L9- Microbial associations with plants Flashcards
What’s in a nitrogenase complex?
- Dinitrogenase- Fe and Mo cofactors
- Dinitrogenase reductase- Fe cofactor
Where do nitrogenase complexes occur?
Free living aerobes
Free living anaerobes
Symbiotic microbes with plants
What do legumes have on their roots?
Specialised organs called nodules, containing bacteria called rhizobia
Where do Rhizobia invade the roots?
Either within the nodule or in the soil, but only fix N2 inside the nodule
How do Rhizobia invade the roots?
- Recognition and attachment at root hair
- Excretion of nod factors cause root hair curling
- Rhizobia penetrate root hair and multiply within an infection thread
- Bacteria in infection thread grow towards root cell
- Formation of bacterioid state within the plant cell
- Continued plant and bacterial cell division
What do Rhizobia in the plant cells differentiate into?
N2- fixing cells called bacteroids
In a mutualistic relationship, what does the plant gain? What does the bacteria gain?
Plant- nitrogen
Bacteria- anaerobic environment for N2 fixation and carbon for energy
What are Mycorrhizal associations?
Fungal associations with plant roots
Where does it occur?
In 95% of all vascular plants
What are the 2 main types of Mycorrhizal associations?
- Ectomycorrhiza- mainly basidiomycetes/trees
2. Endomycorrhiza- mainly zygomycetes/grasses
In ectomycorrhiza, what effect does it have?
No plant cell invasion
Greatly increases effective root surface area
What does the Mycorrhizal fungus do?
Uptake of inorganic nutrients, particularly phosphate
What does the tree provide for mycorrhizal fungus?
Sugars from photosynthesis
What is AM?
Arbuscular mycorrhiza fungus-> where the fungus penetrates the corticol cells of the roots of a vascular plant.
Which group is AM in?
Endomycorrhiza
