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What would be the expected effect on plants if the atmospheric co2 concentration was doubled? what would be the expected effect on plants if the atmospheric co2 concentration was doubled? c4 plants would have faster growth rates; c3 plants would be minimally affected. c3 plants would have faster growth rates; c4 plants would have slower growth rates. all plants would have faster growth rates. c3 plants would have faster growth rates; c4 plants would be minimally affected.
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C3 plants would have faster growth rates; C4 plants would be minimized.
The C3 and C4 pathways are the variants of dark photosynthetic reactions found in green plants. The photosynthetic efficiency of C3 plants is reduced due to the affinity of RuBisCo enzyme for oxygen which leads to the futile path of photorespiration. The RuBisCo enzyme catalyzes the rate – limiting reaction of the C3 pathway. On the other hand, the C4 plants concentrate CO2 around RuBisCo in their hawthorn cells bundle of leaves to minimize photorespiration and show higher rates of photosynthesis.
Increased atmospheric CO2 levels would reduce the photorespiration in C3 plants and allow them to fix CO2 efficiently due to the increased concentration of CO2 around the enzyme RuBisCo. The increased photosynthetic efficiency would help these plants show faster growth rates.
However, the photosynthetic rate of C4 plants is not limited by CO2 concentrations because they themselves reduce photorespiration by spatial separation of primary carboxylation in mesophyll cells and CO2 repair in bundle pollutant cells. Hence, increased levels of CO2 in the atmosphere would have no effect on their photosynthetic rate and growth.