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Mycorrhizas

• Literally means “fungus root” • Fungi form many types of symbioc Fungal Symbiosis associaons – Roots – Underground organs of plants • Mutualisc associaons – Fungus sends nutrients to plant Cassie Doinoff, Andreal Reed, Kae – Plant provides fungus with sugar Allen, and Adie Kurtanich

Types of Mycorrhiza Arbuscular Mycorrhiza (AM)

• Arbuscular mycorrhizas • Most common type of mycorrhiza • Ectomycorrhizas • Found worldwide • Ericoid mycorrhizas – Crop plants • Orchid mycorrhizas – Trees – Herbaceous plants • Monotropoid mycorrhizas • Originally classified as Zygomycota • Now classified in new monophylec group – Glomeromycota

Arbuscular Mycorrhiza (AM) Arbuscular Mycorrhiza (AM)

• Roots show no outward signs of infecon • Fungal hyphae extensively colonize roots • Hyphae can only be seen by special 1. Grow between root corcal cells techniques • Produce large swollen vesicles – Differenal interference contrast microscopy – Storage funcon – Staining • Treat root with strong alkali • Stain with fungal dyes such as trypan blue

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Arbuscular Mycorrhiza (AM) Fig 13.1

• Fungal hyphae extensively colonize roots 2. Penetrate individual root corcal cells • Form tree-like branches known as arbuscules – Main site of nutrient exchange between fungus and cell root – Remain alive for short period of me – Degenerated and replaced

Fig. 13.1. The principal features of arbuscular mycorrhizal (AM) fungi, observed by clearing the root ssues with strong alkali and then staining roots with the fungal dye, trypan blue. Top le: A root heavily colonised by AM fungi, with hyphae that radiate into the soil. Top right: When observed through the depth of the root cortex, AM fungal hyphae are oen seen to run parallel to the root axis, growing between the root corcal cells. These hyphae are irregular, with constricons and bulges, quite unlike the hyphae of most other fungi. They frequently produce large, swollen vesicles within the root ssues. Boom le: some of the external hyphae and hyphal aggregates produce clusters of spores in the soil. Boom right: Some of the root corcal cells are penetrated by hyphae that branch repeatedly to produce intricately branched arbuscules, oen completely filling the root cells. [� Jim Deacon]

Arbuscular Mycorrhiza (AM) Arbuscular Mycorrhiza (AM)

• Spores • Ecological Significance of AM – Large, up to 400 um – AM fungi provides plants with mineral nutrients – Germinate and infect the roots from soil • From an appressorium-like infecon structure on the • Especially phosphorous root surface • Produce extensive hyphal networks in soil • Release acid phosphatases • Absorb phosphate in excess and store it in form of polyphosphates

Arbuscular Mycorrhiza (AM) Fig 13.4

• Host ranges and communies of AM fungi – AM have a wide range of host – Experimental study by Van den Heijden et al. • Plants in natural communies are colonized preferenally by different strains of AM fungi • The diversity of AM fungi in a site can influence the plant biodiversity in natural ecosytems

Fig. 13.4. An increase in the number of different arbuscular mycorrhizal fungi in a soil leads to an increase in plant producvity and plant biodiversity.

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Fig 13.5 Ectomycorrhizas

• Found mainly on woody plants – Coniferous and broad-leaved trees outside of tropics • Such as pine, spruce, oak, beech, and birch – Members of Basidiomycota or Ascomycota – Characterisc feature • Presence of substanal sheath of fungal ssue – Incases the terminal nutrient absorbing rootlets

Fig. 13.5. Total biomass and the biomass of three representave plant species grown in soil with no mycorrhizal fungus (0) or with four separate AM fungal species (A,B,C,D) or a combinaon of all four AM species. Note that the vercal scale of each histogram is different but the largest biomass is shown in each case.

Ectomycorrhizas Ectomycorrhizas

• Ecologically adapted to grow as symbionts • Grouped into two types – Can grow in laboratory on simple media – Generalists – Have lile to no ability to degrade cellulose and • Wide host range lignin • Young trees – Such as Laccaria, Hebeloma, Thelephora terrestris • Rarely have high degree of host-specificity

Ectomycorrhizas Ectomycorrhizas

• Grouped into two types • Fungal Networking – Mature – Extensive network of hyphae and mycelial cords • Host restricted • Link different plants within a habitat • Mature trees • Mycelial connecons retain mineral nutrients • Release proteases – Withdraws nutrients from degenerang mycorrhizas – Providing ectomycorrhiza plants with nitrogen in the form of – Transports nutrients to other funconing mycorrhizas amino acids • Fungal network extends beyond root zone – Mycelial cords transport water from deeper in the soil, beyond the reach of the roots

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Fig 13.7 Fig 13.8

Figure 13.8 A young larch seedling, about 3 cm high, growing in a peatbased substrate Fig. 13.7. Le: Scanning electron micrograph of a cross secon of part of a mycorrhizal root, showing the fungal sheath that surrounds the root. Right: Thin secon of part of an ectomycorrhizal root. The arrowheads show hyphae invading between the root against a sloping face of an observaon chamber. Mycoohizas can be seen at the base corcal cells, forming the Harg net. Nutrient-exchange between the fungus and the root is thought to occur in this interfacial of the stem but almost all the visible growth is mycelial cords that explore the soil for region. nutrients.

Ericoid Mycorrhizas Fig 13.10

• Typical host families – Ericaceae – Epacridaceae • Both families produce coils of hyphae termed “hair roots” • Fungi that produce this mycorrhiza are free- living saprotrophs in soil – Ascomycota Fig. 13.10. Secon through part of the protocorm (basal stem region) of an orchid, Neoa, showing coils of hyphae (termed 'peletons') within the orchid cells.The plant cells were alive at the me of seconing, evidenced by presence of nuclei (the dark granular structures) in two of the orchid cells. [� Jim Deacon]

Ericoid Mycorrhizas Orchid Mycorrhizas

• Grown in culture • Parasic on fungus – Produce septate hyphae with fragmented zigzag • Orchid seeds growth – Small, consists of embryo and few nutrient • Primary role reserves – To provide host plants with nitrogen – Triggered to germinate • Secrete proteinase • Produce few root hairs • Must be colonized by a fungus at an early stage or – Release amino acids from soil organic maer seedling will die

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Orchid Mycorrhizas Orchid Mycorrhizas

• Fungus penetrates orchid embryo and produces • Provide orchids with sole source of hyphal coils carbohydrates during early years of life – Peletons – Most do not emerge above ground or produce • Only last a few days chlorophyll unl 3-5 years old • Degenerate and replaced by further coils in other cells – As many as 200 species never produce chlorophyll • Repeated process provides main source of • Remain dependent on mycorrhizal fungus sugar to developing orchid

Monotropoid Mycorrhizas Monotropoid Mycorrhizas

• Plants of family Monotropaceae lack • Three membered symbiosis chlorophyll – Direct nutrional connecon – Dependent on mycorrhiza fungi for all their • Tree host nutrients • Mycorrhizal fungus • Found in shade beneath forest trees • Parasic higher plant • Fungi involved are Basidiomycota – Radiate into the soil as hyphal networks or mycelial cords • Form hyphal sheath around roots

Summary Lichens

Mycorrhizal type Typical host plants Fungi involved Major Significance • Lichens – symbioc associaons of fungus & Arbucular Many Glomeromycota Phosphorous mycorrhizas uptake from soil photosynthec partner (green alga or Ectomycorrhizas Forest trees Basidiomycota, Nitrogen uptake Ascomycota from soil cyanobacterium) Ericoid mycorrhizas Heathland plants Ascomycota Nitrogen uptake • Involve 2 or more partners from soil Orchid mycorrhizas Orchids Basidiomycota Fungi supply plant – Come together to form disnct new organism with sugars – Form long-term symbioc relaonships Monotropoid Nonphotosynthec Basidiomycota Plants obtain sugars mycorrhizas plants from ectomycorrhizas

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Lichen Partners

• 13,500 to 17,000 species of lichens • Difficult to name & classify since composed of 2 or more organisms • Mycobiont – fungal partner – Usually type of Ascomycota or rarely Basidiomycota • Photobiont – photosynthec partner – Green alga or cyanobacterium

Examples of Lichens

Fungal Lichen Partners Algal Lichen Partners

• Lichen fungi are very specialized & mainly • About 100 types of green algae are lichen found only in lichen partnerships partners • Few species are found in non-symbioc states • Trebouxia – Most common genus associated with lichen • Some species have been grown in lab partnerships – Slow growth – Single-celled rarely found as free-living – Lack enzymes needed to live freely – Found in temperate regions • Trentepohlia – Found in tropical regions

Cyanobacteria Lichen Partners Forms of Lichens

• Found in about 10% of lichens • Lichen thallus – body of lichen • Pelgera • Categories – Most common genus – Foliose • Flat & leaf-like – Found in dog lichen – Frucose • Some lichens have green algae & cyanobacteria • Erect & branch-like • Cephalodia – wart-like structures on lichen – Squamulose surface • Small & scale-like – Crustose – Thought to use nitrogen fixing abilies of • Flat & crust-like cyanobacteria

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Structural Organizaon Physiology: Water Requirements

• Many have well-defined structures • Lack of water • Typical structure – Lichens containing green algae absorb water from – Upper cortex humid air & resume photosynthesis – Medulla – Lichens containing cyanobacteria must absorb – Lower cortex liquid water to resume photosynthesis – Rhizinae – Drought tolerance is likely conferred by • Algal associaons also require gas exchange hydrophobins produced by lichen fungi – Hydrophobin coated fungal hyphae create spaces for gas exchange

Physiology: Nutrient Exchange Physiology: Nutrient Exchange

• Lichen fungi protect photosynthec partner & • Photosynthec partners provide sugars for the absorb nutrients growth of lichen – Very efficient at absorbing nutrients from limited – Give up to 90% of photosynthate to fungal partner environmental resources • Carbohydrates found in lichens – Unfortunately for lichens, also absorb toxins & – Mannitol pollutants – Arabitol • Thus, lichens are rarely found in polluted environments – Ribitol – Glucose

Reproducon & Dispersal Ecology & Significance

• Propagaon • Lichens can live in a variety of environments – In some lichens, fragments break off & are – From tundra to cooled lava flows to tropical transported by wind or animals forests – Isidia – stalk-like structures produced by some • Most significant role of lichens lichens that break off – Contribuon to soil formaon – Soredia – powdery propagules – Dispersal of fungal ascospores & reassembly with photosynthec partner

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Summary Geosiphon pysiform • Unique relaonship • Symbioc associaons between fungal, between mycorrhizal cyanobacterial &/or algal partners and cyanobacteria • Can survive in many environments – Duel organism • Have defined structures • Discovered in Germany • Have several ways to propagate – 1996 • Significant contribuon to soil formaon • Belongs to the arbuscular mycorrhizal Bladders of Geosiphon pyriforme growing (AM) and related fungi on the surface of soil. Courtesy of A. Schuessler

Geosiphon pysiform Geosiphon pysiform • Endocytose cyanobacteria – Leads to a membrane bound symbiosome containing cyanobacteria • Provides fungus with source of sugar – Symbioc • Cyanobacteria depends on phosphate from fungus – Mutualisc

Image courtesy of A. Scheussler & M. Kluge, 2001

Fungus/Insect Mutualism Sirex Wood Wasp

• Several insects have mutalisc associaons • Female injects toxic mucus and Amylostereum with fungi areolatum – Provide the insect with a food source – Laying eggs in bark of damaged trees • Insect ensures mutualism – Mucus kills tree cells – Carrying and transming the fungus – Fungus feeds on the killed wood • Mycangia – Inoculate suitable substrate with spores on the – Insect larva feed on fungus fungus • Aer pupaon, the female adults collect – Tending the substrate to promote growth of the spores from the rong wood fungus • Food source – Store in mycangia to repeat the cycle

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Leaf-Cung Ants

• Ane Ants – Produce large nests – Carries fungus, Leucoagricus, in pouch of mouth – Deposits fungus on suitable plant – Eggs laid as fungus grows – Worker ants bring leaf pieces back to nest, inoculate with fungus – Fungus produces hyphae • Gongylidia or bromaa • Fed to larvae • Provide enzymes needed for degrading plants The wood wasp, Sirex noclio, boring a hole in a weakened tree to deposit eggs and fungal spores. Courtesy of M. P. Cous, J. E. Dolezal and the University of Tasmania

Gardening Termites Wood Boring Beetle

• Do not digest wood • Produce tunnels in damaged trees • Evolved symbiosis with the Termitomyces – Deposit eggs – Found in fungus gardens – Smear with ambrosia fungi • Termites weed out any contaminant fungi • Spores stored in special sacs of beetle • Heavy rainfall – Mycangia – Fungus produces large, mushroom fruitbodies • Developing beetle larvae – Create galleries beneath bark – Feed on fungus

Fungus/Insect Mutualism Quesons

• About 40-60 million years ago, these three 1. Which fungal phylum is associated with types independently evolved the ability to arbuscular mycorrhizas? culture fungi as a source of food. a. Zygomycota • Now all of these fungus-culvang insects and b. Ascomycota their fungal partners are mutually dependent c. Basidiomycota on another. d. Glomeromycota • There is no evidence that they have ever reverted to an independent existence.

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Quesons Quesons

2. T/F – Ectomycorrhizal fungi are classified as 4. Stalk-like structures that aid in propagaon either mature or immature. a. Soredia b. Cephalodia 3. T/F – The primary role of the ericoid c. Isidia mycorrhizas are to provide the host plants d. Rhizinae with sugar.

Quesons Sources

5. Lichens that produce flat crusts on rock, soil, • Deacon, J. Fungal Biology. Cambridge, MA. or tree surfaces Blackwell. 2006. a. Squamulose • hp://www.perspecve.com/nature/fungi/ b. Frucose lichens.html c. Foliose • www-biol.paisley.ac.uk/biorefChlorophyta d. Crustose • www3.isrl.uiuc.edu/~openkeyAlgae/image/ Papilla-pore?N=D • hp://www.lichen.com/vocabulary.html

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