第四部分 阅读理解（共六篇）
第三十五篇
Putting Plants to Work
Using the power of the sun is nothing new. People have had solar-powered calculators and buildings with solar panels for decades. But plants are the real experts : They've been using sunlight as an energy source for billions of years.
Ceils in the green leaves of plants work like tiny factories to convert sunlight, carbon dioxide, and water into1 sugars and starches, stored energy that the plants can use. This conversion process is called photosynthesis. Unfortunately, unless you're a plant, it's difficult and expensive to convert sunlight into storable energy. That's why scientists are taking a closer look at exactly how plants do it.
Some scientists are trying to get plants, or biological cells that act like plants, to work as miniature photosynthetic power stations. For example, Mafia Ghirardi of the National Renewable Energy Laboratory in Golden, Colo. 2, is working with green algae3. She's trying to trick them into producing hydrogen4 instead of sugars when they perform photosynthesis. Once the researchers can get the algae working efficiently, the hydrogen that they produce could be used to power fuel
Cells in cars or to generate electricity,
The algae are grown in narrow-necked glass bottles to produce hydrogen in the lab. During photosynthesis, plants normally make sugars or starches. "But under certain conditions, a lot of algae are able to use the sunlight energy not to store starch, but to make hydrogen. " Ghirardi says. For example, algae will produce hydrogen in an air free environment. It's the oxygen in the air that prevents algae from making hydrogen most of the time.
Working in an air free environment, however, is difficult. It's not a practical way to produce cheap energy. But Ghirardi and her colleagues have discovered that by removing a chemical called sulfate from the environment that the algae grow in, they will make hydrogen instead of sugars, even when air is present.
Unfortunately, removing the sulfate also makes the algae's cells work very slowly, and not much hydrogen is produced. Still, the researchers see this as a first step in their goal to produce hydrogen efficiently from algae. With more work, they may be able to speed the cells' activity and produce larger quantities of hydrogen.
The researchers hope that algae will one day be an easy-to-use fuel source. The organisms are cheap to get and to feed, Ghirardi says, and they can grow almost anywhere: "You can grow them in a reactor, in a pond. You can grow them in the ocean. There's a lot of flexibility in how you can use these organisms. "
词汇:
panel n. 嵌板，发热板，仪器板 miniature adj. 口巧．微型的
carbon dioxide 二氧化碳 algae n. 水藻，海藻
starch n. 淀粉 sulfate n. 硫酸盐，硫酸酯
photosynthesis n. 光合作用
注释:
1. convert.., into... : 将……转换为……
2. Colo. : Colorado，(美国科罗拉多州)的缩写形式
3. Green algae: 绿藻
4.trick them into producing hydrogen: 想方设法使它们产生氢。trick作为动词，有“欺骗、哄骗”的意思，但是在这里的意思是“设法”或“采取措施”。
练习：
1. What does the writer say about plants concerning solar energy?
A) Plants are 'the real experts in producing solar energy.
B) Plants have been used to produce solar energy.
C) Plants have been using solar energy for billions of years.
D) Plants have been a source of solar energy.
2. Why do some scientists study how plants convert sunlight carbon dioxide, and water into sugars and starches?
A) Because they want algae to produce sugars and starches.
B) Because they want green plants to become a new source of energy.
C) Because they want to turn plant sugars to a new form of energy.
D) Because they want to make photosynthesis more efficient.
3. According to the fifth paragraph, under what conditions are algae able to use solar energy to make hydrogen?
A) When there is a lot of oxygen in the air.)
B) When there is no oxygen in the air.
C) When photosynthesis is taking place.
D) When enough starch is stored.
4. Researchers have met with difficulties when trying to make algae produce hydrogen efficiently. Which one of the following is one such difficulty?
A) It is not possible to remove sulfate from the environment.
B) It is not possible to work in an airfree environment to produce hydrogen.
C) It is not easy to make sugars instead of hydrogen.
D) It is too slow for algae to produce hydrogen when the sulfate is removed.
5. What is NOT true of algae?
A) They are easy to grow.
B) They can be a very good fuel source.
C) They are cheap to eat.
D) They can be used in many ways.
6. Why do some scientists study how plants convert sunlight carbon dioxide and water into sugars and starches?
A) Because they want algae to produce sugars and starch.
B) Because they want green plants to become a new source of energy.
C) Because they want to turn plant sugars to a new form of energy.
D) Because they want to make photosynthesis more efficient.
答案与题解：
1．C 根据文章第一段最后一句的意思，c是正确选择：植物从来就利用阳光作为能源。
2．B文章的第三段说，科学家企图将植物或植物类生物细胞作为微型光合能源供应站来研
究，并举例说，他们正在用绿藻进行实验，若成功，绿藻所产生的氢将可用来为汽车的燃料电池充电。所以答案是B。
3．B 文章第四段告诉我们：…algae will produce hydrogen in an air free environment．没有空气的情况肯定就没有氧气了。该段最后一句又说，是氧阻止绿藻制造氢。
4．D选项A、B都不是正确答案，因为短文的第六段告诉我们，remove sulfate和work in
an air free environment都是可能的，但问题是两者都有弊端，使氢的制造不那么容易。D所述内容就是困难之一：绿藻细胞因为没有了sulfate而减缓工作速度，因此产生不了多少氢。
5．C 根据短文最后一段的描述，绿藻可以在任何地方生长，它们是很容易使用的燃料能源，而且用途广泛，所以，A、B、C都是正确的描述，不是答案。C是答案，因为“The organisms are cheap to get and to feed”中的feed是“养殖”的意思，不能解释为“吃”。
