Rate of photosynthesis

• What three factors affect the rate of photosynthesis?

  Light, CO₂, and temperature
• How does light intensity affect the rate of photosynthesis?

  As light intensity increases, the rate of photosynthesis increases steadily up to a certain point
• What happens to the rate of photosynthesis when light intensity exceeds a certain point?

  The rate will no longer increase because another factor becomes limiting
• How can you change the light intensity in a lab setting?

  By moving a lamp closer to or further away from the plant
• What type of graph results from plotting the rate of photosynthesis against the distance of a lamp from the plant?

  A weird-shaped graph
• What is one of the raw materials needed for photosynthesis?

  CO₂
• What happens to the rate of photosynthesis when CO₂ levels increase beyond a certain point?

  The rate no longer increases, indicating CO₂ is not the limiting factor
• What must be true if both light and CO₂ are in plentiful supply?

  The limiting factor for photosynthesis must be temperature
• Why is temperature often a limiting factor for photosynthesis?

  Because enzymes needed for photosynthesis work more slowly at low temperatures
• What happens to enzymes needed for photosynthesis if the temperature gets too high?

  They will be damaged
• At what temperature do enzymes needed for photosynthesis begin to get damaged?

  About 45°C
• What are the three important graphs related to the rate of photosynthesis?

  1. Not Enough Light Slows Down the Rate of Photosynthesis
  2. Too Little Carbon Dioxide Also Slows it Down
  3. The Temperature has to be Just Right
• What are the key points regarding light's effect on photosynthesis?

  • Light provides energy for photosynthesis.
  • Rate increases with light intensity up to a point.
  • Beyond that point, temperature or CO₂ becomes limiting.
• What are the key points regarding CO₂'s effect on photosynthesis?

  • CO₂ is a raw material for photosynthesis.
  • Rate increases with CO₂ up to a point.
  • Beyond that point, temperature becomes the limiting factor.
• What are the key points regarding temperature's effect on photosynthesis?

  • Low temperatures slow down enzyme activity.
  • High temperatures can damage enzymes.
  • Optimal temperature is crucial for effective photosynthesis.
• What does a graph showing the rate of photosynthesis indicate about limiting factors?

  A graph may show more than one limiting factor affecting the rate of photosynthesis.
• How do light intensity and temperature affect the rate of photosynthesis according to the graph?

  Both light intensity and temperature affect the rate of photosynthesis at the start.
• What does it mean when the lines on the graph level off?

  It indicates that the rate of photosynthesis becomes steadily less.
• What does the difference in leveling off between the lines at 15 °C and 20 °C suggest?

  It suggests that temperature was a limiting factor at 15 °C.
• What two factors does the graph on the right show affecting the rate of photosynthesis?

  Light intensity and CO₂ concentration.
• What happens to the lines on the graph when light is no longer the limiting factor?

  Both lines level off when light is no longer the limiting factor.
• What does it indicate when the line at a higher CO₂ concentration levels off at a higher point than at a lower concentration?

  It indicates that CO₂ concentration was a limiting factor at 0.04% CO₂.
• What is the temperature for both lines in the CO₂ concentration graph?

  25 °C.
• How can Canadian pondweed be used to measure the rate of photosynthesis?

  By measuring the rate at which it produces O₂, which corresponds to the rate of photosynthesis.
• What are the steps of the experiment using Canadian pondweed to measure the effect of light intensity on photosynthesis?

  1. Place a source of white light at a specific distance from the pondweed.
  2. Allow the pondweed to photosynthesize for a set time.
  3. Collect the oxygen released in a capillary tube.
  4. Measure the length of the gas bubble to determine O₂ volume.
  5. Control variables like temperature and time.
  6. Repeat the experiment and calculate the mean volume of O₂ produced.
  7. Repeat with the light source at different distances.
• What should be controlled in the experiment measuring the rate of photosynthesis?

  Variables such as temperature and time should be controlled.
• How can the experiment be altered to measure the effect of temperature or CO₂ on photosynthesis?

  By placing the test tube in a water bath at a set temperature or dissolving sodium hydrogencarbonate in the water.
• What is the purpose of sodium hydrogencarbonate in the experiment?

  It provides CO₂ for the pondweed during photosynthesis.
• What can be inferred if the experiment is repeated with different temperatures of water or concentrations of sodium hydrogencarbonate?

  It allows for the investigation of how temperature or CO₂ concentration affects the rate of photosynthesis.
• What happens to the amount of light that reaches pondweed when the lamp is moved away?

  The amount of light decreases.
• How does distance affect light intensity according to the study material?

  As distance increases, light intensity decreases.
• What is the relationship between distance and light intensity described in the material?

  Distance and light intensity are inversely proportional.
• What is the formula that represents the inverse square law?

  light intensity α 1/distance²
• What does the inverse square law imply about halving the distance to a light source?

  If you halve the distance, the light intensity will be four times greater.
• What happens to light intensity when the distance is tripled according to the inverse square law?

  The light intensity will be nine times smaller.
• How can you express light intensity using the formula provided in the study material?

  light intensity = 1/d²
• What is the light intensity when the lamp is 10 cm from the pondweed using the inverse square law?

  light intensity = 0.01 au
• What are the main benefits of using a greenhouse for plant growth?

  • Traps the sun's heat
  • Maintains ideal temperature
  • Allows for artificial light supply
  • Increases carbon dioxide levels
  • Protects from pests and diseases
  • Facilitates the addition of fertilizers
• Why do commercial farmers supply artificial light after sunset?

  To give their plants more quality photosynthesis time.
• How can carbon dioxide levels be increased in a greenhouse?

  By using a paraffin heater that produces carbon dioxide as a by-product.