1 / 31

Plant/Microbe Interactions - Beneficial

Plant/Microbe Interactions - Beneficial. Interactions involving plant roots Rhizoplane - the surface of the plant root, root hairs present large surface area (> 6 m 2 for an average wheat plant). Only 4 - 10% of the rhizoplane is in direct contact with soil microbes.

Download Presentation

Plant/Microbe Interactions - Beneficial

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Plant/Microbe Interactions - Beneficial • Interactions involving plant roots • Rhizoplane - the surface of the plant root, root hairs present large surface area (> 6 m2 for an average wheat plant). Only 4 - 10% of the rhizoplane is in direct contact with soil microbes. • Rhizosphere - the area of the soil directly influenced by plant roots (extremely variable). Soil that remains after shaking off roots.

  2. Plant/Microbe Interactions - Beneficial • Interactions involving plant roots • Rhizosheath - some plants excrete a mucous-like material that cement sand grains together around the root. Most common in dry soils.

  3. Plant/Microbe Interactions - Beneficial • R/S ratio - indicates the importance of the root system to the microbial community. • R  the number or biomass of microbes in the rhizoshphere. • S  the number or biomass of microbes in root-free soil. • R/S typically between 5 and 20, can be >100

  4. Plant/Microbe Interactions - Beneficial • In the rhizosphere (relative to root-free soil) • abundance of Gram-negative rods is higher • abundance of Gram-positive rods and cocci is lower • Reflects the influence of plant root exudates and the selection of organisms with high growth rates

  5. Plant/Microbe Interactions - Beneficial • Root exudates • amino acids (proteins) • keto acids (TCA cycle) • vitamins (enzyme co-factors) • sugars (C and energy)

  6. Plant/Microbe Interactions - Beneficial • Roots surrounded by active microbes produce more exudates than roots in sterile soil. • The roots are not just leaky, there is an interaction with the microbial community. • As a plant grows the community in the rhizosphere changes to fast-growing, growth factor-requiring organisms.

  7. Plant/Microbe Interactions - Beneficial • Microbial populations are clearly benefited by the interaction with roots . . . but what does the plant get? • One major plant benefit is nutrient uptake . . .

  8. Plant/Microbe Interactions - Beneficial • Mycorrhizae • mutualistic associations between fungi and plant roots • fungi become integrated into the root structure • both partners benefit (not a disease)

  9. Mycorrhizal symbioses • Advantages: • Enhancing plant nutrient adsorption • Reducing soil born diseases • Improving plant water resistant

  10. Mycorrhizal Fungi

  11. Mycorrhizae Tree root Fungal hyphae Mycorrhizal structure

  12. Plant/Microbe Interactions - Beneficial • Ectomycorrhizae • fungi form an external sheath on the root and extends into intercellular spaces (not inside individual cells) • approximately 40 mm thick • the root association can be up to 40% fungi by dry weight

  13. Ectomycorrhizae

  14. Plant/Microbe Interactions - Beneficial • Ectomycorrhizae • found in most trees in temperate forests • benefits to the tree include: • drought resistance • pathogen resistance • enhanced nutrient uptake (PO4 and K) • increased tolerance to pH changes • increased root growth

  15. Plant/Microbe Interactions - Beneficial • Ectomycorrhizae • benefits to the fungus includes: • first access to plant exudates • direct benefit from trees photosynthetic activity

  16. Plant/Microbe Interactions - Beneficial • Endomycorrhizae • fungal mycelia penetrate both between cells and inside individual cells • heath, rododendrons, laurels, orchids • the fungal partner does not fix nitrogen, but does seem to enhance the uptake of combined nitrogen

  17. Plant/Microbe Interactions - Beneficial • Endomycorrhizae • orchids are pollinated at night and some mycorrhizal fungi are bioluminescent (insect attraction?) • rRNA sequence data place the origin of the endomycorrhizal fungi at or near the origin of land plants . . . may indicate a long term co-evolution.

  18. Plant/Microbe Interactions - Beneficial • Vesicular-Arbuscular (VA) Endomycorrhizae • the most common of all mycorrhizal associations • Phytobionts : 80% of plant species • wheat, corn, potatoes, beans, soybeans, tomatoes, strawberries, apples, oranges, grapes, cotton, tobacco, tea, coffee, cocoa, sugar cane, sugar maple, rubber . . . • Phylum : Glomeromycota • Genera: Glomus, Paraglomus, Sclerocystis, Acaulospora, Entrophospora, Gigaspora, Scutellospora, Diversispora, Geosiphon, and Archaeospora

  19. Plant/Microbe Interactions - Beneficial • Vesicular-Arbuscular (VA) Endomycorrhizae • extensive network of mycelia that extends well out into the soil surrounding the root hair (vesicle and tree-like shapes) • arbuscules = tree-like • vesicles = intracellular fungal storage structures which are lipid containing bodies

  20. Plant/Microbe Interactions - Beneficial Colonization of a root by an endomycorrhizal fungus (Brundrett et al. 1985 Can. J. Bot. 63: 184).

  21. Plant/Microbe Interactions - Beneficial

  22. Plant/Microbe Interactions - Beneficial • Vesicular-Arbuscular (VA) Endomycorrhizae • benefits to the tree include: • drought resistance • pathogen resistance • enhanced nutrient uptake (combined nitrogen, P, Zn, & Cu) • increased tolerance to pH changes • increased root growth

  23. Interaction of AM & Agricultural Practices • Fertilizer Application : High P • Crop Rotation : non-host plant species • Tillage : reduced / no tillage practices • Liming

  24. Mycorrhizal Dependency

  25. Propagation cycle of AMF a. Spores of (i) Gigaspora, (ii) Glomus, (iii) Entrophospora, and (iv) Acaulospora; b. germinating spore; c. hyphal network and spores; d. hypha and spores around root; e. hyphal penetration inside root; f. intracellular arbuscules; g. intraradical vesicles; h. colonized plant

  26. Inoculum Propagation • Pot-culture propagation - Isolation of AMF pure culture strain : single spore - Choice of a host plant : Allium porrum, Sorgum bicolor, Zea Mays, Paspalum otatum • In vitro propagation on root-organ culture

  27. In Vitro Propagation a. Isolated spores; b. germinating colonized root segment; c. carrot root in culture; d. AMF root-organ culture; e. closer view of an AMF root-organ culture

  28. In Vivo Propagation a. Seeding mycorrhizal substrates; b. mycorrhizal seedling production; c. growth chamber inoculum propagation; d. root growth and colonization; e. colonized seedlings; f. field inoculum propagation

  29. End

More Related