mass transport plants

• What are organic substances that are moved 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 cells that make up 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 allow maximum flow of sugar solution
• What is required for active transport in translocation?

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

  Source and sink of organic substances
• Where is sucrose created in plants?

  In the leaves during photosynthesis
• What happens to water potential in the source cell during translocation?

  It decreases due to sucrose accumulation
• How does water move into the source cell?

  By osmosis from surrounding cells
• What effect does sucrose transport have on hydrostatic pressure in the source cell?

  It increases hydrostatic pressure
• What happens to water potential in the sink cell during translocation?

  It increases as sucrose is used
• How does sucrose move from the sieve tube elements to the sink cells?

  By active transport
• What is the role of hydrogen ions in sucrose transport?

  They create a concentration gradient
• What is co-transport in the context of sucrose movement?

  Transport of sucrose with hydrogen ions
• What happens to the hydrostatic pressure in the sink cell?

  It decreases as water moves out
• What is the purpose of tracer experiments in studying translocation?

  To track the movement of sugars
• How do ringing experiments demonstrate the role of phloem?

  By showing swelling above the ring
• What is translocation in plants?

  • Mass transport of organic substances
  • Movement from source (leaves) to sink (respiring cells)
  • Driven by changes in hydrostatic pressure
• What are the steps involved in translocation?

  1. Sucrose created in leaves
  2. Sucrose transported into companion cells by diffusion
  3. Co-transport with hydrogen ions into sieve tube elements
  4. Water moves in by osmosis, increasing pressure
  5. Sucrose transported to sink cells by active transport
  6. Water moves out of sink cells by osmosis
• What are the methods to investigate translocation?

  • Tracer experiments using radioactively-labeled carbon
  • Ringing experiments to observe swelling above the ring
• What is the significance of the mass flow hypothesis?

  It explains the movement of sugars in plants
• What is the relationship between hydrostatic pressure and translocation?

  Pressure differences drive the movement of sugars
• How do changes in water potential affect translocation?

  They influence the movement of water and sugars
• What is the role of the xylem in relation to phloem?

  Xylem transports water next to phloem
• What is the outcome of removing a ring of phloem from a tree?

  Swelling occurs above the ring
• What happens to the sugars in the sink cells?

  They are used in respiration or converted to starch
• What is transpiration?

  Loss of water vapor from stomata
• What causes water vapor to evaporate from the stomata?

  Evaporation process
• Where are stomata mainly found on leaves?

  On the lower side of the leaf
• What are the four key conditions affecting transpiration rates?

  • Light intensity
  • Temperature
  • Humidity
  • Wind
• How does light intensity affect transpiration rates?

  Higher light intensity increases transpiration rate
• Why does temperature affect transpiration rates?

  Higher temperature increases water molecule kinetic energy
• What is the effect of humidity on transpiration rates?

  Higher humidity decreases transpiration rate
• How does wind affect transpiration rates?

  More wind increases transpiration rate
• What is the cohesion tension theory?

  Explains water movement against gravity in plants
• What is cohesion in the context of water molecules?

  Sticking together of water molecules