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Limiting factors in Photosynthesis

Limiting factors in Photosynthesis. Discuss the limiting factors in photosynthesis with reference to carbon dioxide concentration, light intensity and temperature. Law of limiting factors.

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Limiting factors in Photosynthesis

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  1. Limiting factors in Photosynthesis • Discuss the limiting factors in photosynthesis with reference to carbon dioxide concentration, light intensity and temperature.

  2. Law of limiting factors • The limiting factor for a metabolic process is the factor that is present at the lowest or least favourable value.

  3. Rate of photosynthesis 0.1 0.5 Carbon dioxide conc Carbon dioxide concentration • Average carbon dioxide content of the atmosphere is 0.03-0.04% • Increase in CO2 up to 0.5% will increase the rate of photosynthesis • BUT optimum is 0.1%

  4. With reference to the graph: • What makes 0.1% the optimum figure? • Why is there little point in recording rates above the 0.5% CO2 concentration?

  5. Light intensity • Experiments carried out by Blackmann • At low light intensities, the rate of photosynthesis increases as light increases • Beyond 20 kilolux the rate levels off

  6. Effect of light • Allows opening of stomata so CO2 can enter • Absorbed by chlorophyll excites electrons • Splits water molecules  photolysis

  7. Light intensity and the compensation point

  8. Effect of temperature • Mostly affects enzyme controlled reactions of Calvin cycle • At high light intensity, increase in temperature increase in rate. • At low light intensity, little change. • Above 30oC photosynthesis is reduced at both high and low light intensity- can you suggest why?

  9. Rate of photo synthesis High light intensity Low light intensity Temperature/oC Effect of temp. and light together

  10. What temperature is likely to be the optimum temperature at high light intensity? • What is likely to be the temperature at which photosynthesis stops? • Explain why this happens. Now do questions on p67

  11. Graphs and quiz • http://www.cix.co.uk/~argus/Dreambio/fertilisers%20and%20crops/limiting%20factors.htm

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