Transport in plants

• Water pathways

  • Endodermis- Caspian strip, after water enters the root it travels via the apoplast pathway to the endodermis where the strip forces water and dissolved substances into the cells
  • apoplast- between cells (not membranes)
  • symplast- water enters the cell and moves through cytoplasm (via plasmodesmata)
  • vacuolar- moves through vacuole
• xylem

  • Dead cells with thick cell walls- strengthened by rings of lignin
  • water from roots to leaves
• factors influencing increased transpiration

  • Air movement-removes boundary layer of moist air so increased water potential
  • low relative humidity- increases water potential gradient between air spaces inside leaf and air outside
• phloem

  • Living cells with reduced cytoplasm, cell walls between the main sieve cells form highly perforated sieve plate
  • companion cells- cytoplasmically linked to the phloem sieve cells
  • source= sucrose from photosynthesis is co-transported with hydrogen ions into companion cells leading to active loading, the sucorse decreases water potential so water moves in
  • sink= sucrose is required for respiration, companion cells actively transport sucrose out of phloem