FUNGI AND ITS RELATIONSHIPS
WITH OTHER ORGANISMS
Mutualistics Relationship
 Fungi and Plants: Mycorhizza, Lichen
Parasitic Relationship
 Fungi and Animal or Insects
 Fungi and Humans
MUTUALISM vs PARASITISM
Symbiosis: any situation where two different
species live together.
Mutualism – both partners benefit.
Parasitism – only one partner benefits; typically
reduces the fitness of other.
Commensalism – two species live together
without either harming the other, but where only
one partners benefit.
Mutualism and paratism were extensively
studied.
MUTUALISM vs PARASITISM
FUNGI
MUTUALISM
Fungi association with plants;
Mycorrhiza, Lichens
Fungi association with animals:
Termites and ambrosia beetles
inoculate their chambers with
spores and feed on hyphae
PARASITISM
Fungi association with plants;
Ceratocytis ulmi, Dutch elm
Disease
Fungi association with animals:
Trichophyton sp; causes
athlete’s foot
MUTUALISTICS RELATIONSHIP WITH
PLANTS
MYCORRHIZA
“Myco” meaning fungus, “Rhiza” meaning root.
Mycorrhiza is a mutualistic relationship between a
fungus in the soil and a plant root.
Characteristics:
1) Can increase uptake of plant nutrients such as
phosphorus and nitrogen especially when there is
a low concentration / insoluble form of it in the
soil.
2) Can assist nutrient uptake by plants from dilute
solutions.
TYPES OF MYCORRHIZA
1)
2)
3)
4)
Ectotropic
Vesicular-arbuscular (V-A)
Orchidaceous
Ericaceous
Ectotrophic (sheating) Mycorrhiza
Typically associated with temperate trees.
Ex: Amanita muscaria (fly agaric) with birch or
pine.
Association: Mutualistic: fungus supplies plant
with NH3 and PO43- from soil, plant supplies
fungus with carbohydrates produced during
photosynthesis.
Ectotrophic (sheating) Mycorrhiza
Characteristics:
1) Fungus forms highly
developed
sheath
around roots. Mycelial
strands extend into soil.
2) Intercellular invasion of
cortex to form Hartig’s
net.
3) Root hair formation
suppressed (mycelium
functional equivalent
of root hairs). Root
morphology altered.
Vesicular-arbuscular (V-A)
Mycorrhiza
Most widespread type of mycorrhiza.
Associated with borophytes, ferns,
spermatophytes (especially tropical trees).
Ex: Endogone spp. with grasses.
Association: Mutualistic: fungus supplies plant
with NH3 and PO43- from soil, plant supplies
fungus with carbohydrates produced during
photosynthesis (same as ectotrophic
mycorrhiza).
Vesicular-arbuscular (V-A)
Mycorrhiza
Characteristics:
1) No sheath. Fine hyphae
extend to soil.
2) Intracellular penetration
of middle cortex. No
Hartig’s net. Fungus
form
characteristics
vesicles and arbuscules.
3) Root hairs present. No
apparent alteration of
root morphology.
Orchidaceous Mycorrhiza
Unique to orchid.
Ex: Armillaria mellea (honey fungus) with
Gastropodia elata.
Association: Orchid parasitic on fungus.
Peletons degenerate and supply orchid with
sugars, vitamins and other nutrients obtained by
saprophytic action of fungus outside root.
Orchidaceous Mycorrhiza
Characteristics:
1) Same as V-A.
2) Intracellular
penetration of inner
cortex. Fungus forms
characteristics
coils
(peletons).
3) ± root hairs.
Ericaceous Mycorrhiza
Associated with heather and related plants.
Includes Boletus and monotropa (bird’s nest
plant)
Association: Variable: achlorophyllous plant may
be parasitic on fungus (monotropa type).
Alternatively, mutualistic in heather type.
Ericaceous Mycorrhiza
Characteristics:
1) Variable form; loose
weft
of
hyphae
surrounds
root
(heather) or definite
sheath (Monotropa).
2) Intracellular
penetration of outer
cortex. In Monotropa a
Hartig’s net may be
additionally present.
3) No root hairs, no
epidermal cells.
LICHENS
Mutualistic combination of an alga or blue-green
bacteria (cyanobacterium) with fungus.
ORGANISM
Mycobiont (fungus)
 There are ascomycetes or Basidiomycetes (rarely).
 They are ecologically obligate symbionts.
Phycobiont (alga or bacterium)
 These are green algae (ex: Trebouxia, 70 % of all
lichens) or blue-green bacteria (ex: Nostoc).
 They may be free living.
Main Features of Lichens
RELATIONSHIP BETWEEN ASSOCIATES
Alga (phycobiont) produces and secretes
carbohydrates
Fungus (Mycobiont) may supply minerals to the alga.
Uncertain, no experimental confirmation, phycobiont
may be able to absorb its own minerals from the
substrate.
This association probably enables both partners to
exploit habitat which would be unsuitable for either
alone.
STRUCTURE
There is often a highly organised thallus, with algae
forming a definite layer.
Three Types of Lichens
MORPHOLOGY
Crustose: crust like,
Ex: Xanthoria which is
the common yellowish
lichen on gravestone.
Foliose: Leaf like,
Ex: Parmelia which is
common in woodland.
Fruticose: Shrubby,
Ex: Cladonia which is
common on acid
heathland.
Lichens survive on bare rock, tree trunks,
inhospitable places.
Lichens growing on
a rock.
Lichens growing
on trees.
Lichen Thallus
Ecology and Applications of
Lichens
Lichen killed as SO2 levels rise.
Used as indicator of atmospheric pollution. Lichens
are so efficient at absorbing nutrients from the air
that they can be used to monitor air quality because
some kinds do not survive in polluted air.
Breaking down rocks and starting the process of soil
formation.
Lichens or their products may be used as:
 Dyes (Harris tweed)
 Food (for reindeer herds)
 Antimicrobial (Usnea)
 Indicators (Litmus)