Question 1: Define the term 'limiting factor' in the context of photosynthesis.

Answer: A limiting factor is a condition or resource that restricts the rate of photosynthesis when in short supply or not optimal.

Question 2: List three common limiting factors that can affect the rate of photosynthesis.

Answer: Light intensity, carbon dioxide concentration, and temperature.

Question 3: Explain how light intensity can act as a limiting factor in photosynthesis.

Answer: If light intensity is too low, it provides insufficient energy for the photosynthesis process, thereby limiting the rate at which it occurs.

Question 1: The rate of photosynthesis is measured by the volume of oxygen produced per hour. If a plant produces 240 millilitres of oxygen in 4 hours, what is its average rate of photosynthesis in millilitres per hour?

Answer: 60 ml/hour

Question 2: Calculate the percentage decrease in photosynthesis rate if light intensity drops from 1000 lux to 500 lux, assuming the rate decreases from 80 ml/hour to 50 ml/hour.

Answer: 37.5%

Question 1: Describe an experiment to investigate how temperature affects the rate of photosynthesis. Include the variables you would control and measure, and safety precautions you would take.

Answer: To investigate temperature's effect, set up identical plants in water baths at different temperatures (e.g., 10°C, 20°C, 30°C). Control variables include light intensity, carbon dioxide levels, and water availability. Measure the rate of photosynthesis by oxygen production or starch content after a fixed period. Safety precautions include handling hot water baths carefully to prevent burns, avoiding electrical hazards, and ensuring proper ventilation.

Question 2: Identify two variables that should be kept constant in an experiment testing the effect of light intensity on photosynthesis.

Answer: Temperature and carbon dioxide concentration.

Question 1: A scientific report states that when light intensity increases from 200 to 800 lux, the rate of photosynthesis increases from 20 ml/hour to 60 ml/hour, but further increases in light do not significantly raise the rate. What does this suggest about light as a limiting factor?

Answer: It suggests that light was a limiting factor at lower intensities but no longer limits the rate once it reaches a certain level, indicating saturation.

Question 1: Explain why farmers might optimise conditions such as light, carbon dioxide, and temperature in greenhouses to maximise photosynthesis and crop yield.

Answer: Farmers optimise these conditions because limiting factors can reduce the rate of photosynthesis, which directly affects plant growth and crop yield. By controlling light, CO₂, and temperature, they ensure maximum photosynthesis efficiency, leading to healthier plants and higher productivity.

Question 2: Multiple Choice: Which of the following is NOT a common limiting factor in photosynthesis? A) Light intensity B) Water availability C) Oxygen concentration D) Temperature

Answer: C) Oxygen concentration