L7 Mycorrhizal Symbiosis Flashcards
What type of symbiotic relationship is mycorrhizae?
Mutualistic association.
What are the benefits to the mycobiont and phytobiont in mycorrhizal symbiosis?
- Mycobiont (fungus): Receives carbohydrates and organic compounds.
- Phytobiont (plant): Gains improved nutrient and water uptake.
Name the (4) main types of mycorrhizal associations.
- Ectomycorrhizae
- Endomycorrhizae (Arbuscular mycorrhizae)
- Ericaceous mycorrhizae
- Orchid mycorrhizae
Define mycorrhizal symbiosis and its primary nature.
Mycorrhizal symbiosis is a mutualistic relationship between fungi (mycobiont) and plant roots (phytobiont) that enhances nutrient and water uptake for the plant while providing carbohydrates to the fungus.
Distinguish between the benefits conferred to mycobionts and phytobionts in mycorrhizal associations.
Mycobionts benefit from a consistent carbohydrate source, while phytobionts gain improved access to water and nutrients, especially in nutrient-poor soils.
Identify and describe the four main types of mycorrhizal associations and their key characteristics.
- Ectomycorrhizae (ECM): Form a mantle around roots and a Hartig net in the root cortex; primarily associated with trees.
- Endomycorrhizae (AM): Penetrate root cells, forming arbuscules; widespread across many plant species.
- Ericaceous mycorrhizae: Specific to Ericaceae family plants; adapted to acidic, nutrient-poor soils.
- Orchid mycorrhizae: Essential for seed germination; provide nutrients to non-photosynthetic orchid seedlings.
Compare the diversity of plant and fungal species in ECM and AM associations.
ECM is associated with approximately 2,000 plant species and over 5,000 fungal species, while AM involves around 300,000 plant species with about 230 fungal species.
Analyze the ecological roles of ectomycorrhizal fungi within forest ecosystems.
Ectomycorrhizal fungi enhance tree growth, support nutrient cycling, and facilitate community dynamics by forming relationships primarily with dominant tree species.
Discuss the structural features that differentiate ectomycorrhizae and endomycorrhizae.
ECM fungi form an external mantle and internal Hartig net, while AM fungi create arbuscules and vesicles within the root cells, allowing for nutrient exchange.
Evaluate the implications of mycorrhizal specificity and diversity for plant community dynamics.
Narrow specificity can lead to increased dependency on certain fungal partners, affecting plant distribution and competition; broad specificity enhances resilience and resource utilization.
Describe the mechanisms through which mycorrhizae improve water status in host plants.
Mycorrhizal mycelium increases soil exploration, allowing for better water uptake. Fine fungal hyphae can access water in soil pores inaccessible to root hairs, thereby reducing drought stress.
Explain how mycorrhizal fungi enhance nutrient status in plants, particularly regarding insoluble nutrients.
Fungi secrete enzymes like phosphatases and proteases to mobilize nutrients from organic sources, converting them into forms that plants can absorb, leading to improved overall plant health.
Discuss the protective mechanisms mycorrhizae offer against biotic and abiotic stressors.
Mycorrhizae provide a physical barrier to pathogens, produce antibiotics, and enhance plant tolerance to low pH and heavy metals, thus increasing resilience in challenging environments.
Critique the concept of mycorrhizal networks and their ecological significance.
While mycorrhizal networks facilitate resource sharing and support ecosystem stability, claims about their extent and benefits are sometimes overstated, necessitating careful, evidence-based research.
What type of relationship is mycorrhizal symbiosis?
A mutualistic relationship where both fungi and plants benefit.
