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VOA慢速:关于植物利用水的新发现

上传时间:2010-05-31 18:35   录音时长:3分53秒

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资料原文 |

This is the VOA Special English Agriculture Report.
Scientists have discovered more details about how plants use water.
Their findings could help to engineer plants that grow better and more effectively in conditions with higher levels of carbon dioxide.
Plants naturally take in carbon dioxide they need for photosynthesis,
the process of changing light energy to chemical energy.
The carbon dioxide enters the plants through tiny holes or pores on the surface of leaves.
However, each time a plant takes in one molecule of carbon dioxide gas, it loses hundreds of water molecules.
Scientists say plants lose ninety-five percent of the water they take in through these pores.
Some plants' pores can tighten to save water during conditions of high carbon dioxide.
Other plants are not able to do this as well.
Now, scientists know how these tiny pores tighten in plants.
Julian Schroeder is a professor of biology at the University of California, San Diego.
Mister Schroeder says that carbon dioxide levels in the atmosphere are much higher now than they were in the past.
However, he says, many plants are not closing their pores in order to hold in more water.
He and his team have identified proteins that control the tightening of a plant's pores.
The proteins are enzymes called carbonic anhydrases.
The findings were published last month in the journal Nature Cell Biology.
Mister Schroeder believes the enzymes could be changed in some plants to increase their ability to store water.
The researchers added carbonic anhydrase genes to plants that do not react to higher levels of carbon dioxide.
They observed that for every molecule of carbon dioxide taken in by the plants, they lost forty-four percent less water.
The scientists say the photosynthesis process continued normally in these plants.
They say this suggests that changing plants to save more water will not affect plant growth.
This method might be used to help engineer food crops that are resistant to extremely dry conditions.
The discovery could help farmers meet a growing demand for food as water supplies decrease.
However, the scientists say more research is needed.
And that's the VOA Special English Agriculture report, written by Brianna Blake.
For transcripts, MP3s and podcasts of our reports, visit us on the Web at voaspecialenglish.com.

[参考译文]
这里是VOA特别英语农业报道。
科学家发现了植物利用水的方式的更多细节。
他们的发现可以帮助设计出在二氧化碳水平较高的条件下生长得更好,更高效的植物。
植物自然地吸收光合作用所需的二氧化碳。
光合作用是植物将光能转化为化学能的过程。
二氧化碳通过叶片表面的气孔进入植物体内。
然而,植物每次吸收一个二氧化碳分子需要消耗数百个水分子。
科学家表示,植物吸收的95%的水分都通过这些气孔消失。
在二氧化碳水平较高的环境下,一些植物会收缩气孔,节约水分。
其他植物则做不到。
现在,科学家已经了解到这些微小气孔收缩的机制。
Julian Schroeder是加州大学圣地亚哥分校对生物学教授。
Schroeder表示,现在,大气中的二氧化碳水平比过去高出很多。
然而,许多植物却没有关闭气孔来保持更多水分。
他和他的研究小组鉴别出了控制植物气孔紧缩的蛋白质。
这些蛋白质叫做碳酸酐酶。
该发现发表在上月的《自然-细胞生物学》上。
Schroeder相信,可以对某些植物中的这种酶进行改变,增加植物储水的能力。
研究人员向那些对高二氧化碳水平环境没有反应的植物中加入做碳酸酐酶基因。
他们发现,植物每吸收一个二氧化碳分子失去的水分减少44%。
科学家表示,这些植物的光合作用过程可以继续正常进行。
他们说,这表明,更改植物的基因来保持更多水分不会影响植物的生长。
这种方法可以用来设计抵抗极端干旱环境的粮食作物。
在水供应量减少的情况下,该发现可以帮助农民满足不断增长的粮食需求。
然而,科学家称,目前还需要更多的研究。
这里是美国之音慢速英语农业报道,Brianna Blake. 撰写。
更多信息请访问voaspecialenglish.com.

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