BIO
201: Botany
KINGDOM FUNGI
GENERAL CHARACTERISTICS
Basic features:
Eukaryotic
Multicellular with different cell types
Cell walls of Chitin (except one group)
Heterotrophic -- food from organic source, secrete enzymes into environment
& absorb digested material
Saprophytic -- dead organisms (most
common)
Parasitic -- living organisms
Mutualistic -- living with another
(symbiosis)
Morphology:
have branching filaments = Hyphae
large mass of hyphae = Mycelium
multinucleate cells = Coenocytic
Septate:
with cross walls
Nonseptate:
no cross walls
Reproduction:
dispersal commonly by spores --- many types of spores
most commonly asexual
sexually produced spores typically are resting spores
Taxonomy:
two groups not officially recognized
Lower
fungi -- some place in Kingdom Protista
nonseptate walls
spores in small sporangia
flagellated reproductive cells
include three
groups: Chytridiomycota, Oomycota, Myxomycota
Higher fungi -- true fungi (Kingdom Fungi)
septate cross walls
spores in complex structures
no flagellate reproductive cells
include three
groups: Zygomycota, Ascomycota, Basidiomycota
DIVISION/PHYLUM CHYTRIDIOMYCOTA (chytrids or water molds)
The text puts this group in Kingdom Fungi (pp. 287-288)
Basic features:
aquatic
unicellular and coenocytic (multinucleate)
hyphae are typically haploid (but some diploid) - typically composed of a
microscopic sphere (see fig 14-13)
cell walls of chitin (but some rare reports of cellulose in cell walls?)
have Rhizoids to penetrate food source
Many are parasitic -- on plants & other fungi
some are saprophytic
Asexual
Reproduction:
sporangium with single nucleus that splits off to
produce a flagellate zoospore with one flagellum
Sexual Reproduction:
sporophyte with thick walled sporangium,
meiosis to form spores; they develop into the gametophyte
male gametophyte produces
male gametes
female gametophyte
produces female gametes
fusion of two motile gametes to produce a zygote
which develops into the sporophyte
DIVISION/PHYLUM OOMYCOTA (water molds & mildews)
The text puts this group in Kingdom Protista (pp. 358-360)
Basic features:
aquatic
extensive nonseptate mycelium (unicellular, coenocytic)
hyphae are diploid
cell walls of cellulose
heterotrophic: parasites on fish
plant pathogens
also initial decomposers of dead insects
Asexual Reproduction:
hyphae grow, terminal portions of a mycelium pinch off
to produce Zoospores, each with two (2)
flagella
Sexual Reproduction
(see fig 15-52):
reproductive cells produced by meiosis
several eggs per Oogonium
Antheridium long and
skinny (clavate)
Zygote with thick wall = resting Oospore
growth into sporophyte upon germination
PHYLUM MYXOMYCOTA (plasmodial slime molds)
The text puts this group in Kingdom Protista (pp. 360-362)
Basic features:
terrestrial
no cell walls
vegetative structure = Plasmodium is diploid (coenocytic) (see
photo, p. 343)
Amoeboid - feed by phagocytosis
With adverse environmental conditions (ex. drought) --formation of a hardened Sclerotium (multicellular resting structure)
Sexual
Reproduction (see fig. 15-56):
sporangium development -- meiosis to form 4 haploid
spores
3 of the 4 spores
disintegrate before release
germination into ameboid cells
some cells become
flagellate
fusion to form a zygote which later develops into a new
plasmodium
DIVISION/PHYLUM ZYGOMYCOTA (pin and bread molds)
One of the higher fungi (pp. 288-290)
Basic features:
terrestrial
hyphae haploid, septate
cell walls of chitin
Saprophytic
Produced complex reproductive structure = zygosporangium with one zygospore (details below)
Asexual
Reproduction:
nonmotile spores on aerial sporangia
spores air dispersed
Sexual Reproduction (fig 14-15):
+ & - strains
when come in contact produce Gametangia
initiation of process of Conjugation
(fusion)
two (2) haploid nuclei into a common cell
and fertilize with a thickened wall
= Zygosporangium
Upon germination:
1) development of sporangium
2) meiosis
to form spores
3) development into hyphae of new mycelium
DIVISION ASCOMYCOTA (cup or sac fungi)
a higher fungus (pp.
291-295)
Include: morels, truffles, yeasts, dutch elm disease, corn blight (examples, fig 14-18)
Basic features:
Mainly
terrestrial
Hyphae are septate and monokaryotic (= having one nucleus per compartment)
produce comples reproductive structure = ascocarp with 8 ascospores (see below)
Asexual
Reproduction:
produce a sporangium-like Conidium (pl.= conidia)
within it are spores = Conidiospores
some species - no sexual reproduction seen,
produce only
conidia:
a)
Penicillium
- flavoring in cheese (blue, Roquefort, Camembert) (fig. 15-33a, 15-34a)
b) Aspergillus
- aid in fermentation of soybean to produce Tofu (fig. 15-33b, 15-34b)
Sexual
Reproduction (fig 14-19):
1) haploid mycelium; + & - strains
2) eventual fusion of cellular cytoplasm of two types
to produce dikaryotic cells
(two nuclei per compartment)
process of cytoplasmic
fusion = Plasmogamy
3)
cell division of dikaryotic cells to form Ascocarp
each cell
with + & - nucleus
only exception is that of
yeast (which has diploid cells)
4) eventual
production of zygote by fusion of nuclei = Karyogamy
5) development
of an elongate Ascus (pl.= asci) with sterile paraphyses between
6) subsequent
meiosis to produce 8 haploid ascospores
sexual spores = Ascospores
Three
(3) types of sporocarps:
1) Apothecium - most common, cup-like (fig 14-18a)
cup fungi,
morels
2) Perithecium - small flask-shape with small opening (fig. 14-21c)
3) Cleistothecium - no opening, release by decomposition (fig. 14-21b)
Yeasts: most common
Saccharomyces
single celled, 2n, asexual reproduction by budding
sexual reproduction: meiosis to from 4 ascospores
2(+) & 2(-)
short period
of budding
fusion of a
(+) and a (-) to form the zygote
DIVISION BASIDIOMYCOTA (club fungi)
Yes, a higher fungus (pp. 295-301)
Include: mushrooms (fig. 14-29a-b), puffballs (fig. 14-33a), earthstars
(fig. 14-33d), coral fungi (fig 14-29d), rusts (fig. 14-34), smuts (fig. 14-36)
Basic features:
Mainly
terrestrial
Hyphae are septate and monokaryotic (= having one nucleus per compartment)
produce comples reproductive structure = basidiocarp with 4 basidiospores (see below)
Sexual
Reproduction (fig 14-25):
sexual process similar to that of ascomycetes
1) haploid mycelia of two types (+) & (-)
2) fusion to get dikaryotic mycelia which develop into
sporocarp = Basidiocarp
some zygotes
formed (fertilization)
immediate
meiosis to form 4 Basidiospores on a
Basidium (club-like structure) (fig. 19-18)
wind
dispersal
(link to basidiomycete sexual reproduction drawing)
Basidiocarp structure:
Stipe =
stalk
Cap =
enlarged apex -- with gills or pores
Gills/Pores
= structures on which basidia produced
SYMBIOSIS INVOLVING FUNGI
Symbiosis = living together
Two
types involving fungi:
1) mutualism - both species benefit
2) parasitism - one benefits, one harmed
MUTUALISM
two examples: mycorrhizae &
lichens
A. Mycorrhizae
are the result of fungi in the roots of vascular plants (pp. 340-344)
fungus benefits: obtains photosynthates (esp.: sugar)
plant benefits: obtains minerals (esp.: N, P)
* increases
effective root surface area
* allows
plant to reach more soil volume
this relationship is most common in poor soils
mycelium of fungus develops from roots to soil
Two types
of mycorrhizae based on type of infection (p. 312-315):
1) Ectomycorhhizae (sheathing) (fig. 14-45)
produce compact mantle around root
grow between root cells of epidermis & cortex
not into
cells, not beyond endodermis
results in short, stubby roots
most common in: conifers, oaks, willows
which are infected with
basidiomycetes
2) Endomycorhhizae (internal) (fig. 14-43 & 14-44)
fungal hyphae grow into root cells
within cell walls, NOT cell membrane
mainly in epidermal & cortex cells
most common in angiosperms
(ex.: tulip tree) which are infected by zygomycetes
B Lichens
are the result of a fungus and an algae living together (pp. 306-312)
a) the mycobiont - a fungus
mostly
ascomycetes, but some basidiomycetes
provides a
suitable environment & minerals to algae
b) the photobiont - an algae
an algae
(green) or cyanobacterium
provide
carbohydrate & nitrogen compounds to fungus
symbiosis allows for them to live in very harsh
environments: rock surfaces, tree trunks (fig. 14-42)
ability to survive
related to ability to dehydrate quickly
fungal
surface blocks UV light
PARASITISM
two examples: Dutch elm disease & ergotism
General
comments on parasites of plants:
sources of infection by fungi: 1) spores;
2) thick-walled zygotes
entry via: 1) wounds;
2) stomates; 3) lenticels
severity of infection based on:
1)
resistance or susceptibility of host (genetic)
2) virulence
of pathogen
3)
environmental conditions
A.
Dutch Elm Disease - fungus growing on the American elm (Ulmus
americana)
fungus = Ophiostoma ulmi (an ascomycete)
fungus is carried from tree to tree by the elm beetle
Life
Cycle (please refer to handout from class):
Adult
beetles feed on live portion of tree (A, D)
fungal spores enter at site of physical damage (E)
Mycelia grow
into vascular tissue, esp. xylem (G)
produce conidia with condiospores (H)
Conidiospores
transported throughout the tree via xylem
spores germinate and mycelia spread (B, C)
xylem eventually blocked causing branch or tree death
Sexual
reproduction with production of ascospores (J, K)
Adult
beetles lay eggs in dead tissue (branches)
larvae develop galleries (F)
ascospores germinate and grow in galleries (K, F)
mycelium develops spores (I)
As adult beetles emerge they have spores on them
Spores moved to other tree as adults feed on live branches (A, D)
(link to dutch elm disease diagram)
B.
Ergotism (see note on text, p. 307)
Parasite on fruits of rye (a grain)
an
ascomycete
contain
Lyseric Acid - similar to LSD
Historically related to several epidemics:
994: 40,000
deaths in Europe
1692:
possibly cause of witchcraft affair at Salem
1722: army
of Peter the Great, stopping quest of Turkey