植物生理學(xué)課件：Chapter 5 同化物的運輸與分配

Chapter5同化物的運輸與分配

p146-1671.同化物的運輸2.同化物的裝入與卸出3.同化物的配置與分配4.影響同化物運輸與分配的外部因素Focuson:Section1

Translocationsystemsofassimilateinplant一、代謝的區(qū)室化Section2TranslocationsystemsofassimilateinplantFigure5-1showscompartmentationinplantcell一、代謝的區(qū)室化FruitstoresphotoassimilateLeafmakesphotoassimilateFigure5-4showscompartmentationinplantorgans二、同化物運輸?shù)耐緩剑ㄒ唬┌麅?nèi)和胞間運輸1.胞內(nèi)運輸2.胞間運輸質(zhì)外體和共質(zhì)體Figure5-2Thestructureofplasmodesma數(shù)目多106~107/mm2inplant

Theplasmodesmais3nm,cantransportthelimitedmoleculeof800-1000D,butvirus10000D.Figure5-3showsconceptualmodelforthecell-to-celltraffickingofviralRNA(vRNA)inuninfectedplants.MP：MoveproteinFigure5-4showsaconceptualmodelforcell-to-celltraffickingofspecificproteinsofasizelargerthanpassiveSEL.Plasmodesmafunction：Substancetransportandinformationtransduction.物質(zhì)運輸與信息傳遞Lessresistancetosubstancetransportcellbycellbecauseofnotransmembranetransport.運輸阻力小Suchastheresistanceforplasmamembraneis0.31Ω/m2，fortonoplast0.1Ω/m2andforplasmadesma0.05/Ωm2.3.Shortdistancetranslocationisalternativebetweenapoplastandsymplast

3.共質(zhì)體和質(zhì)外體交替運輸Fig5-3

alternativetransportbetweenapoplastandsymplast葉脈轉(zhuǎn)移細胞的功能（源端裝入，庫端卸出）

Fig5-8TransfercellsTransfercells:Agroupofspecificcellsexistintheterminalinconducttissue,flowerorfruits輸導(dǎo)組織末端及花果器官特化細胞Characteristicsinstructureandmetabolism:Largesurfaceareaofcellbecausecellwallandplasmamembraneshowrugocity(ingrowth).Abundantcytosolandorganelles,highmetabolicactivity.Companioncellsandintermediarycellsareconsideredastransfercells.Mainfunction：Loadingassimilateintophloemfromsourceandunloadingassimilateintosinkcellfromphloemorotherconducttissue.Figure5-10Sieveelementsandcompanioncells（二）器官間的運輸RinggirdlingRinggirdlingforcertaintimeformsahumpFigure5-11RinggirdlingresultsinthehumpFigure5-11conducttissue1.Sievetubeandcompanioncell（SE/CC）areinangiospermFigure5-12amodelofsieveelementandcompanioncellsFigure5-13PhotographofsieveelementandcompanioncellbyelectronmicroscopeP-

protein：與植物各類和篩管分子的成熟度有關(guān).幼嫩篩管：扭曲盤繞的球形或紡錘形成熟篩管：管狀或絲狀的結(jié)構(gòu)功能：促進物質(zhì)運輸；防止汁液的流失。壽命：有長（2-10），有短（一個生長季節(jié)）Section3Phloemtransportofassimilates

Fig5-14Confocalmicroscopeshowsphloemtransport激光共聚焦顯微鏡3.1ElementsofphloemsapHowtogetphloemsap?Figure5-15harvestphloemsapTable5-1phloemsapfromyucca

Totaldrymatter17.1-19.2(%)

K1.68Aminoacid(%)EC(ms/cm)1.03Mg0.051Gln58pH8.0-8.2Ca0.014Val10Components(mg/ml)Na0.0014Ser,Gly7Sucrose150-165Zn0.0021(Iso-)Leu6Glucose2-4Fe0.0041Lys5Fructose2-4Mn0.0005Glu4Protein0.5-0.8Cu0.004Ala2Aminoacid6.3-10.1Mo0.00001Asntrace

TotalP0.301ProtracePi0.105Nitrate0絲蘭Componentsinphloemsap:1.Sugars.Sucrose>90%，asmallnumberofsorbitol,mannitolandoligoseincludingraffinoseandstachyose.Mainsorbitolinroseplantphloem.2.AminoacidsandAmides.Glu

orAteins(enzymes,ATPase)andnuclearacid(smallmRNA).4.Planthormones,ATP,glucolipid,anicacids.Mal.6.inorganicions：cations>anions，mostK+forcations,mostPiforanions,andwithoutNO3-LowerH+,higherpH(7.5-8.5)andK+concentrationinsieveelement;HigherH+concentration,lowerpH(5-6)andK+concentrationoutsidesieveelement.3.2

Transportdirectionisdeterminedbysink-source

1.Fromsourcetosink---bidirectionalway.14CFigure5-16bidirectionalwaySource——metabolicsource,referredastheorgansortissueswhichproduceor/andtransportsoutassimilate,suchasdevelopedleaf，roottuberortuberduringgermination.

Sink——metabolic，referredastheorgansor/andtissueswhichconsumeor/andstoreassimilate,suchasroot，seed,fruit,roottuberandtuberduringdeveloping.Slightringgirdlinginbranchcanenhancefruitsetting.“樹怕剝皮，不怕爛心”？RinggirdlingAfterringgirdlingbranchthebarkcanformahump(hypertrophicgrowth)

.Figure5-13Ringgirdlingresultsinthehump2.Ipsi-lateraltransportofassimilateisdominantFigure5-14Ipsi-lateraltransportofassimilate

3.Assimilatesindifferentsourcesaretranslocatedbydifferentconducttissues.Assimilatemadeinleafistransportedtorootbyphloem.Assimilatestoredintuberistransportedtobudforgerminationbyphloem,too.Assimilatestoredinthetreerootistransportedtobudandyoungleafbyxylem4.RateofassimilatetransportinphloemVelocity,masstransferrate(1)Velocity:thelineardistancetraveledperunittimeInmostplantabout50-250cm/h,suchassoybean84-100,grape60，sugarcane(C4plant)300-600cm/h.Sucroseis107cm/h,PiandH2Oare87cm/h.Masstransferrate,thequantityofmaterialpassingthroughagivencrosssectionofphloemorsieveelementsperunittime.Valuesformasstransferraterangefrom1to15gh–1cm–2ofsieveelements3.4Phloemtranslocationoccursbymasstransfer

1.Pressure-flowhypothesis

Thepressure-flowmodel,firstproposedbyErnstMünchin1930,statesthataflowofsolutioninthesieveelementsisdrivenbyanosmoticallygeneratedpressuregradientbetweensourceandsink(ΔYp).Thepressuregradientisestablishedasaconsequenceofphloemloadingatthesourceandphloemunloadingatthesink..Figure5-15Amodelofpressureflowhypothesis

OsmoticmeterAloading，OsmoticmeterBunloadingBASieveelementP-protein(2).Contractiveproteinhypothesis

P-proteinusesATPtocontractandpushesphloemflow.Figure5-16structureofsieveelement(3)Electroosmoticflowhypothesis-------------------------------------------------------------------+CationflowsPotentialdifference-cationanionFigure5-15illustrationofelectroosmoticflowhypothesis第二節(jié)、同化物的裝入與卸出一、韌皮部的裝入質(zhì)外體途徑、共質(zhì)體途徑細胞壁非質(zhì)體質(zhì)膜胞間連絲葉肉細胞維管束鞘細胞韌皮薄壁細胞伴胞篩管分子共質(zhì)體CO2最小的葉脈源葉中韌皮部裝載示意圖1、裝載途徑：共質(zhì)體途徑；質(zhì)外體途徑2、裝載機理：H+—蔗糖協(xié)同轉(zhuǎn)移模型-質(zhì)外體途徑裝載受載體調(diào)節(jié)，其依據(jù)是：對被裝載物質(zhì)（如蔗糖）有選擇性；需要能量；具有飽和效應(yīng)蔗糖－質(zhì)子同向運輸器質(zhì)外體途徑蔗糖載體ATP酶質(zhì)外體共質(zhì)體外（+）內(nèi)（－）篩管、伴胞SSH+H+H+H+K+K+K+K+PH5.5PH8.5低K+高K+低S高S寡糖轉(zhuǎn)運的多聚體－陷阱模型維管束鞘細胞居間細胞篩分子半乳糖葡萄糖果糖共質(zhì)體途徑二、韌皮部的卸出第三節(jié)、韌皮部的卸出1、卸出途徑：蔗糖先水解后進入代謝庫－質(zhì)外體途徑（1）蔗糖不水解直接進入代謝庫－質(zhì)外體途徑（2）和共質(zhì)體途徑（（3）胞間連絲）2、卸出機理：主動過程；被動過程液泡膜細胞壁質(zhì)膜液泡接受細胞韌皮部細胞（篩管分子、伴胞）庫組織中蔗糖卸出的可能途徑示意圖第三節(jié)同化產(chǎn)物的配置與分配一、配置代謝利用、合成暫時貯藏化合物、輸出到其它二、有機物的分配分配方向：由源到庫，優(yōu)先供應(yīng)生長中心同側(cè)運輸，就近供應(yīng)側(cè)向運輸，源間互補有機物分配－優(yōu)先供應(yīng)生長中心有機物分配－就近供應(yīng)、同側(cè)運輸有機物的同側(cè)運輸有機物分配控制因素供應(yīng)能力：代謝源競爭能力：代謝庫運輸能力：運輸途徑Fig5-20Section5Factorsaffectingassimilatetranslocation

5.1Internalfactors1.Sucrosecontent:

S↑，export↑.2.

ATP↑、Pi↑，TP↑，export↑.Insugarbeet,K/Na↑，starch↑，S↓，export↓.3.Planthormones:IAA、GA、CTK↑，import↑4.Sizeinsink,sink

↑，import

↑.4.2Environmentalfactors1.Water:notenough,waterpotential↓，Pn↓，S↓，resistance↑，transport↓.2.Light:light↓，Pn↓，S↓，export↓Transportduringdaytime>oneatnight.3.Temperature：optimum20-30℃.T↓，transport↓becauseofrespiration↓，energy↓，Pn↓photoassimilate↓，viscosity↑，callose↑.

HighT，transport↓，duetorespiration↑，Pn↓，photoassimilate↓，viscosity↑，callose↑Largerdifferenceintemperaturefavorstransportbecauseofaccumulationofphotoassimilate.4.Mineralnutrition，B、P、K.1.WhatfactorsdeterminewhethertheproductofthePCRcyclewillbeconvertedtostarchinthechloroplastorsucroseinthecytosol?2.Describethestructureofmaturephloemtissue.Whatarecauseshypertrophicgrowthaboveagirdlewound?3.Describethesource–sinkconcept.Towhatextentaresource-sinkrelationshipsinvolvedindeterminingthedirectionandrateoftranslocationinthephloem?4.Howaresugarsloadedintothephloemsievetubersatthesourceandremovedatthesink?5.Distinguishbetweenallocationandpartitioning.Whatfactorsdetermineallocationofcarbonwithinasourceleaf?Whatfactorsdeterminepartitioningbetweenmorethanonepotentialsink?3.5

Loadingandunloadinginphloem1.Phloemloadingisthroughthesucrose–H+

symportersSucrosefrommesophyllcelltoapoplast,thentoSE/CCintosieveelement.Requirementforenergyandagainstconcentrationofsucrose.Fig5-17Thisautoradiographshowsthatlabeledsugarmovesfromtheapoplastintosieveelementsandcompanioncellsagainstitsconcentrationgradientinsugarbeet(Betavulgaris).Labelaccumulatesinthesmallveins,sieveelements,andcompanioncellsofthesourceleaf,indicatingtheabilityofthesecellstotransportsucroseagainstitsconcentrationgradient.(FromFondy1975,courtesyofD.Geiger.)Figure5-18ATP-dependentsucrosetransportinsieveelementloading.Inthecotransportmodelofsucroseloadingintothesymplastofthesieveelement–companioncellcomplex,theplasmamembraneATPasepumpsprotonsoutofthecellintotheapoplast,establishingahighprotonconcentrationthere.Theenergyinthisprotongradientisthenusedtodrivethetransportofsucroseintothesymplastofthesieveelement–companioncellcomplexthroughasucrose–H+

symporter.Figure5-18Polymer-trappingmodelofphloemloading.(2)PhloemunloadingFig5-19Pathwaysforphloemunloading.Thesieveelement–companioncellcomplex(CC/SE)isconsideredasinglefunctionalunit.Thepresenceofplasmodesmataisassumedtoprovidefunctionalsymplasticcontinuity.Anabsenceof