1 . Scientists have discovered how plants manage to live alongside each other in places that are dark and shady. Plants in the deep darkness of a thick forest, where natural supplies are not very great in amount, won’t attempt to top their neighbors in growth as those in moderate (中度的) shade do. In deep shade conditions, it would be a waste of energy and harmful to survival because green shoots would never be able to top their larger neighbors in growth.
So how do plants prevent such growth in deep shade conditions? The secret lies in the clocks insides them, say scientists from the John Ines Centre and the University of Bristol.
They have discovered that when plants notice deep shade, this changes the expression of genes parts of the circadian clock (昼夜节律时钟) — the inner daily timer found in plants and other things. These clock parts perform an additional role in preventing plants from lengthening and overtopping neighbors.
The work identifies a previously unknown role of the circadian clock in controlling plant development and the findings may have possible effects on both natural plant populations and crops. Professor Antony Dodd of the John Innes Centre said, “The biological clock of plants plays a big part in their development and fitness. This work casts new light on a new role of the circadian clock in adapting plants to competition with other plants in their environments.” “It also gives us new insights into how plants adapt to very deep shade, where resources are very limited,” said Professor Kerry Franklin at the University of Bristol.
This work provides evidence for the firmness of the circadian clock in stressful environments, and information that may be useful in developing new generations of crops in a challenging climate.
1. What do plants normally do in moderate shade?A.Struggle to preserve energy. | B.Compete for limited resources. |
C.Try to outgrow their neighbors. | D.Depend on each other to survive. |
A.By changing their gene expression. | B.By making them realize light change. |
C.By helping them adapt to the darkness. | D.By controlling their growth in deep shade. |
A.To share a new discovery about plants. | B.To introduce the role of the circadian clock. |
C.To explain plants secret of living in forests. | D.To compare plants living in certain condition. |
A.How plants face a challenging climate |
B.Why plants respond to different shade levels |
C.Why the circadian clock is vital to plants' growth |
D.How plants become good neighbors in times of stress |
2 . A wildfire kills most things in its path, but despite the flames and intense temperatures, rarely is everything reduced to ashes -and that plays a key role in a forest's regeneration. Just one year after the fire, the survivors dominate the forest, and grasses replace the burnt ground. Wildflowers are abundant bushes and small trees have started to grow, and Jack Pine returned. So, it's an amazing ecological system of creating new forest life when it appears that all is lost, one that has evolved throughout the ages, where fire has always played a vital role.
What does the underlined word "one" in the last paragraph refer to?
A.A fire. | B.A life | C.A time. | D.A system |
3 . Early last summer, I bought some yam(山药)roots for food but days later, a tuber (块茎)left was sprouting(发芽). Thinking it was a waste of money to throw it away, I
In the following months, I
I pulled out the leaves of the yam and began to dig with my fingers carefully for I knew the yam could
In
The whole tuber,
The sight filled me with
A.cooked | B.ruined | C.buried | D.cut |
A.remove | B.produce | C.replace | D.protect |
A.bought | B.threw | C.watered | D.ate |
A.abandoned | B.forgotten | C.injured | D.potted |
A.perform | B.attempt | C.harvest | D.withdraw |
A.stand | B.grow | C.fall | D.break |
A.touched | B.pulled | C.crashed | D.killed |
A.earth | B.root | C.air | D.plant |
A.excitement | B.shame | C.puzzlement | D.terror |
A.in the sky | B.on the top | C.in the bottom | D.under the ground |
A.picking out | B.consisting of | C.giving away | D.taking down |
A.color | B.form | C.voice | D.size |
A.flat | B.long | C.rough | D.weak |
A.choice | B.contribution | C.wish | D.living |
A.skinless | B.endless | C.useless | D.stainless |
A.negotiation | B.struggle | C.cooperation | D.relationship |
A.victory | B.regret | C.envy | D.respect |
A.strengthened | B.changed | C.disappeared | D.remained |
A.barely | B.temporarily | C.purposefully | D.seriously |
A.tough | B.steady | C.common | D.gentle |
4 . The Greenwood fire took its name from the nearby lake where lightning struck on Aug.15, causing a wildfire that burned for weeks. Fueled by drought and wind, its persistence dominated headlines for much of late summer and early fall in Minnesota. When the last flames were finally put out, the northern Minnesota fire had consumed nearly 27,000 acres, countless firefighting resources, and at its worst, the lives that some had built around nearby McDougal Lake. Vast areas of forest were left burned-out, with the black and bare remains of what were once massive pines.
But, despite the destruction left behind, Mother Nature is set to a comeback. When organic matter is burned from the forest floor, seeds dropped by plants and trees begin to take hold, with the sprouting species emerging first. The trees above have died, which sends a chemical signal to the root system that is actually more expansive than just under that tree, and that chemical response encourages those root systems to re-grow. Ten years ago, a fire ripped through 93,000 acres of Minnesota forest in and around the BWCA. Today, that burnt area's rebirth is well underway.
"Here in the Pagami Creek wildfire scar, we have Jack Pine, Red Pine, Black Spruce, Aspen and paper birch-those are our main species, those are the ones that are growing quickly. It's 10 years on, and these trees are 10 to 15 feet tall in many areas," said Kyle Stover from the U.S. Forest Service.
A wildfire kills most things in its path, but despite the flames and intense temperatures, rarely is everything reduced to ashes -and that plays a key role in a forest's regeneration. Just one year after the fire, the survivors dominate the forest, and grasses replace the burnt ground. Wildflowers are abundant bushes and small trees have started to grow, and Jack Pine returned. So, it's an amazing ecological system of creating new forest life when it appears that all is lost, one that has evolved throughout the ages, where fire has always played a vital role.
1. What can we learn about the Greenwood fire?A.It was a natural occurrence | B.It was caused by drought. |
C.it gained half-year fame. | D.It took many people's lives. |
A.Seeding growth is held up. | B.Burnt organic matter hardly functions. |
C.Root systems spread further and wider | D.Chemicals in the soil are in greater demand. |
A.They are flammable | B.They are fire-resistant |
C.They are fire-adapted. | D.They are overgrown. |
A.A fire. | B.A life | C.A time. | D.A system |
5 . Chocolate could soon be a thing of the past, after scientists warned that the cacao plant, from which chocolate is made, could disappear within 32 years.
Over half of the world’s chocolate comes from just two countries in West Africa-Cote d’Ivoire and Ghana-where the temperature, rain, and humidity (湿度) provide the perfect conditions for cacao to grow. But the threat of rising temperatures over the next three decades caused by climate change, is expected to result in a loss of water from the ground, which scientists say could upset this balance.
According to the related data, a temperature rise of just 2.1℃ could spell an end for the chocolate industry worldwide by 2050. Farmers in the region are already considering moving cacao production areas thousands of feet uphill into mountainous area — much of which is currently preserved for wildlife. But a move like this could destroy ecosystems that are already under threat from illegal farming and deforestation.
Part of the problem, according to Doug Hawkins, is that cacao farming methods have not changed for hundreds of years. “Unlike other tree crops that have benefited from the development of modern, high producing kinds and crop management techniques to realize their genetic potential (潜能), more than 90% of the global cocoa crop is produced by small farms with unimproved planting material,” he said, “It means that we could be facing a chocolate decrease of 100,000 tons a year in the next few years.”
Now scientists at the University of California at Berkeley have teamed up with American candy company Mars to keep chocolate on the menu. Using the controversial (有争议的) gene-editing technology known as CRISPR they are trying to develop a type of the cacao plant able to survive in dryer, warmer climates. If the team’s work on the cacao plant is successful, it could remove the need for farmers in West Africa to relocate to higher ground, and perhaps even allow cacao to be grown elsewhere in the world.
1. What do we know about chocolate from the text?A.Chocolate is mainly produced by African countries. |
B.Chocolate will not be produced by 2050 because of climate change. |
C.A new type of chocolate will be produced with the help of CRISPR. |
D.Chocolate will disappear from the menu 30 years later. |
A.Water shortage caused by climate change. |
B.The threat from illegal farming. |
C.The changeable farming method. |
D.The damaged ecosystem. |
A.The act of doing harm to trees. |
B.The act of cutting down or burning the trees in an area. |
C.The act of transplanting trees. |
D.The act of planting trees. |
A.Unconcerned. | B.Supportive. |
C.Negative. | D.Objective. |
As the world
Though Xinjiang has little rainfall, it has a large number of snow-capped mountains, from which meltwater gives cotton abundant water resource. Meanwhile,
Xinjiang is lightly populated and has a vast planting area. It has
The combination of advantaged