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Plant Gas 2. Previously, researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes need to be in environments without oxygen to produce methane. Methane is a greenhouse gas, like carbon dioxide. Gases such as methane and carbon dioxide trap heat in Earths atmosphere and contribute to global warming. 4. With the dried plants, the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C. At 30 degrees C, they found, a gram of dried plant material released up to 3 nanograms of methane per hour. With every 10-degree rise in temperature, the amount of methane released each hour roughly doubled. 6. Because there was plenty of oxygen available, its unlikely that the types of bacteria that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions. Thats another strong sign that the gas came from the plants and not soil microbes. 注释： 2. microbe：细菌，意义同 bacterium，但 microbe 不用作专门术语。 练习： A) It was produced from plants. C) It was produced in oxygen-free environments. 2. To test whether plants are a source of methane, the scientists created ______. B) an environment with the same concentration of oxygen as the Earth has. | 
