Carbon dioxide is the major limiting factor for photosynthesis. The concentration of CO₂ is very low in the atmosphere (between 0.03 and 0.04 per cent). Increase in concentration upto 0.05 per cent can cause an increase in CO₂ fixation rates; beyond this the levels can become damaging over longer periods.
Assertion (A): Carbon dioxide is abundant in the atmosphere for photosynthesis. Reason (R): The concentration of CO2 in the atmosphere is between 0.03 and 0.04 per cent.
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