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Transport Processes (water potential (water potential is the free energy…

- - - - similar function to that of the guard cells
      - they can either accumulate or expel potassium and thus adjust the turgidity and water potential of the cell
    - - these are the molecular pumps which helps in transport of the molecules
      - the number of transfer cells depends on the surface area of the plasma membrane
    - - during night time, the guard cells are in hydraulic equilibrium because of which the water entering the cell and leaving the cell is of same rate
      - at sunrise, potassium is pumped into guard cells which increases solute concentration finally leading stomatal pore to open
  - - - in some plants, sugars are actively transported by sieve elements while in some it is transferred by polymer trap mechanism
      - the actual amount of sugar and other nutrients transported per hour by phloem is called mass transfer
      - phloem is responsible for the transport of sugar
      - sinks are sites that receives the transported phloem sap
    - - movement of water through xylem depends on the properties of water
      - liquid water is cohesive
      - water adheres firmly to soil particles
      - water is heavy and lifting it to the top of a tree needs a lot of energy
    - - water in plant is lost by transstomatal transpiration and transcuticular transpiration
      - a vessel having cavitation means the vessel can never conduct water again
      - cohesion tension hypothesis of water transport is the mostly accepted hypothesis
    - - bulk water movement through xylem is influenced primarily by water loss in the atmosphere
      - whenever the soil has adequate amount of water, water loss is actually advantageous
      - water stress: release of abscisic acid that prevents water loss
      - for healthy and turgid plants, light often controls the guard cell water relation
- - - - completely impermeable: do not allow anything to pass
      - selectively permeable: only allows selective substances to pass
      - freely permeable membrane: allow all solutes to pass freely across the membrane
    - - movement of substances across the membrane against the concentration gradient using energy
      - the energy used to carry out this process is ATP