To understand the effects of elevated atmospheric CO2 on plant growth, my research is designed to test the hypothesis that the increased number of mitochondria in elevated CO2-grown plants is a response to increased energy demand during the daylight hours. My research helps to prove or modify the hypothesis that for C4 plants, the long-term photosynthesis and the number of mitochondria will not increase in elevated CO2 level compared with those in ambient CO2 level. Two monocot species C3 plant wheat (Triticum aestivum) and C4 plant corn (Zea mays) are examined. For C3 plant wheat, growth in elevated CO2 resulted in significant decrease in the number of mitochondria. For C4 plant corn, growth in elevated CO2 resulted in insignificant decrease in the number of mitochondria. I also studied the effect of elevated CO2 on leaf dark respiration in light (RL) and in darkness (RD) in both species. For wheat, growth in elevated CO2 significantly increase the leaf RD and RL and RL / RD ration. For corn, there was no significant change between leaf RD in ambient CO2 and in elevated CO2 concentration. Leaf RL was significantly less in elevated CO2 compared with ambient CO2-grown plants. The RL / RD ratio was significantly lower in elevated CO2 than in ambient CO2. The gas-change results for wheat is consistent with that of previous studies. Due to the lack of data showing increase of mitochondria numbers in wheat, the correlation between increase of leaf dark respiration under illumination and increase of mitochondria numbers cannot be established based on my experiments. But it may suggest that plants do not necessarily need to proliferate mitochondria to meet the energy and materials demands by changing the working efficiency of mitochondria.
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Last updated: 7 May 2001, KAK.