Mycorrhiza Fungi.pptx

Fungi

1. Mycorrhiza Fungi

2. Associations (symbiotic ?) between plant roots and fungi. “Most woody plants require mycorrhizae to survive; most herbaceous plants need them to thrive” Mycorrhizae

3. Mycorrhizae plants leak complex nutrients (sugars, amino-acids, vitamins) fungi store above compounds and provide efficient water and mineral gathering - esp. in poor soils. eg PO 4 , Fe Mycorrhizae very important - > 90% of plants depend on them - some absolutely - some partially (helps counter stress due to pollution or environment, need less fertilizer, grow in more extreme conditions etc).

4. Mycorrhizae 1 . Ectotrophic mycorrhizae (EM) grow on exterior and between cortex cells but never penetrate root cells 2000 sp of plants incl. many important trees eg pines, firs, oaks, beeches and eucalypts depend on EM. about 5000 fungal sp mostly Holobasidiomycetes + a few Ascomycetes

5. Mycorrhizae 2. Endotrophic or vesicular-arbuscular mycorrhizae (VAM or just AM) penetrate inside cells of cortex of root over 300,000 sp of plants - only a few plant families lack VAM (e.g Brassicaceae) only 130 sp of fungi so far - all obligately mycorrhizal - mostly asexual Zygomycetes in the order GLOMALES BUT taxonomy confused - may be many more species.

6. Ectotrophic Mycorrhizae spores or hyphae establish dense infection on root surface ( mantle ) some hyphae penetrate between cortical cells forming the Hartig net - the main interface for exchange fungal hormones make root cells grow to become thicker and branched, root hairs suppressed - result = short stubby roots + extensive fungal hyphae fungal mantle can act as a sink - store plant sugars etc. and also soil minerals a single tree may have several sp. of EM fungi associated with it.

7. Ectotrophic Mycorrhizae Mycobiont usually a Holobasidiomycete (eg Amanita), sometimes an Ascomycete (eg Tuber - truffles) - fruit bodies develop above or below ground Some fungi have wide host range, others species specific. Hosts in Gymnosperms (pines and other conifers), Angiosperms (oaks and other hardwoods) - mostly woody plants. Selection and encouragement of EM very important in forestry. How to select best EM ? - see text pages 263-269.

8. Larix laricina(larch) with Suillus cavipes mycobiont fungus hyphae short stubby roots Pinus strobus with . Amanita muscaria

9. Douglas fir tree 100 feet (30 metres) tall will probably have about 10 8 ectomycorrhizas. These may collectively involve ten or a dozen different fungi Individual ectomycorrhizas remain active for up to 3 years. Forests seem to consist of a mass of interconnected organisms, cooperating and competing together. A single 'clone' of Armillaria ostoyae has colonized an area of about 1500 acres in Washington State, and probably has a mass of hundreds of tons.

10. Short stubby roots (often branched) after infection ectomycorrhizas of Laccaria bicolor with Populus tremuloides. dichotomously branched ectomycorrhizas of a basidiomycete with a conifer.

11. Transverse sections showing Hartig Net Side view of cortical cell surface showing dense coverage of the hyphae (Hartig Net)

12. Seedlings of Douglas fir with and without ectomycorrhizal partners . Photosynthetically fixed carbon has been shown to move from birch to adjacent Douglas fir trees (they have at least 10 mycobionts in common).

13. Vesicular-Arbuscular Mycorrhizae (VAM) (Endotrophic) not detectable to naked eye (no short, stubby and branched roots like EM), no flush of mushrooms Fungus infects root or root hair, grows into cortical region and penetrates cells, developing ‘tree-like’ highly branched hyphae inside - arbuscules - main interface for nutrient exchange. most sp. produce large vesicles - full of lipids

14. Vesicular-Arbuscular Mycorrhizae (VAM) (Endotrophic) Like the EM types, VAM fungi develop an extensive network of hyphae in a wide zone round root has been estimated that 1gm of soil may contain 14km. of hyphae !!!. 20-25% of the soil volume near roots may be hyphae fungus may have a very wide host range - but situation confused by poor taxonomy (what is a species ?) Usually not found on those hosts that have EM Types of VAM present in soil + the pathogens - may be the key factor determining plant diversity at that site.

15. Extramatrical hyphae of Glomus mosseae , an AM fungus - these allow a mycorrhizal plant to exploit several times the volume of soil available to a non-mycorrhizal plant. These hyphae obtain phosphorus and other minerals, plus water for the plant. In return they receive photosynthetic products.