Lecture 18 - nitrogen fixation stuff Flashcards
what is a lichen
combo of fungus and algae/cyanobacteria living in symbiosis
what do both components of the lichen provide
Alga provides sugars
Fungus protects alga from desiccation
How might lichens act as indiactors
Some are sensitive to air pollution
So if they die then indicator of air pollution
How come they are usually primary colonisers
found in harsh conditions so they are usually the first there e.g. On rocks, tree barks, roofs
what family of plants fix N from atmoaphere
fabaceae
Aka legumes
What allows n fixation to occur in fabaceae
mutualistic bacteria in the roots
What two type of bact are in roots of fabaceae
alpha proteobact
Bets proteobact
What two type of bact are in roots of fabaceae
alpha proteobact
Bets proteobact
What enzyme allows n to be fixed
nitrogenase
What does n fixation produce
ammonia and h2
how does the plant prevent bacteria cheating
plant control oxygen supply to nodules where the bact live
So it rewards bacterial growth by giving the nodules oxy
What are mycorrhizas
Mutuslistic associatkon between plant roots and soi fungi
Similar to lichens, but plants and not alage
What does the plant get from the fungi in mycorrhizas
soil derived nutrients e.g. Nitrogen and phosphorus
What doe the fungi get from the plant
Carbom
how many plants % form mychorrizal relationship with fungi
90%
What type of plant can’t provide fungus with crbon
Non photosynthetic orchids
So these take carbons from fungi which have taken it from another plant
What structure in arbuscular mycrrihiza allow more uptake of nutrients
fungi have extra radical mycelium extending unto the soil
How long arbusucules last
5-15 days
Usually when plant needs lots nutrients
What type of plants are arbuscular mycorrhizas usually foundin
angiosperms
Gymnosperms
Pteridophytes
Bryophytes
How much of land flora do ectomycorrihizal host plants make up
3%
Mostly woody planta
How can we experimentall detect carbon flow into fungi
radioactive carbon
Can se ~30% carbon goes into fungi
What experiment used to see how much P the fungi consumes form the plant
mesh experiment
In the mesh that fungi was allowed to pass through, P levels in soil were low cuz fungi used it all
how do plants uptake inorganic mtter
free living microbes in soil convert organic into inorganic that the plant uptakes
but remember this is not as good as the organic uptake from the fungi that goes directly to plant
