Botany Overview

Botany

The study of different types of trees & plants is called Botany.
Theophrastus is called the father of Botany.
Aristotle is known as father of biology.

In the year 1883, Eicher classified the botanical world as under:

1. Cryptogamous Plants (Non-flowering plants)

• These plants do not have flowers or seeds.

• They are classified into the following groups:

A. Thallophyta

• This is the largest group of the plant kingdom.

• The body of plants of this group is thallus-like, i.e., the plant is not differentiated into root, stem, and leaves.

• It is the lowermost group of the plant kingdom.

• There is no conducting tissue.

• It is divided into two groups:

  1. Algae

  2. Fungi

a. Algae

• Study of algae is called Phycology.

• Algae normally have chlorophyll and autotrophic mode of nutrition.

• Its body is thallus-like and may be unicellular, colonial, or filamentous.

• Classification of algae is based on nature of pigment.

Useful Algae:

1. As a food: Porphyra, Ulva, Sargassum, Laminaria, Nostoc etc.

2. In making Iodine: Laminaria, Fucus, Echlonia etc.

3. As manure: Nostoc, Anabana, Kelp etc.

4. In making medicines: Antibiotic Chlorelline from Chlorella and Tincher iodine is made from Laminaria.

5. In research works: Chlorella, Acetabularia, Belonia etc.

• Spirogyra is commonly known as ‘Pond Silk’.

• Note: An astronaut can get protein food, water, and oxygen by sowing Chlorella algae in the tank of the aircraft, so Chlorella is known as space algae.

• Agar is prepared from algae like Gelidium and Gracilaria. It is used to grow microbes and in preparation of ice creams and jelly.

b. Fungi

• Study of fungi is called Mycology.

• Organisms of this group may be unicellular or multicellular.

• Fungi is without chlorophyll, central carrier tissue less, Thallophyta.

• Accumulated food in fungi remains as Glycogen.

• Its cell wall is made up of chitin. Examples: Albugo, Phytophtora, Mucor, Yeast etc.

• Fungi may create serious diseases in plants. Most of the damage is caused by rust and smut.

Main Fungal diseases in plants:

• White rust of crucifer

• Loose smut of wheat

• Rust of wheat

• Early Blight of potato

• Red rot of sugarcane

• Tikka disease of groundnut

• Wart disease of potato

• Brown leaf spot of rice

• Late blight of potato

• Damping off of seedlings etc.

• Rhizopus is a fungi commonly known as ‘bread mould’.

• Heterothallism in fungi was discovered by AF Blakelee.

• Lichens are the association of algae and fungi.

• Lichens developing on rocky substrates are called saxicolous.

• Lichens are the first organisms which colonise bare rock.

• Yeast is unicellular fungi, reproduces through budding.

• The sexual reproductive organ of Aspergillus are antheridium and ascogonium.

B. Bryophyta

• This is the first group of land plants. Approximately 25,000 species are included.

• In bryophyta there is lack of xylem and phloem tissue.

• Plant body may be thallus-like or leafy erect structure as in moss.

• They lack true roots, stem, and leaves.

• This community is also called Amphibian category of the plant kingdom.

• Water conduction takes place in mosses through parenchyma.

• The moss namely Sphagnum is capable of soaking water 18 times its own weight. Therefore, gardeners use it to protect plants from drying while transferring.

• Uses of Sphagnum moss:

  1. As fuel

  2. As antiseptic

C. Pteridophyta

• Plants of this group are mostly found in wet shady places, forests, and mountains.

• The body of plants is differentiated into root, stem, and leaves. Stem remains as normal rhizome.

• Reproduction occurs by spores produced inside the sporangia.

• Sporangia-bearing leaf of a fern is called ‘Sorus’.

• Gametophytic phase is short-lived. The diploid zygote develops into an embryo.

• Gametophyte is called prothallus in pteridophytes.

• Plants of this community have conducting tissues, but xylem does not contain vessels and phloem does not contain companion cells.

Examples: Ferns, Azolla, Pteridium, Lycopodium etc.

• In the neck cell of archegonium of fern, one binucleated cell is present.

• Mosses (Bryophytes) and ferns (Pteridophytes) are called amphibians of the plant kingdom.

• Examples: Marsileo, Fern, and Horse tail.

• Fern and fern allies belong to the kingdom Pteridophyta.

2. Phanerogamous (Flowering Plant)

Plants of this group are well developed. All the plants in this group bear flower, fruit, and seed. Plants of this group can be classified into two sub-groups – Gymnosperm and Angiosperm.

A. Gymnosperm (Naked Seed)

These plants are in the forms of trees and bushes. Plant body is differentiated into root, stem & leaves.

• Plants are woody, perennial, and tall.

• Plant bears naked seed.

• Its tap roots are well developed.

• Pollination takes place through air.

• The longest plant of the Plant kingdom, Sequoia gigentia, comes under it. Its height is 120 meters. This is also called Red Wood of California.

• The smallest plant is Zaimia Pygmia.

• Living fossils of plant are Cycas, Ginkgo biloba, and Metasequoia.

• Ginkgo bioba is also called Maiden hair tree.

• Ovule and antherozoids of Cycas are the largest in Plant kingdom.

• Corolloid root of Cycas helps in absorption of water and fixation of nitrogen.

• The pollen grains of Pinus are so much in number that later it turns into Sulphur showers.

Importance of Gymnosperm

1. As a food – Sago is made by extracting the juice from the stems of Cycas. Therefore, Cycas is called Sago-palm.

2. Wood – The wood of Pine, Sequoia, Deodar, Spruce, etc., is used for making furniture.

3. Vapour oil – We get Tarpin oil from the trees of Pine, Cedrus oil from Deodar tree, and Cedcast oil from Juniperous wood.

4. Tannin – It is useful in tanning and making ink.

5. Resin – Resin is extracted from some conical plants which are used in making varnish, polish, paint, etc. Resin is the product of coniferous tree.

6. Best example of polyembryony – Citrus fruit.

B. Angiosperm (Covered Seed)

In the plants of this sub-group, seeds are found inside the fruits (Concealed Seeds).

• In these plants, root, leaves, flowers, fruits, and seeds are fully developed.

• Plants of this sub-group have seed-coat in seeds.

• On the basis of number of cotyledons, plants are divided into two categories –

  1. Monocotyledon

  2. Dicotyledon

a. Monocotyledon Plants

Those plants which have only one cotyledon in seed.

b. Dicotyledon Plants

Those plants which have two cotyledons in its seed are called dicotyledons.

Additional Information About Angiosperms

• Leaves are the lung of plant.

• Plant from which coca and chocolate are obtained is a shrub.

• Banana is a shrub.

• Trochodendron is a vesselless angiosperm.

• Pulses are obtained from the family Leguminacae.

• From the bark of cinchona, a drug quinine is obtained, used in malaria fever.

• Chloroplast found in sugarcane plant shows dimorphism.

• The maximum fixation of solar energy is done by green plant.

• Golden rice contains B-carotene gene which comes from carrot. It is a variety of rice produced by genetic engineering to biosynthesize B-carotene, a precursor of vitamin A.

• Potato, Tomato, and Brinjal are three different species but all belong to genus Solonum.

• Alphanso is a mango variety which is mostly exported from India.

• The botanical name of macroni wheat is Triticum durum.

• Chopping of an onion makes one cry because of the chemical containing sulphur.

• Maize – Potato – Sugarcane – Moong is the example of crop rotation for two years.

• First herbicide produced in the world is 2, 4-D.

• World's most problematic aquatic weed is Eichhornia crassipes, also known as ‘Terror of Bengal’.

• An artificial method of asexual reproduction, used to produce plant, combining desired stem with favorable root characteristics, is Grafting.

• Water passes from soil into the root by a physical process called osmosis.

• Insectivorous plants grow in soil deficient in nitrogen.

• Pneumatophores are specialized in hydrophytes.

• Drosera is a carnivorous plant.

• Demon grass is used in preparing a natural mosquito repellent.

Scientific Names of Common Plants

Virus

Definition

Study of virus is called virology.

Discovery

Virus was discovered by Russian scientist Ivanovsky in the year 1892 (During the tests of Mosaic disease in tobacco).

In nature, there are ultra microscopic particles known as viruses.
It has both the characters of living and non-living, so it is a connecting link between living & non-living.

Dr. Stanley first isolated the virus causing mosaic disease in tobacco in the form of crystals.

Characteristics of Virus

• Virus is made up of nucleic acid and protein.

• They become active inside living cells or host cells.

• Nucleic acids replicate themselves and reproduce rapidly.

• They cause disease like bacteria & fungi.

Types of Virus (According to Parasitic Nature)

1. Plant Virus – RNA is present as nucleic acid in 75% of plant viruses. Some have DNA as nucleic material.

2. Animal Virus – DNA or sometimes RNA is found in it.

3. Bacteriophage – A virus that infects and replicates within bacteria. They kill the bacteria. Example – T-2 phage. Bacteriophages are composed of nucleic acid molecules surrounded by a protein sheath.

Diseases Caused by Viruses

• In humans, viruses cause diseases like mumps, chicken pox, hepatitis, polio, AIDs, Herpes etc.

• HIV often changes its structure due to the presence of an enzyme reverse transcriptase.

• The enzyme integrase produced by virus allows the integration of HIV-DNA into the host cell DNA.

• EBOLA is a virus that causes ebola fever. Fruit bats are the natural host of the virus, first outbreak in West Africa.

Note: Those viruses in which RNA is found as genetic material are called Retrovirus.

Additional Facts About Virus

• Viruses are parasites which need living cells to reproduce. Outside host, they are similar to chemical substances.

• Virus have no enzyme of their own.

• Many plant and vertebrate animals produce an antiviral substance which inhibits the multiplication of virus called interferon.

• Water of holy Ganga river is pure due to the presence of Bacteriophages.

• The term ACE-2 is talked about in the context of the spread of viral disease.

• Virus cannot be cultured in artificial synthetic medium.

Bacteria

Discovery and History

• It was discovered by Antony Von Leeuwenhook of Holland in the year 1683.

• Leeuwenhook is called the father of Bacteriology.

• In the year 1829 Ehrenberg called it bacteria.

• The year 1843-1892 – Robert Koch discovered the bacteria of Tuberculosis diseases.

• The year 1812-1892 – Louis Pasteur discovered the vaccine of Rabies and pasteurization of milk.

Classification Based on Shape

1. Bacillus: This is rod-like or cylindrical.

2. Round or Cocus: These are round and the smallest bacteria.

3. Comma shaper or Vibrio: Like the English sign (,), example – Vibrio cholera etc.

4. Spirillum: Spring or screw shaped.

Nitrogen-Fixing Bacteria

• Some species of Azotobacter, Azospirillum and Clostridium bacteria live freely in the soil and fix atmospheric nitrogen into the nitrogenous compound.

• The Bacteria capable of converting nitrite to nitrate is Nitrosomonas.

• Anabaena and Nostoc Cynobacteria fix atmospheric nitrogen into soil.

• The species of Rhizobium like Bradyrhizobium bacteria live in the roots of the Leguminous plants capable of converting atmospheric nitrogen into its compound.

  • Example – Peas, Pegion Peas, Gram etc.

• Rhizobium are called symbiotic bacteria.

Harmful Effects

• The harmful substances produced by the microbes are known as Toxins.

Milk Preservation – Pasteurization

• Note: To preserve the milk for many days pasteurization is done.

• There are two methods of pasteurization:

  1. Low Temperature Holding Method (LTH): Milk is boiled at 62.8 degree Celsius for 30 minutes.

  2. High Temperature Short Time Method (HTSt): Milk is boiled at 71.7 degree Celsius for 15 seconds.

Industrial and Commercial Uses

• In leather industry, separation of hair and fat from leather is done by bacteria. This is called tanning of leather.

• Pickles and syrup are kept in salt or in dense liquid of sugar so that in case of bacterial attack bacteria are plasmolysed and destroyed. Therefore, pickles do not get spoiled soon and can be preserved for long time.

• Citrus fruit and pickles are not stored in iron container because it contain organic acid.

• In the cold storage objects are kept at low temperature (-10 degree Celsius to -18 degree Celsius).

Special Bacteria and Discoveries

• Mycoplasma: Smallest known prokaryotic cell causing pleuropneumonia. It is also known as PPLO.

• Waksman got the noble prize for the discovery of antibiotic streptomycin.

• Alexander Fleming discovered first antibiotic - Penicillin.

• Xenobiotics are inherently resistant to microbial attack are called recalcitrant.

• Microbial type culture collection centre is situated at Chandigarh.

• Honey has high concentration of sugar, does not decay because bacteria cannot survive in a solution of high osmotic strength as water is drawn out.

Industrial and Agricultural Applications

• Bacteria are useful for commercial as well as industrial application like fermentation, production of other bioactive molecules.

• Bacterial decomposition of biological material under anaerobic condition is called composting.

• The most extensive use of molasses after fermentation is for producing ethanol.

• Among fungi, virus, bacteria and protozoa the phototrophic nutrition is only found in Bacteria.

Bacterial Characteristics

• Bacteria having flagella all over the body is known as peritrichous.

• Legumes fix nitrogen only through the specialized bacteria that live in their roots nodules.

• Nitrifying bacteria like Nitrosomonas and Nitrobactar convert ammonia or ammonium compounds into nitrates.

• Bacterial genome contains DNA without histone.

• Escherichia coli commonly lives in animal and human intestine.

• In bacteria plasmid is extra-chromosomal DNA.

Antibiotics and Bioactive Molecules

• The most important bacteria which produce maximum number of antibiotics is Streptomyces.

• Antibiotics are the chemical substance produced by living microorganism capable of inhibiting or destroying other microbes.

• Cyanobacteria help farmers by reducing the acidity of soil.

Final Thoughts

Botany is the scientific study of plants, including trees, herbs, and algae, with Theophrastus recognized as its father. The plant kingdom is classified into Cryptogamous (non-flowering) and Phanerogamous (flowering) plants. Cryptogams include Thallophyta, Bryophyta, and Pteridophyta, which reproduce via spores and lack flowers or seeds.

Algae, like Chlorella and Spirogyra, are used for food, medicine, and research, while fungi, such as yeast and Rhizopus, play roles in disease and industrial applications. Flowering plants include Gymnosperms with naked seeds, like Cycas, and Angiosperms with covered seeds, divided into monocots and dicots.

Viruses, discovered by Ivanovsky, are microscopic parasites, and bacteria, identified by Leeuwenhoek, have both beneficial roles in nitrogen fixation and harmful effects via toxins.