Plants are unlikely to soak up more carbon dioxide from the air as the planet warms, research suggests. US scientists found that grassland took up less CO2 than usual for two years following temperatures that are now unusually hot, but may become common. The conclusion parallels a real-world finding from Europe's 2003 heatwave, when the continent's plant life became a net producer, not absorber, of CO2. The latest study is published in the scientific journal Nature. Researchers extracted four intact segments of grassland, about 3 sq m in area and weighing about 12 tonnes each, from the prairies of Oklahoma, and placed them in special chambers at the Desert Research Institute (DRI) in Reno, Nevada. Conditions in the chambers, such as temperature, moisture and sunlight, could be precisely controlled.