NE

Plant Transport

  • Transport in Plants
    • Water and minerals
    • Transport in xylem
    • Transpiration
      • Evaporation, adhesion, and cohesion
      • Negative pressure
    • Sugars
    • Transport in phloem
    • Bulk flow
      • Calvin cycle in leaves loads sucrose in phloem
      • Positive pressure
    • Gas Exchange
    • Photosynthesis
      • CO2 in; O2 out
      • Stomates
    • Respiration
      • O2 in; CO2 out
      • Roots exchange gases within air spaces in soil
  • Water and Mineral Absorption
    • Water absorption from soil
    • Osmosis
    • Aquaporins
    • Mineral absorption
    • Active transport
    • Proton pumps
      • Active transport of H+
  • Mineral Absorption
    • Proton pumps
    • Active transport of H+ ions out of cell
      • Chemiosmosis
      • H+ gradient
    • Creates membrane potential
      • Difference in charge
      • Drives cation uptake
    • Creates gradient
      • Co-transport of other solutes against their gradient
  • Water Flow Through Root
    • Porous cell wall
    • Water can flow through cell wall route and not enter cells
    • Plant needs to force water into cells
  • Controlling the Route of Water in Root
    • Endodermis
    • Cell layer surrounding vascular cylinder of root
    • Lined with impermeable Casparian strip
    • Forces fluid through selective cell membrane
      • Filtered and forced through xylem cells
  • Mycorrhizae Increase Absorption
    • Symbiotic relationship between fungi and plant
    • Symbiotic fungi greatly increase surface area for absorption of water and minerals
    • Increases volume of soil reached by plant
    • Increases transport to hist plant
  • Transport of Sugars in Phloem
    • Loading of sucrose into phloem
    • Flow through cells via plasmodesmata
    • Proton pumps
      • Cotransport of sucrose into cells down proton gradient
  • Pressure Flow in Phloem
    • Mass flow hypothesis
    • “Source to sink” flow
      • Direction of transport in phloem is dependent on plant’s needs
    • Phloem loading
      • Active transport of sucrose into phloem
      • Increased sucrose concentration decreases H2O potential
    • Water flows in from xylem cells
      • Increase in pressure due to increase in H2O causes flow
  • Experimentation
    • Testing pressure flow hypothesis
    • Using aphids to measure sap flow and sugar concentration along plant system