KINGDOM – MYCOTA FUNGI
- Mycology – Study of fungi
- Father of Mycology – Micheli → book: Nova plantarum genera.
- Father of modern mycology – De Bary.
- Father of Indian mycology – B.B. Mundker / E.J. Butler.
- Fungi name given by – Gaspard Bauhin
Fungi are found mostly in humus rich soil. But in the presence of moisture, these can grow on leather, wood, pickle and bread. Some fungi live parasitically in plants, animals and human body. Chloroplast is absent in fungi, so fungi are heterotrophs. Fungi obtain their own food from dead organic matter or living organisms.
EUMYCOTA OR TRUE FUNGI
On the basis of source of food, fungi are of two types:
- Saprophytic - These fungi obtain their own food from dead organic matter such as bread, rotten fruit, vegetable and dung. Nutrition is an absorptive type in saprophytic fungi.
- Parasitic - These obtain their own food from living organism such as plants, animals, and human beings. They obtain nutrition with the help of haustoria.
(i)- Some fungi are found symbiotically associated with algae and form lichens. Some fungi are found symbiotically in the roots of higher plants and form mycorrhiza.
(ii)- The body of fungi is called mycelium. Mycelium is composed of filaments called hypha. (Hypha – plural → Hyphae)
(iii)- Cell wall is present around fungi, which is made up of chitin or fungal cellulose. Some quantity of proteins, lipids & cellulose is also present within chitin.
Note: Cell wall of the members of class-oomycetes is mainly made up of cellulose. In fungi the stored food remains in the form of glycogen and oil.
HETEROTHALLIC AND HOMOTHALLIC SPECIES
1. Heterothallic species - Those species in which fertilization takes place between two genetically different gametes are called as heterothallic species. And this phenomenon is known as heterothallism. In heterothallic condition, the fertilizing gametes are formed on different thallus (mycelium).
Example: Mucor, Rhizopus, Puccinia & Maximum fungi
2. Homothallic species - Those species in which fertilization takes place between two genetically similar gametes are called as homothallic species. And this phenomenon is known as Homothallism. In Homothallic condition, the fertilizing gametes are formed on same thallus.
In fungi, reproduction is of three types:
1. Vegetative reproduction
(a) Fragmentation - Some-times the fungal filament (mycelium) breaks into small pieces due to some reason. Now these pieces form a new fungal filament and starts working like normal filament.
Fig: Fragmentation in Spirogyra
(b) Budding - Sometimes a bud like protuberance is formed in non–mycelial fungus. Now this bud separates from the mother fungi and functions as young fungi. At the time of bud formation the nucleus of mother cell divides mitotically (or amitotically - in yeast) into two daughter nuclei. Out of these two nuclei, one remains within the mother cell while the other migrates to the bud.
(c) Fission - Sometimes the fungal cell divides into two parts along with the nucleus. Now the nuclei go to both cells and each cell starts working as a new cell.
Fig: Process of Fission
Note: Reproduction through bud formation and fission takes place only in non-mycelial form.
2. Asexual reproduction - Asexual reproduction takes place by the formation of different types of spores. These spores are formed by mitotic division.
Spores are of the following types
- They are formed in sporangia.
- Sporangia are formed at the tip of the fungal filament.
- Those fungal filaments on which sporangia are formed are called as sporangiophore. Numerous spores (sporangiospores) are present in the sporangia, that comes out by rupturing of sporangia and germinate to form fungal filaments. The formation of sporangiospores takes place endogenously.
Sporangiospores are of two types:
- Zoospore - When the sporangiospores formed in sporangia are flagellated and motile, then they are called as zoospores. In this condition the sporangia are called as zoosporangia.
- Aplanospore - When sporangiospores are non-flagellated and non-motile then they are called aplanospores.
(b) Conidia - The formation of conidia takes place exogenously. These conidia are formed at the tip of conidiophores
- Conidiophore - Straight fungal filament on which conidia are formed are called conidiophore. Conidiophore may be unbranched, branched, septate or aseptate.
- Conidia - Conidia are formed singly or in chain. Each conidium forms fungal filament (mycelium) by germination.
3. Sexual Reproduction - The structure in which gametes are formed are called gametangia.
Sexual reproduction in fungi completes in three steps:
- Plasmogamy - This is the first stage of sexual reproduction. In this stage, two sex cells fuse with each other but their nuclei do not fuse, due to which a single cell has two nuclei. This binucleate or dikaryotic stage is called dikaryon.
- Karyogamy - In this stage, the nuclei present in the cell fuse with each other, to form a diploid nucleus. This process of formation of a nucleus by the fusion of two pre-existing nuclei is - known as synkaryon.
- Meiosis - In this stage, meiosis takes place in the diploid nucleus due to which again haploid nuclei or haploid cells are formed.
METHODS OF SEXUAL REPRODUCTION
1. Planogametic Copulation
- In this process entire hypha starts working as a sex cell i.e. whole cell starts working as gametangia. Each nucleus of gametangia behaves like gametes.
- After that the gametangia ruptures and its nuclei (gametes) become free.
- Now these gametes fuse with each other to form zygote followed by a
- meiotic division in the zygote. As a result of which haploid spores are formed. Each spore germinates and gives rise to a new mycelium.
2. Gametangial Contact
- In this process, first of all male and female sex organs are formed on two different hyphae of the same mycelium. Male sex organ is called antheridium and female sex organ is called oogonium.
- Mature antheridium & oogonium have one nucleus each. Antheridium and oogonium come close to each other and a fertilizing tube comes out from antheridium and enters the oogonium. The nucleus of antheridium goes to the oogonium through this tube and fuse with its nucleus. As a result of which a diploid zygote known as oospore is formed.
- Now meiotic division takes place in the nucleus of oospore, as a result of which haploid spores are formed. Now each spore germinates and gives rise to a new mycelium.
3. Gametangial copulation
- In this process, gametangia are formed on two different mycelia.
- First of all, a part of hypha becomes swollen and form gametangia. Both the gametangia have many nuclei. These gametangia fuse with each other to form known as zygospore.
- Meiotic division takes place in zygospore, as a result of which haploid spores are formed. Each spore germinates and gives rise to a mycelium.
4. Spermatization - In this process spermatia or pycniospores are formed.
5. Somatogamy -In it, no sex organs are formed. In this process two mycelia come close to each other and get fused.
All the fungi included in this class are called as lower fungi.
Mycelium - The fungal filament (mycelium) of all the fungi included in this class are coenocytic and aseptate. This type of filament is known as acellular coenocytic.
Note: The myceliums of these four classes are same in structure i.e. coenocytic & aseptate. But they are dissimilar on the basis of sexual reproduction.
Alexopolus was a mycologist who did not consider phycomycetes as a class. He dissolved phycomycetes into six different classes out of which four main classes are given below:
- Asexual reproduction – By sporangiospore (Zoospores)
- Sexual reproduction – By Planogametic copulation
- Types of sexual reproduction
- Isogamous - Synchytrium
- Anisogamous - Allomyces
Examples: Synchytrium endobioticum - This fungus causes "Black heart of Potato" or "Wart of Potato" disease.
- Asexual reproduction – By Sporangiospore (Zoospores)
- Sexual reproduction – By Planogametic copulation
- Types of Sexual reproduction
- Isogamous - Plasmodiophora
- Asexual reproduction – By the formation of sporangiospores (zoospores) & conidia.
- Sexual reproduction – By Gametangial contact
- Type of sexual reproduction
- Oogamous - All the members
- Asexual reproduction – By the formation of sporangiospores (aplanospores).
- Sexual reproduction – By Gametangial copulation.
- Types of sexual reproduction
- Isogamous – All the members
1. Pilobolus - It grows on dung, since it is dung loving fungi, therefore, it is called as coprophilous fungi. It prefers to grow on horse dung. It is also called as "Hat thrower" or "fungal shotgun". This name is given on the basis of blasting of sporangium.
Note: Coprophilous fungi - The fungi which grow on dung are called coprophilous.
2. Rhizopus & Mucor - These are known as bread mold – They prefer to grow on bread. The tip of mycelium of Rhizopus is black coloured. Therefore this fungus looks black coloured.
ASCOMYCETES: "The sac fungi"
Mycelium - Septa are found in mycelium of ascomycetes. Pores are present in septa. These pores allow cytoplasm to pass from one cell to other cells. Pores do not allow passing of nucleus.
‘‘Somatogamy’’ Ascospores are formed during sexual reproduction. On this basis, they are named as Ascomycetes.
- There are three stages in sexual reproduction of Ascomycetes w Plasmogamy w Karyogamy w Meiosis.
- Two different mycelium come close to each other and fuse to form dikaryon.
- An outgrowth originates from dikaryon which is called ascogenous hypha. Ascogenous hyphae develop and form a sac like structure which is called ascus (Plural - Asci). Due to this sac-like ascus, ascomycetes are called as sac fungi.
- Both the nuclei reach in ascus and fuse. As a result diploid nucleus is formed. Now meiosis takes place in the nucleus of ascus, as a result of which haploid spores are formed called ascospores.
Note: Eight -ascospores are formed in one ascus but generally 8 ascospores are formed in one Ascus.
- (e) After the formation of ascospores, the mycelium grows around the ascus and forms a covering which is called as fruiting body or ascocarp. 8 ascospores are present in one ascus.
- (f) By the rupturing of ascocarp & ascus, ascospores become free and each ascospore forms a new mycelium.
Three types of fruiting bodies are present in ascomycetes
- Cleistothecium - This is a closed and spherical fruiting body. There is no way for ascospores to come out. After maturation it ruptures and ascospores become free. This type of fruiting body is found in the members of subclass - Plectomycetes eg. of Plectomycetes -Penicillium, Aspergillus, Erysiphe
- Perithecium - This fruiting body is flask like. Pore is present (ostiole) on the apical part of this fruiting body for the elimination of ascospores. On the rupturing of ascus, these ascospores come out of the pore. This type of fruiting body is found in the members of sub-class Pyrenomycetes eg. of Pyrenomycetes - Neurospora, Claviceps
- Apothecium - This fruiting body is like open disc.
- The fruiting body of Morchella is edible, because it is delicious.
- The classification of class-ascomycetes is based on fruiting body.
- Ascus are naked in Yeast, because fruiting body is absent in it. Penicillium :– Blue or Green mold.
- P. notatum - A. Flemming obtained the antibiotic penicillin from it. Penicillin is the first discovered antibiotic. A Flemming was awarded Nobel Prize for it. But now a days more quantity of Penicillin is obtained from P. chrysogenum. A. flemming was a doctor in British army and while working on bacterium Staphylococcus, he by chance discovered the penicillin. Discovery of Penecillin was serendipity i.e. by chance discovery.
- P. griseofulvum - "Griseofulvin" an antifungal antibiotic is obtained from it.
- P. camemberti & P. roqueforti - Both are used in the manufacturing of camemberti cheese and roquefort cheese respectively. Cheese is made by fermentation which is done by fungus.
- Aspergillus - Black or Brown mold or Blacky - smoky mold
- A. proliferans - An antibiotic 'Proliferin' is obtained from it.
- A. fumigatus - It causes many diseases in humans & cattles. These disease are known as "aspergillosis" eg. Aspergillosis of ear – Main cause of ear pain.
- Aspergillosis of lungs – Its symptoms are similar to T.B.
- A. flavus – It prefers to grow on stored food (groundnut, cashewnuts etc.) and fodder. It secrets toxic substances. These toxic substances are known as aflatoxins.
- Aflatoxins – They are carcinogenic i.e. they develop cancer. Aflatoxin causes liver cancer.
- A. niger – Known as weed of laboratory and produce citric acid.
- Claviceps purpurea – It causes "Ergot disease" of Bajra.
- "Ergotin" (drug) is obtained from it.
- A narcotic drug (LSD) is also obtained from it.LSD (Lysergic acid diethylamide) is a hallucinogenic drug.
- Morchella:– The species of Morchella are commonly called as morels. It is an edible fungus.
- Neurospora:– Red or Pink mold → "Drosophila of plant Kingdom". It is used for the study of genetics in Plant kingdom.
Beadle and Tatum proposed "One gene - one enzyme theory" in Genetics by experimenting on Neurospora.
They were awarded Nobel Prize for it.
- Erysiphe - Different species of Erysiphe causes "powdery mildew" disease on plants.
- E. tritici - It causes powdery mildew of wheat.
- E. polygoni - It causes powdery mildew of pea.
- Peziza - It is called as cup fungi.
- Yeast is a unicellular fungus - According to five kingdom classification, it should be placed in Protista. But exceptionally it is placed in Mycota (fungi) because its life cycle is similar to class-Ascomycetes.
- Saccharomyces cerevisiae – It is used as fermentation agent in bakery (bread industry) and brewery (wine industry). SoSaccharomyces cerevisiae is also called‘‘Baker's yeast’’.
- Riboflavin (vitamin B2) is obtained from Saccharomyces cerevisiae.
- Mycelium - Septate and uni or binucleate (dikaryotic) In basidiomycetes, septum are of special type and they are called dolipore septum. One big pore is present between every septum. The boundary of pore is spread on both sides, this boundary is called as parenthesome. Due to the spreading of the boundry on both sides, the shape of septum becomes dome shaped due to which it is called asdolipore septum. These septa allow cytoplasm and nucleus to pass from one cell to other cell.
- Clamp connection - It is a tubular relationship between two neighboring cells. With the help of this connection the nucleus of one cell can migrate to the neighboring cell, due to which the other cell becomes dikaryotic (binucleate). Clamp connection is used to change monokaryotic mycelium to dikaryotic mycelium in basidiomycetes.
Fig: Clamp Mechanism
Sexual reproduction is performed by two methods
This is the most common method of reproduction among the members of Basidiomycetes. E.g. Ustilago, Agaricus, Polyporus, Lycoperdon
- The two mycelium come close to each other.
- Their apical ends fuse with each other (Plasmogamy), as a result of which dikaryon is formed.
- Now, with the help of clamp connection all the cells of mycelium becomes binucleate or dikaryotic.
- Now both the nucleus of each cell fused with each other (karyogamy), due to which each cell becomes diploid. A club-shaped structure is formed on every cell, which is known as basidium.
- After that diploid nucleus comes in to this basidium and divides by meiosis, as a result of which four haploid spores are formed on every basidium, which are known as basidiospores.
- Now the surrounding fungal hyphae grows to form a fruiting body, which is known as basidiocarp.
- Now the basidiospores become free from basidium and produce a new mycelium through germination.
- It is belived that basidium is similar to ascus, because both of them produces spores.
- But basidiospore is different from ascospores because the origin of ascospores is endogenous and that of basidiospores is exogenous.
This type of reproduction is more commonly seen in those fungi which cause rust disease
Three different species of Puccinia develop rust in wheat.
- Puccinia graminis – Black rust or stem rust.
- Puccinia recondita – Brown rust or leaf rust.
- Puccinia striiformis – Yellow rust or stripe rust Puccinia is aheteroecious fungi i.e. the fungus that needs two types of host to complete its life cycle.
Fig: Rust Fungi
- Wheat (Primary host)
- Barberry (Laterl or alternate secondary host)
- Life cycle of Puccinia - called rust cycle
- Rust cycle was discovered by Prof. K.C. Mehta. He has done a lot of hard work on rust.
- Starting of rust disease on wheat plants through aeciospores. i.e. Primary infection takes place through aeciospores and secondary infection takes place through uredospores.
1. Bracket or Shelf fungi - These are epixylic fungi i.e. these like to grow on wood. Their fruiting body is similar to bracket therefore they are called as bracket fungi. eg. Polyporus.
2. Puffballs – These are saprophytic fungi. The fruiting body of puff balls is large and beautiful. If touched, fruiting body bursts violently to release a black powder (basidiospores) out-side. Eg. Lycoperdon, Clavatia.
Note: Clavatia – A drug 'clavatin' is obtained from it. It is an anticancer medicine.
3. Mushrooms – These are umbrella-like fungi often seen growing in grounds during rainy season. Some mushrooms are edible.
- Most delicious mushroom - Agaricus bisporus.
- World's most poisonous mushroom - Amontia muscoides (Poisonous mushrooms are known as Toad - stool).
- Inky cap mushroom – Coprinus muscatus.
4. Smut fungi - It causes smut disease on plant. Smut diseases mainly affect the seeds of crop plants. Smut fungi infect seed and form black sooty spores inside the seed. Eg. Ustilago nuda or Ustilago tritici – It causes “loose smut of wheat.” This disease spreads by infected flowers and seeds.
- Ustilago maydis - Smut of maize. This disease spreads by infected seeds.
- Ustilago hordei - Covered smut of barley
- Ustilago scitaminea - Whip smut of sugarcane Note : Prof. J.C. Luthra discovered a technique to control smut.
5. Agaricus - It is called as "gill fungi" because gills like pores are present in its fruiting body. It is also called fairy rings because its fruiting body looks like rings.
6. Basidiomycetes - It is also called as "club fungi" because a club shaped basidium is formed in it. It is also called as"ray fungi".
It is also called "Fungi Imperfecti", because perfect stage or sexual reproduction is absent in this class of fungi.
Those fungi are included in this class in which sexual reproduction is absent or is not discovered at yet.
- Mycelium - Septate and multinucleate or uninucleate.
- Asexual reproduction - Takes place with the help of conidia.
- Sexual reproduction - Sexual reproduction is absent in this class. Instead, a parasexual cycle is present. parasexual cycle was discovered by Pontecorvo & Roper.
- Parasexual cycle is a method for producing variation in these fungi.
- Importance of Parasexual cycle - Mitotic recombination
- During mitosis, recombination takes place in these fungi due to which variations are developed. e.g. Trichoderma
- Arthrobotrys - These are entomophagous fungi i.e. insect predating fungi. These fungi can be used in biological control of insect pests.
- Dactylella - These are entomophagous fungi i.e. insect predating fungi. These fungi can be used in biological control of insect pests.
The fungi included in this class causes many diseases.
Early blight of Potato.
Tikka disease of groundnut.
Red rot of sugarcane.
Leaf spot of Rice.
Wilt of pigeonpea.
Note: Leaf spot of rice - This disease is known as famine of Bengal (1945).
Trichophyton & Microsporum cause "Ringworm" in humans. E.g. - eczema, itching.
Trichophyton interdigitale and Tenia pedis – cause "Athelete foot disease" in humans. It is also called as "Ring worm of foot".
Fungal hyphae closely packed together to form a false tissue which is called plectenchyma.
Plectenchyma is of two types
- Prosenchyma – It is rather a loosely woven tissue of hyphae. The hyphae composing it do not lose their identity.
- Pseudoparenchyma – In higher fungi the hyphae become woven and interwined into a compact mass. The walls of hyphae in the mass get fused and they lose their individuality. It bears a striking superficial resemblance to the parenchyma tissue of higher plants and is called pseudoparenchyma.