GCSE Biology Unit 2 (6)

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Rate of Photosynthesis

  • The rate of photosynthesis is affected by the amount of light, carbon dioxide and the temperature.
  • Plants also need water for photosynthesis, but when a plant is so short of water that it becomes the limiting factor, it's already in such trouble that this is the least of its worries.
  • The Limiting factor depends in the conditions
  • Any of 3 factors can become the limiting factor.
  • This just means that its stopping photosynthesis from happening any faster.
  • Which factor is limiting at a particular time depends on the environmental conditions:
  • at night, light is the limiting fact
  • in winter, it is often the temperature
  • if it's warm enough and bright enough, the amount of carbon dioxide is usually the limiting factor.
  • Not enough light slows down the rate of photosynthesis
  • Light provides the energy needed for photosynthesis.
  • As the light level is raised, the rate of photosynthesis increases steadily - but only up to a certain point.
  • Beyond that, it won't make any difference because then it'll be the temperature or the carbon dioxide level which is the limiting factor.
  • In the lab or in a greenhouse, you can change the light intensity by moving lamps closer to or further away from your plant.
  • Too little carbon dioxide also slows down the rate of photosynthesis
  • Carbon dioxide is one of the raw materials needed for photosynthesis.
  • As with light intensity, the amount…


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