Limiting Factors of Photosynthesis Objectives Describe how the rate of photosynthesis can be increased. Explain the effects of limiting factors on the rate of photosynthesis. Explain why plants take in carbon dioxide and give out oxygen during the day and do the reverse at night. Key Words  limiting factor • respiration

… how many finished cars can it make in a week? If a car factory can make… 16 engines per week 40 seats per week 58 doors per week 33 windscreens per week … how many finished cars can it make in a week?

The Law of Limiting Factors When a process depends on two or more factors, the rate of that process is limited by the factor which is in shortest supply The rate of photosynthesis in a plant can be limited by: Light intensity Availability of water Availability of carbon dioxide Availability of chlorophyll Temperature

Photosynthesis and the Law of Limiting Factors What you need to know: What factors limit the rate of photosynthesis? How do we explain why certain factors limit the rate of photosynthesis? Can we use the law of limiting factors to explain experimental results?  Question: What does MRS GREN stand for?

Nutrition = Photosynthesis What do the letters below stand for? Remember: as living things plants are respiring all the time M - movement R - respiration S - sensitivity G - growth R - reproduction E - excretion For plants Nutrition = Photosynthesis N - nutrition

How does the rate of bubbles produced vary as light intensity is increased? No. of Bubbles per minute Light Intensity No. of Bubbles per minute Light Intensity No. of Bubbles per minute Light Intensity No. of Bubbles per minute

No. of Bubbles per minute Increasing light intensity has no effect as rate of photosynthesis is limited availability of carbon dioxide, water or chlorophyll Compensation point Rate of photosynthesis equals rate of respiration No. of Bubbles per minute Increasing light intensity increases rate of bubbling (and photosynthesis) Light Intensity Any oxygen produced by photosynthesis is used up in respiration

Complete the questions on the Law of Limiting Factors and Photosynthesis worksheet

a. 2 units of glucose can be made by plant A Question 1: a. 2 units of glucose can be made by plant A b. Light is in shortest supply (6 units of light are needed to make one unit of glucose) c. D (B is limited by the availability of CO2) d. 4 (it will be limited by the availability of water) Question 2: Number of Bubbles per Minute Light Intensity Increasing light intensity increases the rate of photosynthesis Increasing light intensity has little to no effect. This is because the rate of photosynthesis is now limited by the availability of CO2/water/temperature

Amount of Carbon Dioxide in the Atmosphere (arbitrary units) The graph below shows how the amount of CO2 in the atmosphere in the Northern Hemisphere changes through the year Amount of Carbon Dioxide in the Atmosphere (arbitrary units) Describe the changes seen in the graph Suggest a reason for the changes seen in the graph

Plenary activity – true or false? Plants grow faster on warm sunny days Light is required for photosynthesis Oxygen is required for photosynthesis Photosynthesis speeds up in the cold Plants produce glucose by photosynthesis Glucose is converted to starch for storage The equations for respiration and photosynthesis are identical Plants only carry out respiration in the dark Plants carry out respiration for 24 hours a day Plants can use the carbon dioxide from respiration for photosynthesis Plants can use the oxygen from respiration for photosynthesis The limiting factors of photosynthesis include light, temperature and nitrogen levels T F