Cell wallCytosolFig. 36-11: Cell Compartments and Routes for Short-Distrance TransportCytosolVacuolePlasmodesma Vacuolar membranePlasma membranePlasma membrane(a) Cell compartmentsKeyTransmembrane routeApoplastApoplastTransmembrane routeppSymplastApoplastSymplastppypSymplastic routeApoplastic route(b) Transport routes between cellsFig. 36-12: Lateral Transport of Minerals and Water in RootsFig. 36-6: Proton Pumps Provide Energy for Solute TransportCYTOPLASMEXTRACELLULAR FLUIDCYTOPLASMEXTRACELLULAR FLUIDATPH+H+Proton pumpgenerates mem++__H+H+H+H+H+generates mem-brane potentialand gradient.+_H+H+H+++__+Fig. 36-7: Solute Transport in Plant CellsCYTOPLASMEXTRACELLULAR FLUIDK+K+K+K+___+++Cations (K+), forexample, are driveninto the cell by theK+K+K+K+Transport protein__++(a) Membrane potential and cation uptakeinto the cell by themembrane potential.H+H+H+H+H+H+___+++A cell accumulates anions(NO3-), for example, bycoupling their transportH+H+H+H+H+H+H+___+++pg pto the inward diffusionof H+through a co-transporter.(b) Cotransport of an anion with H+H++H+H+H+__++Plant cells can also H+H+H+H+H+H+H+__++Saccumulate a neutralsolute, such as sucrose(S), by co-transportingH+down the steep protongradientHH+H+__++(c) Cotransport of a neutral solute with H+Sgradient.Fig. 36-7: Solute Transport in Plant CellsCYTOPLASMEXTRACELLULAR FLUIDK+K+K+K+___+++Cations (K+), forexample, are driveninto the cell by theK+K+K+K+Transport protein__++(a) Membrane potential and cation uptakeinto the cell by themembrane potential.H+H+H+H+H+H+___+++A cell accumulates anions(NO3-), for example, bycoupling their transportH+H+H+H+H+H+H+___+++pg pto the inward diffusionof H+through a co-transporter.(b) Cotransport of an anion with H+H++H+H+H+__++Plant cells can also H+H+H+H+H+H+H+__++Saccumulate a neutralsolute, such as sucrose(S), by co-transportingH+down the steep protongradientHH+H+__++(c) Cotransport of a neutral solute with H+Sgradient.Fig. 36-7: Solute Transport in Plant CellsCYTOPLASMEXTRACELLULAR FLUIDK+K+K+K+___+++Cations (K+), forexample, are driveninto the cell by theK+K+K+K+Transport protein__++(a) Membrane potential and cation uptakeinto the cell by themembrane potential.H+H+H+H+H+H+___+++A cell accumulates anions(NO3-), for example, bycoupling their transportH+H+H+H+H+H+H+___+++pg pto the inward diffusionof H+through a co-transporter.(b) Cotransport of an anion with H+H++H+H+H+__++Plant cells can also H+H+H+H+H+H+H+__++Saccumulate a neutralsolute, such as sucrose(S), by co-transportingH+down the steep protongradientHH+H+__++(c) Cotransport of a neutral solute with H+Sgradient.Fig. 36-19: Loading of Sucrose into Phloem1Vessel(l )Sieve tube(hl )Source cell(leaf)Loading of sugar (green dots) intoFig. 36-20: Bulk Flow by Positive Pressure (pressure flow) in a Sieve Tube11(xylem)(phloem)(leaf)Loading of sugar (green dots) into the sieve tube at the source reduces water potential inside the sieve-tube elements. this causes the tube to take up water by iH2OH2OSucrose2osmosis.sureH2Oessure2This uptake of water generates a positive pressure that forces the sap to flow along the tube.gative presspositive pre3The pressure is relieved by the unloading of sugar and the consequent loss of water at Sink cellflow by negulk flow by p434the sink.In leaf-to-root translocation, xylem recycels water from(storageroot)Bulk Bu34xylem recycels water from sink to source.SucroseH2OFig. 36-14: Generation of Transpirational Pull5) Water from xylem is pulled into the di ll d i t4) The increased tension shown in step 3 pulls CuticleXylemsurrounding cells and air spaces to replace the water that was lost.water from surrounding cells and air spaces.CuticleXylemUpperepidermis3) Evaporation causes the air-water interfaceMesophyllMicrofibrils incell wall ofhll llwater interface to retreat farther into the cell and to become more curved.MesophyllLAirspacemesophyll cell2) First, water vapor lost by transpiration ildbLower epidermisCuticleStomais replaced by evaporation from water coating the mesophyll cells.Microfibril(cross section)WaterfilmAir-waterinterface1) In transpiration, water vapor (shown as blue dots) diffuses from the moist air spaces of the leaf to the drier air outside via stomataFig. 36-17: Mechanisms ofRadially orientedcellulose microfibrilsGuard cells turgid/Stoma open Guard cells flaccid/Stoma closedMechanisms of Stomatal Opening and ClosingCellwallVacuoleGuard cell(a) Changes in guard cell shape and stomatal opening andclosing (surface view)Guard cells turgid/Stoma open Guard cells flaccid/Stoma closedH2OH2OH2OH2OH2OH2OK+HOHOH2OH2OHO(b) Role of potassium in stomatal opening and closingH2OH2OH2OAbscisic Acid Signaling and Ion Channel Functions in Guard CellsChannel Functions in Guard CellsCa2+Ca2+Indep.ECl-= 58mV/(z) x log([Cl-]out/[Cl-]in)10 times more anions inside cell than outside celloutside cell.26 days of droughtZ.M. Pei et al. Schroeder.
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