translocation

• Photosynthesis


  Carbon dioxide + water creates glucose and oxygen
• Organic substances


  Substances containing carbon
• Flm tissue


  Responsible for transporting organic substances made in the leaf during photosynthesis up and down the plant
• Siv tube elements


  • End walls are perforated
  • Living cells without a nucleus
  • Very few organelles
• Companion cells


  • Provide the ATP required for active transport of sucrose into the siv tube elements
• Mass flow hypothesis


  1. Source (where organic substances are created)

  2. Sink (where organic substances are used)

  3. Water potential differences drive mass flow
• Translocation


  1. Photosynthesis in source cells creates organic substances

  2. Sucrose actively transported from source to siv tube elements

  3. Sucrose lowers water potential, causing water influx and high pressure

  4. Sucrose transported to sink cells by mass flow due to pressure differences
• Tracers and ringing experiments can prove the flm transports organic substances
• Mass transport of organic substances in plants is called translocation