1 . The Mystery of Why Sunflowers Turn to Follow the Sun — Solved

Scientists have answered a burning question central to sunflowers: Why do young flowers always face the sun over the course of a day?

And also: Once sunflowers become full-grown, why do they stop tracking the sun and only face east?

In a newly-published article, researchers claim that a young plant’s sun-tracking (also called heliotropism) can be explained by circadian rhythms — the behavioural changes tied to an internal clock that humans also have, which generally follows a 24-hour cycle.

“Growth rates on the east side were high during the day and very low at night, whereas growth rates on the west side were low during the day and higher at night,” the journal article says.

The researchers tied plants up so they couldn’t move or turned them away from the sun — and they found those flowers eventually had “fewer organic materials and less leaf area” than flowers that could move with the sun.

Full-grown sunflowers respond differently to the sun. According to the article, “As overall growth slows down, the circadian clock ensures that the plant reacts more strongly to light early in the morning than in the afternoon or evening, so it gradually stops moving westward during the day.”

The researchers compared full-grown flowers facing east with those they turned to face west, and found that east-facing flowers attracted five times as many helpful pollinators. That’s because the east-facing flowers heat up faster and bees like warm flowers.

“Just like people, plants depend on the daily rhythms of day and night to function,” Anne Sylvester, director of the National Science Foundation’s Plant Genome (基因组). Research Programme said in a press release. “Sunflowers, like solar panels, follow the sun from east to west. These researchers explore information in the sunflower genome to understand how and why sunflowers track the sun.”

UC Berkeley professor and co-author of the study, Benjamin Blackman, believes that the connection between circadian rhythms and growth could be applicable to other researches. “The more general point, that one of the circadian clock’s adaptive functions is to regulate the timing and strength of growth responses to environmental signals, is one that I think will apply to a broad range of qualities and species.” he said.

1. What did the researchers discover when they tied the sunflowers up?________

A．They still tracked and faced towards the sun.

B．They grew faster during the daytime than they did at night.

C．Their growth rates were lower than those of flowers facing the sun.

D．The growth rates on the west side were higher than those on the east.

2. Why do sunflowers move westward less when they are fully-grown?_______

A．Because they will not be affected by light anymore.

B．Because they would stop growing up if they faced west.

C．Because they are not active at all during afternoons or evenings.

D．Because they are more sensitive to light in the early morning from the east.

3. What may the underlined word “pollinators” (Para.7) refer to?_______

A．Bees.

B．Plants.

C．Energy.

D．Researchers.

4. What is the possible direction of future study, according to Benjamin Blackman? _______

A．Exploring information in the sunflower genome.

B．Comparing human’s circadian rhythms with sunflowers’.

C．Comparing full-grown flowers facing east with those facing west.

D．Exploring how circadian rhythms affect the growth of other species.

2 . Covered in lush fur, the thickest in the animal kingdom, sea otters (海獭) can live their entire lives in the ocean, feeding heavily upon seafloor animals such as shellfish. They are often seen to eat clams(蛤), which bury themselves in meadows of eelgrass (大叶藻场),   a wide-ranging plant species growing in water. Eelgrass meadows where sea otters dig for clams become partly bare, which is commonly a concern for ecologists.

As it turns out, the meadows with otters are healthier, with more eelgrass, according to a new study published in Science. That's because by gently disturbing the seabed, the otters make the plants flower and produce seeds. What's more, their digging provides more space and sunlight for seeds to settle and grow. The enhanced genetic diversity caused by sea otters could make eelgrass more adaptable to present and future threats.

The finding is a powerful example of how animals such as otters influence their ecosystems beyond predation (捕食), often in unseen and little-known ways, says study leader Erin Foster, a research associate at the Hakai Institute. It also means sea otters, an endangered species, are vital to their environments and give eelgrass, which is in danger worldwide, a better chance at staying healthy and surviving.

Seagrass habitats are also important for many fish, providing food for animals, absorbing, and filtering harmful pollution and bacteria from the water. "Genetic diversity typically strengthens the adaptability of species, and considering the challenges we're facing…this will be important for eelgrass meadows, and from this aspect, the impact the otters are having deserves our lasting concern," says Foster.

1. What do we know about sea otters?

A．They live part of their lives underwater.	B．They mainly feed on sea animals like fish.
C．They eat clams beneath eelgrass meadows.	D．They become a new concern for ecologists.

2. How does the author develop paragraph 2?

A．By giving opinions.	B．By presenting reasons.
C．By clarifying concepts.	D．By comparing results.

3. Why does the author mention the endangered condition of eelgrass?

A．To provide examples of sea otters' predation.

B．To show the urgency to protect the environment.

C．To highlight the role of otters in their ecosystems.

D．To warn against the potential risk of climate change.

4. What does Foster think of the impact otters have on underwater meadows?

A．Overestimated.

B．Noteworthy.

C．Temporary.

D．Unpredictable.

3 . Contrary to the long­held belief that plants in natural world are always in competition, new research has found in bad environments mature (成熟的) plants help smaller ones — and thrive as a result. The research team, led by Dr.Rocio Pérez­Barrales studied adult and young plants in the “ecological desert” of soil in the south­east of Spain.

The findings could have significance for those managing bad environments like coastal areas. Dr.Pérez­Barrales said, “What we have found surprising is that a strong large plant, called a ‘nurse’， shields a young one, and it also produces more flowers than those of similar size growing on their own.” Dr.Pérez­Barrales and her team studied plant growth in southern Spain for over three months during summer and found that the young and “nurse” are more likely to thrive when grown together, compared to either plant growing alone.

The young plants benefit from shade, more moisture and more nutrients, from the leaf litter (落叶层) of the “nurse” plants, and probably higher bacteria and fungus (真菌) in the soil. As it matures, the “nurse” plant grows more flowers than those similar ones nearby growing alone, greatly increasing its chances of producing seeds and reproducing. Besides, vegetation of “nurse” and facilitated plants with more flowers might be able to attract a greater number and variety of pollinators (传粉昆虫) in an area. In turn, it supports insect and soil life, and even provides a larger range of different fruit types for birds and mammals. This is the greatest achievement of the ecosystem.

The research is likely to be of value to those who manage to protect plants in hostile and harsh environments, such as shingle and sand­dune (沙丘) ecosystems, which are considered at high risk due to human action and climate change. Most home gardeners and farmers are happy with the research as well, but the findings might be of more value to those who garden in harsh places.

1. What's the finding of the study?

A．The mature and smaller plants benefit each other when growing together.

B．Large plants sacrifice themselves for the smaller ones.

C．Young plants compete with the adults for larger space.

D．Young plants struggle to survive in harsh environments.

2. Why is a plant called a “nurse”？

A．Because it produces more flowers.

B．Because it competes with a larger one.

C．Because it protects and helps the young.

D．Because it grows well in bad environments.

3. What does the underlined word “This” in Paragraph 3 refer to?

A．The natural selection.

B．The biodiversity (生物多样性) in an area.

C．The improvement of the soil.

D．The high rate of animal reproduction (繁殖).

4. What does the last paragraph mainly talk about?

A．The effects of the research on agriculture.

B．The shortcomings of the research at present.

C．The influence of the research on climate change.

D．The significance of the research findings in some fields.

4 . How to Control Weeds When Planting

No matter what you choose to grow in the garden, at some point, you will have to deal with unwanted plants, known as weeds.     1     Even a tomato plant can become a weed if it grows where you don’t want it to.

    2     Weeds can bring many problems. They steal nutrients and water. Weeds can also bring harmful bugs and diseases into your garden. Some weeds release chemicals that can slow the growth of nearby plants.

It is important to note that some weeds are not all bad. In fact, you can eat them. Dandelions (蒲公英) are also viewed as a weed by many people.     3     And you can eat or use nearly every part of the plant. But even other weeds can do good things in our garden. The roots of weeds can prevent the soil from being blown away by wind or washed away by rain.

However, left to grow on their own, weeds can take over a garden. To slow the growth of weeds, add a layer of weed-free, organic material to the top of your garden, around the plants.     4    

A simple and effective method of weed control is to break up the surface layer of the soil. But you must do this regularly. Do not turn the soil over.     5     If you turn the soil over, you give those seeds the light and air they need to grow. Probably the best way to fight some weeds is to eat them! Just make sure they are, in fact, eatable.

A．But their leaves are also full of nutrients.

B．This makes it difficult to reshape a garden.

C．A weed is just a plant growing in the wrong place.

D．This improves the soil and keeps weeds from growing.

E．Besides being unwanted, what else do weeds do to a garden?

F．Buried in the soil are weed seeds, waiting for the right conditions.

G．So, before we hurry outside to kill all the weeds, consider their good side.

5 . Greenhouse gas emissions would rise if all farms in England and Wales went organic. Though the emissions of each farm would go down, much more food would have to be imported, as the amount they would produce would decrease greatly.

“The key message from my perspective is that you can't really have your cake and eat it,” says Laurence Smith, now at the Royal Agricultural University in the UK, who was part of the team that ran the numbers. Smith is a supporter of organic farming and says “there are a lot of merits of the organic approach”, but his analysis shows that organic farming has downsides too.

Farming and changes in land use, such as cutting down forests, are responsible for a third of all greenhouse gas emissions. That means reducing farming emissions and the land needed for farming is required to limit further global warming.

Smith and his colleagues found that emissions per unit of food are, on average, 20 per cent lower for organic crops and 4 per cent lower for organic animal products. However, organic harvests per hectare (公顷) are also lower on average. For wheat and barley, for instance, harvests are just half of those of conventional farms. This means 1.5 times as much land would be needed to grow the same amount of these foods.

The estimated increase in emissions varies greatly, depending on where the extra farmland comes from. If only half comes from turning grassland into farms, the increase could be as low as 20 per cent. If grassland that would otherwise have been reforested is turned into farmland, emissions could nearly double.

This doesn't necessarily mean people should stop eating organic produce, says Smith. People might choose organic food for other reasons, such as to reduce their pesticide exposure (though contrary to popular belief, organic farmers do use pesticides) or for the sake of wildlife.

Going 100 per cent organic could also harm global biodiversity. The extra land used for farming would mean the land available for wildlife would be smaller and more fragmented (碎片化的).

Smith says the best option may be to use some organic and conventional farming methods at the same time.

1. Why may greenhouse gas emissions increase if a country goes organic?

A．Organic farms take longer to build.

B．The agricultural output will increase greatly.

C．The emissions of each farm unit will increase.

D．Greater demand for imported food will be created.

2. What does the underlined word “merits” in Paragraph 2 probably mean?

A．Changes.

B．Challenges.

C．Advantages.

D．Differences.

3. What did Smith and his colleagues find?

A．Organic harvests per unit are greater than traditional harvests.

B．Organic farming needs more farmland to feed a country.

C．Global warming could be brought under control.

D．Land was not used in a responsible way.

4. What is Smith's proposal?

A．Stopping using pesticides.

B．Eating less organic produce.

C．Going back to traditional farming.

D．Adopting mixed farming methods.

6 . For many people, catching a smell of freshly cut grass is a pleasant sign that warmer weather is here to stay. For the grass, however, this scent signals an entirely different story.

The smell we associate with freshly cut grass is actually a chemical SOS, one used by plants to beg nearby creatures to save them from attack. After all, when danger strikes —whether it's gardening equipment or a hungry caterpillar — plants can't lift their roots and run. They must fight where they stand. To protect themselves, plants employ a string of molecular (分子) responses. These chemical communications can be used to poison an enemy, warn surrounding plants of dangers or attract helpful insects to perform needed services.

Clearly, plants can communicate. But does that mean they can feel pain? According to some researchers, plants release gases that are the equivalent of crying out in pain. Using a laser-powered microphone, researchers have picked up sound waves produced by plants releasing gases when cut or injured. Although not audible to the human ear, the secret voices of plants have revealed that cucumbers scream when they are sick, and flowers cry when their leaves are cut.

There's also evidence that plants can hear themselves being eaten. Researches show that plants understand and respond to chewing sounds made by caterpillars dining on them. As soon as the plants hear the noises, they respond with several defense mechanisms.

For some researchers, evidence of these complex communication systems — giving out noises via gas when in pain — signals that plants feel pain. Others argue that there cannot be pain without a brain to register the feeling. Still more scientists infer that plants can exhibit intelligent behavior without possessing a brain or conscious awareness.

As they grow, plants can change their paths to avoid obstacles or reach for support with their tendrils (卷须). This activity comes from a complex biological network distributed through the plants' roots, leaves and stems. This network helps plants reproduce, grow and survive.

1. What does the smell of freshly cut grass signal?

A．Warmer weather.	B．Being poisonous.
C．Cry for help.	D．The need of services.

2. How do plants convey their pain?

A．By giving out gases.	B．By changing the color of their leaves.
C．By producing audible sound waves.	D．By sharing it through the root systems.

3. What makes plants' intelligent behavior possible?

A．Their tendrils.	B．Their biological network.
C．Their communication systems.	D．Their conscious awareness.

4. What is the best title for the text?

A．Do plants feel pain?	B．How plants protect themselves?
C．Do plants communicate?	D．How plants grow and reproduce?