1. Scientists have been studying natural sources of methane(甲烷，沼氣) for decades but hadn’t regarded plants as a producer, notes Frank Keppler, a geochemist(地球化學(xué)家) at the Max Planck Institute for Nuclear Physics in Heldelberg, Germany. Now Keppler and his colleagues find that plants, from grasses to trees, may also be sources of the greenhouse gas. This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.

　　2. Previously, researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes(微生物) 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 Earth’s atmosphere and contribute to global warming.

　　3. In its experiments, Keppler’s team used sealed chambers (室，房間;腔) that contained the same concentration of oxygen that Earth’s atmosphere has. They measured the amounts of methane that were released by both living plants and dried plant material, such as fallen leaves.

　　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(微克) of methane per hour. (One nanogram is a billionth of a gram.) With every 10-degree rise in temperature, the amount of methane released each hour roughly doubled.

　　5. Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions(散發(fā)，發(fā)射)tripled(增加三倍;) when living and dead plant was exposed to sunlight.

　　6. Because there was plenty of oxygen available, it’s unlikely that the types of bacteria(bacterium的復(fù)數(shù)，細菌) that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions. That’s another strong sign that the gas came from the plants and not soil microbes.

　　7. The new finding is an “interesting observation,” says Jennifer Y. King, a biogeochemist(生物地球化學(xué)家) at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane, they may prevent plant-produced methane from reaching the atmosphere. Field tests will be needed to assess the plant’s influence, she notes.

　　注釋：

　　1. the Max Planck Institute for Nuclear Physics in Heldelberg, Germany：馬克思·普朗克核物理研究所，位于德國海德堡。海德堡系德國西南部城市，在巴登-符騰堡州的內(nèi)卡河畔。海德堡大學(xué)是德國歷史最悠久的大學(xué)。

　　2. microbe：細菌，意義同 bacterium(bacteria的單數(shù)形式)，但 microbe 不用作專門術(shù)語。

　　3. St. Paul：圣保羅，美國明尼蘇達州首府。

　　練習(xí)：

　　1. What was scientists’ understanding of methane?

　　A) It was produced from plants.

　　B) It was not a greenhouse gas.

　　C) It was produced in oxygen-free environments.

　　D) It traps more heat than any other greenhouse gas.

　　2. To test whether plants are a source of methane, the scientists created ______.

　　A) an oxygen-free environment.

　　B) an environment with the same concentration of oxygen as the Earth has.

　　C) a carbon dioxide-free environment.

　　D) an environment filled with the greenhouse gas

　　3. Which statement is true of the methane emissions of plants in the experiment?

　　A) The lower the temperature, the higher the amount of methane emissions.

　　B) Living plants release less methane than dried plants at the same temperature.

　　C) When exposed to sunlight, plants stop releasing methane.

　　D) The higher the temperature, the greater the amount of methane emissions.

　　4. What of the following about methane is Not mentioned in the passage?

　　A) Plants growing in soil release methane.

　　B) Plants growing in water release methane.

　　C) Soil microbes consume methane.

　　D) Microbes in plants produce methane.

　　5. What is the beneficial point of some microbes consuming plant-produced methane?

　　A) Methane becomes less poisonous.

　　B) Methane is turned into a fertilizer.

　　C) Less methane reaches the atmosphere.

　　D) Air becomes cleaner.

　　題目詳解：

　　1.先看標(biāo)題，推測文章主題：Plant(植物) Gas(氣體)，即植物能產(chǎn)生某種氣體。什么氣體?我們很快掃視文章發(fā)現(xiàn)文中有一個詞共出現(xiàn)了14次，它就是Methane(沼氣，學(xué)名甲烷)，因此標(biāo)題中的gas就是指Methane。我們知道城市垃圾、煤礦、碳泥沼等會產(chǎn)生甲烷，從未聽說植物有這種可能性。所以可以說這是人類的又一次新的發(fā)現(xiàn)，它有助于我們重新認(rèn)識全球變暖與溫室氣體之間的關(guān)系。

　　2.接下來看問題，了解它們的類型，要針對問題的提法對癥下藥。通讀后我們發(fā)現(xiàn)，五個問題仍是細節(jié)題為主，這樣我們就可以一邊按文章的寫作順序精讀，一邊準(zhǔn)確回答問題。而且，我相信大家還會學(xué)到不少新的詞匯和知識!

　　3.看第1題：

　　What was scientists’ understanding of methane?科學(xué)家們對于沼氣過去有什么樣的理解?(注意謂語動詞時態(tài)!)

　　A) It was produced from plants.它是由植物產(chǎn)生的。

　　B) It was not a greenhouse gas.它不是溫室氣體。

　　C) It was produced in oxygen-free environments. 它是在缺氧環(huán)境中產(chǎn)生的。

　　D) It traps more heat than any other greenhouse gas.它比其它任何一種溫室氣體吸熱都多。