植物體內有機物運輸和分配演示文稿

植物體內有機物運輸和分配演示文稿本文檔共25頁；當前第1頁；編輯于星期日\16點41分植物體內有機物運輸和分配本文檔共25頁；當前第2頁；編輯于星期日\16點41分BOX:transfercells(轉移細胞)Therateatwhichmaterialcanbeactivelytransporteddependsonthenumberofmolecularpumpspresent,whichinturndependsonthesurfaceareaoftheplasmamembrane:Thelargerthemembrane,themoremolecularpumpsitcanhold.Incertainspecializedtransfercells,thewallsaresmoothontheoutersurfacebuthavenumerousfinger-likeandridgelikeoutgrowthsontheinnersurface.Theplasmamembraneispressedfirmlyagainstalltheconvolutionsandthushasamuchlargersurfaceareathanitwouldifthewallwereflat.Consequently,roomisavailableformanymolecularpumps,andhigh-volumetransportcanoccuracrossthesetransferwalls.Transfercellsarefoundinareaswhererapidshortdistancetransportisexpectedtooccur:inglandsthatsecretesalt,inareasthatpassnutrientstoembryos,andinregionswheresugarisloadedintooroutofphloem.本文檔共25頁；當前第3頁；編輯于星期日\16點41分(a)Oncereleasedfromacell,amoleculediffusesinaseriesofrandomshortpathsasitcollideswithandbouncesoffothermolecules.Probabilityfavorsitsenteringaneighboringcell(molecules1,2,and3),butitcandiffuselaterallyalongthewallaswell(molecules4and5).(b)Inmanyglands,theapopIastislarge,somovementbetweencellsmaybefasterandeasierthanmovementwithincells.Suchglandsoftenhavealiningofcompacttissuethatisolatesthegland,preventingthesecretedmaterialfrompermeatingthewholeregion.本文檔共25頁；當前第4頁；編輯于星期日\16點41分6.1.2longdistancetransport

(長距離運輸)6.1.2.1pathway(途徑)：phloem(韌皮部)。Girdlingexperiment(環(huán)割試驗)、radioactivetracer(同位素示蹤技術)及諺語“樹怕扒皮”等可以證明，同化物運輸?shù)耐緩绞蔷S管組織的韌皮部。本文檔共25頁；當前第5頁；編輯于星期日\16點41分水分和同化物運輸?shù)耐緩奖容^本文檔共25頁；當前第6頁；編輯于星期日\16點41分Diagramshowingbasicelementsinthecirculationofwater,inorganicions,andassimilatesintheplant.Waterandinorganicionstakenupbytherootmoveupwardinthexyleminthetranspirationstream.Somemovelaterallyintotissuesoftherootandstem,whileothersaretransportedtogrowingplantpartsandmatureleaves.Intheleaves,substantialamountsofwaterandinorganicionsaretransferredtothephloemandareexportedwithsucroseintheassimilatestream.

本文檔共25頁；當前第7頁；編輯于星期日\16點41分Asearlyastheseventeenthcentury,MarcelloMalpighiofItalynoticedthat,whenaringofbarkwasremovedfromastem(a),thetissuesabovetheringbecameswollen(b).Hecorrectlyinterpretedthisphenomenonasnewgrowthofwoodandbarktissuesstimulatedbyanaccumulationoffoodmovingdownfromtheleavesandinterceptedatthering.Malpighistudiedtheeffectofringingatdifferenttimesoftheyearandfoundthatnoswellingoccurredduringthewintermonths.Girdlingexperiment(環(huán)割試驗)本文檔共25頁；當前第8頁；編輯于星期日\16點41分14CO2示蹤技術：TwoleafletsofabroadbeanplantwereenclosedinaPlexiglascontainerandexposed14CO2andlightfor35minutes.Duringthattime,14CO2wasincorporatedintosugars,whichwerethentransportedtootherpartsoftheplant.本文檔共25頁；當前第9頁；編輯于星期日\16點41分6.1.2.2韌皮部組成由篩管(sievetube)、伴胞(companioncell)和薄壁細胞組成.篩管分子(sieveelement,SE)：除含有質膜、內質網、質體和線粒體，其它細胞器降解消失，具有韌皮蛋白(phloemprotein,P-蛋白)。篩管與伴胞形成篩管分子-伴胞復合體(sieveelement-companioncellcomplex,SE-CC)本文檔共25頁；當前第10頁；編輯于星期日\16點41分(a)Longitudinal(radial)viewofsecondaryphloemofyew(Taxuscanadensis),showingverticallyorientedsievecells,strandsofparenchymacells,andfibers.Partsoftwohorizontallyorientedrayscanbeseentraversingtheverticalcells.(b)Detailofportionofthesecondaryphloemofyew,showingsieveareas,withcallose(stainedblue)onthewallsofthesievecells,andalbuminouscells.本文檔共25頁；當前第11頁；編輯于星期日\16點41分6.1.2.3運輸同化物的種類

汁液干物質10～25%，多數(shù)為糖，其余為氨基酸(谷氨酸和天冬氨酸)、蛋白質、無機離子、有機離子和植物內源激素。利用蚜蟲吻針法方法證明。本文檔共25頁；當前第12頁；編輯于星期日\16點41分(a)Aphid(Longistigmacaryae)feedingonabasswood(Tiliaamericana,椴木)stem.Adropletof"honeydew"canbeseenemergingfromtheaphid.(b)Aphotomicrographshowingpartofthemodifiedmouthparts(stylets)oftheaphidinasievetubeofthesecondaryphloemofthebasswoodstem.Anarrowpointstothetipsofthestylers.本文檔共25頁；當前第13頁；編輯于星期日\16點41分6.2韌皮部運輸機理運輸方向：從源(source)到庫(sink)。源是指產生或提供同化物的器官或組織，如功能葉、胚乳等；庫是指消耗或積累同化物的器官或組織，如根、莖、果實、種子等。運輸過程包括韌皮部裝載、運輸和韌皮部卸出三個部分Assimilatemovementissaidtofollowasource-to-sinkpattern.Theprincipalsourcesofassimilatesolutesarethephotosynthesizingleaves,butstoragetissuesmayalsoserveasimportantsources.Allplantpartsunabletomeettheirownnutritionalneedsmayactassinks,thatis,importersofassimilates.Thus,storagetissuesactassinkswhentheyareimportingassimilatesandassourceswhentheyareexportingassimilates.本文檔共25頁；當前第14頁；編輯于星期日\16點41分6.2.2.1Concept(概念)：是指光合產物從葉肉細胞到篩管分子-伴胞復合體(sieveelement-companioncellcomplex)的整個過程。第一步：白天，葉肉細胞光合形成的磷酸三碳糖從葉綠體運到胞質溶膠；晚上，可能以葡萄糖狀態(tài)離開葉綠體，轉變?yōu)檎崽?某些植物后來會將蔗糖轉變?yōu)槠渌\輸糖)。第二步：葉肉細胞的蔗糖運到葉片細脈的篩分子附近。第三步：篩分子裝載，即糖分運入篩分子和伴胞。糖分和其他溶質從源運走的過程稱為輸出。韌皮部裝載(phloemloading)本文檔共25頁；當前第15頁；編輯于星期日\16點41分質外體(apoplastic)和共質體(symplastic)同化物生產區(qū)同化物積累區(qū)同化物輸出區(qū)質外體運輸共質體運輸裝載途徑本文檔共25頁；當前第16頁；編輯于星期日\16點41分裝載機理(限質外體)在篩分子或伴胞質膜中的ATP酶，不斷地將H+泵到質外體(細胞壁)。質外體的H+濃度比共質體高，形成質子梯度作為推動力。通過ATP酶釋放的能量，推動細胞內H+的輸出和外界K+的輸入，以維持膜內外的質子梯度。蔗糖與質子沿著這個梯度經過蔗糖-質子同向運輸器(sucrose-protonsymporter)，一起進入篩分子-伴胞復合體。

本文檔共25頁；當前第17頁；編輯于星期日\16點41分本文檔共25頁；當前第18頁；編輯于星期日\16點41分運輸機理壓力流動學說(pressureflowhypothesis)：源端(葉肉細胞)將蔗糖裝載入SE-CC，接著木質部水分通過滲透作用也進入SE-CC，由此產生高的膨壓。而在庫端(如貯藏根)，當糖被卸出時，水分也離開韌皮部，于是膨壓很低。源端和庫端之間就存在膨壓差，它推動篩管內容物的集流，穿過篩孔沿著系列篩分子向前運行，最終進入庫細胞。

本文檔共25頁；當前第19頁；編輯于星期日\16點41分本文檔共25頁；當前第20頁；編輯于星期日\16點41分Sugarisactivelyloadedintothesievetubeatthesource.Withtheincreasedconcentrationofsugar,thewaterpotentialisdecreased,andwaterfromthexylementersthesievetubebyosmosis.Sugarisremoved(unloaded)atthesink,andthesugarconcentrationfalls;asaresult,thewaterpotentialisincreased,andwaterleavesthesievetube.Withthemovementofwaterintothesievetubeatthesourceandoutofitatthesink,thesugarmoleculesarecarriedpassivelybythewateralongtheconcentrationgradientbetweensourceandsink.本文檔共25頁；當前第21頁；編輯于星期日\16點41分(a)Assucrose(s)isactivelytransportedintosieveelements,ΨsandΨcellbecomemorenegative,movingawayfromequilibriumwithcompanioncellsandotherneighboringcells.Watermovesintothesieveelements,squeezingphloemsapoutthroughthesievepores.Becausethesugarywaterescapesthroughsievepores,highpressuredoesnotbuildup,sothepressurepotentialdoesnotriseandstoptheinfluxofwater.Thewaterpotentialsofsieveelementsandsurroundingcellsneverreachequilibriumaslongassucroseisbeingpumped.Thesourceoftheglucosemaybephotosynthesisorthebreakdownofstarch.(b)Insinks,sucroseisactivelytransportedoutofsieveelements,andallprocessesworkinreversecomparedwithsources.Insomesinks,mostofthesucroseisconvertedtoglucoseandthenpolymerizedtostarch(storageorgans),isrespired(mosttissues),orisusedtoconstructnewcompounds(growingtissues).本文檔共25頁；當前第22頁；編輯于星期日\16點41分BOX:P-protein