TINJAUAN KRITISTINJAUAN KRITIS

Judul “Microsymbiont” tanah dalam Judul “Microsymbiont” tanah dalam Sistem AgroforestrySistem Agroforestry

Jenis-jenis organisme Bakteri Nitrogen-Jenis-jenis organisme Bakteri Nitrogen-Fixation yang lain?Fixation yang lain?

Perkiraan konstribusi Nitrogen ke dalam Perkiraan konstribusi Nitrogen ke dalam tanah?tanah?

Jenis-jenis Mycorrhiza?Jenis-jenis Mycorrhiza?

MIKROORGANISME TANAH

DALAM SISTEM AGROFORESTRY

SymbiosisSymbiosis = close and intimate = close and intimate association of two species; a “living association of two species; a “living together”together”

Terms:Terms: MacrosymbiontMacrosymbiont – higher plant – higher plant MicrosymbiontMicrosymbiont – microorganism – microorganism

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)

Estimated Average Rates of Biological NEstimated Average Rates of Biological N22

FixationFixationOrganism or systemOrganism or system NN22 fixed (kg ha fixed (kg ha-1-1 y y-1-1))

Free-living microorganismsFree-living microorganismsCyanobacteria Cyanobacteria Azotobacter Azotobacter Clostridium pasteurianumClostridium pasteurianum

25250.30.3

0.1-0.50.1-0.5

Grass-Bacteria associative symbiosesGrass-Bacteria associative symbiosesAzospirillumAzospirillum 5-255-25

Cyanobacterial associationsCyanobacterial associationsGunnera Gunnera AzollaAzollaLichensLichens

10-2010-20300300

40-8040-80

Leguminous plant symbioses with rhizobiaLeguminous plant symbioses with rhizobia

Grain legumes (Grain legumes (Glycine,Glycine, Vigna, Lespedeza, PhaseolusVigna, Lespedeza, Phaseolus))

Pasture legumes (Pasture legumes (Trifolium, Medicago, LupinusTrifolium, Medicago, Lupinus))

50-10050-100

100-600100-600

Actinorhizal plant symbioses with Actinorhizal plant symbioses with FrankiaFrankia

AlnusAlnus

HippophaëHippophaë

CeanothusCeanothus

CoriariaCoriaria

CasuarinaCasuarina

40-30040-300

1-1501-150

1-501-50

50-15050-150

5050

Rank of Biological Nitrogen Fixation

NN22 fixing system fixing system Nitrogen Fixation Nitrogen Fixation (kg N/ha/year)(kg N/ha/year)

Rhizobium-Rhizobium-legumelegume

50 - 60050 - 600

Cyanobacteria- Cyanobacteria- mossmoss

10 - 30010 - 300

Rhizosphere Rhizosphere associationsassociations

5 - 255 - 25

Free- livingFree- living 0.1 - 250.1 - 25

Types of Biological Nitrogen FixationTypes of Biological Nitrogen Fixation

Free-living (asymbiotic)Free-living (asymbiotic) CyanobacteriaCyanobacteria AzotobacterAzotobacter

AssociativeAssociative RhizosphereRhizosphere––AzospirillumAzospirillum LichensLichens–cyanobacteria–cyanobacteria Leaf nodulesLeaf nodules

SymbioticSymbiotic Legume-rhizobiaLegume-rhizobia Actinorhizal-Actinorhizal-FrankiaFrankia

Biological Nitrogen Fixation: The Symbiosis

N2

N2

N2

NH3

N2 represents the largest pool of biologically active nitrogen in terrestrial ecosystems reaching 27,000 g N per m3.

Taxonomy of RhizobiaTaxonomy of Rhizobia

GenusGenus SpeciesSpecies Host plantHost plantRhizobiumRhizobium leguminosarum bv. trifoliileguminosarum bv. trifolii

“ “ bv. viciaebv. viciae “ “ bv. phaseolibv. phaseolitropicitropicietlietli

TrifoliumTrifolium (clovers) (clovers)PisumPisum (peas), (peas), ViciaVicia (field beans), (field beans), LensLens (lentils), (lentils), LathyrusLathyrusPhaseolusPhaseolus (bean) (bean)PhaseolusPhaseolus (bean), (bean), LeucaenaLeucaenaPhaseolusPhaseolus (bean) (bean)

SinorhizobiumSinorhizobium melilotimelilotifrediifrediisahelisaheliterangateranga

MelilotusMelilotus (sweetclover), (sweetclover), MedicagoMedicago (alfalfa), (alfalfa), TrigonellaTrigonellaGlycineGlycine (soybean) (soybean)SesbaniaSesbania Sesbania, AcaciaSesbania, Acacia

BradyrhizobiumBradyrhizobium japonicumjaponicumelkaniielkaniiliaoningenseliaoningense

GlycineGlycine (soybean) (soybean)GlycineGlycine (soybean) (soybean)GlycineGlycine (soybean) (soybean)

AzorhizobiumAzorhizobium caulinodanscaulinodans SesbaniaSesbania (stem nodule) (stem nodule)

‘‘Meso rhizobium’Meso rhizobium’ lotilotihuakuiihuakuiicicericiceritianshanensetianshanensemediterraneummediterraneum

LotusLotus (trefoil) (trefoil)AstragalusAstragalus (milkvetch) (milkvetch)CicerCicer (chickpea) (chickpea)

CicerCicer (chickpea) (chickpea)

[Rhizobium][Rhizobium] galegaegalegae GalegaGalega (goat’s rue), (goat’s rue), LeucaenaLeucaena

PhotorhizobiumPhotorhizobium spp.spp. AeschynomeneAeschynomene (stem nodule) (stem nodule)

RHIZOBIUMRHIZOBIUM

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.

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

indeterminateThis outcome is controlled by the plant host

Formed on tropical legumes by 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.

Determinate nodules

www.agsci.ubc.ca/courses/agro/426/AGRO426.kronstad.rhizobium.01.ppt

Indeterminate nodules

Formed on temperate legumes (pea, clover, alfalfa);typically by Rhizobium spp.

Cylindrical nodules with a persistent meristem;nodule growth creates zones of different developmentalstages

www.agsci.ubc.ca/courses/agro/426/AGRO426.kronstad.rhizobium.01.ppt

Rhizobium Root Nodules

Nodulation in LegumesNodulation in Legumes

Nodule Formation Nodule Formation

Once inside the coritcal cell, the bacteria Once inside the coritcal cell, the bacteria multiple and dedifferentiatemultiple and dedifferentiate

Infected root cells swell and stop dividingInfected root cells swell and stop dividing After dedifferentiation, the Rhizobium are After dedifferentiation, the Rhizobium are

referred to as a bacteroid referred to as a bacteroid After formation, the bacteroid begin to After formation, the bacteroid begin to

express nif and fix genes and the plant express nif and fix genes and the plant expresses late nodulin genes expresses late nodulin genes

F R A N K I AF R A N K I A

Actinorhizal Plant Hosts Actinorhizal Plant Hosts (Non-Legum)(Non-Legum)

FamilyFamily GeneraGenera

BetulaceaeBetulaceae AlnusAlnus

CasuarinaceaeCasuarinaceae Allocasuarina, Casuarina, Ceuthostoma, GymnostomaAllocasuarina, Casuarina, Ceuthostoma, Gymnostoma

MyricaceaeMyricaceae Comptonia, MyricaComptonia, Myrica

ElaeagnaceaeElaeagnaceae Elaeagnus, HippophaElaeagnus, Hippophaë, Shepherdiaë, Shepherdia

RhamnaceaeRhamnaceae Ceanothus, Colletia, Discaria, Kentrothamnus, Retanilla, Ceanothus, Colletia, Discaria, Kentrothamnus, Retanilla, Talguenea, TrevoaTalguenea, Trevoa

RosaceaeRosaceae Cercocarpus, Chamaebatia, Cowania, Dryas, PurshiaCercocarpus, Chamaebatia, Cowania, Dryas, Purshia

CoriariaceaeCoriariaceae CoriariaCoriaria

DatiscaceaeDatiscaceae DatiscaDatisca

FrankiaFrankia and Actinorhizal Plants and Actinorhizal Plants

Actinomycetes (Gram +, filamentous); septate Actinomycetes (Gram +, filamentous); septate hyphae; spores in sporangia; thick-walled hyphae; spores in sporangia; thick-walled vesiclesvesicles

Frankia vesicles showing thick walls that confer protection from oxygen. Bars are 100 nm.

Beberapa Tipe Mycorrhizae Yang Beberapa Tipe Mycorrhizae Yang Telah Dikenal Telah Dikenal

VAM (Vescicular Arbuscular VAM (Vescicular Arbuscular Mycorrhyzae)Mycorrhyzae)

ECM (Ectomycorrhyzae)ECM (Ectomycorrhyzae) EctendomycorrhyzaeEctendomycorrhyzae Ericoid mycorrhyzaeEricoid mycorrhyzae Orchid mycorrhyzaeOrchid mycorrhyzae

Endo- and EctomycorrhizaEndo- and Ectomycorrhiza

Wide-spread association:Wide-spread association: Gymnosperms: 100% infectedGymnosperms: 100% infected Dicots: 83% infectedDicots: 83% infected Monocots: 79% infectedMonocots: 79% infected

Three parts to mycorrhizal associations:Three parts to mycorrhizal associations: RootRoot Fungal structures in close association with the Fungal structures in close association with the

rootroot External myceliumExternal mycelium

Endo- and EctomycorrhizaEndo- and Ectomycorrhiza

EctomycorrhizasEctomycorrhizas Fungal tissue largely outside the rootFungal tissue largely outside the root Primarily found in woody species, but also Primarily found in woody species, but also

some ferns and monocotssome ferns and monocots EndomycorrhizasEndomycorrhizas

Large fraction of the fungal tissue is within the Large fraction of the fungal tissue is within the root cortical cellsroot cortical cells

Frequently occur on herbaceous plants, also Frequently occur on herbaceous plants, also some tropical treessome tropical trees

Endo- and EctomycorrhizaEndo- and Ectomycorrhiza

Vesicular arbuscular mycorrhiza (VAM)Vesicular arbuscular mycorrhiza (VAM) Type of endomycorrhiza with specialized Type of endomycorrhiza with specialized

structures (vesicles and arbuscules)structures (vesicles and arbuscules) Fungi belong to Glomales (Fungi belong to Glomales (GlomusGlomus largest largest

genus)genus) Considered the most ancient type of Considered the most ancient type of

mycorrhizal symbiosismycorrhizal symbiosis Roots of more than 80% of all plant species Roots of more than 80% of all plant species

are infected with VAM-forming fungiare infected with VAM-forming fungi

Endo- and EctomycorrhizaEndo- and Ectomycorrhiza

VAM infection processVAM infection process Spores are found in the soil, or fungi may Spores are found in the soil, or fungi may

colonize from other plant rootscolonize from other plant roots Forms an Forms an appressoriumappressorium only on host plants, only on host plants,

colonizes through colonizes through passage cellspassage cells of exodermis of exodermis Hyphae remain in cortex and don’t penetrate Hyphae remain in cortex and don’t penetrate

through endodermis to stelethrough endodermis to stele Ecomycorrhiza infection processEcomycorrhiza infection process

Form a mantle of fungal hyphaeForm a mantle of fungal hyphae Hyphae penetrate intercellular into the cortex, Hyphae penetrate intercellular into the cortex,

forming forming Hartig netHartig net

Perbedaan Antara ECM dan VAM Perbedaan Antara ECM dan VAM Secara Garis BesarSecara Garis Besar

ECM ECM (Ectomycorrizae)(Ectomycorrizae)

VAM (Vescicular VAM (Vescicular Arbuscular Mycorrhizae)Arbuscular Mycorrhizae)

Umumnya BasidiomycetesUmumnya Basidiomycetes Umumnya EndogonalesUmumnya Endogonales

Terdapat pada jenis pohon Terdapat pada jenis pohon membentuk Hartig net membentuk Hartig net antara sel-sel cortexantara sel-sel cortex

Terdapt pada tumbuhan Terdapt pada tumbuhan kecil Hyphae masuk kecil Hyphae masuk langsung ke dalam sel-sel langsung ke dalam sel-sel cortexcortex

Membentuk mantel yang Membentuk mantel yang menyelimuti akarmenyelimuti akar

Tidak membentuk mantelTidak membentuk mantel

Puluhan ribu jenis cendawanPuluhan ribu jenis cendawan Hanya puluhan jenisHanya puluhan jenis

Hyphae bisa jauh dari akarHyphae bisa jauh dari akar Hyphae tumbuh dekat akarHyphae tumbuh dekat akar

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

ENDOMYCCORHIZA

ECTOMYCORRHIZA

http://www.irwantoshut.co.cc/