Fungi
Definition; Fungi are eukaryotic, achlorophyllous, heterotrophic organisms with a cell wall, reproducing by spores (asexual or sexual).
General Features
|
Character |
Fungi |
|
Nature |
Eukaryotic, filamentous, non-vascular organisms |
|
Cell Wall |
Present (mainly chitin or cellulose) |
|
Nutrition |
Heterotrophic (saprophytic, parasitic or symbiotic) |
|
Chlorophyll |
Absent |
|
Reserve Food |
Glycogen and oil |
|
Vegetative Body |
Mycelium made of hyphae |
|
Nucleus |
True nucleus with nuclear membrane |
|
Habitat |
Soil, water, air, plant and animal debris |
|
Mode of Reproduction |
Asexual and Sexual reproduction |
Vegetative Structure
- Hypha (plural: Hyphae): Thread-like filament forming the basic unit of fungal body.
- Mycelium: Network of hyphae forming the fungal thallus.
- Types of Hyphae:
- Septate: With cross-walls (e.g., Ascomycota, Basidiomycota).
- Aseptate / Coenocytic: Without cross-walls (e.g., Zygomycota).
- Types of Mycelium:
- Intercellular: Between host cells.
- Intracellular: Inside host cells.
Reproduction in Fungi
i) Asexual Reproduction
Occurs repeatedly in the life cycle; produces asexual spores (without fusion of nuclei).
Common Asexual Spores:
|
Type |
Description |
Example |
|
Sporangiospores |
Produced inside sporangium (endogenous). |
Rhizopus |
|
Conidia |
Formed externally on conidiophores. |
Penicillium, Aspergillus |
|
Chlamydospores |
Thick-walled resting spores. |
Fusarium, Alternaria |
|
Oidia |
Fragmented hyphae acting as spores. |
Candida |
|
Zoospores |
Motile spores with flagella (in water molds). |
Phytophthora, Pythium |
ii) Sexual Reproduction
Involves fusion of nuclei (karyogamy) and meiosis.
Three basic stages:
- Plasmogamy – fusion of cytoplasm
- Karyogamy – fusion of nuclei
- Meiosis – reduction division to form sexual spores
Sexual Spores:
|
Type |
Formed in |
Example |
|
Oospore |
Oogonium (Oomycetes) |
Phytophthora |
|
Zygospore |
Zygosporangium (Zygomycetes) |
Rhizopus |
|
Ascospore |
Ascus (Ascomycetes) |
Neurospora |
|
Basidiospore |
Basidium (Basidiomycetes) |
Puccinia |
Economic Importance of Fungi
Beneficial:
- Used in fermentation (yeast – Saccharomyces).
- Antibiotics (Penicillin from Penicillium notatum).
- Organic acid production (citric acid from Aspergillus niger).
- Mycorrhizal association enhances plant nutrition.
Harmful:
- Cause plant diseases (e.g., Phytophthora infestans – late blight).
- Food spoilage.
- Mycotoxin production (Aspergillus flavus – aflatoxin).
Important One-Liners
|
Question |
Answer |
|
Cell wall of true fungi is made up of? |
Chitin |
|
Reserve food of fungi? |
Glycogen & oil |
|
Example of coenocytic fungus? |
Rhizopus |
|
Motile spores in fungi are called? |
Zoospores |
|
Fungi lacking septa? |
Phycomycetes |
|
Resting spore of Fusarium? |
Chlamydospore |
|
First discovered antibiotic from fungus? |
Penicillin |
