职称英语理工类的阅读理解文章及练习(1)

　　Scientists have been studying natural sources of methane for decades but hadnt regarded plants as a producernotes Frank Kepplera geochemist at the Max Planck Institute for Nuclear Physics in HeldelbergGermany.Now Keppler and his colleagues find that plantsfrom grasses to treesmay also be sources of the greenhouse gas.This is really surprisingbecause most scientists assumed that methane production requires an oxygen-free environment. 　　In its experimentsKepplers team used sealed chambers that contained the same concentration of oxygen that Earths atmosphere has.They measured the amounts of methane that were released by both living plants and dried plant materialsuch as fallen leaves. 　　Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour.Methane emissions tripled when living and dead plant was exposed to sunlight. 　　The new finding is an interesting observation, says Jennifer Y.Kinga biogeochemist at the University of Minnesota in St.Paul3.Because some types of soil microbes consume methanethey may prevent plant-produced methane from reaching the atmosphere.Field tests will be needed to assess the plants influenceshe notes.