Ectomycorrhiza Flashcards
What type of plants do ectomycorrhiza typically colonize
Trees, woody plants
What percentage of trees are colonized by ectomycorriza compared to plants colonized by endomycorrhiza
10% of trees colonized by ectomycorrhiza; 90% of plants colonized by endomycorrhiza
Which phyla of fungus form the majority of ectomycorrhizal relationships
Basidiomycetes
Which phyla of fungus form the majority of endomycorrhizal relationships
Ascomycetes
True or false: ectomycorrhiza penetrate the root cells of the plants that they colonize
false, they grow around and in between the cells
A loose weft of hyphae that is formed around the plant cell
Hartig net
Hyphae that are established outside of the root
Mantle
Characteristics of roots that are colonized by an ectomycorrhizal fungus
Different color, thicker, lots of dichotomous branching, no root hairs
Do ectomycorrhizal fungus show host specificity
No, they do not show a high degree of host specificity
Apoplast
the space in between the cells
What is delivered into the apoplast from the plant, then taken up by the fungus
Sucrose
What are harvested by the fungus from the environment, then delivered into the apoplast to be taken up by the plant
Phosphate, amino acids, and peptides
Why is the tree completely dependent on the fungus after colonization
Because the relationship results in the loss of root hairs and encasement of the feeder roots by the fungus, so all minerals that enter the root must enter through the hyphae
What percentage of a tree’s net photosynthate is allocated to the fungus
10%
What happens to fungi that are grown outside of the ectomycorrhizal relationship?
The do not fruit, grow poorly, and are unable to degrade cellulose (the principal diet of basidiomycetes)
How long is the typical life span of an ectomycorrhizal relationship
Three years
Two reasons why the ectomycorrhizal relationship eventually ends
The roots outgrow the fungus and the tree roots might be colonized by fungus that is better adapted to the new soil.
The interlocking network of fungi and plants that communicate through the fungal hyphae
the “wood-wide-web”
Three genera of Basidiomycetes that commonly form ectomycorrhizal relationships
Amanita, Boletus, and Tricholoma
Genus of Ascomycete that forms ectomycorrhizal relationships
Tuber
Genus of Zygomycete that forms ectomycorrhizal relationships
Endogone (VERY RARE)
A “menage a trois” network involving two plants and one fungus where one plant does not photosynthesize
Monotropoid mycorrhiza
Which features to monotropoid mycorrhiza and ectomycorrhiza share
A mantle and hartig net
A nutrient transfer hyphae that punctures the cell wall, but not the membrane.
fungal peg
What does the monotropic plant give to the fungus?
nothing
Where does the fungus in a monotropoid mycorrhiza get its carbohydrates
A photosynthesizing third party, usually a pine
Examples of the three participants in a monotropoid relationship
Monotropa (monotropic plant), Boletus (fungus), and Pinus (third party photosynthesizer)
Why are orchids completely dependent on fungi for the first 2-11 years of life
they go through a non-photosynthetic phase during this time
Why are orchids called “mycorrhizal cheaters”
They give nothing back to their fungal benefactor
The genus and phylum of the most common orchid mycorrhiza
Rhizoctonia spp. (Basidiomycete anamorph)
Why are orchid mycorrhiza considered endomycorrhiza
They have a hyphal structure that penetrates the plant cell wall, then degenerates after a few days
Peloton
a dense mass of coiled hyphae that invaginates the membrane within the cell wall of orchid root hairs
What is the typical lifespan of a peloton
a few days
Why is the orchid mycorrhizal relationship thought to be still evolving
the fungus sometimes infects the orchid, killing the embryo, so it is a balancing act
Mycorrhiza that has mantle and branches characteristic of ectomycorrhiza, but also penetrates the cell and forms a peloton.
Erecoid mycorrhiza
What characteristics do Erecoid mycorrhiza and ectomycorrhiza share
they both have a mantle and branches
Why are Erecoid mycorrhiza called “ectendo” mycorrhiza
They exhibit features of both ecto- and endomycorrhiza
Why is it difficult to choose the proper ectomycorrhizal inoculant
a toxic species can cause illness/fatalaties or a desirable food species can be over-harvested
Dog shit fungus
Pisolithus tinctorius, an earthball
Lichen
a relationship between a fungus and an alga
Mycobiont
the fungus, which is the dominant partner and determines the shape of the lichen
Photobiont
the alga that lives and photosynthesizes within the fungal thallus, providing carbon compounds
Which is the dominant partner in the lichen relationship
The fungus, which is 95% of the biomass
Why are lichen considered “balanced parasitism”
The relationship is an exploitation by the fungs; the alga can live perfectly fine on its own but is captured by the fungal component
What percentage of food synthesized by the alga is taken by the fungal hyphae
50%
Unicellular alga component found in 80% of all lichen
Trebouxia
Filamentous green algae that is a component in 10% of all lichen
Trentepohlia
Cyanobacteria component found in 10% of all lichen
Nostoc
What is the name of a lichen containing all three components
Lobaria
What role does the cyanobacteria play in the lichen
It does nitrogen fixation
Soredia
Little balls of hyphae-wrapped algae that serve as somatic propagules (reproductive structures)
Cephalodium
The internal, brown clump of cyanobacteria
Isidia
A finger-like growth containing both the photobiont and mycobiont components that grows up from the thallus and breaks off. (Somatic propagule)
Podetia
Large, upright, branched structures that often have cups at the top that may bear soredia
98% of the mycobiont components are
Ascomycetes
Why are the sexual spores formed by lichens so strange
They do not contain an algal component, so they must find their own appropriate photobiont before they can start a new generation of lichen
Many lichen are constantly resynthesized because
The are finding different alga to capture
The fungal solution for finding an appropriate photobiont is:
Cleptobiosis
Cleptobiosis
stealing a photobiont from another exhisting lichen
Lichenicolous lichen
lichen that are growing on top of another because the top lichen has poached the photobiont from the bottom one
A flask-shaped structure bearing conidia
pycnida
Who determines a lichen’s shape
the fungal component
Lichen that looks “painted on”
Crustose lichen
Lichen with a lobed appearance
Folios
Bush-like lichen
Fructiose
Lichen with upturned scale-like squamules
Squamulose
Loose, powdery, soredia-like material lacking an outer cortex and not producing fruiting bodies
Leprose
What happens if a mycobiont is grown without a photobiont
It grows as an undifferentiated mass of hyphae
Under what conditions will the fungus and the alga form lichen
When both parties are completely debilitated, the fungus will “embrace” the alga and the alga will “allow” itself to be co-opted.
Cell wall proteins that polymerize via hydrophobic interactions, which make the lichen very hydrophobic
Hydrophobins
A fungal feeding structure, similar to an arbuscule, that dimples the membrane but doesn’t puncture it
Haustoria
A disaccharide that interacts with the membrane to create a liquid crystalline form when dehydrated and doesn’t leak when rehydrated
Trehalose
How much do lichen grow per year and why
1-4 mm/year because they are dried for most of the year.
How old is the oldest estimated lichen
4500 years old
Measuring the diameter of the largest lichen species on a rock surface to determine how long the rock has been exposed
Lichenometry
Which shape of lichen is the most useful to Lichenologists
Crustose, because it is the slowest grower
What is the Hawksworth and Rose Lichen Scale used to measure
Air pollution
Why are lichen so sensitive to air pollution
Lichen rely on rain to obtain minerals, but acid rain destroys lichen
Three important roles that lichen play in nature
Food for animals, used as nests by birds, and soil formation
Pedogenesis
Soil formation
Cryptobiotic soil
soil that contains lichen with cyanobacteria, which provides the bulk of nitrogen fixation in an ecosystem
