Lecture 10 - mycorrhiza Flashcards
what is the role or mycorrhizal fungi?
absorb nutrients from soil and pass these on to plants
what do the fungi get from the plants?
The plants supply the fungi with sugar and lipid from photosynthesis = a mutualistic symbiosis
what is the main type of mycorrhiza plants use? describe them
arbuscular - branched tree like structures within the cells within the roots - act as an interface where carbon passes from the plant to the fungus and in return the plant receives nutrients into its roots that have been transported from the soil via the fungus from a range of different chemical sources
what is an important part of the fungus?
the interface of the fungus to the soil - takes up the nutrients
how do the fungi reach more nutrients than the plants?
-Hyphal lengths of the fungus are much longer than the roots and very small so they can go into very small pores
4 ways we measure arbuscular mycorrhizal fungi?
- look at what’s inside the roots - microscopy
- Measure biomass by using the molecular marker lipid not only found in mycorrhizal fungi - some bacteria contain it - if there is a lot around it is likely to be the main source of the lipid)
- Most common now is use of DNA extraction and DNA frequency work
- Traditionally the spores of fungi where sieved out of soils and separated using sucrose gradient centrifugation - a lot of the original taxonomy of the fungi was based on spore morphology etc - turns out there is loads of cryptic species we didn’t even know where there because the spores were similar or not very obvious etc
describe the recent problem with DNA identification of fungi
- Standard primers used for DNA identification of AM fungi do not detect Mucoromycotina (another group of fungi). Their importance has been hidden until recently. This has set back the use of DNA quite significantly - very controversial
- A subject that has advanced very rapidly in the last year
why are the root systems of crops important?
mycorrhiza attach to the roots
what effect does tillage have on roots?
- When comparing tillage and no tillage - there is a lot more root with no tillage - probably due to structural differences in the soil
3 important roles of mycorrhiza
huge roles in:
1) transporting nutrient and carbon
2) influences soil structure and chemical changes
3) interactions with other microbes e.g. endosymbiotic bacteria inside the hyphae
primarily why do plants support hyphae networks?
- Primarily to obtain phosphorus
- Fungi allow the extraction of P from pores in soil which are too small for plant roots or root hairs to access. There is increased effective volume of soil exploited by mycorrhizal plants
describe the relationship between phosphorus in the environment and the uptake by the plants?
- In P limited systems- as P becomes available the plants grow bigger until they are satisfied
- The role of mycorrhiza in plant P uptake and plant growth depends on plant and fungal characteristics
e. g. AM fungi produce different amounts of extraradical mycelium, and this directly affects their soil P uptake
can mycorrhiza tap into pools of organic P not accessible by plants?
- Evidence of mycorrhizal fungi directly tapping in to a range of different organic sources of phosphorus more effectively than can non-mycorrhizal plants
what do mycorrhiza often synergistically operate with and what is the advantage of this?
with plant-growth promoting rhizobacteria and some bacteria involved in P solubilisation may help reduce the need to add P fertilizers - may be approach to use P that’s already been added instead of adding more
what does tillage do to fungi?
- Experiment looking at tillage intensities found that conventional ploughing and disking disrupts AM fungal networks and reduces P uptake - active hyphae is greater when there is no tillage
