Mycorrhizal Fungi Flashcards
What are the four types of Myccorhizal fungi?
- Arbuscule Myccorhizal fungi (AM, VAM)
- Ecto-mycorrhizal fungi (EM)
- Ericoid mycorrhizal fungi
- Orchid mycorrhizal fungi
What are the defining features of arbuscule Myccorhizal fungi
- Symbiosis with 2/3 of all land plants
- Host species include: grasses. agricultural crops (wheat, corn, legumes), tropical trees, herbs, bryophytes
- Fungi
- Anatomy include arbuscules that cover the plant root cell with a hyphal coretx.
- Hyphae protuding externally from the root (which act as roots)
What are the defining features of Ecto-mycorrhizal fungi
- Hosted mainly by temperate tree species
- Anatomy includes a ‘Hartig net’ that lies between plant roots cells with a rich concentration of hyphae forming a mantle outside the root.
What are the defining features of Ericoid mycorrhizal fungi
- hosted by most ericaceae species
- Hyphal coils in enlarged cortical cells
- No mantle or Hartig net
- External hyphae remain relativley close to root
What are the defining features of Orchid mycorrhizal fungi
- Orchids are obligate dependent on Mycorrhiza which require the carbon provision due to small seed size
- Orchid seeds will often parasitize fungal hyphae (peletons) when germinating
- usually saprotrophic fungi (live in leaf litter/soil)
parasitised by orchids
What are the ecosystem functions of mycorrhizal fungi
- They are important for nitrogen cycling where nitrogen in the air is inaccessible to plants, mycorr. fungi are able to access nitrogen from decomposing matter in the soil and provide plants access to this nitrogen.
- Provide plants with nutrients that are limiting within their specific habitat (Read 1991). For example, The hyphae act as roots that allow the extension of resource access and uptake (Giovanetti et al. 2001). For example, the uptake of phosphorous in Bromus grasses is positively correlated to t hyphal length
- Carbon cycling where carbon that is produced through plant photosynthesis is actively absorbed by mycorrhizal fungi storing vast amounts of carbon underground. This was shown by following the path of 14C isotopes (Leake et el 2002)
- Nutrient exchange with plants where 4-50% of plant carbon is absorbed. EMF provides 40-98% of plant nitrogen and 33-80% of plant phosphorous. AMF provides 10-99% of plant phosphorous
- By providing more phosphorous demanding species such as herbs with extra P, it allows them to compete with less demanding plan species such as grasses
- contribute significantly to soil aggregation and structure
- increase the biomass of plants in nutrient poor soils (van der Heijden et al 1998)
Are mycorrhizal fungi host specific? What impact does this have on their ecosystem functions?
No, this allows one fungal organism to simultaneously colonise and interconnect a number of plants. This allows for the effective establishment of a network between plants with the following functions:
- Indirect transfer of carbon between trees (inter and intraspecific transfer). klein et al. 2016; Van der Heijden 2016).
- Facilitates communication between plants about herbivory such as aphids (Babikova et al. 2013)
What benefits do mycorrhizal fungi have in agricultural applications
- It has been shown that inclusing of mycorr. fungi in crop soil reduces the amount of nitrogen wash off, subsequently improving yields for maize (bender and van der heijden 2015).
- This also prevents nitrogen conatmination in surrounding areas
Discuss the impact of mycorr. fungi on plant growth and plant diversity
Plants vary in their response to mycorr. fungi.
Discuss the impact of different mycorr. fungi and fungal diversity on plant growth, plant diversity, plant productivity, plant nutrition and soil structure for various habitat types ie. grassland
AMF promote plant eveness and plant diversity in Euro grassland. Some plant species have been shown to have a very strong dependnency on mycorrh. fungi for development. Ultimatley AMF enhance the number of plant species that can coexist. but some mycorr. species may also inhibit plant species growth where plants are not well adapted to them.
What can suppress the uptake of phosphorous in mycorr. fungi
certain types of bacteria (Svenningsen et al. 2018)
What is Mycorrhizal symbiosis? How is it different from a mutualistic interaction?
Interaction of two species that live together (plant and fungus) that may not always be beneficial for both parties mutualism is a +/+ interaction
Why is mycorrhizal fungus found in so many ecosystems
It is very old. Mycorr hyphae are very well adapted to forage for food and is more beneficial for plants to form symbiotic relationship rather than to source it themselves
What are mycorrhizal networks
- Colonisation of two different plants by a single fungus organism
- allows carbon transfer on some occasisions such as between a flax and sorghum species (Walder et al 2012)
- Plant reciprocates fungus individuals that are supplying resources such as phosphorous as shown be Kiers et al. (2011)
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Draw a rank abundance diagram of a plant community with 5 species in a situation with AMF. 2 grasses, 2 herbs and 1 beech tree seedling. The plant community gets invaded by an EMF. Make a new rank abundance diagram to represent what would change. Explain why
- see notes for graph
- grass species or herbs would be doing the best with the beech tree the worst, because most herbs need AMF, but temperate trees require EMF. when the fungal community changes the EMF allows the beecjh tree to improve in growth. meanwhile the grasses and herbs would remain the same because grasses usually dont have any MF symbiosis and herbs already have AMF available.
