第三节植物根系对水分的吸收Absorption of water by third plant rootsWord格式文档下载.docx
- 文档编号:3819020
- 上传时间:2023-05-02
- 格式:DOCX
- 页数:17
- 大小:21.22KB
第三节植物根系对水分的吸收Absorption of water by third plant rootsWord格式文档下载.docx
《第三节植物根系对水分的吸收Absorption of water by third plant rootsWord格式文档下载.docx》由会员分享,可在线阅读,更多相关《第三节植物根系对水分的吸收Absorption of water by third plant rootsWord格式文档下载.docx(17页珍藏版)》请在冰点文库上搜索。
Rootcap
Theroothairzone
Rootvolume,roothairnumber
Blackwheatinthebox,andthemeasurementoftheroothairs,atotallengthoftenthousandkilometers,adaylongoutofthenewrootandroothairatotallengthof5kilometers.
Ithasadeeprootandawidedistribution
Therootofwheatissoluble1.5-2m,cornismorethan2m,appletreeis10-12meters.
2.thepositionofrootabsorbingwater
Themainpartofrootabsorptionisatthetipoftheroot,
Inthetransplantationofseedlingsshouldbeavoidedwhenrootinjury.
roottip
Thestrongestwaterabsorptioncapacity
Thereasonofthewaterabsorptioncapacityoftheroothairzone:
(1)theroothairzonehasmanyrootabsorptionarea(5~10times);
(2)theexternalroothairzonecoveredbypectinviscosity,stronghydrophilicity,andisbeneficialtotheadhesionandabsorptionofsoilparticles;
(3)conductingtissueoftheroothairzonedeveloped,theresistancetowatermovement
1.plastidpathway
2.apoplasticpathway
Theradialtransportpathwayfromthesoilthroughroothairs,cortexandendodermis,parenchymacellsintothewatercolumntubetwo:
Itreferstothemovementofwaterfromthecytoplasmofacellthroughplasmodesmatatothecytoplasmofanothercell.Slowermovingspeed.
Plastidpathwayandapoplasticpathwayofrootwaterabsorption
Watermovesthroughthecellwall,intercellularspace,etc.withoutprotoplasm,andmovesrapidly.
Theapoplastoftherootisdividedintotwopartsbytheendodermis:
theapoplastoutsidetheendodermisandtheapoplastoutsidetheendodermis
Thestripoftheendothelialcellwall
Waterentersthecellonlythroughtheprotoplasmoftheendodermis.Thatis,enteringtheplastid.Apoplasticspace-endothelialcellprotoplastlayer(plastid)-apoplasticspace(catheter).
Apoplast
Theendodermis,includingroothairs,cortexcelllayer,cellwallandintercellularspace
Kjeldahlband
Suberification,filmandthewallclosetogether.Waterandsolutecan'
tpassthroughfreely.
Internalapoplast
Insidetheendothelium,includingthematureductsandthemiddlecolumn.
Accordingtothepowerofwaterabsorption,therearetwowaysofplantrootwaterabsorption:
activeabsorptionofwater
passiveabsorptionofwater
Mainmode
(1)rootpressureandactivewaterabsorption
1.rootpressure
Activewaterabsorptionisthewaterabsorptioncausedbythephysiologicalactivityofrootsystem.Itisgenerallybelievedthattherootforceofactivewaterabsorptionisrootpressure.
Rootpressure(rootpressure)-thepressurethatcauseswatertorisefromtherootsbecauseofthephysiologicalactivityofplantroots.
Bleeding
Spitwater
Twophenomenathatconfirmrootpressure:
Ifitiscutofffromthebaseoftheplantneartheground,itisnotlongbeforealiquiddropcomesoutofthewound.Thephenomenonoffluidspillingfrominjuredorbrokenplanttissueiscalledbleeding.Theeffluentwasbleedingsap.
Thecomponentsofbleedingsapincludewater,inorganicsubstance,organicsubstanceandplanthormone,andthemetabolismoftheheelcanbestudiedaccordingtothebleedingcurrent.
Theamountofbleedingcanberegardedasanindexofphysiologicalactivityofrootsystem.
Noinjuredplants,suchasinthesoilmoisturesufficient,suitabletemperature,humidenvironment,thetiporedgeofthebladealsohasthephenomenonofliquidsecretion,thisphenomenoniscalledwaterspitting(guttation).
Themechanismof2.rootpressuregeneration
Maincontent:
Theextracellularsubstanceoutsidetheendodermis,endothelium(corticalcellwall,intercellularspace)andtheapoplast(middlecolumnduct)withintheendodermisformapermeablesystem,
Themetabolicactivityoftherootendodermistoproduceectoplasmbodyandendotheliallayertotheouterbodybetweentheendoplasmicreticulumandthewaterpotentialdifference,smoothwaterpotentialdifferencepenetrationintotherootcatheterthroughtheendotheliallayer.
Penetrationtheory
Howdoestherootcanalandtheouterfluidestablishtheosmoticsystem?
WithfoursuberificationthickenedendotheliallayerontheCasparianstrip,cannotallowfreewaterandnutrientsthrough.
Watercanonlytransportinwardsthroughtheprotoplasmofendothelialcells.
Thewholeendodermiscellislikeaselectivepermeablemembraneseparatingthemiddlecolumnfromthecortex.
Aslongasthereiswaterpotentialdifferencebetweenthewaterinthemiddlecolumnandthewaterinthecortex,thewaterwillpassinandoutthecolumnthroughthepermeation.
Whyisthewaterpotentialinthecatheterlowerthanthatoftheouterfluid?
Thesoluteinthesoilcandiffusewiththewaterthroughtheapoplasttotheroot,andwhenitreachestheendodermis,thediffusionissuppressedbythestrip.
BecauseofthehighconcentrationofO2inthecortex,itispossibletoproduceenoughstrongrespirationandgenerateenoughenergytofacilitatetheactiveabsorptionofions.Throughtheactivetransport,theionsaretransportedtotheparenchymacellsofthestelethroughtheplasmodesmata.
Theionsinthemiddlecolumndiffusetotheapoplast(especiallytheduct)alongtheconcentrationgradient,whichincreasestheionconcentrationinthecatheteranddecreasesthewaterpotential.
Thiscreatesawaterpotentialgradientacrosstheendodermis,wherewaterentersthecolumnthroughosmosistoproducerootpressure.
Throughmetabolism
Experimentalphenomenasupportingpermeationtheory:
Whentheplantrootsareplacedinpurewater,thebleedingvelocityisaccelerated;
Ifyouplantrootsinconcentratedsolution,thewoundflowisreduced,andthebleedingsapisevensuckedback;
Thus,theformationofrootpressureisaosmoticprocess,andisrelatedtothemetabolismofplants.
Activewaterabsorptionisusuallynottherootsystem'
sactiveabsorptionofwateritself
Buttheplantactiveabsorbsolutebymetabolicenergy,resultinginthecatheterthewatersolutionislowerthantheoutsidethewatersolution,thewaterispassivelyalongthewaterpotentialgradientfromtheoutsideintothecatheter,realpowerflowisthewaterpotentialdifference.
(two)transpirationtensionandpassivewaterabsorption
1.passivewaterabsorption
Thewayofabsorbingwaterthroughtranspirationforceiscalledpassivewaterabsorption.
2.transpirationpull(transpirationalpull)
Becausetranspirationproducesaseriesofwaterpotentialgradients,theforcethatcauseswatertoriseinthetubeiscalledtranspirationpull.
Theproportionofactivewaterabsorptionandpassivewaterabsorptionintheprocessofplantwaterabsorptionvarieswithplantgrowthandtranspirationrate.Usuallytranspirationofplants,especiallytalltrees,themainwaytoabsorbwaterispassivewaterabsorption.Activewaterabsorptionisthemainmodeofwaterabsorptiononlywhentheleavesarenotexpandedorfalleninthespring,andatnightwhenthetranspirationrateisverylow.
Activewaterabsorptionandpassivewaterabsorption
Four.Conditionsaffectingrootwaterabsorption
Thefactorsthataffectthesoilwaterpotentialandrootwaterpotentialaffecttherootabsorptionofwater.
(1)soilmoisturestatus
Soilmoisturecanbedividedintothreeparts:
1.gravitywater
2.hygroscopicwater(orboundwater)
3.capillarywater
Theamountofavailablewaterinthesoildirectlyaffectsthewaterabsorptionoftherootsystem
Fieldwaterholdingcapacity
Excludingallgravitywater,retainingallcapillarywaterandhygroscopicwater,thepercentageofsoilmoistureandsoildryweightiscalledfieldcapacity.Usuallyaround20%.
Maximumwaterholdingcapacity
Saturatedwaterholdingcapacity.Watercontentwhenallthevoidsinthesoilarefilledwithwater.Usuallyaround40%.
Whenthesoilwatercontentisabout70%ofthefieldwatercapacity,thesoilfertilityisgood.
Temporarywilting(temporarywilting)
Permanentwilting(permanentwilting)
Permanentwiltingcoefficient(permanentwiltingcoefficient):
thepercentageofsoilmoistureandsoildryweightwhenplantsarepermanentlywilting.
Itisrelatedtosoilparticlesize,soilcolloidnumber,cropspeciesandsoon.Coarsesand,finesand,loamandclayincreasesuccessively.
Wilt
(two)soiltemperature
Lowtemperaturecanreducethewaterabsorptionrateofrootsystem
Soiltemperatureistoohighforrootwaterabsorptionisalsounfavorable.
(three)soilaerationstatus
Inthewellventilatedsoil,thewaterabsorptioncapacityofrootsystemisstronger.
Soilaerationnotonlycauseswaterabsorptionobstruction,butalsocausesrootpoisoningdeathforalongtime.
Becauseofpoorsoilaeration,O2contentdecreased,CO2concentrationincreased,theshorttermcanmaketheeffectofrootrespirationdecreased,rootpressure,thuspreventingwater;
alongtime,itwillca
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 第三节 植物根系对水分的吸收Absorption of water by third plant roots 三节 植物 根系 水分 吸收 Absorption
链接地址:https://www.bingdoc.com/p-3819020.html