Plant Transport Systems and Transpiration

• What are phloem tubes primarily made of?

  Long cells called sieve tube elements
• What is the function of the perforated end walls in sieve tube elements?

  To allow phloem to flow through
• Why can't sieve tube elements survive on their own?

  They have no nucleus and rely on companion cells
• What do companion cells do for sieve tube elements?

  They carry out the functions for both themselves and the sieve cells
• What is the main substance transported by phloem?

  Food substances, mainly sugars
• What is translocation in plants?

  The movement of food substances around the plant
• What are xylem tubes primarily made of?

  Dead cells joined end to end
• What is the role of lignin in xylem tubes?

  It strengthens and waterproofs the cell walls
• What do xylem tubes transport from the roots to the leaves?

  Water and mineral salts (ions)
• What causes transpiration in plants?

  The evaporation and diffusion of water from a plant’s surface
• Where does most transpiration occur in a plant?

  At the leaves
• How does transpiration create a shortage of water in leaves?

  Water evaporation and diffusion create a slight shortage
• What happens to water as a result of transpiration?

  More water is drawn up from the rest of the plant through the xylem
• What is the relationship between transpiration and the roots of the plant?

  Water is drawn up from the roots to replace the lost water
• Why do leaves have stomata?

  To allow for gas exchange
• How does the water inside the plant compare to the air outside?

  There’s more water inside the plant than in the air outside
• What is the benefit of the transpiration stream for plants?

  It helps keep the plant cool and provides water for photosynthesis
• How does transpiration create turgor pressure in plant cells?

  By providing a constant supply of water to the cells
• What role does transpiration play in mineral uptake by plants?

  It allows minerals to be brought in from the soil along with water
• What is the difference in the direction of transport between phloem and xylem?

  • Phloem transports food substances both up and down
  • Xylem transports water and minerals only up
• What are the benefits of transpiration for plants?

  1. Keeps the plant cool
  2. Provides water for photosynthesis
  3. Creates turgor pressure for support
  4. Brings in minerals from the soil
• Why is there a continuous upward flow of water in plants?

  Due to the constant transpiration creating a shortage of water in leaves
• What is the main topic discussed in the material?

  Transpiration in plants
• How does light intensity affect the transpiration rate?

  Increased light intensity raises the transpiration rate by opening stomata for CO₂ intake.
• What happens to the stomata in the dark?

  In the dark, stomata begin to close, reducing water loss.
• How does temperature influence transpiration?

  Higher temperatures increase the energy of water particles, speeding up transpiration.
• What role does air movement play in transpiration?

  Increased air movement helps water vapor to diffuse away from the leaf, enhancing transpiration.
• Why do plants need to balance water loss with water uptake?

  To prevent excessive water loss during dry conditions while still cooling the plant.
• What adaptations do plants have to reduce water loss?

  • Waxy cuticle on leaves to prevent water loss.
  • Stomata primarily located on the lower surface of leaves.
  • Smaller stomata in hot climates to conserve water.
• What is the function of guard cells in relation to stomata?

  Guard cells control the opening and closing of stomata.
• How do guard cells respond when water supplies are low?

  Guard cells close the stomata to conserve water.
• What is the shape of guard cells and how does it affect their function?

  Guard cells have a kidney shape that allows them to open and close stomata effectively.
• What structural features of guard cells assist in their function?

  Thin outer walls and thickened inner walls help guard cells open and close stomata.
• When do stomata typically open and close, and why?

  Stomata open during the day for photosynthesis and close at night to conserve water.
• How much water does a big tree lose from its leaves daily?

  About 1000 litres of water.
• What must roots do to replace the water lost by a tree?

  Roots must draw a significant amount of water from the soil.
• Why do stomata close when the soil is dry?

  To prevent excessive water loss when water is scarce.
• How does darkness affect stomata and transpiration?

  In darkness, stomata close, reducing transpiration.
• What are the main factors affecting transpiration rate in plants?

  1. Light intensity
  2. Temperature
  3. Air movement
• What are the consequences of excessive transpiration for plants?

  • Risk of dehydration
  • Reduced photosynthesis
  • Potential for wilting