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Chapter 12, Motor cells adjust water potential, adhesion can decrease the…

- - - - Cooling water
      - Reducing pressure on it
      - Or lowering it
    - - When a large amount of sugar is added to a beaker of pure water
        
        Can no longer flow or easily dissolve things
        
        Water molecules adhere to the sugar molecules
      - When water adheres to a substance - forms hydrogen bonds
        
        Capacity to do work has decreased
      - sponge added to beaker pure water
        
        Water molecules adhere to the sponge material
        
        Can no longer flow or easily dissolve things
    - - Water can be heated
      - Or elevated
      - Put under pressure
  - - - And the water potential increases
      - The pressure potential increases
    - - units of pressure
        
        Usually in megapascals (MPa) or bars
      - One megapascal is approximately equal to
        
        Or 10 atmospheres of pressure
        
        Pure water at one atmosphere of pressure
        
        Is defined as having a water potential of zero
        
        10 bars
    - - When something is compressed
    - - And the water potential
      - So does the pressure potential
    - - When something is stretched
  - - - And cannot diffuse easily
      - Water's free energy because water molecules interact with solute molecules
- - - - Water and Nutrients transported from
    - - Phloem Sap
        
        two elements heal
        
        p-protein
        
        fine network
        
        adjacent to plasma membrane
        
        inner surface uninjured
        sieve elements
        
        callose
        
        polymer
        
        stays if under pressure
        
        contributes to plug
        
        precipitates into a flocculant mass
        
        p-protein plug
        
        p-protein too large
        
        creates plug
      - extremely diverse
      - sugars unloaded from
        sieve elements
    - - cross sectional area of phloem
        
        Specific Mass Transfer
      - Sugars/Nutrients
      - phloem per hour
      - excluding water
    - - Conducting cells
      - companion cells
      - functional unit
    - - Monosaccharides to disaccharides
      - permeable
      - conducting cell plasma membrane
    - - Sugar to Sieve elements
      - sieve tube members
      - sieve cells
    - - molecular pumps
      - active transport
  - - - Water loss to Humidity
      - hydrophobic
      - efficient isolation
    - - Water loss through Cuticle
    - - Water content that Changes with Habitat
      - lichens extreme example
    - - Hydrogen bonding breaking and water column breaks
      - act like broken cable
      - molecules above drawn upward
    - - Space between the Break
      - "air bubble"
      - expands until hit solid surface
      - cannot pass through pit membrane
    - - strong tendency to diffuse
      - intercellular space
      - widely accepted model
    - - Adhesive #
        
        Interact with other substances
        
        almost all substances react with water
      - Cohesive
        
        Force on one molecule acts on neighboring one
        
        water molecules interact strongly