Transport of phloem

• What are organic substances moved around in plants?

  Sugars like glucose
• What is the key function of leaves in plants?

  Photosynthesis
• What is the basic word equation for photosynthesis?

  Carbon dioxide + water → glucose + oxygen
• Why are glucose and other sugars considered organic substances?

  They contain carbon
• What is the role of phloem in plants?

  Transporting organic substances
• What are the two key cell types in phloem tissue?

  Sieve tube elements and companion cells
• What is a feature of sieve tube element cells?

  They have perforated end walls
• Why do sieve tube elements lack a nucleus?

  To maximize flow of sugar solution
• What is required for active transport in translocation?

  ATP from companion cells
• What is the mass flow hypothesis related to?

  Transport from source to sink
• What is the source in the mass flow hypothesis?

  Leaves during photosynthesis
• What is the sink in the mass flow hypothesis?

  Respiring cells
• How does water move into the source cell?

  By osmosis
• What happens to the hydrostatic pressure in the source cell?

  It increases
• What causes the movement of the sugary solution in the phloem?

  Difference in hydrostatic pressure
• How is sucrose transported from the companion cell to the sieve tube elements?

  By co-transport with hydrogen ions
• What happens to the water potential in the sink cell?

  It becomes more positive
• What is the effect of sucrose transport on the sink cell?

  It decreases the water potential
• What is the purpose of tracer experiments?

  To track the location of sugars
• How does radioactive carbon help in tracing sugars?

  It labels sugars in the plant
• What happens in ringing experiments?

  Phloem is removed, causing swelling
• What is the conclusion from ringing experiments?

  Phloem transports sugars
• What is translocation in plants?

  • Mass transport of organic substances
  • Primarily sucrose and glucose
  • From source (leaves) to sink (respiring cells)
  • Driven by hydrostatic pressure changes
• What are the key processes involved in translocation?

  1. Active transport of sucrose into phloem
  2. Osmosis of water into phloem
  3. Pressure differences drive movement
  4. Co-transport with hydrogen ions
• What are common methods to investigate translocation?

  • Tracer experiments with radioactive carbon
  • Ringing experiments to observe swelling
• What are the implications of translocation for plant health?

  • Essential for energy supply
  • Supports growth and development
  • Affects overall plant vitality