2.19 understand how varying carbon dioxide concentration, light intensity and temperature affect the rate of photosynthesis

Limiting factors – Anything that will limit the rate of photosynthesis.

Light intensity 

  • No light = no photosynthesis (exchange of gas can’t physically occur as the stomata do not open in dim conditions)
  • As light level increase, so does the rate of photosynthesis, as the stomata open to allow the exchange of gasses
  • However there will come a point when there is no corresponding increase to the rate of photosynthesis, because another factor will become rate limiting.

Carbon dioxide 

  • During the day (the point of highest temperature and light intensity for maximum kinetic energy therefore the fastest point at which photosynthesis can occur), A leaf has to exchange a large volume of air – as air only contains 0.04% of carbon dioxide, it needs enough to pacify sufficient amounts of CO2 into the chloroplasts of leaves.
  • Like CO2 concentration, there will come a point when there is no corresponding increase to the rate of photosynthesis, because another factor will become rate limiting.

Temperature

  • Generally enzymes work faster at warmer temperatures. At optimum temp, the photosynthetic enzymes and substrate molecules collide faster, increasing the rate of photosynthesis.
  • However, if the temperature is too hot, enzymes will denature and the rate of photosynthesis will decline, hence the fall in the graph.

Limitingfactorsgraphs.gif

 

Another rate limiting factor of photosynthesis is transpiration rate; however as transpiration rate is described in more detail in another post, feel free to browse the other posting 🙂

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