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 /5pAnl/ n.嵌板，发热板，仪器板  

starch /stB:tF/ n. 淀粉

miniature /5minjEtFE/ adj.口巧．微型的

sulfate /5sQlfeit/ n. 硫酸盐，硫酸酯

carbon dioxide 二氧化碳  

photosynthesis /7fEutEu5sinWEsis/ n. 光合作用

algae /5AldVi:/ n. 水藻，海藻  

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       

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.

Passage Three
All the useful energy at the surface of the earth comes from the activity of the sun. The sun heats and feeds mankind. Each year it provides men with two hundred million tons of grain and nearly ten million tons of wood.
Coal, oil, natural gas, and all other fuels are stored-up energy from the sun. Some was collect ed by this season’s plants as carbon compounds. Some was stored by plants and trees ages ago.
Even waterpower derives from the sun. Water turned into vapor by the sun falls as rain. It courses down the mountains and is converted to electric power.
Light transmits only the energy that comes from the sun’ s outer layers, and much of this energy that is directed toward the earth never arrives. About nine-tenths of it is absorbed by the atmosphere of the earth. In fact; the earth itself gets only one half-billionth of the sun’ s entire output of radiant energy.

A:directly from the sun B:from the sun' s activity C:from energy stored by the sun D:from radiation of the sun

Passage 5
The energy which the sun radiates goes in every direction, and only a minute part of it falls on the earth. Even so, it represents power of about 5,000,000 horsepower (马力)per square mile per day; the sun gives us as much energy every minute as mankind utilizes in a year. At present, we use this energy in directly, and it is our final source of power. Coal represents the chemical action of the sun on green plants thousands of years ago. Water power results from the rain formed by vapor which comes from the evaporation of power. Coal represents the rain formed by vapor which comes from the evaporation of water under the sunshine. Even windmills operate because of air currents set in motion by the different heating affects of the sun in different places. Some day, through chemistry or some type of solar engine, we shall harness this great source of energy more directly. Already a scientist has worked out an engine, surprisingly efficient, in with the sun’ s rays are concentrated through mirrors on a tube of water to create steam.

A:Even windmill' s action depends on the sun. B:The sun produces enormous energy for man to make use of. C:Some day man will be able to utilize 100 % of the solar energy that gets to the earth. D:The sun produces different heating effects in different places.

The energy produced by the sun ______.

A:is easy to store B:poses similar problems to the other newer energy sources C:poses very few problems D:poses different problems from the other newer energy sources

Passage Three All the useful energy at the surface of the earth comes from the activity of the sun. The sun heats and feeds mankind. Each year it provides men with two hundred million tons of grain and nearly ten million tons of wood. Coal, oil, natural gas, and all other fuels are stored-up energy from the sun. Some was collect ed by this season’s plants as carbon compounds. Some was stored by plants and trees ages ago. Even waterpower derives from the sun. Water turned into vapor by the sun falls as rain. It courses down the mountains and is converted to electric power. Light transmits only the energy that comes from the sun’ s outer layers, and much of this energy that is directed toward the earth never arrives. About nine-tenths of it is absorbed by the atmosphere of the earth. In fact; the earth itself gets only one half-billionth of the sun’ s entire output of radiant energy.

A:directly from the sun B:from the sun' s activity C:from energy stored by the sun D:from radiation of the sun

Cars have traditionally been wasteful beasts. Every time a drop of gas explodes inside a cylinder(气缸), the energy gets passed along from the piston(活塞) to the crankshaft(曲轴), flywheel(飞轮), gearbox, drivetrain, and axles(轮轴). By the time the wheels actually turn, four fifths of the original energy has disappeared. The electric car goes a long way toward reducing wasted energy by replacing the internal-combustion engine with batteries. Even so, electric cars destroy about 60 percent of the energy because mechanical parts are still used to deliver energy from the bakeries to the wheels. Lately, though, engineers have come up with a far more efficient way to accomplish the same task: by using magnets in the wheels.
Why do electric cars still waste much of the energy

A:Because they have replaced the internal-combustion engine with bakeries. B:Because they still use mechanical paas to transfer energy to the wheels. C:Because they use magnets in the wheels which add weight to the car. D:Because batteries are not powerful enough to drive the cars.

Less Is More It sounds all wrong--drilling holes in a piece of wood to make it more resistant to knocks．But it works because the energy from the blow gets distributed throughout the wood rather than focusing on one weak spot．The discovery should lead to more effective and lighter packaging materials. Carpenters have known ________(51)centuries that some woods are tougher than others．Hickory(山核桃木)，for example，was turned into axe handles and cartwheel spokes(轮辐)because it Can absorb shocks without breaking．White oak，for example，is much more easily damaged，_________ (52)it is almost as dense．Julian Vincent at Bathe University and his team were convinced the wood’s internal structure could explain the differences． Many trees have tubular(管的)vessels that run _________ (53)the trunk and carry water to the leaves．In oak they are large，and arranged in narrow bands，but in hickory they are smaller，and more evenly distributed．The researchers _________ (54)this layout might distribute a blow’s energy throughout the wood．soaking up a bigger hit．To test the idea，they drilled holes 0.65 millimetres across into a block of spruce(云杉)，a wood with _________ (55)vessels，and found that _________ (56)withstood a harder knock．_________ (57)when there were more than about 30 holes per square centimetre did the wood’s performance drop off． A uniform substance doesn’t cope well with knocks because only a small proportion of the material is actually _________ (58)．All the energy from the blow goes towards breaking the material in one or two places，but often the pieces left _________ (59)are pristine(未经破坏的)． But instead of the energy being concentrated in one place，the holes provide many weak spots that all absorb energy as they break，says Vincent．“You are controlling the places_________ (60)the wood breaks，and it can then absorb more _________ (61)，more safely．”The researchers believe the principle could be applied to any material- _________ (62)example．to manufacture lighter and more protective packaging．It could _________ (63)be used in Car bumpers，crash barriers and armour for military vehicles，says Ulrike Wegst， _________ (64)the Max Plank Institute for Mental Research in Stuttgart．But she emphasizes that you _________ (65)to design the substance with the direction of force in mind．“The direction of loading is crucial，”she says．

A:water B:air C:energy D:safety