Lecture #3 Flashcards
What kind of organisms fix N2?
Only prokaryotes
-Bacteria
What is in the Phylum Proteobacteria?
Rhizobium (fixes N2 in nodules of legumes)
What is in the Phylum Cyanobacteria?
Nostoc which are in Lichens
Anabaena which lives inside water ferns and fixes N2
What is in the Phylum Anctinobacteria?
Frankia which fixes N2 for non-legumes
What does the pink in Rhizobium do?
Protects bacterial cells from O2
-Excludes O2 from the N2 fixing process because N2 can’t be fixed in the presence of O2
Why does Rhizobium have Leghemoglobin?
To allow the bacterium to keep O2 out of the N2 fixation process
-redirects it
What does the Phylum Glomeromycota form?
forms endomycorrhizal associations with most land plants
-Liverworts and angiosperms
What is important about the Phylum Ascomycota?
May associate with selected cyanobacteria and or green algae to FORM LICHENS
What does the Phylum Basidiomycota form?
Associations with roots of selected vascular plants to form ectomycorrhizae
What would happen if theses symbioses hadn’t occurred?
Plants would have remained in the oceans and would have not migrated to land
What do endomycorrhizal associations do?
Fungi penetrates root cells
- Fungus goes indie of the root cortical cells of the plant.
- It branches out within the cell in order to maximize the surface area for nutrient exchange
- all branches are surrounded by the plasma membrane, not inside the cytoplasm
Why do some fungi form vesicles?
- Mainly just for storage
- Or if the root dies, the vesicles remain to reproduce again
What do ectomycorrhizal associations do?
Fungi grow in-between plant root cells
- there is a thick layer of fungus on the outside of the root tip
- fungus explores the soils for water and nutrients and bring it back to the root
- Root tip doesn’t experience the outside world
What is a Lichen?
Dual organism
- Symbiosis with a mycobiont which forms the structure and obtained nutrients
- Photobiont (green algae or cyanobacteria) which produces the photosynthetic sugars
Are lichens an evolutionary group?
No, they are just a guild
What is the mycobiont within a Lichen?
It is the fungus that produces the structure of the lichen and how it gets its nutrients and water
What are the 3 different forms of Lichens?
Foliose
Fruticose
Crustose
Do lichens reproduce sexually or asexually?
Both
What are the possible ways that Lichens reproduce asexually?
- Finger-like structures on the surface (breaks off)
- Small lobes (breaks off)
- SOR, powdery balls are fungal filaments wrapped around the cell (falls off)
How can a Lichen reproduce sexually?
There is the sexual part the shoots spores out of it.
- needs an algal partner in order to become a new Lichen
- Produces a lot of spores to increase the chances of coming into contact with and algal partner
Where does the sexual reproduction happen within a Lichen?
In the fungus (mycobiont)
What are Rhizines?
Root like structures BUT ARE NOT ROOTS
-hold the lichen down
What kind of cells contain the spores in order for lichens to reproduce sexually?
Tubular cells
Why do Lichens have bright colours?
They are from secondary metabolites which act as sunscreen