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Chapter 30 Fungi: Recyclers, Killers, and Plant Partners. Biology 101 Tri-County Technical College Pendleton, SC. Fungi Characteristics. ALL are heterotrophic organisms with absorptive nutrition NO photosynthetic members of this kingdom

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chapter 30 fungi recyclers killers and plant partners

Chapter 30 Fungi: Recyclers, Killers, and Plant Partners

Biology 101

Tri-County Technical College

Pendleton, SC

fungi characteristics
Fungi Characteristics
  • ALL are heterotrophic organisms with absorptive nutrition
    • NO photosynthetic members of this kingdom
  • Some are saprobes that absorb nutrients from dead matter; others are parasites that absorb nutrients from living hosts; and some live in mutualism with other organisms
  • Unicellular and multicellular species
characteristics cont
Characteristics, cont.
  • Cell walls (if present) possess complex polysaccharide chitin
  • Most fungi have complex body forms
  • All the fungi produce spores
    • asexual, sexual, or both
  • Only one phylum (Chytridioimycota) has spores or gametes that possess flagella
what a body
What a body…
  • Most fungi NOT unicellular but whether they can be called multicellular is questionable
  • Vegetative (feeding) body of fungus called a mycelium
  • Mycelium composed of rapidly growing individual tubular filaments called hyphae (hypha)
body cont
Body, cont.
  • Within most hyphae, there is NO division into separate cells so organelles (even nuclei) can move around (COENOCYTIC HYPHAE)
  • May be more appropriate to call fungi “multinucleate”
  • Some hyphae are subdivided into cell-like compartments by incomplete cross walls called septa (septum)
  • Those with septa said to have SEPTATE HYPHAE
body cont1
Body, cont.
  • Certain modified hyphae called rhizoids anchor members of Chytridiomycota to their substrate
  • Tubular body of fungus give it a unique relationship with its environment
  • Has enormous surface area-to-volume ratio which is marvelous adaptation to absorptive nutrition
  • Able to tolerate highly hypertonic environment and temperature extremes
modes of reproduction
Modes of Reproduction
  • Asexual reproduction takes many forms
    • production of haploid spores within sporangia
    • production of naked spores at tips of hyphae (condia = dust)
    • Cell division by unicellular fungi (equal division or asymmetrical division = bud)
    • Fragmentation by simple breakage of the mycelium
modes cont
Modes, cont.
  • Sexual reproduction rather unique because often NO morphological distinction between male/female individuals/structures
  • There is genetically determined distinction between two or more mating types
  • Individuals of same mating type cannot mate with each other but can mate with different mating type
  • This prevents self-fertilization
more on the modes yeehaw
More on the modes..yeehaw!!
  • In many fungi, zygote nuclei formed by sex reproduction ONLY diploid nuclei in life cycle
  • These nuclei undergo meiosis, producing haploid nuclei that wind up in spores
  • Haploid nuclei (either method) germinate and nuclei divide mitotically to produce hyphae
enough on modes already
Enough on modes, already
  • Some use dikaryon stage to reproduce sexually
  • Plasmogamy, karyogamy, dikaryon, heterokaryon
  • No gamete cells, only gamete nuclei
  • These hyphae are neither 2N or N, but rather they are dikaryotic (N + N)
  • Dikaryosis most significant genetic peculiarity of fungi
  • Aquatic microorganisms with cells walls of chitin
  • Either parasitic or saprobic
  • Reproduce both asexually and sexually
  • Only fungi that have flagella at any life cycle stage
  • Allomyces is best example
  • Have coenocytic hyphae and produce NO motile cells
  • Zygote only diploid cell in life cycle
  • Rhizopus stolonifer is black bread mold (and will hide on the onions…)
  • Can reproduce asexually and sexually
  • Distinguished by production of sacs called asci (sexual reproduction structure)
  • Septate hyphae
  • Divided into two groups on basis of asci
  • Euascomycetes (true) possess ascocarp (specialized fruiting structure that contains/protects the asci)
  • Hemiascomycetes (half) do NOT possess ascocarp
ascomycetes cont
Ascomycetes, cont.
  • Hemiascomycetes are microscopic with many unicellular species
  • Saccharomyces cerevisiae (yeast)
  • Reproduce asexually by “budding”
  • Sexual reproduction produces ascospores
  • Euascomycetes include filamentous fungi known as the “molds”
ascomycetes iii
Ascomycetes, III
  • Many (euascomycetes) are parasites (Chestnut blight/Dutch Elm disease)
  • Also includes the cup fungi: morels and truffles
  • Penicillium (antibiotic/Chamembert & Roquefort)
  • Asperigillus (soy sauce/sake/aflatoxins
  • **Reproduce asexually by means of condia and sexually by a dikaryon
  • Club fungi that includes puff balls, bracekt fungi, commercial mushrooms, some parasites, and some symbionts
  • Usually have septate hyphae
  • Basidium (swollen cell at tip of hyphae) characteristic sexual reproductive structure
  • Basidiospores contains spores
  • Some have cap (pileus) which has gills on underside
  • Great numbers of basidia develop on gills
let s talk sex but quietly
Let’s talk sex..but quietly
  • Zygomycota reproduce sexually when adjacent hyphae of two different mating types release pheromones which cause them to grown together
  • These hyphae produce gametangia that fuse to form zygosporangia containing zygospores
  • Zygosporangia develop thick, multilayered walls that protect the zygospores
zygomycota cont
Zygomycota, cont.
  • Highly resistant zygospores may remain dormant for months before their nuclei undergo meiosis and a sporangium sprouts
  • Sporangium contains product of meiosis—haploid nuclei that are incorporated into spores
  • Spores disperse and geminate to form new generation of haploid hyphae
  • Enough on budding already…
  • Sexual reproduction includes formation of dikaryon
  • Nuclei from male structure on one hypha enter female making structure on hypha of compatible mating type
  • Dikaryotic ascogenous (asci-forming) hyphae develop from dikarytoic female mating structure
ascomycota cont
Ascomycota, cont.
  • Introduced nuclei divide simultaneously with host nuclei
  • Eventually asci form at tip of ascogenous hyphae
  • Only with formation of asci, do nuclei finally fuse
  • Nuclear division and meiosis of diploid nucleus takes place within individual asci
  • Meiotic products incorporated into ascospores that are ultimately released to begin new haploid generation
  • Basidiomycota are the “club fungi”
  • After nuclei fuse in basidium, diploid nucleus undergoes meiosis and four haploid nuclei are incorporated into haploid basidiospores which form on tiny stalks
  • Basidiospores typically forcibly discharged from basidia
  • Called the “imperfect” fungi
  • Mechanisms of sexual reproduction readily distinguish members of four phyla from one another
  • Many fungi, however, lack a sexual stage or their stage has NOT yet be identified
  • Fungi not yet classified in one of four phyla are placed together as “imperfect”
  • Is holding area for species whose sexual reproduction stage (if any) has not been identified
  • Mycorrhiza is mutualistic relationship between root hairs of plant and a fungus
  • Ectomycorrhizae: fungus wraps around root, >ing surface area for absorption of water and minerals
    • Mass of fungi (like sponge) help hold water in area of root
    • Infected roots branch extensively and become swollen and club-shaped
mycorrhiza cont
Mycorrhiza, cont.
  • Endomycorrhizae: infection internal to root with no hyphae visible on root surface
  • Fungus obtains organic compounds from plant while increasing absorption of water and minerals (esp. phosphorus) by plant
  • Fungus may provide certain growth hormones and protect plant from attack by microorganisms
mycorrhiza cont1
Mycorrhiza, cont.
  • Been suggested this relationship ALLOWED plants to survive move to land
  • Plants with active mycorrhizae are deeper green and may resist drought and temperature extremes between than plants of same species with little or no mychorrhizae development
  • Attempts to introduce plants to new areas have fialed until bit of soil from native land was provided
  • Lichen is mutualistic relationship between a fungus and a photosynthetic microorganism (cyanobacterium or green algae)
  • Are found in all sorts of exposed habitats
  • Important pioneer organisms and help in the soil cycle
  • Very sensitive to air pollution because they are unable to excrete toxic substances they absorb
  • Chattanooga, Tennessee