WK - Plant Microbiomes Below Ground II Flashcards
What are the types of Plant Symbioses? (3)
Mutualism: Both organisms benefit.
Commensalism: One organism benefits, the other is unaffected.
Parasitism: One organism (parasite) benefits at the expense of the other.
What are some types of Mycorrhizal fungi? (3)
- Endomycorrhizal fungi (e.g., Arbuscular, Ericoid, Orchid)
- Ectomycorrhizal fungi
- Ectendomyccorhizal fungi (e.g., Arbutoid mycorrhizae)
What are the features of Mycorrhizal fungi? (5)
- Mutualistic relationship with plants
- Exchange nutrients (P, N) for carbon
- Greater water access
- Improve plant stress tolerance
- Common in most terrestrial plants
What are some characteristics of Arbuscular Mycorrhizal Fungi? (6)
- Phylum: Glomeromycota
- Relationship dates back ~400-500 million years
- Key structure: Arbuscules (tree-like structures for nutrient exchange)
- Vital for plant transition to land (possibly with Mucoromycota)
- Found in ~80% of plant species
- Obligate symbionts
What is an Arbuscule? (2)
- A tree-like structure formed by fungal hyphae inside plant root cells
- Increases surface area for nutrient exchange
What factors stimulate the Arbuscular Mycorrhizal Fungi (AMF) Partnership? (4)
- Strigalactones: Plant hormones that initiate AMF signaling
- Lipochitooligosaccharide Mycorrhizal Factor (Myc factor)
- Common Symbiosis Pathway: Shared molecular pathway for symbiosis
- β-monoacylglycerol: Lipid essential for fungal growth, not synthesized by AMF
What are some characteristics of Ectomycorrhizal Fungi (ECM)? (6)
- Phyla: Ascomycota and Basidiomycota
- Associates primarily with trees, especially in temperate forests
- Key structures: Mantle and Hartig net
- Evolved independently about 80 times in fungi
- Likely evolved from fungal saprotrophs that lost enzymes
- Can degrade soil organic matter
What enzymes do Ectomycorrhizal Fungi produce, and what is their role? (3)
- Produce extracellular enzymes (e.g., cellulases, hemicellulases, polyphenoloxidases)
- Thought to contribute to the degradation of plant litter components
- Provides an advantage for acquiring nitrogen in nitrogen-limited temperate forests
What are the Mantle and Hartig Net in Ectomycorrhizal Fungi? (3)
- Mantle: A dense sheath of fungal tissue surrounding the root
- Hartig Net: A network of fungal hyphae that penetrates between root cells, facilitating nutrient exchange
Function: Exudates and water must pass through the mantle; hyphae penetrate intercellularly but not intracellularly
What are some characteristics of Ericoid Mycorrhizal Fungi? (6)
- Phylum: Primarily Ascomycota and some Basidiomycota
- Associate with Ericaceae species (e.g., blueberries)
- Key characteristic: Coils
- Commonly found in acidic, infertile heathlands and high altitudes
- Some can form Ectomycorrhizal associations with trees
- Retain more degradation genes than Ectomycorrhizal fungi
What are some characteristics of Orchid Mycorrhizal Fungi? (5)
- Phylum: Primarily Basidiomycota (Agaricomycetes)
- Key characteristic: Coils
- Associate with Orchids
- Myco-heterotrophic: Depend on fungi for nutrients
- Retain more degradation genes than Ectomycorrhizal fungi
What are the characteristics and functions of Coils (Pelotons) in Ericoid and Orchid Mycorrhizal Fungi?
Orchid:
- Coils: Loosely coiled hyphae within root cells
- Function: Orchid seeds may absorb carbon from hyphae or acquire carbon and nitrogen by digesting pelotons/coils (likely from fungal trehalose > glucose)
Ericoid:
- Coils: Tightly coiled fungal hyphae within plant root cells, common in ericaceous plants (e.g., heaths)
- Function: Carbon (C) exchange for nutrients
What are some characteristics of Arbutoid Mycorrhizal Fungi? (4)
- Phylum: Basidiomycota
- Key characteristic: Ectendomyccorhizal
- Associates with small Ericaceae trees and shrubs
- Genera: Arbutus and Arctostaphylos
What are some characteristics of Monotropoid Mycorrhizal Fungi? (6)
- Phylum: Basidiomycota
- Associates with subfamily Monotropoideae (Ericaceae)
- Completely achlorophyllous plants (lack chlorophyll)
- Key characteristics: Hartig net and fungal peg
- No penetration of plant cells
- Myco-heterotrophic: Depend on fungi for nutrients
What are some examples and characteristics of Plant Parasitism? (3)
Achlorophyllous Plants:
- Plants that lack chlorophyll and cannot photosynthesize
- Depend entirely on other organisms for nutrients
Orchids
- Some orchids engage in mycoheterotrophy
- Obtain nutrients from fungi associated with other plants
Striga (Witchweed)
- A genus of parasitic plants that infects the roots of host plants, mainly crops like maize and sorghum
- Attaches to host roots and extracts water and nutrients
- Can significantly reduce crop yields
What is Mycorrhizal Parasitism? (2)
Definition: A form of parasitism where non-photosynthetic plants (e.g., some orchids) exploit mycorrhizal fungi for nutrients.
Process: Mycorrhizal fungi form connections with photosynthetic host plants, facilitating nutrient exchange. Parasitic plants access these fungi, indirectly siphoning carbon and nutrients from the host plant.
What is Root Nodule Symbiosis? (5)
- Nitrogen-fixing root nodule symbiosis (Rhizobia)
- Paraphyletic: Alphaproteobacteria and betaproteobacteria
- Relationship of ~100Mya
- Key characteristic: Nodules
- Vital for nitrogen acquisition
What factors stimulate the Rhizobial Partnership? (4)
- Flavonoids: Plant compounds that initiate signaling
- Lipochitooligosaccharides (Nod factor): Recognized by Nod Factor Receptor 1 (NFR1) and NFR5
- Common Symbiosis Pathway: Involves calcium spikes
- Nodulation Signaling Pathway: Evolved for Arbuscular Mycorrhizal Fungi (AMF) interactions
