Biology

• What is the function of the waxy cuticle?

  Impermeable so water is not lost
• What is the function of the upper and lower epidermis?

  Protection of mesophyll from pathogens
• What is the function of the palisade mesophyll?

  Have lots of chloroplasts for absorbing sunlight
• What is the function of the spongy mesophyll?

  Have air spaces for optimal gas exchange
• What is the function of guard cells?

  Controls opening and closing of stomata
• What is the function of stomata?

  Lets in gases, mainly CO2 for photosynthesis
• What is diffusion?

  The net movement of particles down the concentration gradient
• What is osmosis?

  The net diffusion of water across a membrane
• What is active transport?

  The net movement of particles up the concentration gradient
• What factors affect the rate of movement in cells?

  Distance, temperature, SA to volume ratio, concentration gradient
• What happens to a plant cell in a dilute solution?

  Water moves in, turgid cell
• What happens to a plant cell in a concentrated solution?

  Water moves out, plasmolysis of cell
• Why don't unicellular organisms need a transport system?

  They have a high surface area to volume ratio
• What does osmosis transport?

  Water
• What does active transport in plants transport?

  Mineral ions e.g. nitrates
• What does diffusion in plants transport?

  Gases e.g. O2 and CO2
• What are the adaptations of root hair cells?

  Large surface area, large vacuole, many mitochondria
• What is the role of xylem?

  Moves water and mineral ions from roots
• What are two adaptations of xylem?

  Dead hollow cells, walls lined with lignin
• What is the role of phloem?

  Moves products of photosynthesis up and down
• What are the adaptations of phloem?

  End to end cells with sieve plates
• What is transpiration?

  The evaporation of water from the surface of a plant
• What is stage 1 of transpiration?

  Water is lost from mesophyll tissues through evaporation
• What is stage 2 of transpiration?

  Transpiration pulls water up xylem due to osmosis
• What is stage 3 of transpiration?

  More water is drawn up from the soil
• What absorbs water in plants?

  Root hair cells
• What is the order of the transpiration stream?

  Soil, root hair cells, root cortex, xylem
• What are the four functions of the transpiration stream?

  • Supplies water for photosynthesis
  • Carries mineral ions dissolved in water
  • Stops plant from being turgid
  • Allows for evaporation for cooling
• What are the four factors that affect the rate of transpiration?

  Light intensity, humidity, wind speed, temperature
• Why does light intensity affect the rate of transpiration?

  Stomata opens more to allow in CO2
• Why does humidity affect the rate of transpiration?

  High humidity reduces diffusion of water
• Why does temperature affect the rate of transpiration?

  Higher temperature increases rate of evaporation
• Why does wind speed affect the rate of transpiration?

  Wind moves away water vapour to maintain gradient
• What is a weight potometer?

  Polythene bag containing plant to measure mass change
• What is a volume potometer?

  Measures volume of air bubble per unit time
• What are the stages of transpiration?

  1. Water lost from mesophyll through evaporation
  2. Transpiration pulls water up xylem
  3. More water drawn up from soil into root hair cells