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
