Plant-Microbe Interactions
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Transcript of Plant-Microbe Interactions
Plant-Microbe Interactions
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
INTERAKSI TANAMAN-MIKROBAPlant-microbe interactions diverse – from the plant
perspective:• Negatif – e.g. Parasitis/ Pathogenik• Neutral• Positif – Simbiotik
Pokok bahasan important positive interactions with respect to plant abundance and distribution – related to plant nutrient and water supply:
Dekomposisi BOT Mycorrhizae Fiksasi N2
Rhizosphere
Peranan interaksi ini dalam siklus NSUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
I. Dekomposi Bahan OrganikPemasok utama hara tanaman – terutama N & P
A. Bahan mentahSoil organic matter derived primarily from plants –
• Mainly leaves and fine roots• Wood can be important component in old growth forests
Input rates –• Generally follow
rates of production • Deciduous =
evergreen
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
B. Proses-Proses
1. Fragmentasi Bahan Organik • Breakdown of organic matter (OM) into smaller bits = humus• By soil ‘critters’ – including nematodes, earthworms, springtails,
termites• consume and excrete OM incomplete digestion
nematode
springtail (Isotoma viridis) termites
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
2. Mineralisasi Bahan Organik• Breakdown OM senyawa an-organik• Microbial process: accomplished by enzymes excreted
into the soil
Microbial uptakeIm
mobiliz
ation
Plant uptake
NitriteNO2
-
NitrateNO3
-
energy fornitrifying bacteria*
Nitrification
For Nitrogen
proteins(insoluble)
aminoacids
energy for heterotrophic bacteria
proteases
AmmoniumNH4
+
Mineralization
* In 2 steps by 2 different kinds of bacteria – (1) Nitrosomonas oxidize NH3 to nitrites + (2)
Nitrobacter oxidize nitrites to nitrates SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
NH4+Protein mineralization
NO3-
Serapan Tanaman
1) Nitrate (NO3-)
• Lebih disenangi oleh tanaman,
lebih mudah diserap• Even though requires conversion
to NH4+ before be used lots of
energy
• vs. taking up & storing NH4+
problematic • More strongly bound to soil
particles• Acidifies the soil • Not easily stored
C. Serapan N oleh Tanaman – Chemical form taken up can vary
2) Ammonium (NH4+ ) –
Digunakan langsung oleh tanaman dalam tanah yang nitrifikasinya lambat (mis. Tanah basah)
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
proteins NH4+
mineralization
microbial uptake
immobilization
NO3-
nitrification
Serapan Tanaman
aminoacids
3) Beberapa jenis tanaman menyerap sedikit asam amino (mis. glycine)
• Circumvents the need for N mineralization• Difasilitasi oleh adanya mycorrhiza
Penyerapan langsung
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
D. Kontrol thd Kecepatan Dekomposisi BO1) Temperature –
• Warmer is better• <45°C
2) Moisture – intermediate is best • Too little desiccation • Too much limits O2 diffusion
T
Soil Moisture %
Respirasi Mikroba Tanah
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
3) Faktor Tanaman – Kualitas biomasa seresaha) Rasio C:N biomasa seresah ( = Konsentrasi N)• If C relative to N high N limits microbial growth
• Immobilization favored• N to plants
Decomposition rateas fn(lignin, N)
Deciduous forest sppb) Material struktural tanaman• Lignin – complex polymer, cell walls
• Confers strength with flexibility – e.g. oak leaves
• Relatively recalcitrant• High conc. lowers decomposition
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
c) Senyawa sekunder tanaman
• Kontrol dekomposisi Bahan organik oleh:
Bind to enzymes, blocking active sites lower mineralizationN compounds bind to phenolics greater immobilization by soilPhenolics C source for microbes greater immobilization by microbes
• Anti-herbivore/microbial• Common are phenolics – e.g. tannins
– Aromatic ring + hydroxyl group, other compounds
OH
R
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
A. Hubungan Simbiotik antara tanaman (akar) & fungi tanah
• Plant provides fungus with energy (C)• Fungus enhances soil resource uptake
Penyebarannya:• Occurs ~80% angiosperm spp • All gymnosperms• Sometimes an obligate relationship.
II. Mycorrhiza = Jamur Akar
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
B. Kelompok utama Mycorrhiza: 1) Ectomycorrhiza –
• Fungus forms “sheath” around the root (mantle)• Grows in between cortical cells = Hartig net – apoplastic
connection
• Occur most often in woody spp
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
2) Endomycorrhiza –Fungi menembus sel-sel akar
• Common example is arbuscular mycorrhizae (AM)• Found in both herbaceous & woody plants• Arbuscule = exchange site
Arbuscule in plant cell
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
C. Fungsi Mycorrhiza:
1) Peranan penghubung tanaman-tanah:a) Increase surface area & reach for absorption of soil water & nutrients
b) Increase mobility and uptake of soil P
c) Provides plant with access to organic N
d) Protect roots from toxic heavy metals
e) Protect roots from pathogens
2) Efek hara tanah thd mycorrhiza
• Intermediate soil P concentrations favorable
• Extremely low P – poor fungal infection• Hi P – plants suppress fungal growth
– taking up P directly
• Kejenuhan N
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
III. Fikisasi N2
N2 abundant – chemically inert
N2 must be fixed = converted into chemically usable form
• Lightning• High temperature or pressure (humans)• Biologically fixed
Nitrogenase – Ensim Katalisis N2 NH3
Expensive process – ATP, Molybdenum
Anaerobik : Memerlukan struktur khusus
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
Simbiosis dengan tumbuhan – Mutualism
• Prokaryote receives carbohydrates•Plant may allocate up to 30% of its C to the symbiont
• Tumbuhan menyediakan tapak anaerobik – Bintil akar• Tumbuhan menerima N
A. Hanya terjadi pada organisme Prokaryote:• Bacteria (e.g. Rhizobium, Frankia)• Cyanobacteria (e.g. Nostoc, Anabaena)
Free-living in soil/water – heterocysts Symbiotic with plants – root nodules Loose association with plants
Anabaena with heterocysts
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
• Those with N2-fixing symbionts form root “nodules”– anaerobic sites that “house” bacteria
soybeanroot
Contoh sistem simbiotik fiksasi N2 oleh tumbuhan
1) Legumes (Fabaceae)• Widespread• bacteria = e.g., Rhizobium spp.
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
Problem Toksisitas O2
• Symbionts regulate O2 in the nodule with leghemoglobin• Different part synthesized by the bacteria and legume
Cross-section of nodules of soybean nodules
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
Symbionts mengendalikan O2 dalam bintil akar dengan membentuk leghemoglobin
1. An oxygen carrier (in legumes) to prevent oxygen toxicity for the bacterium
2. different pieces synthesized by the bacteria (heme) and in the plant (protein)
2) Simbiosis tumbuhan Non-legume:• “Actinorhizal”= associated with actinomycetes (N2-fixing bacteria)
• genus Frankia• Usually woody species – e.g. Alders, Ceanothus
Ceanothus velutinus - snowbrush
Ceanothus roots, withFrankia vesicles
Bacteria in root or small vesicles
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
Buffaloberry (Shepherdia argentea)- actinorhizal shrub (Arizona)
• Bacteria in root or small vesicles
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
(2) Simbiosis tumbuhan Non-legume1. “Actinorhizal”= associated with actinomycetes (N2-fixing
bacteria)2. genus Frankia3. Usually woody species – e.g. Alders, Ceanothus4. Bacteria occur in root or small vesicles
B. Makna Ekologis Fiksasi N2
(1). Important in “young” ecosystems –Young soils low in organic matter, N
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
Ecological importance of N2 fixation
(1) Most important in “young” ecosystems (early in primary
succession) -young soils are low in organic matter, and thus N, which is often a limiting nutrient for
plant growth• e.g., newly exposed (glaciated) or newly laid down rock (volcanic), • recently denuded
landscapes(human activities, directly or
indirectly – bulldozing, erosion
2) Plant-level responses to increased soil N conc:Some plants (facultative N-fixers) respond to soil N concentration • Plant shifts to direct N uptake• N fixation • Number of nodules decreases
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
Plant-level: responses on N-fixing plants to high soil N conc:
In some plants (facultative N-fixers) – • As N conc , N fixation decreases• Plant shifts to direct N uptake• #nodules decreases
3) Kompetisi: Interaksi tumbuhan fiksasi NN2-fixing plants higher P, light, Mo, and Fe requirements
Poor competitors• Competitive exclusion less earlier in succession
• Though - N2 fixers in “mature” ecosystems
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
Competition – N-fixers and plant community interactionsbecause N2 fixing plants have higher P, light, Mo, and Fe requirements .They are believed to be poor competitors;• chances for competitive exclusion lower earlier in
succession (although there are N2 fixers in “mature” ecosystems)
e.g. of plants important in early stages of succession: • lupines, alders, clovers, Dryas
IV. Kehilangan N dari ekosistem
• Leaching to aquatic systems• Kebakaran Penguapan• Denitrifikasi N2, N2O to atmosfir– Closes the N cycle!
• Bacteria mediated• Anaerobik.
Natural N cycle
PLANT
PLANT
REMAINS
N2O
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
From - Peter M. Vitousek et al., "Human Alteration of the Global Nitrogen Cycle - Causes and Consequences," Issues in Ecology, No. 1 (1997), pp. 4-6.
ANTHROPOGENICSOURCES
Annual release(1012 g N/yr)
Fertilizer 80Legumes, other plants 40Fossil fuels 20Biomass burning 40Wetland draining 10Land clearing 20Total from human sources 210
Altered N cycle
NATURAL SOURCES
Soil bacteria, algae, lightning, etc. 140
Annual release(1012 g N/yr)
Annual release of fixed N2 (1012 g = teragram, trillion gr)Source: Peter M. Vitousek et al., "Human Alteration of the Global Nitrogen Cycle: Causes and Consequences," Issues in Ecology, No. 1 (1997), pp. 4-6.
V. Interaksi RhizosphereJaring-jaring makanan bawah tanah
Zone within 2 mm of roots – hotspot of biological activity
• Roots exude C & cells slough off = lots of goodies for soil microbes lots of microbes for their consumers (protozoans, arthropods)
• “Free living” N2-fixers thrive in the rhizosphere of some grass species
Fine root
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt
RINGKASAN
• Plant–microbial interactions play key roles in plant nutrient dynamics
Decomposition – mineralization, nitrification … immobilization, denitrification …
Rhizosphere – soil foodweb
Mycorrhizae – plant-fungi symbiosis
N fixation – plant-bacteria symbiosis
• Highly adapted root morphology and physiology to accommodate these interactions
• N cycle, for example, significantly altered by human activities
SUMBER: culter.colorado.edu/~kittel/Slides18_13Nv07.ppt