The Effect Of Carbondioxide and Nitrogen on Achillea millefolium L. and Agropyron repens L.
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Atmospheric levels of carbon dioxide (C02) and soil nitrogen (N) are increasing due to anthropogenic activities. To investigate the effects of the increase in these two global change factors, an experiment was conducted at the BioCON (Biodiversity, C02, and Nitrogen; http://biocon.fr.umn.edu ) site at the University of Minnesota's Cedar Creek Natural History Area. For this study, I determined leaf net photosynthesis was for two C3 species, Achillea millefolium L., which is a forb, and Agropyron repens L., which is a grass. I measured Leaf net photosynthesis using a portable photosynthesis system. In addition to this I measured physiological variables associated with leaf net photosynthesis and photosynthetic enzyme activity were examined. There was a significant change in photosynthetic capacity in response to elevated C02 at high N in Achillea millefolium L. This was not the case for Agropyron repens (L.) Beauv. Additionally, elevated C02 had a significant enhancement effect on photosynthesis for Achillea millefolium at both N levels (mean enhancement of 40%), but no significant effect on Agropyron repens photosynthesis. N treatment was found to have no significant effect on photosynthesis in both Achillea millefolium and Agropyron repens. This study indicates that, while C02 and N levels may continue to rise, plant photosynthesis and hence plant growth may not rise concurrent with these factors. These data also bring into question the sustainability of the C02 sink that plants currently provide that partially slows the rise in global atmospheric C02 levels.