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有些树在高温天气下 会流汗

kira86 于2018-06-07发布 l 已有人浏览
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盛夏酷暑,人在房间里都热得受不了,而在太阳下暴晒的树该如何存活?它们通过流汗给自己祛暑。
    小E英语欢迎您,请点击播放按钮开始播放……
树.jpg
Some Trees Beat Heat with Sweat
有些树在高温天气下 会流汗
Here's a short piece from the May 2018 issue of the magazine, in the section we call Advances: Dispatches from the Frontiers of Science, Technology and Medicine:
以下内容是本杂志五月刊的一个短篇节选,我们称之为“进展:来自科学、技术和医学前沿的报告”:
Sweaty Trees, by Yasemin Saplakoglu
亚塞明·沙普拉克奥卢《流汗的树》
Recent summer temperatures in parts of Australia were high enough to melt asphalt. As global warming cranks up the heat and climatic events intensify, many plants may be unable to cope. But at least one species of eucalyptus tree can withstand extreme heat by continuing to "sweat" when other essential processes taper off, a new study finds.
澳大利亚部分地区最近的夏季气温高到足以融化沥青。随着全球变暖所导致的日益加剧的高温和气候问题, 许多植物可能无法应对。但一项新研究发现, 至少有一种桉树能经受住酷热的考验,因为当其他必要的过程逐渐减弱时,它们会不停地“出汗”。
As plants convert sunlight into food, or photosynthesize, they absorb carbon dioxide through pores on their leaves. These pores also release water via transpiration, which circulates nutrients through the plant and helps cool it by evaporation. But exceptionally high temperatures are known to greatly reduce photosynthesis - and most existing plant models suggest this should also decrease transpiration, leaving trees in danger of fatally overheating. Because it is difficult for scientists to control and vary trees' conditions in their natural environment, little is known about how individual species handle this situation.
植物将阳光转化为食物,即“光合作用”,也就是植物通过通过叶子上的毛孔吸收二氧化碳。毛孔通过蒸腾作用释放水分,蒸腾作用可以使养分在植物周身循环,并通过蒸发来帮助植物冷却。但众所周知,异常的高温会大大降低光合作用,而且大多数现存的植物模式都表明异常的高温会减少蒸腾,让植物处于致命的高温危险之中。由于科学家很难控制和改变树木在自然环境中的生长条件,所以对于单个物种如何处理这种情况,人们知之甚少。
Ecologist John Drake of the S.U.N.Y. College of Environmental Science and Forestry and his colleagues grew a dozen Parramatta red gum (Eucalyptus parramattensis) trees in large, climate-controlled plastic pods that isolated the trees from the surrounding forest for a year in Richmond, Australia. Six of the trees were grown at ambient air temperatures and six at temperatures three degrees Celsius higher. The researchers withheld water from the surface soil of all 12 trees for a month to simulate a mild dry spell, then induced a four-day "extreme" heat wave: They raised the maximum temperatures in half of the pods (three with ambient temperatures and three of the warmer ones) - to 44 degrees C.
纽约州立大学环境科学与林业科学学院的生态学家约翰. 德雷克和他的同事们在澳大利亚里士满,在一打大型的、温度可控的塑料隔离舱内分别种植了帕拉玛塔赤桉树,隔离舱可将树木与周围的环境隔离开,测试时间长达一年。其中六棵树在与周围空气温度一致的环境下生长,另外六棵树在比周围环境温度高3度的环境下生长。研究人员让所有12棵树的表层土壤断水一个月来模拟一个轻度干旱的状态,然后引起了连续四天的“极端”热浪:科学家们将一半塑料仓的最高温度升高(其中三个与周围温度一样、另三个要高三度的塑料仓)至44℃。
Photosynthesis ground to a near halt in the trees facing the artificial heat wave. But to the researchers' surprise, these trees continued to transpire at close-to-normal levels, effectively cooling themselves and their surroundings. The trees grown in warmer conditions coped just as well as the others, and photosynthesis rates bounced back to normal after the heat wave passed, Drake and his colleagues reported these findings in Journal in Global Change Biology.
当树木面对人工热浪时,光合作用几乎停止。但让研究者们吃惊的是,这些树木的蒸腾水平几近正常,有效地冷却自己以及周围的环境。在温度更高环境生长的树木同在周围环境生长的树木应对得一样好,光合速率在热浪过后就恢复正常,德雷克和他的同事《全球变化生物学》一刊上报道了这些发现。
The researchers think the Parramatta red gums were able to effectively sweat - even without photosynthesis - because they are particularly good at tapping into water deep in the soil. But if a heat wave and a severe drought were to hit at the same time and the groundwater was depleted, the trees may not be so lucky, Drake says.
研究人员认为,帕拉玛塔赤桉树在即使没有光合作用的情况下,也能够有效地出汗,是因为它们特别擅长于在土壤深处挖掘到水。德雷克说:“但是,如果热浪和严重旱灾同时发生时,以及地下水枯竭时,这些树木就不会那么幸运了。”
Other scientists call the finding encouraging. "It's definitely good news," says Trevor Keenan, an ecologist at Lawrence Berkeley National Laboratory, who was not part of the study. "It would be very interesting to know how this translates to other species," he adds. Drake hopes to conduct similar experiments with trees common in North America.
其它科学家称这一发现令人鼓舞。劳伦斯伯克利国家实验室的生态学家特雷弗·基南说到“这绝对是个好消息。真不知道其它物种是否也适用于此理论。”特雷弗·基南本人并未参与此项研究。而德雷克希望对北美常见的树木进行类似的实验。
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