The increased levels of greenhouse gases, particularly carbon dioxide, have led

Question

The increased levels of greenhouse gases, particularly carbon dioxide, have led some scientists to postulate that terrestrial plants will increase their rates of carbon fixation through photosynthesis in response. However, plant physiology experiments to date show mixed results. One surprising result was that, though plants did increase their rates of photosynthesis for a time, with continued exposure to elevated levels of carbon dioxide, plants responded by actually synthesizing less of the photosynthetic enzyme rubisco and reduced the rates of photosynthesis to rates comparable with lower concentrations of carbon dioxide. This phenomenon is called downregulation. This is of concern because some atmospheric scientists are looking to enhanced plant growth to remove the excess carbon dioxide from the atmosphere.

Considering this and the concepts presented in this unit, propose a response to the following statement. Explain your answer and give an example supporting your position:

Because of physiological limitations such as downregulation, plants will not increase their uptake of carbon dioxide in response to increased levels in the atmosphere, and will not increase their relative significance in the removal and sequestration of carbon dioxide. Do you agree or disagree?

Explanation / Answer

I agree that plants will not increase their uptake of carbon dioxide in response to increased levels in the atmosphere. This is due to downregulation. The plants are not able to tolerate high levels of carbon dioxide and hence intake of CO2 reduces. One example would be today's situation where we see high levels of CO2 responsible for global warming. Plants are able to take in CO2 and convert it into O2 but this is not happening. Hence the plants are not used to such high levels of CO2.

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