1、2023年1月19日星期四维管植物的运输维管植物的运输Overview:Pathways for Survival of vascular plant(維維管植物存活途徑管植物存活途徑)For vascular plants,the evolutionary journey(演化之旅)onto land involved the differentiation of the plant body into roots and shoots(植物體分化為根與枝條)Vascular tissue transports nutrients throughout a plant;such transp
2、ort may occur over long distances(長途運輸)Figure 36.1Key Concepts Concept 36.1:Physical forces drive the transport of materials in plants over a range of distances Concept 36.2:Roots absorb water and minerals from the soil Concept 36.3:Water and minerals ascend from roots to shoots through xylem(木質部)Co
3、ncept 36.4:Stomata help regulate the rate of transpiration(蒸散作用)Concept 36.5:Organic nutrients are translocated through the phloem(韌皮部)Concept 36.1:Physical forces drive the transport of materials in plants over a range of distancesTransport in vascular plants occurs on three scales(三種尺度/三種層次)Transp
4、ort of water and solutes by individual cells,such as root hairs(個別細胞水與溶質的運輸)Short-distance transport of substances from cell to cell at the levels of tissues and organs(組織與器官內細胞間物質的短距離運輸)Long-distance transport within xylem and phloem at the level of the whole plant(整株植物木質部與韌皮部的長距離運輸)A variety of ph
5、ysical processes(物理過程物理過程)are involved in the different types of transport(眾眾 多物理過程介入或參與不同型式的運輸多物理過程介入或參與不同型式的運輸)Figure 36.2MineralsH2OCO2O2CO2O2H2OSugarLight Sugars are produced byphotosynthesis in the leaves.5 Sugars are transported asphloem sap to roots and otherparts of the plant.6 Through stoma
6、ta,leaves take in CO2 and expel O2.The CO2 provides carbon forphotosynthesis.Some O2 produced by photosynthesis is used in cellular respiration.4Transpiration,the loss of waterfrom leaves(mostly throughstomata),creates a force withinleaves that pulls xylem sap upward.3 Water and minerals aretranspor
7、ted upward fromroots to shoots as xylem sap.2 Roots absorb waterand dissolved mineralsfrom the soil.1 Roots exchange gases with the air spaces of soil,taking in O2 and discharging CO2.In cellular respiration,O2 supports the breakdown of sugars.7(木質液木質液)(木質液木質液)(蒸散作用蒸散作用)(韌皮液韌皮液)Selective Permeabilit
8、y of Membranes:A Review膜的選擇通透性膜的選擇通透性-各種膜系統各種膜系統 The selective permeability(選擇通透性)of a plant cells plasma membrane(細胞膜)Controls the movement of solutes into and out of the cell Specific transport proteins/transportor(專一性輸送蛋白)Enable plant cells to maintain an internal environment different from their
9、 surroundings Solutes in cell:cation(陽離子),anion(陰離子),neutral solute(中性溶質)The Central Role of Proton Pumps(質子唧筒質子唧筒)Proton pumps(質子唧筒)in plant cells Create a hydrogen ion gradient(氫離子梯度)that is a form of potential energy(潛能)that can be harnessed(=used)to do work(作功)Contribute to a voltage known as a
10、membrane potential(膜電位),also a kind of potential energyFigure 36.3CYTOPLASMEXTRACELLULAR FLUIDATPH+H+H+H+H+H+H+H+Proton pump generates membrane potentialand H+gradient.+Proton pump細胞質細胞質細胞外液細胞外液 Plant cells use energy stored in the proton gradient(氫離子梯度)and membrane potential(膜電位),both of which are
11、potential energy To drive the transport of many different solutesFigure 36.4a+CYTOPLASMEXTRACELLULAR FLUIDCations(,for example)are driven into the cell by themembrane potential.Transport protein(transportor)K+K+K+K+K+K+K+K+(a)Membrane potential and cation uptake(陽離子的吸收陽離子的吸收)+transporter細胞質細胞質細胞外液細胞
12、外液 In the mechanism called cotransport(共同運輸)A transport protein(cotransporter)couples the passage of one solute to the passage of anotherFigure 36.4bH+H+H+H+H+H+H+H+H+H+H+H+NO3 NO3 NO3 NO3 NO3 NO3 +NO3(b)Cotransport of anions(陰離子的共同運輸陰離子的共同運輸)H+of through acotransporter.Cell accumulates anions(,for
13、example)by coupling their transport to theinward diffusion 共同運輸蛋白共同運輸蛋白高濃度高濃度H+低濃度低濃度NO3-低濃度低濃度H+高濃度高濃度NO3-cotransporter細胞質細胞質細胞外液細胞外液Figure 36.4c The“coattail”effect of cotransport(共同運輸)Is also responsible for the uptake of the sugar sucrose(neutral solute)by plant cellsH+H+H+H+H+H+H+H+H+H+SSSSSPla
14、nt cells canalso accumulate a neutral solute,such as sucrose(),bycotransporting down thesteep protongradient.SH+H+H+S+(c)Cotransport of a neutral solute(中性溶質的中性溶質的共同運輸)cotransporter細胞外液細胞外液細胞質細胞質低濃度低濃度H+高濃度高濃度sugar高濃度高濃度H+低濃度低濃度sugar報告完畢報告完畢敬請指教敬請指教！？！？！？！？！？！？！？！？！？！？！？！？Effects of Differences in W
15、ater Potential水勢差的效應水勢差的效應 To survive plants must balance water uptake and loss Differences in water potential drive water transport in plant cells(水勢差驅動植物細胞中的水份運輸)Osmosis(滲透作用)Determines the net uptake or water loss by a cell Is affected by solute concentration and pressure Osmotic pressure(滲透壓)in
16、animal cellslow osmotic pressure=low solute=high waterhigh osmotic pressure=high solute=low water Direction of moving water low osmotic pressure=low solute=high waterhigh osmotic pressure=high solute=low water Isotonic solution(等張溶液)、hypertonic solution(高張溶液)、hypotonic solution(低張溶液)watersolutewater
17、 Water potential(水勢)Is a measurement that combines the effects of solute concentration and pressure Determines the direction of movement of water Water Flows from regions of high water potential to regions of low water potential Solute(溶質溶質)WaterSoluteInOutMembraneHow Solutes and Pressure Affect Wat
18、er Potential Both pressure and solute concentration Affect water potential The solute potential of a solution Is proportional to the number of dissolved molecules Pressure potential Is the physical pressure on a solutionQuantitative Analysis of Water Potential(水勢水勢)The addition of solutes reduces wa
19、ter potentialFigure 36.5a0.1 MsolutionH2OPurewater P=0 S=0.23 =0.23 MPa =0 MPa(a)High solute=Low water potentialLow solute=High water potential Application of physical pressure(物理性壓力)Increases water potential(水勢)H2O P=0.23 S=0.23 =0 MPa =0 MPa(b)H2O P=0.30 S=0.23 =0.07 MPa =0 MPa(c)Figure 36.5b,c Ne
20、gative pressure(負壓)Decreases water potentialH2O P=0 S=0.23 =0.23 MPa(d)P=0.30 S=0 =0.30 MPaFigure 36.5dWater potential(水勢)Affects uptake and loss of water by plant cellsIf a flaccid cell(鬆弛細胞鬆弛細胞)is placed in an environment with a higher solute concentrationThe cell will lose water and become plasmo
21、lyzed(膜壁分離)Figure 36.6a0.4 M sucrose solution:Initial flaccid cell:Plasmolyzed cellat osmotic equilibriumwith its surroundingsP=0S=0.7P=0S=0.9P=0S=0.9 =0.9 MPa =0.7 MPa =0.9 MPa If the same flaccid cell is placed in a solution with a lower solute concentration The cell will gain water and become tur
22、gid(膨脹)Distilled water:Initial flaccid cell:Turgid cellat osmotic equilibriumwith its surroundings P=0 S=0.7 P=0 S=0 P=0.7 S=0.7Figure 36.6b =0.7 MPa =0 MPa =0 MPa Turgor(膨壓)loss in plants causes wilting(萎凋)Which can be reversed when the plant is watered(澆水)Figure 36.7報告完畢報告完畢敬請指教敬請指教！？！？！？！？！？！？！？！
23、？！？！？！？！？Aquaporin Proteins and Water Transport Aquaporins(水孔蛋白水孔蛋白)Are transport proteins(運轉蛋白)in the cell membrane that allow the passage of water Do not affect water potentialThree Major Compartments(區間區間)of Vacuolated Plant Cells Transport is also regulated By the compartmental structure of plan
24、t cells Compartmentation(區間化/區隔化/間隔化)Cell wall(細胞壁)Cytosol(細胞質液)Vacuole(液胞)The plasma membrane(細胞膜)Directly controls the traffic of molecules into and out of the protoplast Is a barrier between two major compartments(區間),the cell wall and the cytosolCell compartments(細胞間隔細胞間隔)：同一細胞內：同一細胞內The third m
25、ajor compartment in most mature plant cells is the vacuole,a large organelle that can occupy as much as 90%of more of the protoplasts volume The vacuolar membrane(液胞膜液胞膜)regulates transport between the cytosol and the vacuoleFigure 36.8aTransport proteins in the plasma membrane regulate traffic of m
26、olecules between the cytosol and the cell wall.Transport proteins inthe vacuolar membrane regulate traffic of molecules between the cytosol and the vacuole.3.Plasmodesma(細胞質連絡絲細胞質連絡絲)1.Vacuolar membrane(tonoplast)(液胞膜液胞膜)2.Plasma membraneCell wallCytosolVacuoleCell compartments.The cell wall,cytosol
27、,and vacuole are the three maincompartments of most mature plant cells.(a)Three compartments In most plant tissuesThe cell walls and cytosol are continuous from cell to cell The cytoplasmic continuumIs called the symplast(共質體/合胞體)The apoplast(離質體/非原質體/質外體)Is the continuum of cell walls plus extracel
28、lular spacesTissue compartments(組織間隔組織間隔)：不同細胞間：不同細胞間Figure 36.8bKeySymplastApoplastThe symplast is thecontinuum ofcytosol connectedby plasmodesmata.The apoplast isthe continuumof cell walls andextracellularspaces.Apoplast1.Transmembrane route2.Symplastic route3.Apoplastic routeSymplastTransport rou
29、tes between cells.At the tissue level,there are three passages:the transmembrane,symplastic,and apoplastic routes.Substances may transfer from one route to another.(b)(共質體途徑共質體途徑)(質外體途徑質外體途徑)(質外體質外體)(共質體共質體)(穿越細胞膜途徑穿越細胞膜途徑)Functions of the Symplast and Apoplast in Transport Water and minerals can tr
30、avel through a plant by one of three routes Out of one cell,across a cell wall,and into another cell Via the symplast(共質體/合胞體)Along the apoplast(離質體/非原質體/質外體)Bulk Flow in Long-Distance Transport長距離運輸的巨流長距離運輸的巨流 In bulk flow(巨流)Movement of fluid(sap)in the xylem and phloem is driven by pressure diffe
31、rences(壓力差)at opposite ends of the xylem vessels(木質部導管)and phloem sieve tubes(韌皮部篩管)報告完畢報告完畢敬請指教敬請指教！？！？！？！？！？！？！？！？！？！？！？！？Concept 36.2:Roots absorb water and minerals from the soil Water and mineral salts(礦物鹽)from the soil Enter the plant through the epidermis of roots and ultimately flow to the s
32、hoot systemLateral transport(側向運輸側向運輸)of minerals and water in rootsFigure 36.9卡氏帶卡氏帶維管束維管束導管導管(1)Uptake of soil solution by the hydrophilic walls of root hairs provides access to the apoplast.Water and minerals can then soak into the cortex along this matrix of walls.(2)Minerals and water that cros
33、sthe plasma membranes of roothairs enter the symplast.(3)As soil solution moves alongthe apoplast,some water andminerals are transported intothe protoplasts of cells of theepidermis and cortex and thenmove inward via the symplast.(4)Within the transverse and radial walls of each endodermal cell is t
34、he Casparian strip,a belt of waxy material(purple band)that blocks the passage of water and dissolved minerals.Only minerals already in the symplast or entering that pathway by crossing the plasma membrane of an endodermal cell can detour around the Casparian strip and pass into the vascular cylinde
35、r.(5)Endodermal cells and also parenchyma cells within thevascular cylinder discharge water and minerals into theirwalls(apoplast).The xylem vessels transport the waterand minerals upward into the shoot system.Casparian stripPathway along apoplast Pathway throughsymplastPlasmamembraneApoplasticroute
36、SymplasticrouteRoot hairEpidermisCortexEndodermisVascular cylinderVessels(xylem)Casparian stripEndodermal cell卡氏帶卡氏帶(共質體途徑共質體途徑)(質外體途徑質外體途徑)(共質體共質體途徑途徑)(質外體途徑質外體途徑)345表皮表皮皮層皮層內皮內皮4512The Roles of Root Hairs,Mycorrhizae,and Cortical Cells Much of the absorption of water and minerals occurs near root
37、tips,where the epidermis is permeable to water and where root hairs are located Root hairs account for much of the surface area of roots Most plants form mutually beneficial relationships(互利共生)with fungi,which facilitate(促進)the absorption of water and minerals from the soil Roots and fungi form myco
38、rrhizae(菌根),symbiotic structures(共生結構)consisting of plant roots united with fungal hyphae(菌絲)Figure 36.102.5 mm菌根菌根是真菌與根的共生結合是真菌與根的共生結合 Once soil solution enters the roots The extensive surface area of cortical cell membranes enhances uptake of water and selected mineralsThe Endodermis:A Selective S
39、entry(選擇性進入選擇性進入)The endodermis(內皮層內皮層)Is the innermost layer(最內層)of cells in the root cortex Surrounds the vascular cylinder and functions as the last checkpoint(最後關卡)for the selective passage of minerals from the cortex(皮質)into the vascular tissue(維管束組織)Water can cross the cortex(皮層)Via the sympla
40、stic(共質體的)or apoplastic route(質外體的路徑)The waxy Casparian strip(卡氏帶)of the endodermal wall(內皮細胞壁)Blocks apoplastic transfer of minerals from the cortex to the vascular cylinder報告完畢報告完畢敬請指教敬請指教！？！？！？！？！？！？！？！？！？！？！？！？Concept 36.3:Water and minerals ascend(升高)from roots to shoots through the xylemPlants
41、 lose an enormous amount of water through transpiration,the loss of water vapor from leaves and other aerial parts of the plantThe transpired water must be replaced by water transported up from the rootsMineralsH2OCO2O2CO2O2H2OSugarLightFactors Affecting the Ascent of Xylem SapXylem sap(木質部汁液)Rises
42、to heights of more than 100 m in the tallest plantsPushing Xylem Sap:Root Pressure(根壓根壓)At night,when transpiration is very low Root cells continue pumping mineral ions into the xylem of the vascular cylinder,lowering the water potential Water flows in from the root cortex(根的皮層)Generating root press
43、ure(根壓)in the xylem Root pressure(根壓)sometimes results in guttation(點泌作用),the exudation(滲出作用)of water droplets(小水滴)on tips of grass blades or the leaf margins(葉緣)of some small,herbaceous eudicots(草本的真雙子葉植物)Figure 36.11報告完畢報告完畢敬請指教敬請指教！？！？！？！？！？！？！？！？！？！？！？！？Pulling Xylem Sap:The Transpiration-Cohesi
44、on-Tension Mechanism(拉升木質液拉升木質液：蒸散作用內聚力蒸散作用內聚力-附著力附著力-張力的作用機制張力的作用機制)Water is pulled upward by negative pressure(負壓)in the xylemTranspirational Pull(蒸散作用的拉力蒸散作用的拉力)Water vapor in the airspaces of a leaf Diffuses down its water potential gradient and exits the leaf via stomata Transpiration produces
45、negative pressure(tension)in the leaf which exerts a pulling force(拉力)on water in the xylem,pulling water into the leaf Evaporation causes the air-water interface to retreat farther into the cell wall and become more curved as the rate of transpiration increases.As the interface becomes more curved,
46、the water films pressure becomes more negative.This negative pressure,or tension,pulls water from the xylem,where the pressure is greater.CuticleUpper epidermisMesophyllLower epidermisCuticleWater vaporCO2O2XylemCO2O2Water vaporStomaEvaporation At first,the water vapor lost bytranspiration is replac
47、ed by evaporation from the water film that coats mesophyll cells.In transpiration,water vapor(shown as blue dots)diffuses from the moist air spaces of the leaf to the drier air outside via stomata.AirspaceCytoplasmCell wallVacuoleEvaporationWater filmLow rate oftranspirationHigh rate oftranspiration
48、Air-water interfaceCell wallAirspaceY Y=0.15 MPaY Y=10.00 MPaFigure 36.12Air-spaceCohesion and Adhesion in the Ascent of Xylem Sap(木質液上升時的凝聚力與附著力木質液上升時的凝聚力與附著力)The transpirational pull(蒸散作用拉力)on xylem sap Is transmitted(傳導/傳遞)all the way from the leaves to the root tips and even into the soil soluti
49、on Is facilitated by cohesion and adhesion(凝聚力與附著力)水份在樹木中的上升作用水份在樹木中的上升作用 Ascent of xylem sap(木質液的上升)Xylem sapOutside air Y Y=100.0 MPaLeaf Y Y(air spaces)=7.0 MPaLeaf Y Y(cell walls)=1.0 MPaTrunk xylem Y Y=0.8 MPaWater potential gradientRoot xylem Y Y=0.6 MPaSoil Y Y=0.3 MPaMesophyll cellsStomaWate
50、r moleculeAtmosphereTranspirationXylemcellsAdhesionCell wallCohesion,by hydrogenbondingWater moleculeRoot hairSoil particleWaterCohesion and adhesionin the xylemWater uptakefrom soil Figure 36.13水勢梯度水勢梯度Xylem Sap Ascent by Bulk Flow:A Review The movement of xylem sap(木質液)against gravity(重力/萬有引力)Is m
