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1、http://bailiedu.com托福听力TPO19原文Lecture3下面就让小编来为大家介绍一下托福听力TPO19原文中Lecture3的文本内容吧，大家要好好
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能够给准备托福听力的同学带来帮助。TPO19Lecture3MarineBiologyProfessor：Ok,todaywearegoingtocontinueourdiscussionofplantlifeincoastal
saltm
2、arshes5ofNorthAmerica.Saltmarshesareamongtheleastinvitingenvironments
forplants.Thewaterissalty,thereislittleshadeandtheoceantidecomesinandout,
constantlyfloodingthemarsh,sothevarietyofplantsfoundinsaltmarshesislimited,
butthereisaplantgenusthatthriv
3、esthere,theSpartina.Infact,theSpartinagenus
isthedominantplantfoundinsaltmarshes.YoucanfindonetypeoftheSpartina,Saltmarsh
Cordgrass,growinginlowmarshareas.Inhighermarshareas,youarelikelytofinda
SpartinacommonlycalledSalt-meadowHay.SohowistheSpartinaa
4、bletosurviveinan
envrionmentthatwouldkillmostplants?well,itisbecausesaltmarshgrasseshavefound
waystoadapttotheconditionsthere.Firstofall,theyareabletowithstandhighlysaline
conditions.Onereallyinterestingadaptationistheabilitytoreversetheprocessof
osm
5、osis6Typically,theprocessofosmosisworks...Well,whenwatermovesthroughthewall
ofaplantcell,itwillmovefromthesidecontainingwaterwiththelowestamountofsalt
intothesidecontainingthehighestamountofsalt.soimaginewhatwouldhappenifatypical
plantsuddenlyfoundit
6、selfinsaltwater,thewatercontainedintheplantcells,that
iswaterwithverylittlesaltwouldbedrawnouttowardtheseawater,waterwithalot
ofsalt.Soyoucanseethefreshwatercontainedintheplantwillberemovedandtheplant
willquicklyloseallitswateranddehydrate.Butwhatabo
7、uttheSpartinas,well,they
allowacertainamountofsalttoentertheircells,bringingthesaltcontentofthewater
withintheplant,toaslightlyhigherconcentrationthanthatofthesurroundingseawater.
Soinsteadoffreshwatermovingoutoftheplantcells,saltfromtheseawaterenter
8、s,
reverseosmosis,andthisactuallystrengthensthecells.Anotheradaptationtothesaltyenvironmentistheabilitytoexcreteexcesssaltbacktotheenvironment.That’swhyyoumightseeaSpartinashimmeringinthesunlight.What’sreflectingthelightisnotsaltfromseawaterthathasev
