Plant nutrition

• What processes occur in the leaf during the day?

  Respiration and photosynthesis
• What gas is produced as a metabolic waste during respiration?

  Carbon dioxide
• What gas is produced as a metabolic waste during photosynthesis?

  Oxygen

  
• What is the overall movement of gases in a leaf during the day?

  • Carbon dioxide enters the leaf via stomata by diffusion
  • Oxygen exits the leaf via stomata by diffusion
• What is the role of the upper epidermis in a leaf?

  It is a transparent layer of cells that lets light through

  
• What is the function of the palisade mesophyll layer?

  It is densely packed with chloroplasts for light absorption
• Why does the spongy mesophyll layer have many air spaces?

  To increase the surface area for diffusion of carbon dioxide
• What is the purpose of stomata on the underside of the leaf?

  To increase carbon dioxide diffusion into the leaf
• What do guard cells do in relation to stomata?


  They open the stomata to allow carbon dioxide to diffuse into the leaf

  
• What is the role of vascular bundles in a leaf?

  To transport water to the leaf
• Why are there no stomata where evaporation is highest?

  To reduce water loss, ensuring more water for photosynthesis
• What is the shape of the leaf and why?

  The leaf is broad and thin to increase surface area for light absorption
• How does the thickness of the leaf affect carbon dioxide diffusion?

  The leaf is thin to reduce diffusion distance for carbon dioxide
• What is a limiting factor in photosynthesis?


  A limiting factor is something that stops the rate of photosynthesis from increasing further

  
• What are the three main limiting factors affecting the rate of photosynthesis?

  1. Light intensity
  2. Carbon dioxide concentration
  3. Temperature

  
• How can you determine which factor is limiting the rate of photosynthesis from a graph?

  If the rate is still increasing, the factor on the x-axis is limiting; when it plateaus, something else is limiting

  
• What does the presence of starch in a leaf indicate?

  It indicates that photosynthesis has occurred
• How can starch be tested for in a leaf?

  By using iodine, which turns blue-black if starch is present
• What must be done to a leaf before testing for starch?

  The leaf must be boiled to stop chemical reactions and then placed in boiling ethanol to remove the waxy layer
• What safety precaution should be taken when using iodine?

  Wear safety glasses to protect your eyes
• Why should the Bunsen burner be turned off before using ethanol?

  To reduce the chance of a fire as ethanol is flammable
• What would you expect if a leaf was kept in the dark?

  The leaf would not have photosynthesized and therefore would not have any starch present
• What does it mean if a leaf or part of a leaf is white?

  It does not have chlorophyll and therefore will not photosynthesize
• What are variegated leaves?

  Leaves that are part white and part green
• What is the process of de-starching a plant?

  • Place the plant in the dark
  • It uses up all starch by digesting it into glucose
  • Ensures any starch present after investigation is produced during that investigation
• What effect does adding soda lime have in an investigation?

  It removes any carbon dioxide in that part
• Why are mineral ions important for plants?

  They are required for general plant health
• How are mineral ions absorbed by plants?

  By root hair cells from the soil, often by active transport
• What are nitrates needed for in plants?

  To make amino acids which make up proteins
• What happens to a nitrate deficient plant?

  It would be smaller than expected and older leaves would turn yellow
• What are phosphates needed for in plants?

  To make DNA and cell membranes
• What are the symptoms of a phosphate deficient plant?

  It would have purple leaves and short roots
• What is potassium needed for in plants?

  For enzymes of respiration and photosynthesis to work
• What are the symptoms of a potassium deficient plant?

  It would have dead spots and yellow leaves
• What is magnesium needed for in plants?

  For the production of chlorophyll
• What are the symptoms of a magnesium deficient plant?

  It would have yellow leaves