Week 20: (A) Plant-Microbe Associations Flashcards
What are the positives of plant-microbe associations?
Essential for C and N recycling
Important Norplant growth (water and minerals)
Important to strengthen plant health
What are the negatives of plant-microbe associations?
Detrimental to plant health
Threat to crop production for human food and energy
Threat to natural ecosystems
what are the 3 types of microbes that effect plants? And… what do they do ?
The good- symbiosis/mutualism
The bad- Disease
The ugly- Decomposition
What is the effect of mutualism?
enhances reproduction and nutrient uptake
What is the plant in symbiosis with?
Root symbionts
plants form mutualistic, symbiotic associations with soil microorganisms
The plant gains nutrients, the symbionts gain sugars derived from photosynthesis
What are 2 major symbionts of plants?
-Most plants; mycorrhizal fungi
Extensive fungal surface area facilitates nutrients and water uptake
-Some plants; Nitrogen-fixing bacteria
Bacterial-containing nodules form to facilitate nitrogen fixation.
What are the 2 different types of associations of the Mycorrhizal fungi?
ecto or end-mycorrhizal
What are features of the ectomycorrhizal?
Fungi proliferate outside the root between cells (do not penetrate)
Only associated with a ams all number of land plants ~3%
What are key features of endomycorrhizal?
Fungi proliferate within cells
Associated with large number of land plants ~80%
What are examples ectomycorrhizal fungo?
gourmet truffles
the poisonous fly agaric
What structure do EM make? (ecto)
mesh network
What structure do arbuscular mycorrhizal fungo make? (endo)
tree like structures inside cell
What are the benefits to the tree-like structure?
The fungus gets sugar produced by photosynthesis
The arbuscule provides a large surface area for nutrient change
The plant gets N2 and Phosphorus from the soil
Why do we need to obtain N2 from soil?
not readily available due to triple bond
The soil contains nitrogenase enzyme, promotes nitrogen fixation
N2–> 2NH3
What is the communication between rhizobia and plant?
two-way signalling
What is the first step in two way signalling?
The plant root produces a flavonoid chemical that attracts rhizobia
What is the second step in 2-way signalling?
The bacterium produces a Nod factor, identifying it as a symbiont
What is the third step in 2-way signalling?
The plant prepares to form a symbiotic nodule structure
What are the decomposition bacteria and fungi called?
saprophytes
What are saprophytes essential for?
recycling C and N
What are 6 key features of saprophytes?
- Feed off dead / organic matter (plant and animal)
- Fungi and bacteria
- Digest then absorb
- Extracellular (secreted) enzymes
- Carbohydratases, lipases, proteases
- Essential for N and C recycling
Why is it hard to degrade plant material?
plants feature cell walls
What is the formation of plant cell walls?
formed by hemicellulose, cellulose and lignin
How do saprophytes degrade cells walls?
lignin degradation, followed by decomposition
If no saprophytes = no C and N recycling
