1．古树保护的意义；2．古树保护面临的问题；3．你的建议。
注意：1．词数100左右；2．可以适当增加细节，以使行文连贯。
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2 . Triantha Occidentalis, commonly known as the western false asphodel (西部假水仙), which has been known to science since 1879, is a herb-like plant found in abundance along North America’s West Coast. But it is only recently that researchers discovered the innocent-looking plant’s desire for insects.
“We had no idea it was carnivorous (食肉的),” says botanist Sean Graham. “This was not found in some exotic tropical location, but really right on our doorstep in Vancouver. You could exactly walk out from Vancouver to this field site.”
While studying the plant, the researchers noticed that Triantha Occidentalis lacked the same gene as other carnivorous plants. Since the plant grows in the same wet, sunny habitat with nutrient-poor soil as other carnivorous plants, they wondered if it caught insects for nutrition as well. “And at the same time they have sticky stems (茎),” Graham said. “So, I wonder if this could be a sign that it might be carnivorous.”
To test whether it is carnivorous, scientists marked fruit flies with nitrogen-15 isotopes (氮-l5同位素). By collecting the plants the fruit flies visited and comparing the nitrogen levels of different plants, the researchers found that Triantha Occidentalis was able to get more than half of the nitrogen it needed, suggesting that it absorbs nitrogen from the fruit flies. Additionally, the digestive enzyme (消化酶) released by the sticky hairs in flower stems was similar to that found in other carnivorous plants.
Usually, the deadly trap of carnivorous plants grow far away from the flower to prevent accidentally killing pollinators (授粉者), while the western false asphodel traps insects near flowers. The scientists say this is the first time they have met the deadly trap on the flower’s stem, and the sticky hairs on the stem of Triantha Occidentalis can only catch small insects, not the larger bees or butterflies involved in pollination.
“It’s a good reminder that we still don’t know much about the ecology of a lot of individual plant species, even in well-known environments,” says Dr. Qianshi Lin.
1. What does Graham stress in paragraph 2?| A．The discovery is made in the local place. |
| B．Carnivorous plants grow in the hottest places. |
| C．Triantha Occidentalis is very common. |
| D．Vancouver is home to various carnivorous plants. |
| A．The nitrogen. | B．The digestive enzyme. |
| C．The flower. | D．The nutrition. |
| A．Its fruit. | B．Its leaves. |
| C．Its stem. | D．Its roots. |
| A．A new species of local flower is discovered. |
| B．A carnivorous flower in the wild grows well. |
| C．A flower gives off strange smell to attract insects. |
| D．An innocent-looking plant turns out to be carnivorous. |
3 . Though they have a small figure, plants are armed with a metabolic (新陈代谢) system that allows them to collect, store and spend hard-earned energy for their survival. Perhaps the best-known part in this plant metabolic network is their ability to turn light into sugars and other forms of energy through photosynthesis (光合作用), a unique ability that allows plants to live in different environments.
But a plant’s dependence on sunlight has always presented one key question: What happens to a plant’s energy supply when night falls and sunlight becomes no longer available? A study published on Monday in the journal Proceedings of the National Academy of Sciences answered the question. Researchers report that a key factor to a plant’s ability to keep energy and survive the darkness of each nightfall rests in what experts call the circadian clock (生物钟).
Circadian clocks are basically chemical timekeepers each plant owns that allow them to work out the passage of time and the duration of their chemical reactions, and give them a rough idea of their daily routine every 24 hours. Experts say like most clocks, these inner timepieces for plants also come with an alarm of sorts. Through a network of genes and cells, researchers say that plants have an inborn ability to adjust (调整) their clocks each night for the benefit of their own survival. Through this network they can know the rising and falling of the sun, how long each night will last and how much energy they need to keep to make it to each morning. This alarm, according to researchers, can single-handedly tell plants how to adjust their nightly metabolic schedule—and give their energy supply suitably—every night with shocking correctness.
The study shows that experts came to this conclusion after experimenting with genes inside Arabidopsis, a small flowing plant related to cabbage. In these plants, researchers discovered a collection of genes largely controlled by a special thing known as superoxide (过氧化物), which is often linked to a plant’s metabolism.
1. What is the plant metabolic network most famous for?| A．Taking in sugars. | B．Helping grow faster at night. |
| C．Collecting energy from others. | D．Making energy with sunlight. |
| A．How plants survive the night. |
| B．How sunlight affects plants’ circadian clock. |
| C．How long plants’ energy lasts during the night. |
| D．How the circadian clock gives plants information. |
| A．It sometimes can’t work well. | B．It can adjust according to the weather. |
| C．It is controlled by some genes and cells. | D．It differs from one plant to another. |
| A．How cabbage can survive the night. |
| B．What is a plant’s metabolism. |
| C．What role superoxide plays in the circadian clock. |
| D．What genes control the speed of plants’ growth. |
