Scientific American magazine reported this week on an article in Nature about some results of experiments on C3 plants in plots grown under increased CO2.  The article can be found by clicking here.  In the test plots, which were grown in open-top chambers containing up to 584 parts per million CO2 (compared to 400 ppm in the free atmosphere), zinc and iron levels were reduced by up to 15%.  Carbon dioxide is known to increase plant growth, especially in C3 plants like wheat, rice, barley, and some legumes like soybeans.  The test plots on C4 plants like corn did not show as much reduction as the C3 plants but some reduction was still observed.