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Ch13: Transport Process, unnamed - Coggle Diagram

- - - - (all lipid/protein cell membranes are differentially permeable)
      - water passes through all membranes (goes faster if aquaporins are present) (channels on cell membrane)
      - molecular pumps: use energy of ATP to force molecules across the membrane (active transport)
      - the plasma membrane allows movement into/out of the cell
      - intracellular transport: vesicles migrate through the cytoplasm and fuse w/another organelle
- - - - if the water potentials of two regions are equal, equilibrium, there is no net movement of water
      - water potentials must always be considered in pairs or groups
- - - - K ions are actively transported to guard cells when they need to open
      - once inside, the K ions cannot leave
      - water potential in adjacent cells becomes less negative as a result
      - after the guard cells are open, potassium pumping stops, then the process is reversed
- - - - in other species phloem is loaded by the polymer trap mechanism
      - as sugar accumulates in sieve tube elements, the protoplasm becomes more concentrated (osmotic and water potential becomes more negative)
        
        water rushes into the sieve tube elements, protoplasm is squeezed through to other cells
    - - transport of sugar/other nutrients transferred by phloem per hour, mass transfer
      - sinks: sites that receive transported phloem sap
      - P-protein/P-protein plugs seal broken sieve elements to prevent sap loss
- - - - when stomatal pores are open, they lose water
      - water molecules have a strong tendency to diffuse from intercellular spaces to the atmosphere
      - this water loss is called transstomatal transpiration
      - some water is lost directly through the cuticle: transcuticular transpiration
    - - water is very adhesive, its molecules interact strongly with polymers of the cell walls of tracheids and vessel elements
  - - - if the leaf has adequate moisture content, light and CO2 are the normal controlling factors
      - for most healthy plants, light most often controls guard cell water relations
        
        (stomata closed at night, open during day)
        
        blue light is important
        
        presence of light also leads to photosynthetic fixing of CO2, decrease of internal CO2 may also lead to stomatal opening
      - all of these mechanisms are overridden by a much more powerful mechanism triggered by water stress
      - abscisic acid is released when leaves are dehydrated
      - immediately causes guard cells to close stomatal openings