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TINJAUAN KRITIS

TINJAUAN KRITIS. MIKROORGANISME TANAH DALAM SISTEM AGROFORESTRY. Judul “Microsymbiont” tanah dalam Sistem Agroforestry Jenis-jenis organisme Bakteri Nitrogen-Fixation yang lain? Perkiraan konstribusi Nitrogen ke dalam tanah? Jenis-jenis Mycorrhiza?.

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TINJAUAN KRITIS

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  1. TINJAUAN KRITIS MIKROORGANISME TANAH DALAM SISTEM AGROFORESTRY • Judul “Microsymbiont” tanah dalam Sistem Agroforestry • Jenis-jenis organisme Bakteri Nitrogen-Fixation yang lain? • Perkiraan konstribusi Nitrogen ke dalam tanah? • Jenis-jenis Mycorrhiza?

  2. Symbiosis = close and intimate association of two species; a “living together” • Terms: • Macrosymbiont – higher plant • Microsymbiont – microorganism

  3. Some Nitrogen Fixing Organisms • Free living aerobic bacteria • Azotobacter • Beijerinckia • Klebsiella • Cyanobacteria (lichens) • Free living anaerobic bacteria • Clostridium • Desulfovibrio • Purple sulphur bacteria • Purple non-sulphur bacteria • Green sulphur bacteria • Free living associative bacteria • Azospirillum • Symbionts • Rhizobium (legumes) • Frankia (alden trees)

  4. Estimated Average Rates of Biological N2 Fixation

  5. Rank of Biological Nitrogen Fixation

  6. Types of Biological Nitrogen Fixation Free-living (asymbiotic) • Cyanobacteria • Azotobacter Associative • Rhizosphere–Azospirillum • Lichens–cyanobacteria • Leaf nodules Symbiotic • Legume-rhizobia • Actinorhizal-Frankia

  7. N2 NH3 Biological Nitrogen Fixation: The Symbiosis N2 represents the largest pool of biologically active nitrogen in terrestrial ecosystems reaching 27,000 g N per m3. N2 N2

  8. RHIZOBIUM

  9. Taxonomy of Rhizobia

  10. RHIZOBIUM

  11. A few legumes (such as Sesbania rostrata) have stem nodules as well as root nodules. Stem nodules (arrows) are capable of photosynthesis as well as nitrogen fixation.

  12. Symbiotic Rhizobia are classified in two groups: Fast-growing Rhizobium spp. whose nodulation functions (nif, fix) are encoded on their symbiotic megaplasmids (pSym) Slow-growing Bradyrhizobium spp. whose N-fixation and nodulation functions are encoded on their chromosome. There are also two types of nodule that can be formed: determinate and indeterminate This outcome is controlled by the plant host

  13. Determinate nodules Formed ontropical legumesby Rhizobium and Bradyrhizobium Meristematic activity not persistent - present only during early stage of nodule formation; after that, cells simply expand rather than divide, to form globose nodules. www.agsci.ubc.ca/courses/agro/426/AGRO426.kronstad.rhizobium.01.ppt

  14. Indeterminate nodules Formed ontemperate legumes (pea, clover, alfalfa); typically by Rhizobium spp. Cylindrical nodules with a persistent meristem; nodule growth creates zones of different developmental stages www.agsci.ubc.ca/courses/agro/426/AGRO426.kronstad.rhizobium.01.ppt

  15. Rhizobium Root Nodules

  16. Nodulation in Legumes

  17. Nodule Formation • Once inside the coritcal cell, the bacteria multiple and dedifferentiate • Infected root cells swell and stop dividing • After dedifferentiation, the Rhizobium are referred to as a bacteroid • After formation, the bacteroid begin to express nif and fix genes and the plant expresses late nodulin genes

  18. FRANKIA

  19. F R A N K I A

  20. Actinorhizal Plant Hosts (Non-Legum)

  21. Frankia and Actinorhizal Plants • Actinomycetes (Gram +, filamentous); septate hyphae; spores in sporangia; thick-walled vesicles Frankia vesicles showing thick walls that confer protection from oxygen. Bars are 100 nm.

  22. MYCORRHIZA

  23. Beberapa Tipe Mycorrhizae Yang Telah Dikenal • VAM (Vescicular Arbuscular Mycorrhyzae) • ECM (Ectomycorrhyzae) • Ectendomycorrhyzae • Ericoid mycorrhyzae • Orchid mycorrhyzae

  24. Endo- and Ectomycorrhiza • Wide-spread association: • Gymnosperms: 100% infected • Dicots: 83% infected • Monocots: 79% infected • Three parts to mycorrhizal associations: • Root • Fungal structures in close association with the root • External mycelium

  25. Endo- and Ectomycorrhiza • Ectomycorrhizas • Fungal tissue largely outside the root • Primarily found in woody species, but also some ferns and monocots • Endomycorrhizas • Large fraction of the fungal tissue is within the root cortical cells • Frequently occur on herbaceous plants, also some tropical trees

  26. Endo- and Ectomycorrhiza • Vesicular arbuscular mycorrhiza (VAM) • Type of endomycorrhiza with specialized structures (vesicles and arbuscules) • Fungi belong to Glomales (Glomus largest genus) • Considered the most ancient type of mycorrhizal symbiosis • Roots of more than 80% of all plant species are infected with VAM-forming fungi

  27. Endo- and Ectomycorrhiza • VAM infection process • Spores are found in the soil, or fungi may colonize from other plant roots • Forms an appressorium only on host plants, colonizes through passage cells of exodermis • Hyphae remain in cortex and don’t penetrate through endodermis to stele • Ecomycorrhiza infection process • Form a mantle of fungal hyphae • Hyphae penetrate intercellular into the cortex, forming Hartig net

  28. Perbedaan Antara ECM dan VAM Secara Garis Besar

  29. Figure. Schematic structure of a vesicular-arbuscular mycorrhiza (VAM).

  30. ENDOMYCCORHIZA

  31. ECTOMYCORRHIZA

  32. TERIMA KASIH http://www.irwantoshut.co.cc/

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