, Euglena, protozoa).
• Fungi – heterotrophic, absorptive, chitin wall.
• Plantae – multicellular autotrophs with cellulose wall.
• Animalia – multicellular heterotrophs without cell wall.
• Merits and demerits (viruses and lichens not placed).

Q4. Describe Carl Woese's three-domain system.

• Based on 16S rRNA sequence comparison (1990).
• Domain Bacteria: true bacteria and cyanobacteria.
• Domain Archaea: methanogens, halophiles, thermoacidophiles.
• Domain Eukarya: protists, fungi, plants, animals.
• Shows archaea are closer to eukaryotes than to bacteria in some features; give the comparison table.

Q5. Write a note on the contributions of Leeuwenhoek, Pasteur and Koch.

• Leeuwenhoek: first saw microbes with a simple microscope.
• Pasteur: swan-neck flask experiment, pasteurisation, vaccines for anthrax and rabies.
• Koch: isolated causes of anthrax and tuberculosis; Koch's postulates; pure culture on solid media.

Exam tip

Learn the classification table with scientist and year, and the Bacteria–Archaea–Eukarya comparison. Short notes on Mycoplasma and Archaea are often asked.

Quick summary

Viruses are very small infectious particles that can multiply only inside a living host cell. They are made of nucleic acid (DNA or RNA) covered by a protein coat. They show both living and non-living characters, so they are called a link between living and non-living things. This topic covers their structure, types, multiplication and the diseases they cause in plants.

Key points

• The word virus means "poison" in Latin. Viruses (विषाणू) pass through bacteria-proof filters.
• D. J. Ivanowsky (1892) showed that the agent of tobacco mosaic disease passes through bacterial filters.
• M. W. Beijerinck (1898) called the infectious fluid "contagium vivum fluidum" (living infectious fluid).
• W. M. Stanley (1935) crystallised Tobacco Mosaic Virus (TMV) and received the Nobel Prize in 1946.
• A complete virus particle is called a virion. It has a nucleic acid core and a protein coat called the capsid, made of sub-units called capsomeres.
• A virus has either DNA or RNA, never both. Most plant viruses have single-stranded RNA (e.g. TMV).
• Some animal viruses (e.g. influenza, HIV) have an outer lipid envelope.
• Viruses have no cell wall, no ribosomes and no own metabolism. They are obligate intracellular parasites.
• Living characters: they multiply inside a host, have genetic material, and can mutate.
• Non-living characters: they can be crystallised, have no respiration or metabolism, and are inactive outside a host.
• Shapes: rod-shaped (TMV), spherical/polyhedral (poliovirus, adenovirus), complex/tadpole-like (T4 bacteriophage).
• Viruses that attack bacteria are called bacteriophages.

Important terms

• Virion – a complete, infective virus particle outside the host.
• Capsid – the protein coat around the nucleic acid.
• Capsomere – a protein sub-unit of the capsid.
• Bacteriophage – a virus that infects bacteria (e.g. T4 phage of Escherichia coli).
• Viroid – a small, naked circular RNA without protein coat; causes potato spindle tuber disease (discovered by T. O. Diener, 1971).
• Prion – an infectious protein particle without nucleic acid.
• Lytic cycle – virus multiplies and bursts (lyses) the host cell.
• Lysogenic cycle – viral DNA joins the host DNA (as a prophage) and is copied with it without killing the cell.

Key facts

• Common plant viral diseases: tobacco mosaic, yellow vein mosaic of bhindi (lady's finger), leaf curl of papaya and tomato, bunchy top of banana.
• Viruses spread in plants through insects (aphids, whiteflies), grafting, seeds and contact.

5 important questions

Q1. What is a virion?

A virion is a complete virus particle that can infect a host. It has a nucleic acid core (DNA or RNA) covered by a protein capsid. Some virions also have an outer envelope.

Q2. Why are viruses called a link between living and non-living?

Inside a host they multiply and mutate like living things. Outside a host they are inactive, can be crystallised and show no metabolism, like non-living matter.

Q3. Describe the structure of TMV with a labelled diagram.

• Rod-shaped, helical virus.
• Central single-stranded RNA coiled in a helix.
• Protein coat (capsid) of many identical capsomeres arranged spirally around the RNA.
• Hollow central canal along the length.
• Diagram labels: RNA strand, capsomeres, capsid, central hollow core.

Q4. Explain the lytic cycle of a bacteriophage.

1. Attachment (adsorption) of tail fibres to the bacterial cell wall.
2. Penetration: tail sheath contracts and viral DNA is injected; the empty coat stays outside.
3. Synthesis: viral DNA takes control and makes new viral DNA and proteins.
4. Assembly (maturation) of new phage particles.
5. Release: the host cell bursts (lysis) and new phages are set free.

Q5. Give the general characters of viruses.

• Ultramicroscopic; seen only with an electron microscope.
• Obligate parasites; multiply only inside living cells.
• Contain either DNA or RNA.
• No cell wall, cytoplasm or enzymes for metabolism.
• Can be crystallised; host-specific.
• Cause diseases in plants, animals and humans.

Exam tip

Always draw TMV and T4 phage with clear labels. Remember the scientists and years: Ivanowsky 1892, Beijerinck 1898, Stanley 1935.

Quick summary

Bacteria are single-celled prokaryotic organisms found almost everywhere: in soil, water, air and inside other organisms. They have no true nucleus and no membrane-bound organelles. This topic covers their discovery, shapes, cell structure, nutrition, reproduction and importance.

Key points

• Antonie van Leeuwenhoek first saw bacteria (1676) with his simple microscope. He is called the father of microbiology. Robert Koch is called the father of bacteriology.
• Bacteria (जीवाणू) are prokaryotes: DNA lies free in the cytoplasm in a region called the nucleoid.
• Shapes: coccus (spherical), bacillus (rod), spirillum (spiral), vibrio (comma-shaped).
• Cocci may occur as diplococcus (pairs), streptococcus (chains), staphylococcus (grape-like bunches).
• Cell wall is made of peptidoglycan (murein). This makes it different from the cellulose wall of plants.
• On the basis of Gram staining (Christian Gram, 1884), bacteria are Gram-positive (stain violet, thick peptidoglycan) or Gram-negative (stain pink/red, thin peptidoglycan with outer membrane).
• Ribosomes are of the 70S type.
• Many bacteria have small circular extra DNA called plasmids.
• Flagella help in movement; pili/fimbriae help in attachment and conjugation.
• Reproduction: mainly asexual by binary fission; some form endospores to survive bad conditions.
• Genetic recombination occurs by conjugation, transformation and transduction (no true sexual reproduction).

Important terms

• Nucleoid – region holding the single circular DNA.
• Plasmid – small, circular, self-replicating extra-chromosomal DNA.
• Capsule / slime layer – sticky layer outside the cell wall; gives protection.
• Mesosome – infolding of plasma membrane; thought to help in respiration and cell division.
• Endospore – thick-walled resting spore formed inside the cell.
• Conjugation – transfer of DNA from donor to recipient cell through a sex pilus.
• Transformation – uptake of free DNA from surroundings (Griffith, 1928).
• Transduction – transfer of DNA by a bacteriophage.

Key facts

• Nutrition types: autotrophic (photosynthetic, e.g. green sulphur bacteria; chemosynthetic, e.g. Nitrosomonas, Nitrobacter) and heterotrophic (saprophytic, parasitic, symbiotic).
• Useful bacteria: Rhizobium (nitrogen fixation in root nodules of legumes), Lactobacillus (curd), Streptomyces (antibiotics like streptomycin), Azotobacter (free-living nitrogen fixer).
• Harmful bacteria: Xanthomonas citri (citrus canker), Xanthomonas oryzae (bacterial blight of rice), Mycobacterium tuberculosis (TB), Vibrio cholerae (cholera).

5 important questions

Q1. Differentiate between Gram-positive and Gram-negative bacteria.

Gram-positive bacteria have a thick peptidoglycan wall and retain crystal violet, appearing purple. Gram-negative bacteria have a thin peptidoglycan layer with an outer lipid membrane and appear pink after counterstaining with safranin.

Q2. What is a plasmid?

A plasmid is a small, circular, double-stranded DNA found in bacteria outside the main chromosome. It replicates on its own and may carry genes for antibiotic resistance. Plasmids are used as vectors in genetic engineering.

Q3. Describe the ultrastructure of a bacterial cell with a labelled diagram.

• Outer capsule/slime layer, then cell wall (peptidoglycan), then plasma membrane.
• Mesosome formed by infolding of membrane.
• Cytoplasm with 70S ribosomes, food granules, plasmids.
• Nucleoid with circular DNA, no nuclear membrane.
• Flagellum and pili on surface.
• Labels: capsule, cell wall, plasma membrane, mesosome, nucleoid, ribosome, plasmid, flagellum, pili.

Q4. Explain reproduction in bacteria.

1. Binary fission: DNA replicates, cell elongates, a cross wall forms, two daughter cells result.
2. Endospore formation in bad conditions (e.g. Bacillus, Clostridium).
3. Recombination: conjugation (Lederberg and Tatum, 1946), transformation (Griffith), transduction (Zinder and Lederberg, 1952).

Q5. Give the economic importance of bacteria.

• Nitrogen fixation and soil fertility (Rhizobium, Azotobacter).
• Decomposition of dead matter; recycling of nutrients.
• Dairy (curd, cheese), vinegar, retting of fibres (jute, hemp).
• Antibiotics, vitamins, enzymes; genetic engineering (E. coli).
• Harmful: plant diseases, human diseases, food spoilage.

Exam tip

Draw a neat labelled bacterial cell. Name one example for every type of nutrition; examiners like specific names.

Quick summary

Cyanobacteria (blue-green algae) are photosynthetic prokaryotes. They were earlier studied with algae as Myxophyceae, but their cell structure is bacterial. This topic covers their general characters, cell structure, the type studies Nostoc and Oscillatoria, and their importance in nitrogen fixation and agriculture.

Key points

• Cyanobacteria are prokaryotes: no true nucleus, no chloroplast, no mitochondria; 70S ribosomes.
• They are among the oldest organisms on Earth; fossil stromatolites are about 3.5 billion years old. They made the early atmosphere rich in oxygen.
• Pigments: chlorophyll a, c-phycocyanin (blue), c-phycoerythrin (red) and carotenoids. Phycobilins sit in phycobilisomes on the thylakoids.
• Stored food: cyanophycean starch and cyanophycin granules (protein).
• Cell has an outer coloured chromoplasm and inner colourless centroplasm (with DNA).
• Cells often have a mucilage sheath; no flagella at any stage.
• Gas vacuoles help planktonic forms float.
• Heterocysts – large, thick-walled, pale cells that fix atmospheric nitrogen using nitrogenase; they lack photosystem II, so no oxygen is produced inside.
• Akinetes – thick-walled resting spores that survive bad seasons.
• Reproduction is only vegetative and asexual: fission, fragmentation, hormogonia, akinetes. No sexual reproduction.

Important terms

• Hormogonium – short piece of trichome cut off between dead or separation cells; grows into a new filament.
• Trichome – row of cells of a filament without the sheath.
• Separation disc (necridium) – dead biconcave cell that breaks a trichome into hormogonia.
• Water bloom – dense surface growth of cyanobacteria in nutrient-rich water.
• Biofertiliser – living organism that adds nutrients to soil, e.g. Anabaena, Nostoc.

Key facts

• Uses: nitrogen fixation in paddy fields (Anabaena, Nostoc, Tolypothrix); Anabaena azollae in the water fern Azolla; Spirulina as protein-rich food; reclamation of usar (alkaline) soils.
• Harmful: toxic water blooms (Microcystis), bad smell and taste in drinking water, damage to buildings.

5 important questions

Q1. What are heterocysts?

Heterocysts are large, thick-walled, pale cells found in filaments of Nostoc and Anabaena. They have polar nodules at the junction with neighbour cells and are the site of nitrogen fixation because they keep oxygen away from nitrogenase.

Q2. Why are cyanobacteria called prokaryotes?

Because they have no membrane-bound nucleus, no plastids and no mitochondria; DNA lies free in the centroplasm and ribosomes are 70S, like bacteria.

Q3. Describe the structure and reproduction of Nostoc.

• Colony of beaded, unbranched trichomes in a common gelatinous matrix.
• Cells round or barrel-shaped; heterocysts at intervals.
• Hormogonia formed by breaking at heterocysts.
• Akinetes formed in unfavourable conditions; germinate later.
• Labelled diagram: trichome, sheath, vegetative cell, heterocyst, akinete.

Q4. Give an illustrated account of Oscillatoria.

• Free-living, blue-green, unbranched trichomes; no heterocysts.
• Short disc-like cells; terminal cell convex, may have a calyptra.
• Shows oscillating (to-and-fro) movement.
• Reproduction by hormogonia formed between separation discs.

Q5. Discuss the economic importance of cyanobacteria.

• Biological nitrogen fixation in rice fields; Azolla–Anabaena biofertiliser.
• Food and supplement: Spirulina.
• Soil reclamation; pioneers on bare rock.
• Harmful blooms and toxins in ponds and reservoirs.

Exam tip

Draw Nostoc with a clear heterocyst and akinete, and Oscillatoria with separation discs – the comparison table above is a ready-made answer for "distinguish between".

Quick summary

Algae are simple, mostly aquatic, chlorophyll-bearing thalloid plants. Their body is not divided into root, stem and leaf. They range from single cells (Chlamydomonas) to large seaweeds. This topic covers general characters, Fritsch's classification, life cycles of type examples and economic importance.

Key points

• Study of algae is phycology (phycos = seaweed). Algae is called शैवाल / शेवाळ in Marathi.
• Body is a thallus; no vascular tissue.
• Found in fresh water, sea water, moist soil, tree bark; some live in symbiosis (lichens).
• Cell wall mostly of cellulose. Food stored as starch (green algae), floridean starch (red algae), laminarin and mannitol (brown algae).
• Pigments: chlorophyll a in all; others decide colour – chlorophyll b (green), fucoxanthin (brown), phycoerythrin (red).
• Sex organs are unicellular and not covered by a jacket of sterile cells.
• No embryo formation after fertilisation.
• Reproduction: vegetative (fragmentation), asexual (zoospores, aplanospores, akinetes), sexual (isogamy, anisogamy, oogamy).
• F. E. Fritsch (1935, 1945) divided algae into 11 classes in "The Structure and Reproduction of the Algae".
• Main classes: Chlorophyceae, Xanthophyceae, Bacillariophyceae, Phaeophyceae, Rhodophyceae, Myxophyceae (Cyanophyceae).

Important terms

• Thallus – plant body not divided into root, stem and leaf.
• Pyrenoid – protein body in the chloroplast around which starch is stored.
• Isogamy – fusion of similar gametes.
• Oogamy – fusion of a large non-motile egg with a small motile sperm.
• Heterocyst – thick-walled cell in blue-green algae that fixes nitrogen (e.g. Nostoc).
• Zygospore / Oospore – thick-walled zygote.

Key facts

• **Life cycle of Spirogyra: filamentous green alga with ribbon-shaped spiral chloroplasts. Sexual reproduction by conjugation** – scalariform (ladder-like, between two filaments) or lateral (between cells of the same filament). Zygospore undergoes meiosis; only one of four nuclei survives. Life cycle is haplontic.
• ***Oedogonium*:** oogamous; shows cap cells; may be macrandrous or nannandrous (dwarf males).

5 important questions

Q1. What is a pyrenoid?

A pyrenoid is a dense protein body found in the chloroplast of many algae. Starch is deposited around it. It is seen clearly in Spirogyra and Chlamydomonas.

Q2. Name the pigments of brown and red algae.

Brown algae have fucoxanthin with chlorophyll a and c. Red algae have r-phycoerythrin and phycocyanin with chlorophyll a (and d in some).

Q3. Describe the life cycle of Spirogyra.

• Haploid filament; each cell has spiral chloroplasts with pyrenoids.
• Vegetative reproduction by fragmentation.
• Scalariform conjugation: two filaments lie side by side, conjugation tubes form a ladder; contents of male cell move to female cell.
• Fusion forms diploid zygospore.
• Zygospore undergoes meiosis; 3 nuclei degenerate; one haploid germling grows.
• Diagram labels: cell wall, chloroplast, pyrenoid, nucleus, conjugation tube, zygospore.

Q4. Give the general characters and classification of algae according to Fritsch.

• Thalloid, autotrophic, mostly aquatic.
• Pigments and stored food differ by class.
• Sex organs unicellular, no jacket, no embryo.
• Fritsch: 11 classes based on pigments, stored food, flagella and reproduction (list the main six with examples).

Q5. Explain the economic importance of algae.

• Food: Ulva, Porphyra, Spirulina (protein-rich).
• Agar-agar from red algae (Gelidium, Gracilaria); alginic acid from brown algae.
• Nitrogen fixation in paddy fields by blue-green algae (Nostoc, Anabaena).
• Diatomaceous earth used in filters and polishes.
• Harmful: water blooms, poisoning of water.

Exam tip

Learn one table of classes with pigment, food and example. A labelled Spirogyra conjugation diagram is very common in exams.

Quick summary

This topic covers three advanced algae often asked as type studies: Chara (green alga, Charophyceae), Ectocarpus (brown alga, Phaeophyceae) and Polysiphonia (red alga, Rhodophyceae). For each, learn the thallus structure, reproduction and life cycle, with labelled diagrams.

Key points

• Chara (stonewort): freshwater, attached by rhizoids; main axis with nodes and internodes; whorls of branches at nodes; often coated with calcium carbonate.
• Chara has the most advanced sex organs among algae: female nucule (oogonium) above and male globule (antheridium) below, at the same node.
• Nucule has a crown of 5 corona cells and 5 spirally twisted tube cells; globule has 8 shield cells, manubria and antheridial filaments.
• Chara life cycle is haplontic; the zygote (oospore) undergoes meiosis on germination and forms a protonema.
• Ectocarpus: marine, branched filamentous brown alga with a prostrate and an erect system (heterotrichous).
• Ectocarpus bears unilocular sporangia (meiosis → haploid zoospores) and plurilocular sporangia (mitosis → diploid zoospores) on the diploid plant.
• Gametes are pear-shaped with two laterally inserted unequal flagella. Fertilisation is isogamous to physiologically anisogamous.
• Ectocarpus shows isomorphic alternation of generations (diplohaplontic).
• Polysiphonia: marine red alga; each axis has a central siphon surrounded by pericentral siphons; cells joined by pit connections.
• Polysiphonia has three free-living or attached phases: gametophyte (n), carposporophyte (2n) on the female plant, and tetrasporophyte (2n). Life cycle is triphasic (haplo-diplobiontic).

Important terms

• Nucule / globule – female and male sex organs of Chara.
• Heterotrichous – thallus with prostrate and erect parts.
• Trichogyne – receptive hair-like tip of the red algal carpogonium.
• Cystocarp – urn-shaped structure on the female Polysiphonia that holds carpospores.
• Tetraspore – one of four haploid spores formed by meiosis in a tetrasporangium.

Key facts

5 important questions

Q1. What are corona cells?

Corona cells are the five small cells that form a crown on top of the nucule (oogonium) of Chara. They are formed by the tips of the five spiral tube cells.

Q2. Distinguish between unilocular and plurilocular sporangia of Ectocarpus.

Unilocular sporangia are single-chambered; the nucleus divides by meiosis and gives haploid zoospores. Plurilocular sporangia are many-chambered; they form diploid zoospores by mitosis that repeat the sporophyte.

Q3. Describe the sex organs and fertilisation in Chara.

• Nucule: oogonium, 5 tube cells, 5 corona cells; single egg.
• Globule: 8 shield cells, manubrium, capitulum, antheridial filaments with biflagellate antherozoids.
• Antherozoids enter between corona cells; fertilisation forms oospore.
• Oospore → meiosis → protonema → new plant. Labelled diagram of a node with both organs.

Q4. Explain the life cycle of Ectocarpus.

• Diploid sporophyte with both kinds of sporangia.
• Haploid zoospores → haploid gametophytes (look the same).
• Gametes fuse → diploid zygote → sporophyte.
• Isomorphic alternation of generations; draw a cycle diagram.

Q5. Describe the triphasic life cycle of Polysiphonia.

• Haploid male and female gametophytes; spermatia and carpogonium with trichogyne.
• Fertilised carpogonium → carposporophyte inside cystocarp → diploid carpospores.
• Carpospores → diploid tetrasporophyte → tetrasporangia → meiosis → haploid tetraspores.
• Tetraspores → male and female gametophytes. Three phases: n, 2n, 2n.

Exam tip

Diagrams decide marks here: a Chara node with nucule above and globule below, Ectocarpus sporangia, and the Polysiphonia life-cycle chart. Remember "nucule up, globule down".

Quick summary

Fungi are eukaryotic, achlorophyllous, heterotrophic organisms with a body made of thread-like hyphae. They live as saprophytes, parasites or symbionts. This topic covers general characters, classification, type examples and the importance of fungi.

Key points

• Study of fungi is mycology. Fungi are called बुरशी in Marathi.
• P. A. Micheli is called the father of mycology.
• Body is a mycelium, a network of hyphae. Hyphae may be septate (with cross walls) or aseptate and coenocytic (many nuclei in common cytoplasm).
• Cell wall is made mainly of chitin (fungal cellulose in some lower forms).
• No chlorophyll; food stored as glycogen and oil, not starch.
• Nutrition: saprophytic (Rhizopus, Mucor), parasitic (Puccinia, Albugo), symbiotic (lichens, mycorrhiza).
• Parasitic fungi absorb food through special hyphal branches called haustoria.
• Asexual reproduction: sporangiospores, conidia, zoospores, oidia, chlamydospores; yeast reproduces by budding.
• Sexual reproduction has three stages: plasmogamy (fusion of cytoplasm), karyogamy (fusion of nuclei) and meiosis.
• In many fungi a dikaryotic stage (n + n) lies between plasmogamy and karyogamy.

Important terms

• Hypha – single thread of a fungal body.
• Mycelium – mass of hyphae.
• Conidia – asexual spores formed at the tip of conidiophores (e.g. Penicillium, Aspergillus).
• Ascus – sac-like structure in which ascospores (usually 8) are formed.
• Basidium – club-shaped structure bearing basidiospores (usually 4) externally.
• Mycorrhiza – association between a fungus and plant roots.
• Dikaryon – cell with two unfused nuclei of different strains.

Key facts

• Albugo candida causes white rust of crucifers (mustard).
• Puccinia graminis tritici causes black (stem) rust of wheat; it is heteroecious (wheat is the primary host, barberry the alternate host) and has five spore stages.
• Penicillium notatum – source of penicillin (Alexander Fleming, 1928).

5 important questions

Q1. What is a coenocytic mycelium?

A coenocytic mycelium has hyphae without cross walls, so many nuclei lie in one common mass of cytoplasm. Example: Rhizopus and Albugo.

Q2. Define haustoria.

Haustoria are small hyphal outgrowths of parasitic fungi that enter host cells and absorb food. Example: Albugo.

Q3. Describe the life cycle of Rhizopus (bread mould).

• Mycelium of aseptate hyphae: stolons, rhizoids and sporangiophores.
• Asexual: sporangia on sporangiophores; columella inside; sporangiospores spread by air.
• Sexual: conjugation between + and – strains (heterothallic); progametangia → gametangia fuse → zygospore.
• Zygospore germinates after meiosis to form a germ sporangium.
• Labels: stolon, rhizoids, sporangiophore, sporangium, columella, spores, zygospore.

Q4. Give the life cycle of Puccinia graminis tritici.

• On wheat: uredospores (red rust stage, repeat infection) then teleutospores (black rust stage).
• Teleutospore germinates to form basidium and four basidiospores.
• Basidiospores infect barberry leaf: pycnidia (spermogonia) on upper side and aecidia (cluster cups) on lower side.
• Aecidiospores carried back to wheat.
• Thus five spore types: uredospore, teleutospore, basidiospore, pycniospore, aecidiospore.

Q5. Discuss the economic importance of fungi.

• Food: mushrooms (Agaricus), yeast in bread and alcohol.
• Medicines: penicillin, griseofulvin; ergot alkaloids.
• Enzymes and organic acids (citric acid from Aspergillus niger).
• Decomposers; mycorrhiza helps plants absorb phosphorus.
• Harmful: plant diseases (rusts, smuts, wilts), food spoilage, aflatoxins, ringworm.

Exam tip

Remember the three stages of sexual reproduction (plasmogamy, karyogamy, meiosis). For Puccinia, write the spore stage on each host in a neat table.

Quick summary

This topic covers three fungi that are common type studies: Albugo (white rust, an oomycete), Penicillium (green/blue mould, an ascomycete) and Agaricus (mushroom, a basidiomycete). Learn their mycelium, asexual and sexual reproduction, life cycle and importance, with labelled diagrams.

Key points

• Albugo candida is an obligate parasite causing white rust of crucifers (mustard, radish, cabbage). White blister-like pustules appear on leaves and stems.
• Albugo mycelium is coenocytic (aseptate, many nuclei) and intercellular; it absorbs food through small knob-like haustoria.
• Asexual: sporangiophores below the host epidermis cut off chains of sporangia (basipetal); sporangia release biflagellate zoospores in water.
• Sexual: oogamous – antheridium and oogonium; fertilisation tube; thick-walled oospore.
• Penicillium: saprophyte on bread, fruits and leather; mycelium septate, branched.
• Asexual by conidia borne on a brush-like penicillus – conidiophore → metulae → phialides (sterigmata) → chains of conidia.
• Sexual stage (rare): ascogonium and antheridium; asci with 8 ascospores inside a closed cleistothecium.
• Penicillium notatum gave penicillin (Alexander Fleming, 1928). Others make cheese (P. roquefortii, P. camemberti).
• Agaricus (button mushroom, A. bisporus): saprophyte on humus and dung. Underground mycelium forms an above-ground basidiocarp (fruit body) with stipe, pileus, gills and annulus.
• Gills carry the hymenium with basidia; each basidium bears 4 (2 in A. bisporus) basidiospores on sterigmata. Mycelium passes through primary (n), secondary (dikaryotic, n + n) and tertiary stages.

Important terms

• Haustorium – absorbing branch of a parasitic hypha inside a host cell.
• Coenocytic – hypha without cross walls, with many nuclei.
• Conidium – non-motile asexual spore cut off at the tip of a hypha.
• Cleistothecium – closed ascocarp without an opening.
• Dikaryon – cell with two genetically different nuclei (n + n).
• Clamp connection – hook-like bridge that keeps dikaryotic cells paired in basidiomycetes.

Key facts

5 important questions

Q1. What is a penicillus?

A penicillus is the brush-like conidial apparatus of Penicillium. A conidiophore branches into metulae, which bear flask-shaped phialides; each phialide cuts off a chain of conidia.

Q2. Name the disease caused by Albugo and give one symptom.

Albugo candida causes white rust of crucifers. Shiny white pustules form on leaves and stems; infected flower parts become swollen and deformed.

Q3. Describe the asexual and sexual reproduction of Albugo.

• Club-shaped sporangiophores under the epidermis; basipetal chains of sporangia; epidermis bursts.
• Sporangia germinate in water to give biflagellate zoospores, which infect new plants.
• Sexual: oogonium with periplasm and ooplasm, antheridium; fertilisation tube; thick-walled oospore with warty exine.
• Oospore germinates to release zoospores. Diagrams: T.S. of infected leaf, oogonium.

Q4. Give an account of the structure of the basidiocarp of Agaricus.

• Stipe, pileus, annulus (remains of veil); gills on the underside.
• T.S. of gill: trama, sub-hymenium, hymenium with basidia and paraphyses.
• Basidium: karyogamy then meiosis → four basidiospores on sterigmata.
• Labelled diagrams of the fruit body and gill section.

Q5. Discuss the economic importance of Penicillium.

• Penicillin from P. notatum and P. chrysogenum.
• Cheese ripening (Roquefort, Camembert).
• Griseofulvin and organic acids.
• Harmful: spoilage of fruits (blue/green mould of citrus), bread and leather.

Exam tip

A three-column comparison like the table above is useful for "distinguish" questions. Always draw the penicillus and the gill T.S. neatly – they are very common diagram questions.

Quick summary

Fungi often live in close partnership with other organisms. The most important example is mycorrhiza – a mutually useful association between a fungus and the roots of a higher plant. This topic covers types of mycorrhiza, how each partner benefits, other fungal associations (lichens, endophytes, fungi with insects) and their use as biofertilisers.

Key points

• The term mycorrhiza ("fungus-root") was coined by A. B. Frank in 1885. More than 80% of land plants form mycorrhiza.
• It is symbiosis (mutualism): the plant gives sugars to the fungus; the fungus gives water and minerals, especially phosphorus, to the plant.
• Ectomycorrhiza: fungus forms a thick mantle around the root tip and a Hartig net between cortical cells; it does not enter the cells. Seen in pine, oak, eucalyptus. Fungi are mostly basidiomycetes.
• Ectomycorrhizal roots are short, swollen and branched, with no root hairs.
• Endomycorrhiza: hyphae enter the cortical cells. The main type is arbuscular mycorrhiza (AM), earlier called VAM, formed by fungi of Glomeromycota (e.g. Glomus).
• AM fungi form arbuscules (tree-like branches inside cells, site of exchange) and vesicles (storage sacs). Found in most crops – wheat, maize, legumes.
• Special endomycorrhiza: orchid mycorrhiza (fungus feeds the tiny orchid seedling) and ericoid mycorrhiza.
• Ectendomycorrhiza shows both a mantle and cell penetration.
• Benefits to plants: better uptake of P, Zn, Cu and water; drought tolerance; protection from root pathogens; better soil structure.
• Other associations: lichens (fungus + alga), endophytes living inside leaves and stems, fungus-growing ants and termites.

Important terms

• Mantle – sheath of fungal hyphae around an ectomycorrhizal root.
• Hartig net – network of hyphae between cortical cells.
• Arbuscule – finely branched fungal structure inside a root cell.
• Vesicle – swollen lipid-filled storage structure of AM fungi.
• Biofertiliser – living microbes used to improve plant nutrition.

Key facts

5 important questions

Q1. Define mycorrhiza.

Mycorrhiza is a mutually beneficial association between a fungus and the roots of a higher plant. The fungus absorbs minerals and water for the plant and receives carbohydrates in return.

Q2. What are arbuscules?

Arbuscules are tree-like, much-branched hyphae formed inside cortical cells by AM fungi. They are the main site of exchange of nutrients between fungus and plant.

Q3. Distinguish between ectomycorrhiza and endomycorrhiza.

Use the table: hyphae inside or outside cells, mantle, Hartig net, arbuscules and vesicles, fungal groups, host examples. Add a labelled diagram of each.

Q4. Explain the role of mycorrhiza in agriculture and forestry.

• Phosphorus uptake from poor soils; less fertiliser needed.
• Drought and salt tolerance.
• Protection against root pathogens.
• Essential for pine plantations and orchid seed germination.
• Used as AM biofertiliser inoculum in nurseries.

Q5. Write a note on fungal associations other than mycorrhiza.

• Lichens: fungus with alga or cyanobacterium.
• Endophytes: fungi living harmlessly inside plants, sometimes giving pest resistance.
• Fungus gardens of ants and termites.
• Parasitic associations (rusts, smuts) for contrast.

Exam tip

For a short note on mycorrhiza, always give the definition, Frank 1885, the two types with one example each, and the phosphorus benefit. Draw a root T.S. showing mantle and Hartig net.

Quick summary

Lichens are dual organisms formed by a close, long-term association of an alga and a fungus. The fungus gives shelter, water and minerals; the alga makes food by photosynthesis. They grow on rocks, tree bark and soil, even in very harsh places. This topic covers their types, structure, reproduction and importance.

Key points

• Lichens are called दगडफूल in Marathi (the spice "dagadphool" is a lichen).
• The association is called symbiosis (mutualism). The fungal partner is the mycobiont; the algal partner is the phycobiont (photobiont).
• Fungal partner is mostly an Ascomycete (ascolichens), rarely a Basidiomycete (basidiolichens).
• Algal partner is usually a green alga (Trebouxia) or a blue-green alga (Nostoc).
• The fungus forms most of the body and decides its shape.
• Lichens are slow-growing and very sensitive to air pollution, especially sulphur dioxide (SO₂). They do not grow in polluted cities.
• They are pioneer colonisers on bare rocks; they secrete acids that break rocks and start soil formation.
• Study of lichens is called lichenology.

Important terms

• Crustose – crust-like lichen, firmly stuck to the substratum (e.g. Graphis, Lecanora).
• Foliose – leaf-like, flat lobed lichen, loosely attached by rhizines (e.g. Parmelia, Peltigera).
• Fruticose – shrub-like, branched, erect or hanging lichen (e.g. Usnea, Cladonia).
• Soredia – small groups of algal cells wrapped in fungal hyphae; used for vegetative reproduction.
• Isidia – small outgrowths on the upper surface that break off and grow into new lichens.
• Rhizines – root-like hyphal strands for attachment.
• Bioindicator – organism whose presence or absence shows the quality of the environment.

Key facts

• **Internal structure (heteromerous foliose lichen, e.g. Parmelia):**
• Upper cortex – compact fungal hyphae.
• Algal zone (gonidial layer) – algal cells among loose hyphae.
• Medulla – loosely arranged hyphae with air spaces.
• Lower cortex – compact hyphae giving rhizines.
• Homoiomerous thallus: algal cells evenly spread through the thallus. Heteromerous: algae in a definite layer.
• Reproduction: vegetative (fragmentation, soredia, isidia), asexual (fungal spores) and sexual (only the fungal partner forms apothecia or perithecia).

5 important questions

Q1. What are lichens?

Lichens are composite organisms made of an alga and a fungus living together in mutual benefit. The alga makes food; the fungus gives protection and absorbs water and minerals. Example: Parmelia, Usnea.

Q2. Why are lichens called pollution indicators?

Lichens absorb water and gases directly from the air and cannot get rid of toxic substances. They die quickly in air polluted with sulphur dioxide. Their absence near cities shows polluted air.

Q3. Classify lichens on the basis of thallus form with examples.

• Crustose: flat crust, firmly attached, no lower cortex – Graphis, Lecanora.
• Foliose: leaf-like lobes, attached by rhizines – Parmelia, Peltigera.
• Fruticose: shrubby, branched, attached by a small disc – Usnea, Cladonia.
• Draw one sketch of each form.

Q4. Describe the internal structure of a foliose lichen.

• Upper cortex of thick-walled, closely packed hyphae.
• Algal layer just below with algal cells and hyphae.
• Medulla of loose hyphae; stores water, allows gas exchange.
• Lower cortex with rhizines.
• Labels: upper cortex, algal zone, medulla, lower cortex, rhizines.

Q5. Write the economic importance of lichens.

• Pioneers of plant succession on rocks; help soil formation.
• Food: reindeer moss (Cladonia rangiferina) for animals; some used as spice (dagadphool).
• Dyes: litmus is obtained from lichens such as Roccella.
• Medicines: usnic acid has antibiotic action.
• Bioindicators of air pollution.
• Harmful: some damage stone monuments and glass.

Exam tip

Learn the three forms with one example each and the term "mycobiont/phycobiont". Litmus from lichens is a favourite one-mark fact.

Quick summary

Palaeobotany is the study of plants of the past, known from their fossils. Fossils tell us how plant groups appeared and changed through geological time. This topic covers what fossils are, how they form, the main types of fossils, the geological time scale, important fossil plants and the work of Birbal Sahni.

Key points

• Fossil – any remains or trace of an ancient organism preserved in rocks (usually sedimentary rocks).
• Fossilisation needs quick burial in mud or sand, lack of oxygen, and slow replacement or compression by minerals.
• Petrifaction – plant tissues replaced by minerals (silica, calcite); cell details are preserved. Best for anatomy.
• Compression – plant part flattened by pressure; thin carbon film remains.
• Impression – only the outline print on rock, no organic matter.
• Cast and mould – a hollow mould filled later by minerals forms a cast (e.g. pith casts of Calamites).
• Coal balls – lumps of petrified plants found in coal seams.
• Types of fossils:
• Fossil plant parts are often found separately, so each part gets its own form genus name, e.g. Lepidodendron (stem), Stigmaria (root), Lepidostrobus (cone).
• Radiometric dating (uranium–lead, potassium–argon) gives the age of rocks; carbon-14 dates only young material (up to about 50,000 years).
• Rhynia (Devonian, Rhynie chert, Scotland) – among the earliest vascular land plants: dichotomous leafless axes with terminal sporangia.
• Other key fossils: Lepidodendron (giant club moss), Calamites (giant horsetail), Lyginopteris (seed fern), Williamsonia (Bennettitales, Jurassic India).
• Birbal Sahni (1891–1949), father of Indian palaeobotany, described the Pentoxyleae (Pentoxylon) from the Rajmahal Hills and founded the Birbal Sahni Institute of Palaeosciences, Lucknow (1946).

Important terms

• Form genus – name given to an isolated fossil organ.
• Index fossil – fossil of a short time range used to date rocks.
• Chert – fine-grained silica rock that preserves fossils well.
• Coal – rock formed from compressed plant matter of ancient swamp forests (mainly Carboniferous).

Key facts

5 important questions

Q1. What is a petrifaction?

A petrifaction is a fossil in which the original tissues are slowly replaced by minerals like silica or calcium carbonate, so the internal cell structure is preserved and can be studied in thin sections.

Q2. Who is called the father of Indian palaeobotany?

Prof. Birbal Sahni. He studied Indian fossil plants, described Pentoxylon from the Rajmahal Hills, and founded the institute at Lucknow now named after him.

Q3. Describe the process of fossilisation and the types of fossils.

• Quick burial, lack of oxygen, mineral replacement, pressure.
• Types: petrifaction, compression, impression, cast and mould, coal ball – with one line and an example each.
• Note on form genera.

Q4. Explain the geological time scale with reference to plant evolution.

• Eras: Palaeozoic, Mesozoic, Cenozoic.
• Write the table: first land plants, pteridophyte age, gymnosperm age, angiosperm age.
• Mention coal formation in the Carboniferous.

Q5. Give an account of Rhynia.

• Devonian; Rhynie chert, Scotland.
• Rhizome with rhizoids; erect, leafless, dichotomously branched aerial axes.
• Protostele; stomata on epidermis.
• Terminal, elongated sporangia with homosporous spores.
• Importance: shows the simple structure of early vascular plants.

Exam tip

Learn three fossil types with one example each and five rows of the time scale. A short note on Birbal Sahni is a favourite question in Maharashtra universities.

Quick summary

Bryophytes are the simplest land plants. They need water for fertilisation, so they grow in moist, shady places. They are called the "amphibians of the plant kingdom". The main plant body is the gametophyte; the sporophyte depends on it. This topic covers characters, classification and the life cycles of Riccia, Marchantia, Anthoceros and Funaria.

Key points

• Bryophytes have no true roots, stem or leaves; they are fixed by rhizoids.
• No vascular tissue (xylem and phloem absent).
• The dominant, independent plant is the gametophyte (haploid, n).
• The sporophyte (diploid, 2n) is attached to and depends on the gametophyte for food (partly or fully).
• Sex organs are multicellular and jacketed: male antheridium, female archegonium (flask-shaped, with neck and venter).
• Sperms (antherozoids) are biflagellate and swim in water to reach the egg.
• After fertilisation an embryo is formed (they are embryophytes).
• Life cycle shows clear alternation of generations (heteromorphic).
• Classification: Hepaticopsida (liverworts – Riccia, Marchantia), Anthocerotopsida (hornworts – Anthoceros), Bryopsida (mosses – Funaria, Sphagnum, Polytrichum).

Important terms

• Thallus – flat, dorsiventral body of liverworts.
• Rhizoids – hair-like structures for attachment; smooth-walled and tuberculate in liverworts, multicellular in mosses.
• Protonema – green, branched, filamentous juvenile stage of mosses that grows from a spore.
• Capsule – spore-producing part of the sporophyte.
• Elaters – hygroscopic cells in the capsule that help scatter spores (Marchantia).
• Pseudoelaters – elater-like cells in Anthoceros.
• Gemma cup – cup-like structure in Marchantia bearing gemmae for vegetative reproduction.
• Peristome – teeth at the mouth of moss capsule that help spore dispersal.

Key facts

• Sphagnum (peat moss) forms peat used as fuel and in gardening; it holds a lot of water.

5 important questions

Q1. Why are bryophytes called amphibians of the plant kingdom?

They live on land but need water for fertilisation, as their sperms must swim to the archegonium. So they depend on both land and water, like amphibians.

Q2. What is protonema?

Protonema is a green, branched filament that grows from a germinating moss spore. Buds on it develop into leafy gametophores. Example: Funaria.

Q3. Describe the sporophyte of Funaria with a labelled diagram.

• Parts: foot (in gametophore), long seta, capsule.
• Capsule: apophysis (with stomata), theca (spore sac, columella, air spaces) and operculum.
• Annulus below operculum; peristome teeth (outer and inner rows) control spore release.
• Calyptra (from archegonium wall) covers young capsule.
• Labels: foot, seta, apophysis, columella, spore sac, annulus, peristome, operculum, calyptra.

Q4. Give the general characters of bryophytes.

• Thalloid or leafy; rhizoids; no vascular tissue.
• Gametophyte dominant and independent.
• Jacketed sex organs; biflagellate sperms; water needed.
• Embryo formed; sporophyte dependent.
• Heteromorphic alternation of generations.

Q5. Explain the life cycle of Marchantia.

• Dichotomously branched thallus with gemma cups (vegetative reproduction).
• Dioecious: antheridiophore (lobed disc) on male, archegoniophore (star-like rays) on female plant.
• Sperms swim to archegonia; zygote forms embryo.
• Sporophyte: foot, seta, capsule with spores and elaters.
• Spores (after meiosis) germinate into new thalli.

Exam tip

Always state "gametophyte dominant, sporophyte dependent" – it is the key difference from pteridophytes. Practise the Funaria capsule L.S. diagram.

Quick summary

Riccia (a liverwort) and Anthoceros (a hornwort) are two important type studies of bryophytes. Riccia has the simplest sporophyte among bryophytes, while Anthoceros has the most advanced one. This topic covers their thallus, sex organs, sporophyte and life cycle.

Key points

• Riccia (class Hepaticopsida, order Marchantiales): small, dichotomously branched, dorsiventral thallus on moist soil; a median dorsal groove; rhizoids and scales below.
• Thallus V.S.: upper photosynthetic zone of vertical chlorophyllous filaments with air canals, and lower storage zone of colourless cells.
• Rhizoids are of two types: smooth-walled and tuberculate. Multicellular scales are present on the ventral side.
• Sex organs (antheridia and archegonia) are sunk in the dorsal groove; flask-shaped archegonium with neck and venter.
• ***Riccia* sporophyte is the simplest: only a capsule** – no foot, no seta. It stays embedded in the thallus.
• All inner cells of the capsule form spores (no elaters). Spores are released only when the thallus decays.
• Anthoceros (class Anthocerotopsida): dark green lobed thallus; each cell has one large chloroplast with a pyrenoid (like algae).
• Ventral mucilage cavities contain the cyanobacterium Nostoc (fixes nitrogen). Only smooth rhizoids; no scales.
• Sex organs are endogenous (develop inside the thallus).
• ***Anthoceros* sporophyte: bulbous foot, a meristematic (intercalary) zone and a long horn-like capsule. It grows for a long time. The capsule has a central columella, spores, pseudo-elaters and a green wall with stomata** – it can photosynthesise, so it is partly independent.

Important terms

• Tuberculate rhizoid – rhizoid with peg-like ingrowths on the inner wall.
• Columella – central sterile column in the capsule.
• Pseudo-elaters – multicellular, branched sterile cells among spores in Anthoceros.
• Intercalary meristem – zone at the base of the Anthoceros capsule that keeps adding tissue.
• Spore tetrad – group of four spores formed by meiosis.

Key facts

5 important questions

Q1. Why is the sporophyte of Riccia called the simplest?

Because it is only a capsule, without foot and seta. All inner cells are fertile (no columella, no elaters) and it remains enclosed in the thallus.

Q2. What are pseudo-elaters?

They are sterile, multicellular, often branched cells found among the spores in the Anthoceros capsule. They help in spore dispersal but lack the spiral thickening of true elaters.

Q3. Describe the internal structure of the Riccia thallus.

• Dorsal photosynthetic zone with chlorophyllous filaments and air canals.
• Ventral storage zone with starch-filled cells.
• Lower epidermis bearing smooth and tuberculate rhizoids and scales.
• Labelled V.S. diagram.

Q4. Describe the sporophyte of Anthoceros.

• Foot embedded in thallus; intercalary meristem; long capsule.
• Capsule L.S.: epidermis with stomata, green assimilatory tissue, sporogenous layer, central columella of 16 cell rows, spores and pseudo-elaters.
• Dehiscence by two valves from the tip.
• Semi-independent nature; draw L.S.

Q5. Compare Riccia and Anthoceros.

Use the comparison table above, and add habitat and the importance of Anthoceros as a link in the origin of the land plant sporophyte.

Exam tip

The Anthoceros capsule L.S. and the Riccia thallus V.S. are the two most-asked bryophyte diagrams after Funaria. Learn the comparison table for "distinguish" questions.

Quick summary

Pteridophytes are the first true vascular plants. They have xylem and phloem but no seeds and no flowers. They are often called "vascular cryptogams" or "seedless vascular plants". The main plant body is the sporophyte. This topic covers characters, classification, stelar types and life cycles of Selaginella, Equisetum and ferns.

Key points

• Pteridophytes (नेचे वनस्पती, ferns and their allies) grow mostly in moist, shady places.
• The plant body is a sporophyte (2n), differentiated into true root, stem and leaves.
• Vascular tissue is present, but xylem has tracheids (no vessels, except a few like Selaginella), and phloem has no companion cells.
• Leaves may be small (microphylls, e.g. Lycopodium, Selaginella, Equisetum) or large (megaphylls, e.g. ferns).
• Spores form in sporangia, often borne on special leaves called sporophylls. Sporophylls may form a compact strobilus (cone).
• Most are homosporous (one kind of spore, e.g. Lycopodium, Equisetum, Pteris). Some are heterosporous (microspores and megaspores, e.g. Selaginella, Marsilea, Salvinia).
• Spores grow into a small, free-living gametophyte called the prothallus.
• Sex organs are antheridia and archegonia; water is needed for fertilisation.
• Heterospory in Selaginella is seen as the first step towards the seed habit.

Important terms

• Stele – central vascular cylinder of stem and root.
• Protostele – solid core of xylem surrounded by phloem (simplest type).
• Siphonostele – stele with a central pith.
• Dictyostele – siphonostele broken into separate strands (meristeles) by leaf gaps (ferns).
• Sorus (sori) – group of sporangia on the underside of fern leaves.
• Indusium – protective flap covering a sorus.
• Ligule – small tongue-like outgrowth at the base of the leaf of Selaginella.
• Rhizophore – leafless, root-producing branch in Selaginella.

Key facts

• Selaginella stem shows trabeculae (radial elongated endodermal cells) holding the stele in an air space.
• Equisetum stem has vallecular canals, carinal canals and a central canal; spores have elaters.
• Young fern leaves are coiled (circinate vernation).

5 important questions

Q1. Why are pteridophytes called vascular cryptogams?

They have vascular tissues (xylem and phloem) but reproduce by spores and not by seeds or flowers. "Cryptogam" means plants with hidden reproduction.

Q2. What is heterospory? Give an example.

Heterospory is the formation of two kinds of spores: small microspores (forming male gametophytes) and large megaspores (forming female gametophytes). Examples: Selaginella, Marsilea.

Q3. Describe the life cycle of Selaginella.

• Sporophyte: creeping stem with four rows of ligulate leaves and rhizophores.
• Strobilus with microsporophylls (microsporangia) and megasporophylls (megasporangium with usually four megaspores).
• Microspore → reduced male gametophyte → antherozoids.
• Megaspore → female gametophyte with archegonia, partly inside the spore wall.
• Fertilisation in water → embryo with suspensor → new sporophyte.
• Diagram labels: strobilus, microsporangium, megasporangium, ligule, rhizophore.

Q4. Explain the types of stele in pteridophytes.

• Protostele: haplostele (Selaginella some species), actinostele, plectostele (Lycopodium).
• Siphonostele: ectophloic (phloem outside) and amphiphloic (phloem both sides).
• Solenostele and dictyostele (ferns).
• Polystele (several steles, Selaginella some species).
• Mention that the stelar theory was given by Van Tieghem and Douliot (1886).

Q5. Write the general characters of pteridophytes.

• Sporophyte dominant; true roots, stem, leaves.
• Xylem with tracheids, phloem without companion cells.
• Sporangia on sporophylls; homosporous or heterosporous.
• Gametophyte (prothallus) small, independent.
• Water needed for fertilisation; embryo formed; no seeds.

Exam tip

Compare bryophytes and pteridophytes in a table: which generation is dominant, vascular tissue, and spore type. Draw the T.S. of Selaginella stem with trabeculae.

Quick summary

Equisetum (horsetail) and Marsilea (water clover) are two pteridophyte type studies. Equisetum is a homosporous plant with jointed, ribbed stems and spores with elaters. Marsilea is an aquatic heterosporous fern whose spores form inside hard bean-like sporocarps. This topic covers their external form, anatomy, reproduction and life cycle.

Key points

• Equisetum (class Sphenopsida) – the only living genus of its group; called "horsetail" or "scouring rush" (silica in the stem).
• Sporophyte has an underground rhizome and aerial stems with clear nodes and internodes. Internodes are ribbed (ridges and furrows).
• Leaves are tiny, scale-like and fused into a sheath at each node; photosynthesis is done mainly by the green stem.
• Stem T.S.: ridges with sclerenchyma, vallecular canals under furrows, carinal canals in vascular bundles (opposite ridges), and a central pith cavity. Stele is an eustele-like siphonostele.
• Sporangia are borne on umbrella-shaped sporangiophores grouped in a terminal strobilus (cone).
• Homosporous: all spores look alike; each spore has 4 hygroscopic elaters (bands from the outer wall) that coil and uncoil with humidity and help dispersal.
• Gametophyte is a small green prothallus; antherozoids are multiflagellate.
• Marsilea (order Salviniales/Marsileales, water fern): creeping rhizome in mud; long-petioled leaves with 4 leaflets (like a clover); shows sleep movements.
• Rhizome T.S.: amphiphloic siphonostele (solenostele), aerenchyma with air chambers in the cortex.
• Sporangia develop inside a hard, bean-shaped sporocarp on a short stalk near the petiole base.
• Heterosporous: microsporangia with many microspores and megasporangia with one megaspore, both in the same sorus. The sporocarp opens in water by a swelling gelatinous ring (sorophore) that carries the sori out.
• Gametophytes are very reduced and develop inside the spore wall (endosporic). Heterospory is seen as a step towards the seed habit.

Important terms

• Sporangiophore – stalked, peltate structure bearing sporangia (Equisetum).
• Elaters – hygroscopic bands on Equisetum spores.
• Sporocarp – hard capsule containing sori in Marsilea.
• Sorophore – gelatinous ring that swells and pulls the sori out of the sporocarp.
• Heterospory – production of two kinds of spores (micro and mega).
• Endosporic development – gametophyte develops inside the spore wall.

Key facts

5 important questions

Q1. What are elaters in Equisetum?

Elaters are four band-like appendages formed from the outer layer of the spore wall. They are hygroscopic: they coil in moist air and uncoil in dry air, helping spores to move and disperse in groups.

Q2. What is a sporocarp?

A sporocarp is a hard, bean-shaped, stalked reproductive body of Marsilea. It contains sori with both microsporangia and megasporangia and can survive drought for many years.

Q3. Describe the anatomy of the aerial stem of Equisetum.

• Ribbed outline; epidermis with silica and stomata in furrows.
• Hypodermal sclerenchyma under ridges; chlorenchyma under furrows.
• Vallecular canals in the cortex; endodermis; vascular bundles with carinal canals.
• Central pith cavity. Labelled T.S. diagram.

Q4. Give an account of reproduction in Marsilea.

• Sporocarp structure; sori on a gelatinous sorophore.
• Germination of sporocarp in water.
• Microspores → male gametophyte with antherozoids; megaspore → female gametophyte with one archegonium.
• Fertilisation in water → embryo → new sporophyte. Draw the sporocarp L.S.

Q5. Write a note on heterospory and seed habit.

• Heterospory in Selaginella and Marsilea.
• Retention of megaspore, endosporic female gametophyte, reduction to one megaspore — steps leading to the seed.
• Compare with gymnosperm ovule.

Exam tip

For Equisetum, remember "carinal canal opposite ridge, vallecular canal opposite furrow". For Marsilea, the sporocarp section and germination in water are favourites.

Quick summary

Gymnosperms are seed plants whose seeds are naked, that is, not enclosed in a fruit. They have no ovary and no flowers. Most are woody trees or shrubs, many of them evergreen conifers. This topic covers their characters, classification, type examples (Cycas, Pinus, Gnetum) and importance.

Key points

• Gymnosperm means "naked seed" (gymnos = naked, sperma = seed). In Marathi, अनावृत्तबीजी वनस्पती.
• Plant body is a sporophyte with root, stem and leaves.
• Ovules are borne openly on megasporophylls (scales); pollen on microsporophylls.
• Sporophylls are usually grouped in cones (strobili): male cones and female cones.
• Xylem has tracheids (vessels absent, except in Gnetales); phloem has no companion cells.
• Pollination is by wind (anemophily). Pollen lands directly on the ovule at the micropyle (pollination drop).
• Female gametophyte (endosperm) is formed before fertilisation and is haploid (n).
• Polyembryony (more than one embryo in a seed) is common.
• No double fertilisation; no fruit formation.
• Cycas has motile, multiflagellate sperms – among the largest sperms in plants.

Important terms

• Coralloid roots – coral-like, upward growing roots of Cycas containing blue-green algae (Anabaena, Nostoc).
• Megasporophyll – leaf-like structure bearing ovules.
• Nucellus – tissue inside the ovule where the megaspore forms.
• Integument – protective covering of the ovule.
• Archegonial chamber – space above archegonia where fertilisation happens (Cycas).
• Winged pollen – pollen of Pinus with two air sacs for wind dispersal.
• Dwarf shoot – short shoot of Pinus bearing needles (needle-like leaves).

Key facts

• Cycas is dioecious; female plant bears loose megasporophylls (no compact female cone).
• Pinus is monoecious; the seed takes about two years from pollination to maturity.
• Ephedra gives ephedrine (used for asthma); Pinus gives turpentine and resin; Taxus gives taxol (anti-cancer).

5 important questions

Q1. Why are gymnosperms called naked-seeded plants?

Their ovules lie exposed on megasporophylls and are not enclosed in an ovary. After fertilisation the seeds remain uncovered, as no fruit is formed.

Q2. What are coralloid roots?

Coralloid roots are short, branched, upward-growing roots of Cycas that look like coral. They contain nitrogen-fixing blue-green algae such as Anabaena in their cortex.

Q3. Describe the structure of the ovule of Cycas.

• Large, orthotropous ovule with a single thick integument.
• Integument has three layers: outer fleshy, middle stony, inner fleshy.
• Nucellus with a beak and pollen chamber at the top.
• Female gametophyte (endosperm) with archegonia at the micropylar end.
• Labels: micropyle, integument, nucellus, pollen chamber, archegonium, female gametophyte.

Q4. Give the general characters of gymnosperms.

• Woody perennial plants, mostly evergreen.
• Naked ovules on sporophylls; cones present.
• Tracheids in xylem; no companion cells.
• Wind pollination; haploid endosperm formed before fertilisation.
• No fruit; polyembryony common.

Q5. Write the economic importance of gymnosperms.

• Timber: Pinus, Cedrus, Abies (soft wood).
• Resin and turpentine from Pinus; Canada balsam from Abies.
• Food: sago from Cycas pith; edible seeds of Pinus gerardiana (chilgoza).
• Medicines: ephedrine, taxol.
• Ornamental plants: Cycas, Thuja, Araucaria.

Exam tip

Remember three unique points: haploid endosperm, naked seeds, and no fruit. Draw the L.S. of the Cycas ovule neatly.

Quick summary

Morphology is the study of the external form of plants. This topic covers the normal form and functions of the root, stem and leaf of angiosperms and their modifications for storage, support, protection and other special jobs. It is a base for taxonomy and for identifying plants in the practical exam.

Key points

• Root – develops from the radicle, grows down, has no nodes, buds or leaves, and has a root cap.
• Tap root system (dicots: mustard, gram) and fibrous root system (monocots: wheat, rice). Roots growing from any part other than the radicle are adventitious.
• Storage: conical (carrot), fusiform (radish), napiform (beet, turnip); tuberous adventitious roots (sweet potato).
• Support: prop roots (banyan), stilt roots (maize, sugarcane).
• Respiration: pneumatophores (Rhizophora, mangroves).
• Others: epiphytic roots with velamen (orchids), haustoria (Cuscuta), nodules (legumes).
• Root modifications:
• Stem – develops from the plumule; has nodes, internodes and buds; bears leaves, flowers and fruits.
• Underground stem modifications (have nodes and buds): tuber (potato), rhizome (ginger, turmeric), corm (Colocasia, Amorphophallus), bulb (onion).
• Sub-aerial: runner (grass, Oxalis), stolon (strawberry), offset (Pistia, water hyacinth), sucker (mint, chrysanthemum).
• Aerial: stem tendril (grapevine, passion flower), thorn (Bougainvillea, citrus), phylloclade (Opuntia), cladode (Asparagus), bulbils.
• Leaf – lateral, flat outgrowth of the stem at a node with an axillary bud. Parts: leaf base, petiole, lamina; stipules may be present.
• Venation: reticulate (dicots) and parallel (monocots). Leaves are simple or compound (pinnate – neem; palmate – silk cotton).
• Phyllotaxy: alternate (hibiscus), opposite (guava, Calotropis), whorled (Alstonia).
• Leaf modifications: leaf tendril (pea), spines (Opuntia, Aloe margins), phyllode (Australian Acacia), pitcher (Nepenthes), fleshy scale leaves (onion).

Important terms

• Adventitious root – root arising from stem, leaf or any part other than the radicle.
• Velamen – spongy water-absorbing tissue on orchid aerial roots.
• Phylloclade – flattened green stem of many internodes that does the leaf's work.
• Phyllode – flattened green petiole working as a leaf.
• Phyllotaxy – arrangement of leaves on the stem.

Key facts

5 important questions

Q1. Why is the potato a stem and not a root?

Because the potato has "eyes" which are nodes with axillary buds, and scale leaves. Roots never have nodes or buds.

Q2. What are pneumatophores?

Negatively geotropic, aerial roots of mangrove plants growing in marshy saline soil. They have pores (lenticels) through which air reaches the submerged roots.

Q3. Describe the modifications of roots with examples.

Group into storage, support, respiration and special functions; give at least eight examples with labelled sketches of carrot, banyan prop roots and pneumatophores.

Q4. Describe underground modifications of stem.

• Tuber, rhizome, corm, bulb – structure, how each shows stem characters, examples.
• Role in storage and vegetative propagation. Add sketches.

Q5. Explain the modifications of leaves.

• Tendrils, spines, phyllodes, pitchers, bladders (Utricularia), scale leaves.
• One line on how each helps the plant; sketches of pea tendril and Nepenthes pitcher.

Exam tip

In "identify and give reasons" practicals, always name the organ, the modification and one proof (nodes, buds, position). The table above is a quick revision sheet.

Quick summary

The cell is the basic unit of life. A plant cell is a eukaryotic cell with a rigid cell wall, large vacuole and plastids. This topic covers the cell theory, the ultrastructure of the plant cell as seen under the electron microscope, the structure and functions of each organelle, and the fluid mosaic model of the plasma membrane.

Key points

• Cell theory: Schleiden (1838, plants) and Schwann (1839, animals); Virchow (1855) added omnis cellula e cellula – every cell comes from a pre-existing cell.
• Cell wall: primary wall (cellulose, hemicellulose, pectin), secondary wall (cellulose with lignin) and middle lamella (calcium pectate) between cells. Plasmodesmata connect neighbouring cells.
• Plasma membrane: fluid mosaic model (Singer and Nicolson, 1972) – a phospholipid bilayer with proteins floating in it; selectively permeable.
• Nucleus: double nuclear envelope with pores, nucleoplasm, chromatin and nucleolus (rRNA synthesis, ribosome assembly).
• Mitochondria: double membrane; inner membrane folded into cristae with F₀–F₁ particles; matrix has its own circular DNA and 70S ribosomes. Site of aerobic respiration (Krebs cycle, ETS) – "powerhouse of the cell".
• Chloroplast: double envelope, stroma and thylakoids stacked into grana; light reactions in thylakoids, Calvin cycle in stroma; own DNA and 70S ribosomes.
• Mitochondria and chloroplasts are semi-autonomous; the endosymbiotic theory says they came from ancient bacteria.
• Endoplasmic reticulum: rough ER (with ribosomes, protein synthesis) and smooth ER (lipid synthesis).
• Golgi apparatus (dictyosomes in plants): packages and modifies proteins; forms the cell plate during cytokinesis and makes wall polysaccharides.
• Ribosomes: 80S in cytoplasm (60S + 40S); 70S in plastids and mitochondria; site of protein synthesis.
• Vacuole: large central sac surrounded by tonoplast; holds cell sap, keeps turgor.
• Microbodies: peroxisomes (photorespiration) and glyoxysomes (fat to sugar in oily seeds).

Important terms

• Plasmodesmata – cytoplasmic channels through cell walls joining adjacent cells.
• Cristae – folds of the inner mitochondrial membrane.
• Granum – stack of thylakoids in a chloroplast.
• Tonoplast – membrane around the vacuole.
• Semi-autonomous organelle – organelle with its own DNA and ribosomes that can divide on its own.

Key facts

5 important questions

Q1. Why are mitochondria and chloroplasts called semi-autonomous?

Because they have their own circular DNA, 70S ribosomes and can make some of their own proteins and divide by fission, but they still depend on nuclear genes for most proteins.

Q2. What is the middle lamella?

It is the thin cementing layer, mainly of calcium and magnesium pectate, that holds the walls of two neighbouring plant cells together.

Q3. Describe the fluid mosaic model of the plasma membrane.

• Proposed by Singer and Nicolson (1972).
• Phospholipid bilayer with hydrophilic heads outside, hydrophobic tails inside.
• Integral and peripheral proteins; glycoproteins and glycolipids on the surface.
• "Fluid": lipids and proteins move sideways. Labelled diagram; functions of the membrane.

Q4. Give the ultrastructure and functions of the chloroplast.

• Outer and inner membranes, stroma, thylakoids, grana and stroma lamellae.
• Pigments and photosystems in thylakoids; enzymes of Calvin cycle in stroma.
• DNA, ribosomes, starch grains, plastoglobuli. Labelled diagram.

Q5. Draw and describe the ultrastructure of a plant cell.

Label wall, plasma membrane, nucleus, nucleolus, ER, Golgi, mitochondria, chloroplast, ribosomes, vacuole and tonoplast, peroxisome; one-line function of each.

Exam tip

Practise the labelled ultrastructure diagrams of the plant cell, mitochondrion and chloroplast. Remember: 80S in cytoplasm, 70S in organelles.

Quick summary

Cells multiply by cell division. Mitosis gives two daughter cells with the same chromosome number as the parent and is used for growth and repair. Meiosis halves the chromosome number and produces variation; it happens during spore or gamete formation. This topic covers the cell cycle, the stages of mitosis and meiosis, and their importance.

Key points

• Cell cycle = interphase (G₁, S, G₂) + M phase (karyokinesis + cytokinesis). DNA doubles in the S phase. Non-dividing cells rest in G₀.
• Mitosis (equational division) occurs in meristems – root tip and shoot tip.
• Prophase: chromatin condenses into chromosomes, each with two sister chromatids; nucleolus and nuclear envelope disappear; spindle forms.
• Metaphase: chromosomes line up at the equatorial (metaphase) plate; spindle fibres attach at kinetochores. Best stage to count and study chromosomes.
• Anaphase: centromeres split; sister chromatids move to opposite poles.
• Telophase: chromosomes reach poles and uncoil; nuclear envelope and nucleolus reappear.
• Cytokinesis in plants is by cell plate formation (from Golgi vesicles), growing from the centre outwards; in animals by furrowing.
• Meiosis (reductional division) happens in spore mother cells (anthers and ovules) – one DNA doubling, two divisions, four haploid cells.
• Prophase I has five sub-stages: leptotene (thin threads), zygotene (pairing of homologues = synapsis, synaptonemal complex), pachytene (bivalents/tetrads; crossing over), diplotene (homologues separate except at chiasmata), diakinesis (terminalisation of chiasmata).
• Anaphase I separates homologous chromosomes (not chromatids) – this halves the number.
• Meiosis II is like mitosis: sister chromatids separate.
• Importance: mitosis keeps chromosome number constant; meiosis keeps the number constant across generations and creates variation by crossing over and independent assortment.

Important terms

• Chromatid – one of the two identical halves of a duplicated chromosome.
• Bivalent / tetrad – a pair of homologous chromosomes (four chromatids) in prophase I.
• Chiasma – X-shaped point where non-sister chromatids crossed over.
• Synapsis – pairing of homologous chromosomes in zygotene.
• Cell plate – partition formed between daughter nuclei in plant cytokinesis.

Key facts

5 important questions

Q1. What is a chiasma?

A chiasma is the X-shaped point of contact between non-sister chromatids of homologous chromosomes, seen in diplotene. It marks the place where crossing over has occurred.

Q2. Why is meiosis called reductional division?

Because the chromosome number is halved: a diploid (2n) cell forms four haploid (n) cells, since homologous chromosomes separate in anaphase I.

Q3. Describe the stages of mitosis with diagrams.

• Prophase, metaphase, anaphase, telophase – main events of each.
• Cytokinesis by cell plate.
• Diagrams from an onion root tip squash.
• Significance of mitosis.

Q4. Describe prophase I of meiosis.

• Leptotene, zygotene, pachytene, diplotene, diakinesis – events and diagrams.
• Synaptonemal complex, recombination nodules, chiasma formation and terminalisation.

Q5. Give the significance of meiosis and distinguish it from mitosis.

• Constant chromosome number across generations; variation; basis of evolution and plant breeding.
• Use the comparison table above.

Exam tip

Remember the order of prophase I with "Little Zebras Play During Days" (leptotene, zygotene, pachytene, diplotene, diakinesis). Onion root tip is the standard slide for mitosis; onion/Tradescantia flower bud for meiosis.

Quick summary

A tissue is a group of cells with a common origin and similar function. Plant tissues are of two main types: meristematic (dividing) and permanent (non-dividing). Permanent tissues are simple or complex. This topic also covers tissue systems and the anatomy of root, stem and leaf.

Key points

• The word "tissue" was coined by N. Grew. Tissue is ऊती in Marathi.
• Meristematic tissue: small, living cells with dense cytoplasm, large nucleus, thin cellulose walls, no intercellular spaces; they keep dividing.
• By position, meristems are apical (root and shoot tips; increase length), intercalary (base of internodes, e.g. grasses) and lateral (vascular cambium and cork cambium; increase girth).
• By origin: primary meristems (from embryo) and secondary meristems (from permanent tissue, e.g. cork cambium).
• Simple permanent tissues have one type of cell: parenchyma, collenchyma and sclerenchyma.
• Complex permanent tissues have more than one type of cell: xylem and phloem.
• Xylem conducts water and minerals; elements: tracheids, vessels, xylem parenchyma, xylem fibres.
• Phloem conducts food; elements: sieve tubes, companion cells, phloem parenchyma, phloem fibres.
• Only xylem parenchyma is living in xylem; only phloem fibres are dead in phloem.
• Three tissue systems (Sachs): epidermal, ground and vascular tissue systems.

Important terms

• Parenchyma – living, thin-walled cells; storage, photosynthesis (chlorenchyma), buoyancy (aerenchyma).
• Collenchyma – living cells thickened at corners with cellulose and pectin; gives flexibility (e.g. hypodermis of dicot stem).
• Sclerenchyma – dead cells with lignified walls; fibres and sclereids (stone cells in pear).
• Tracheid – long, dead, lignified cell with tapering ends.
• Vessel – tube formed of cells joined end to end with dissolved end walls.
• Sieve plate – perforated end wall of a sieve tube.
• Casparian strip – band of suberin on the radial walls of endodermal cells.
• Bulliform cells – large cells in the upper epidermis of grass leaves; help leaf rolling.

Key facts

• Root: radial vascular bundles; exarch xylem. Dicot root usually 2–4 (up to 6) xylem bundles; monocot root many (more than 6) xylem bundles with a large pith.
• Stem: endarch xylem (protoxylem towards centre).
• Dicot leaf: dorsiventral; palisade and spongy mesophyll. Monocot leaf: isobilateral; only spongy mesophyll.

5 important questions

Q1. Define meristem and give its types by position.

A meristem is a group of actively dividing cells. By position it is apical (tips of root and shoot), intercalary (base of internodes) and lateral (cambium, increasing girth).

Q2. Differentiate between collenchyma and sclerenchyma.

Collenchyma is living and thickened at corners with cellulose and pectin; it gives flexible support. Sclerenchyma is dead, with uniform lignified walls; it gives rigid strength.

Q3. Describe xylem with its elements.

• Complex tissue conducting water and minerals upward; also gives support.
• Tracheids: dead, elongated, lignified, with pits.
• Vessels: dead, tube-like; main conducting element in angiosperms.
• Xylem parenchyma: living; stores food; radial conduction.
• Xylem fibres: dead; mechanical support.
• Protoxylem forms first, metaxylem later.

Q4. Describe the internal structure of a dicot stem with a labelled diagram.

• Epidermis with cuticle and multicellular hairs.
• Cortex: collenchymatous hypodermis, parenchyma, endodermis (starch sheath).
• Pericycle of sclerenchyma patches.
• Vascular bundles in a ring: conjoint, collateral, open, endarch.
• Large parenchymatous pith and medullary rays.
• Labels: cuticle, epidermis, hypodermis, cortex, endodermis, pericycle, phloem, cambium, xylem, pith.

Q5. Compare the anatomy of dicot and monocot root.

• Xylem bundles: dicot 2–6; monocot many.
• Pith: absent or small in dicot; large in monocot.
• Secondary growth: present in dicot; absent in monocot.
• Both have epiblema with root hairs, cortex, endodermis with Casparian strips, pericycle, radial bundles, exarch xylem.

Exam tip

Diagrams carry many marks here. Practise T.S. of dicot stem, monocot stem, dicot root and dicot leaf with all labels.