VOA慢速英语2010年-Agriculture Report - New Understanding

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 photosynthesis¹, 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 molecule² of carbon dioxide gas, it loses hundreds of water molecules³.

Scientists say plants lose ninety-five percent of the water they take in through these pores. Some plants' pores can tighten⁴ 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 tightening⁵ of a plant's pores. The proteins are enzymes⁶ 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 genes⁷ 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 resistant⁸ 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 transcripts⁹, MP3s and podcasts of our reports, visit us on the Web at voaspecialenglish.com.

　
 

1 photosynthesis   

n.光合作用

参考例句：

• In apple trees photosynthesis occurs almost exclusively in the leaves.苹果树的光合作用几乎只发生在叶内。
• Chloroplasts are the structures in which photosynthesis happens.叶绿体就是光合作用发生的地方。

2 molecule   

n.分子，克分子

参考例句：

• A molecule of water is made up of two atoms of hygrogen and one atom of oxygen.一个水分子是由P妈̬f婘̬ 妈̬成的。
• This gives us the structural formula of the molecule.这种方式给出了分子的结构式。

3 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

4 tighten   

v.(使)变紧；(使)绷紧

参考例句：

• Turn the screw to the right to tighten it.向右转动螺钉把它拧紧。
• Some countries tighten monetary policy to avoid inflation.一些国家实行紧缩银根的货币政策，以避免通货膨胀。

5 tightening   

上紧，固定，紧密

参考例句：

• Make sure the washer is firmly seated before tightening the pipe. 旋紧水管之前，检查一下洗衣机是否已牢牢地固定在底座上了。
• It needs tightening up a little. 它还需要再收紧些。

6 enzymes   

n. 酶，酵素

参考例句：

• It was said that washing powders containing enzymes remove stains more efficiently. 据说加酶洗衣粉除污更有效。
• Among the enzymes which are particularly effective are pepsin, papain. 在酶当中特别有效的是胃朊酶、木瓜酶。

7 genes   

n.基因( gene的名词复数 )

参考例句：

• You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因，所以能够活得很长。 来自《简明英汉词典》
• Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪

8 resistant   

adj.(to)抵抗的，有抵抗力的

参考例句：

• Many pests are resistant to the insecticide.许多害虫对这种杀虫剂有抵抗力。
• They imposed their government by force on the resistant population.他们以武力把自己的统治强加在持反抗态度的人民头上。

9 transcripts   

n.抄本（ transcript的名词复数 ）；转写本；文字本；副本

参考例句：

• Like mRNA, both tRNA and rRNA are transcripts of chromosomal DNA. tRNA及rRNA同mRNA一样，都是染色体DNA的转录产物。 来自辞典例句
• You can't take the transfer students'exam without your transcripts. 没有成绩证明书，你就不能参加转学考试。 来自辞典例句