植物的營養問題(NutritionofPlants)

土壤營養：Water,Mineralelements

空氣營養：Photosynthesis

(光合作用)有收無收在于水!why?1.1

Theimportanceofwaterinplants

1.2

Waterabsorptionbyindividualplantcell1.3

Waterabsorptionbywholeplant1.4

Watertransportationinplantbody1.5Transpiration1.6

PhysiologicalbasesofrationalirrigationChapter1WaterMetabolismofPlants為什么“有收無收在于水”？植物水分代謝的三個過程：吸收水分(cell)植物水分代謝的三個過程：吸收水分(plant)植物水分代謝的三個過程：水分在植物體內運輸植物水分代謝的三個過程：水分的排出(lose)怎樣合理灌溉(Irrigate)1.1Theimportanceofwaterinplants

1.1.1FunctionsofwaterinplantlifeLifeoriginatedfromsea.Nowater,nolife!MaincomponentoflivingplantcellVacuole(液泡)(90-95%)失水

干旱

代謝紊亂

原生質破壞

死亡Sameplantsunderdifferentenvironments: Shadeandwet?——Sunnyanddry?Differentorgansandtissuesofoneplant:Watercontentofdifferent

kindsofplant:

mango?——rice?Humanbody?Watercontentofplant:80-95%(differentplanttypes) Leaf?——Stem,dormantbud,matureseed?Freewater(自由水)：距離膠粒較遠可以自由流動的水分。Statusofwaterinplant(canorcannotmovefreely).Why?Boundwater(束縛水)：靠近膠粒而被膠粒吸附束縛不易自由流動的水分。Cytoplasm(細胞質)ismainlycomposedofproteins,isacolloidal(膠體)system.Proteinshavehydrophobic(疏水)groupsinside,andhydrophilic(親水)groupsoutside.Hydrophilicgroupsarecohesive(adhesive)towater.Therefore,manywatermoleculesareadsorbed(吸附)onthesurfaceofproteins.Somewaterparticipates

directlyinmetabolism(光合、呼吸、合成、分解等),someisrequiredbyplanttosurviveunderbad(stress)conditions?NodistinctboundaryproteinRatiooffreewater/boundwater:moreimportant

代謝旺盛細胞、組織、器官：高休眠、越冬：低Freewaterparticipatesdirectlyinmetabolism(suchasphotosynthesis,respiration,etc.).Itscontentregulatestherateofmetabolism.自由水含量越大，植物代謝越旺盛。Boundwaterdoesnotparticipatedirectlyinmetabolism,butisrequiredbyplanttosurviveunderbad(stress)conditions.束縛水含量與植物抗性大小有密切關系。Absolutecontentoffreewater/boundSolventforsubstanceabsorptionandtransportation:

不能吸收固態物，物質（礦質、碳水化合物）要溶于水中才能運輸。（施肥后淋水）Keepsplantsintheirshape：膨脹

膨壓(Turgorpressure)；失水

wilting(萎蔫)。水是極性分子(polarmolecule)hydrogenbond1.1.2Somephysical/chemicalpropertiesofwater

GoodsolventHydrogenbonds,thenthefollowing:O,N…

Highsurfacetension(表面張力)

air-waterinterface; cohesion(內聚力):H2O-H2O adhesion(粘著力):H2O-Solidphase(CW) capillarity(毛細管作用)

Highspecificheat(比熱)

bufferplanttemperaturefluctuations

Highlatentheatofvaporization(汽化熱)

44kJ/molat25oC,thehighest

coolthemselvesBackCell:structuralandfunctionalunitofplantbodyAbsorption=movementofwateracrossplasmamembraneandvacuolemembrane(tonoplast)1.2Waterabsorptionbyindividualplantcell

concentrationgradient,diffusioncoefficient系數1.2.1.1Diffusion(擴散):shortdistance,individual1.2.1PathwaysofwateracrosscellmembraneThrough

aquaporin水孔蛋白:waterchannelproteinsonplasmamembraneandtonoplast(液泡膜)1.2.1.2Mass(集體)

flowAquaporin+PiAquaporin-P

Ca+dependent蛋白激酶Rate:fasterthandiffusionDirection:noHowtomeasurewaterenergyinasystem(cell)?Movementofwater

needsenergy(水往低處流)1.2.2Osmotic(滲透)absorptionofwater(adrivingforce?)1.2.2.1Waterpotential(水勢)Chemicalpotential(化學勢,J/mol):totalfreeenergycontainedinagivensubstanceofonemole.Thermodynamics:totalenergyinonesystem

freeenergy(自由能):performingworkboundenergy(束縛能):notperformingworkWaterpotential(水勢):ifthegivensubstanceiswater.J/mol植物生理學上的水勢概念(waterpotential,ψw):是指水的化學勢除以水的偏摩爾體積(volume/molar,18x10-6m3/mol)水勢的單位：化學勢單位為J/mol(N·m/mol)

偏摩爾體積的單位為m3/mol

兩者相除得N/m2

為壓力單位Pa(pascal)Theabsolutevalueofwaterpotentialisdifficulttodetermine.Inplantphysiology,thewaterpotentialofpurewaterissettobezero.純水的水勢為零！純水的自由能最大，水勢也最高!?Waterpotentialofsolutions:Negative,Why?Solutionsψw(MPa)PurewaterHoaglandsolutionSeawater1mol.L-1sucrose1mol.L-1

KCl0-0.05-2.50-2.69-4.501.2.2.2ComponentsofΨwofplantcells滲透勢(solute/osmoticpotential)

Ψs:由于溶質顆粒的存在，降低了水的自由能。Negative?Positive?Ψs=-iCRT(van’tHoffequation) i： Dissociatingcoefficient C： Molarconcentration R： Gasconstant(8.32J/mol.K) T： Absolutetemperature(K,Kelvin)襯質勢(matric

potential)Ψm:

細胞膠體物質親水性和毛細管對自由水束縛而引起水勢降低的值。Negativeorpositive?壓力勢(pressurepotential)Ψp:

PressurecausedPositive/Negative?Turgorpressure(膨壓)inplant細胞中的親水膠體？Cellulose(纖維素)inCW,proteinsinprotoplast,starches(淀粉)incytoplasm。親水性:蛋白質>淀粉>纖維素

Legumeseeds吸漲作用(imbibition)重力勢(gravitypotential)Ψg:

由于重力的作用Ψw=Ψs+Ψp+Ψm Dry/ImmaturecellsΨw=Ψs+ΨpMaturecells水分移動需要能量，因此，水分一定是從高勢區域順著能量梯度（energygradient）流到低勢區域，也就是說，水分由水勢高處流到水勢低處。Whatwillhappenwhenthereisamembrane(non-permeable,semi-permeable)betweenhighandlowwaterpotentialarea?1.2.2.3Osmosis(滲透作用)半透膜（Semi-permeablemembrane）：讓水分子通過而溶質分子不能透過的一種薄膜。種皮、膀胱、皮膚……（燙傷起泡，加鹽消之）Plasmamembranesofplantcellsareselectivelypermeablemembranes:waterandsmallunchargedsubstanceslargersolutesandchargedsubstancesStructureofplantplasmamembranefunnelSemipermeablemembrane水分從水勢高的系統通過半透膜向水勢低的系統移動的現象，就稱為滲透作用(Osmosis)。

CW：全透性

Plasmamembrane：選擇透性

Protoplastlayer：選擇透性

Tonoplast：選擇透性1.2.2.4(Mature)plantcellisanosmoticsystemPlasmolysis質壁分離

anddeplasmolysis質壁分離復原tellusthatmatureplantcellisanosmoticsystemH?flerdiagramTherelationshipbetweenwaterpotentialandcellvolume1.2.2.6WatermovementbetweencellsDirection:by

waterpotentialgradient,notbyΨp!Ψs=-1.4MPaΨp=+0.8MPaΨs=-1.2MPaΨp=+0.4MPaABΨs=-1.4MPaΨp=+0.8MPaΨs=-0.8MPaΨp=+0.4MPaCDΨw=-0.6MPaΨw=-0.8MPaΨw=-0.6MPaΨw=-0.4MPaBackWholeplant:rootleafRoothairzoneDon’tdamagethesezonesduringtransplanting!1.3.1Where?1.3Waterabsorptionbywholeplant

1.3.2PathwaysPlasmodesmata

胞間連絲Casparianstrip

凱氏帶質外體途徑共質體途徑跨細胞途徑Casparianstrip

凱氏帶1.3.3Motivepower1.3.3.1Rootpressure:植物根系的生理活動使液流從根部上升的壓力，稱為根壓。0.05～0.5MPaWaterpotentialgradient:How?Bleeding:從受傷或折斷的植物組織溢出液體的現象，叫做傷流。傷流液（bleedingsap）

Guttation吐水LiquiddropletsLeavesoryoungflowerssecretewaterdropletsthroughhydathodes水孔

locatedatthemarginsoftheleavesorflowers.Absorption>transpiration?Mechanismofrootpressure?solutesΨwselectivelypermeableendodermis+activeabsorptionofsolutes1.3.3.2Transpirationpull(蒸騰拉力)Rootpressure可將水壓多高?0.05～0.5MPa20.4m

Gianttrees?

Sequoiasempervirens

北美紅杉,ThetallesttreeonEarthtoday

is112.5m

Cutflower?Inthesoil:AvailablewaterinthesoilAirconditionsinthesoil:sunnyafterrain?Soiltemperature:ice?Concentrationofsoilsolutions:afterfertilization?Intheair:?1.3.4EnvironmentalfactorsaffectingthewaterabsorptionbyrootsBack1.4Watertransportationinplantbody1.4.1PathwayA:FromsoiltorootB:FromroottoleafC:Fromleaftosubstomatalcavity氣孔下腔throughlivingcellsthroughdeadcells:xylem(vessel導管andtracheid管胞)1.4.2RateThroughlivingcells:slowInxylem:fast(3-45m/h)1.4.3PowerofwatertransportationinxylemRootpressure:pushTranspiration:pullContinuous?Howcanwatercolumnsinxylemkeepcontinuous?Transpiration-cohesion-tensiontheory(蒸騰—內聚力—張力學說):H.H.Dixon(Ireland)GravityPull(transpiration)Cohesion20MPaTension0.5~3MPa>BackAproblemofairbubblesinthevesselelement?Cutflower?1.5Transpiration(蒸騰作用)Lossofwaterfromtheplant

guttation:liquid transpiration:gasOnly1-5%waterkeptinplantbodyWhereisthe95-99%?Why?Waste?Transpiration

(蒸騰作用):水分以氣體狀態，通過植物體的表面(主要是葉子)，從體內散失到體外的現象。Maindrivingforceforwaterabsorptionandtransportation(Howaboutrootpressure?)MaindrivingforcefortheabsorptionandtransportationofmineralsandorganiccompoundsCooldowntheleaves:latentheatofvaporization(sweat)1.5.1PhysiologicalfunctionsoftranspirationYoung: Stem,branches:lenticular(皮孔)transpirationMatureLeaf:cuticular(角質,5-10%)

stomatal(氣孔)transpiration(90-95%)1.5.2Siteoftranspiration1.5.3Stomatatranspiration1.5.3.1StomatastructureSmallSmallChloroplast1.5.3.2MechanismsofstomatamovementStomata:sosmall(1-2%ofleafarea),how? Yourlunch:?????????

Perimeterdiffusion（周長擴散）Stomatalmovement:openintheday,closeatnight.Why?starch-sugarconversiontheoryinorganicionuptaketheorymalate(蘋果酸)productiontheoryAnincreaseinguardcellturgorpressureopensthestomata;adecreaseclosesit.How?Day:

保衛細胞的葉綠體在光照下進行光合作用，消耗二氧化碳，使細胞內pH增高，淀粉磷酸化酶(starchphosphorylase)便水解淀粉為葡萄糖-1-磷酸，細胞里的水勢下降，副衛細胞(或周圍表皮細胞)的水分進入保衛細胞，氣孔便張開。Night:

呼吸產生的二氧化碳使保衛細胞的pH下降，淀粉磷酸化酶便把葡萄糖-1-磷酸合成為淀粉，細胞液濃度降低，水勢升高，水分從保衛細胞排到副衛細胞(或周圍表皮細胞)，氣孔便關閉。Evidence:differentpHsolutionsStarch-sugarconversiontheoryF.E.Lloyd(1908)Sucroseisanosmoticallyactivesoluteinguardcells保衛細胞的質膜上具有光活化H+泵ATP酶(light-activatedH+-pumpingATPase)Day:

光合磷酸化產生ATP，在分泌H+到細胞壁的同時，把外邊的K+吸收到細胞中來，同時伴隨Cl-的進入，水勢降低，水分進入保衛細胞，氣孔張開；Night:?Evidence:將蠶豆葉片表皮放在不同濃度的KCl溶液中;鴨跖草保衛細胞的K+濃度；InorganicionuptaketheoryDay:

當保衛細胞內的部分CO2被利用時，pH上升，剩余的CO2就轉變成重碳酸鹽(HCO3-)。HCO3-與糖酵解作用產生的PEP，在PEPcase作用下，形成草酰乙酸，進一步還原為蘋果酸，水勢降低，水分進入保衛細胞，使氣孔張開。Night:?Evidence:葉片表皮細胞的蘋果酸水平和氣孔開度具有密切的正相關。

Malate

(蘋果酸)productiontheoryThreetheoriescombined

LightTemperatureConcentrationofCO2WaterWindPlanthormones:Abscisic

Acid(ABA)1.5.3.3Factorsinfluencingstomatamovement1.5.4Insideandoutsidefactorsaffectingtranspiration

擴散力氣孔內外蒸汽壓差蒸騰速率∝——————∝————————————

擴散途徑阻力氣孔阻力+氣孔外擴散層阻力1.5.4.1OutsidefactorsLight:openstomata,gradientRH:gradientTemperature:gradientWind:gentle,strong1.5.4.2Insidefactors

StomatafrequencyStomataapertureVolumeofsubstomatalcavityTranspirationrate（蒸騰速率）:植物在一定時間內單位葉面面積蒸騰的水量。Transpirationratio（蒸騰比率）:植物每消耗1kg水時所形成的干物質質量（g）。Transpirationcoefficient（蒸騰系數）/Waterrequirement（需水量）:植物制造1g干物質所需水分