Lecture 10: Growth & sexual reproduction Flashcards
(59 cards)
1
Q
spore:
A
small, reproductive structures.
DORMANT
2
Q
hyphae:
A
long, branching filamentous structure. Main mode of vegetative growth
3
Q
Mycelium:
A
collective name for mass of hyphae
4
Q
Mycelium are great of ___, bad for ____
A
great for ABSORPTION
bad for WATER LOSS
5
Q
fungal diversity is highest in
A
tropics
6
Q
Germination (Spore –> hyphae) only occurs when conditions are right
A
moisture & nutrients
7
Q
Hyphae structure:
A
chain of cells:
CONTAINING: golgi, vacuole, lipid body, nucleus, mitochondrion, cell wall, plasma membrane.
CELLS SEPARATED BY SEPTUM
8
Q
cells in hyphae are surrounded by a
A
tubular cell wall
9
Q
the major structural polymer in fungal cell walls is typically
A
CHITIN - long chain polymer, v tough
10
Q
glucans –>
A
really long glucose polymers, crosslink the chitin
11
Q
4 layers to the fungi cell wall: (INNER TO OUTER)
A
- Chitin microfibrils & protein
- Mainly protein
- The reticulum - glucans and protein
- outer mixed glucans
12
Q
FUNCTIONS of the fungi cell wall
A
- maintain cell shape
- Barrier to external world (e.g. prevents osmotic lysis)
- molecular sieve
- cellular protection (melanised for UV protection)
- physiology (binding site for enzymes)
- antigenic properties (regulates interactions with other organisms)
13
Q
septa are?? (septum)
A
- divide some fungal cell by internal cross-walls
- usually perforated by large pores (large enough for organelles to flow between cells) -> movement/ communication between cells
14
Q
hyphae grow from the
A
TIP
15
Q
branching:
A
outgrowth a little way behind the tip
16
Q
hyphae deposition of organelles:
A
at growing tip:
- mitochondrion more abundant (ENERGY)
- vesicles adding new section to the cel wall
- denser cytoplasm in younger plants
further in from tip:
- storage granule(for lipids, glycogen etc)
- less dense cytoplasm in older parts
- vacuole
17
Q
fungi are heterophiboc/ homophobic?
A
heterotrophic: most acquire external sources of food (like animals)
18
Q
whats ‘food’ to fungi ?
A
simple sugars, polypeptides and more complex carbohydates.
19
Q
how do fungi get there food?
A
EXTRACELLULAR DIGESTION
20
Q
2 types of substances carried in vesicles
A
- carrying digestive enzymes
- cell-wall components
21
Q
Extracellular digestion:
A
- golgi apparatus packages proteins into membrane-bound organelles
- vesicles carrying precursors are transported to the tip along microtubules & actin filaments
- vesicles fuse and released digestive enzymes (e.g. amylases, lipase, proteases)
- resulting organic molecules are taken via plasma membrane proteins
22
Q
fungal colony structure:
A
- extension zone
- productive zone
- fruiting zone
- aged zone
23
Q
extension zone:
A
hyphae are extending into the unexploited medium, seeking out fresh nutrients
24
Q
productive zone:
A
hyphae linked by anastomososis into a network. Net increase in biomass
25
Anastomosis:
fusion between hyphae. Means of communication with itself
26
fruiting zone:
Initiation of fruit bodies. Turnover of storage reserves
27
aged zone:
Decline phase. Hyphae become vacuolated and empty of protoplasmic contents. Autolysis (self-digestion) occurs
28
indeterminate growth:
- Each ring is a single genototype of Armillaria bulbosa
- Largest colony found is over 600m in diameter -Growth rate consistently ~ 0.2m per year
- Age ~ 1500 y
- Estimate that the fresh weight is at least 10,000kg
- Communication over large distance maintained by anastomosis
29
a spore germinated to form a
hyphae
30
collection of hyphae is called a
mycelium (huge SA)
31
hyphae grow at the __ and branch __
Hyphae grow at the tip, branch just behind
32
Fungi mating types:
are +/- NOT sexes (m/f)
33
do all fungi reproduce sexually?
Notallfungireproducesexuallyand many that do are isogamous; thus, the terms "male" and "female" do not apply.
34
isogamy:
gametes similar size & structure
35
homothallic species:
able to mate with themselves (mate type switching)
36
heterothallic species:
only isolates of opposite mating types can mate.
37
4 types of fungi (phylogeny)
- zygomycota (zygomycetes)
- imperfect fungi
- Ascomycota (ascomycetes)
- Basidiomycota (basidiomycetes)
38
2 "higher fungi" (subkingdom Dikarya)
- Ascomycota (ascomycetes)
| - Basidiomycota (basidiomycetes)
39
how are the major phyla classified
- mainly on the basis of their sexual reproductive structures
- also hyphae structure
40
imperfect fungi explanation
- no sexual stage known
| - polyphyletic group of species not yet placed in any existing group. 25,000 species
41
non-septate hyphae
(aka coenocytic)
- ZYGOMYCOTA
- more primitive
- one cell with many nuclei
42
septate hyphae
- Ascomycota (ascomycetes)
- Basidiomycota (basidiomycetes)
- more advanced
- dividers (septa) between the cells
43
Basidiobycota
| -a.k.a Club fungi
-Includes these groups: Mushrooms, puffballs, stinkhorns, bracket fungi, jelly fungi ,boletes, chanterelles, earth stars, smuts, bunts, rusts
~31,500 series described
44
Basidium (pl. basidia) are
microscopic, spore-producing structure. The presence of basidia is one of the main characteristics of the Basidiomycota
45
each basidium usually bears
4 sexual spores (basidiospores)
46
Basidiomycota: Sexual reproduction
1.Spores land and germinate. =HAPLOID (n)
2. Hyphal union. Hyphae fuse and PLASMOGAMY occurs =Dikaryotic (n+n)
3. Fruiting body (BASIDIOCARP) develops aboveground. Gills are lined with HYMENIUM (the tissue layer where the cells develop into basidia)
4. KARYOGAMY occurs (fusion of haploid nuclei) in the basidium
= DIPLOID (2n)
5. Meiosis occurs. Basidiospores are formed and released =HAPLOID (n)
47
bioluminescence aids???
spore dispersal??
- prosthetic LED-illuminated acrylic mushrooms can be used to study insect behaviour
- insects that can disperse fungal spores are attracted to light at night
- Bioluminesecence peaks at night when it is most visible and thus saves energy
- Why in tropical forests? Little wind flow
48
plasmogamy:
cytoplasm of two parent cells fuses together without the fusion of nuclei
49
Dikaryotic:
the two nuclei of two cells pair off and cohabit without fusing (neither truly diploid or haploid) *CONDITION UNIQUE TO THE FUNGI *
50
karyogamy:
final step in the process of fusing together two haploid eukaryotic cells, and refers specifically to the fusion of the two nuclei
51
Ascomycota a.k.a Sac fungi. includes:
- yeasts, truffles, morrels and Penicillium, also many animal & plant pathogens
- Largest phylum of fungi (>64000 sp)
52
Ascus (pl. Asci)
microscopic, sac-like, sexual structure i which spores are formed; defining feature of the Ascomycota
53
typically how many spores per ascus
8
54
Ascomycota: sexual reproduction
- ascospores (n) release (active or passive)
- formation of GAMETANGIA
- nuclei migration
- dikaryotic mycelium (n+n)
- fruiting body (ascocarp) forms, including HYMENIUM
- karyogamy occurs (2n)
- meiosis
- mitosis (n)
55
Ascomycota: specific mating structure interaction
-A very fine hyphae (trichogyne) emerges from one gametangium (ascogonium)
• It merges with a gametangium (antheridium) of the other fungal isolate.
• The nuclei in the antheridium then migrate into the ascogonium
56
HYMENIUM:
the tissue layer where the cells develop into asci in the bottom of the cup
57
Zygoymcota a.k.a conjugating fungi.
| includes:
- molds, plant symbionts, pathogens to plants and animals (e.g Fly death fungus)
- Small phylum of fungi (>1050 sp) and most primitive
58
Zygomycota: sexual reproduction
- hypha of two different mating types (+/-) come together
- Gametangia formed (n)
- Plasmogamy occurs gives zycosporangium
- fertilisation (karyogamy)
- DIPLOID (2n) multinucleate zygospore are within zygosporangium
- meiosis occurs
- sporangium forms on top of sporangiophore
- releases spores AND REPEAT
59
when does dikaryotic stage occur in all fungi
between plasmogamy and karyogamy (fertilisation)
