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Questions and Answers
What type of lichen has algal cells evenly distributed throughout?
What type of lichen has algal cells evenly distributed throughout?
All mycorrhizae are formed by septate fungi.
All mycorrhizae are formed by septate fungi.
False
Name two types of mycorrhizae.
Name two types of mycorrhizae.
Ectomycorrhizae and Arbuscular mycorrhizae.
The __________ is the fungal layer found in the structure of lichens.
The __________ is the fungal layer found in the structure of lichens.
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Match the following mycorrhizae types with their characteristics:
Match the following mycorrhizae types with their characteristics:
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Which of the following is NOT a use of lichens?
Which of the following is NOT a use of lichens?
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Mycorrhizal associations can enhance plant growth and competitiveness.
Mycorrhizal associations can enhance plant growth and competitiveness.
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What type of spores do lichens primarily reproduce with?
What type of spores do lichens primarily reproduce with?
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What type of fungi live at the expense of dead organic matter?
What type of fungi live at the expense of dead organic matter?
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All fungi are parasitic organisms that live at the expense of other organisms.
All fungi are parasitic organisms that live at the expense of other organisms.
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What is the primary benefit of endophytes to their host plants?
What is the primary benefit of endophytes to their host plants?
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Lichens are a mutualistic association between a fungus and an _____ partner.
Lichens are a mutualistic association between a fungus and an _____ partner.
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Match the types of fungal interactions with their definitions:
Match the types of fungal interactions with their definitions:
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Which of the following is a character of lichens?
Which of the following is a character of lichens?
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The mycobiont in lichens provides organic nutrients to the photobiont.
The mycobiont in lichens provides organic nutrients to the photobiont.
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Name one method used for isolating fungal tissue samples.
Name one method used for isolating fungal tissue samples.
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Study Notes
Ecological Groups of Fungi
- Fungi are heterotrophic organisms
- Heterotrophic life in fungi is categorized into:
- Saprobic: Feed on dead organic matter
- Parasitic: Feed on a host organism (algae, plants, fungi, animals)
- Biotrophic: Colonize a living host
- Necrotrophic: Kill the host first, then colonize it
- Symbiotic: Mutualistic relationship benefiting both the fungus and its partner
Symbionts and Endophytes
- Fungi living on the exterior of their hosts are called epiphytes
- Fungi living within host tissue are called endophytes
- Endophytes:
- Protect host plants from insect herbivores and other fungal pathogens
- Used as bioregulators to enhance resistance to diseases
- Provide biological control against certain pathogens and weeds
Methods for Isolation
- Tissue pieces are sterilized:
- 60 seconds in 70% ethanol
- 2-5 minutes in NaOCI (1-3%, depending on tissue type)
- 60 seconds in 70% ethanol (to remove NaOCI)
- Tissue samples are plated on PDA amended with streptomycin (1 mL/L)
- Incubated at 25°C
- Emerging fungal colonies are hyphal-tipped and transferred to PDA slants for identification
B: Symbionts
Lichens
- Lichens are beneficial mutualistic associations between a fungus and an alga.
- Mycobiont: The fungal partner in a lichen
- Photobiont: The photosynthetic partner (either a green alga or cyanobacterium)
Characters of Lichens
- Worldwide distribution, often found in extreme environments (Arctic, Antarctic, deserts)
- Occur on soil, plants, animals, rocks, decorations, etc.
- Rare in polluted areas; intolerant of industrial pollutants (especially sulfur dioxide)
- Mycobiont usually makes up 90% of the thallus and is typically an ascomycete (mostly inoperculate discomycetes), or less commonly a basidiomycete (e.g., Omphalina, Multiclavula)
- Photobiont may be a green alga, cyanobacterium, or both
- Algae and cyanobacteria fix carbon; cyanobacteria fix nitrogen
Advantages to the alga
- Mechanical protection from injuries and high light by being tightly enveloped by hyphae
- Improved water relations and resistance to desiccation
- Provides minerals
Advantages to the fungus
- Organic nutrients (carbon and nitrogen) provided by the photobiont
- Lichenized fungi have greater longevity
- Most lichenized fungi are not found free-living in nature
Structure of Lichens
- Cortex (upper and/or lower)
- Medulla (fungal layer)
- Algal layer
Types of Lichens
- Stratified lichen: Algal cells are not distributed through the lichen
- Non-stratified lichen: Algal cells are distributed throughout the lichen
Uses of Lichens
- Food
- Dyes
- Essential oils for perfumes and soaps
- Bioactive compounds (antiviral, antibacterial)
- Nesting/bedding material
- Poisons
Reproduction of Lichens
- Sexual spores (ascospores & basidiospores)
- Conidia
Mycorrhizae
- Symbiotic association between a fungus and the root of vascular plants
- 95% of all vascular plants are involved in mycorrhizae
- Believed that the symbiotic association of plant roots and fungi led to modern vascular plants
Types of Mycorrhizae
- Ectomycorrhizae
- Ectendomycorrhizae
- Endomycorrhizae
- Arbuscular mycorrhizae (AM)
- Ericoid endomycorrhizae
- Orchid endomycorrhizae
1-Ectomycorrhizae
- Form a sheath (covering the root tip)
- The fungus grows between plant cells, producing a hartig net (extensive network of intercellular hyphae between epidermal and cortical cells)
- Septate fungi (Ascomycetes)
2-Ectendomycorrhizae
- Different from Ectomycorrhizae in that some hyphae actually penetrate into the root cells
- Septate fungi (Basidiomycetes)
3-Endomycorrhizae (Arbuscular mycorrhizae)
- Hyphae enter the plant cells, producing vesicles (swollen spherical or oval structures) or arbuscules (finely dichotomously branching hyphae invaginations) to increase the surface area between hyphae and cytoplasm
- Major site of nutrient exchange between the fungus and plant
- Non-septate fungi (zygomycota)
B) Ericoid Endomycorrhizae
- The fungus penetrates the plant cells, consisting of dense coils of hyphae in the root cells.
- Septate fungi (Ascomycetes)
- Ericoids are trees such as tea and blue berry
C) Orchid Endomycorrhizae
- Hyphae penetrate cells of the embryo and form coils called pelctons
- Septate fungi (Basidiomycetes)
- Orchids are plants which produce flowers like orchids and vanilla (flowering monocot plants)
Functions of Mycorrhizae
- Increase the plant's competitiveness, depending on the environment and improve plant growth
- Wet environments: Increase nutrient availability (especially phosphate)
- Arid environments: Aid in water uptake, increasing transpiration rates compared to non-mycorrhizal plants
Mycorrhization Helper Bacteria
- Symbiotic bacteria trapped within mycorrhizal fungi (cytoplasm of ectomycorrhizae and arbuscular mycorrhizae)
- Play a role in mycorrhizal relationships
- The main function of bacterial symbionts in ectomycorrhizal fungi is to contribute to nitrogen (N) metabolism by assisting in the synthesis of essential amino acids
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Description
Explore the diverse ecological roles of fungi with this quiz. Learn about saprobic, parasitic, and symbiotic fungi and their importance in ecosystems. Delve into the fascinating relationships between fungi and their hosts, including epiphytes and endophytes.
