1 . Four Best Plants to Give as Gifts
Choosing a gift for someone is always a challenge. Giving plants is one way to try if the recipient is already a plant-lover. Here are some sure to impress as thoughtful gifts.
Jade Plant
The jade plant is a large succulent (肉质植物) that makes a perfect gift for someone who’s mastered parenting succulents. With a woody stem (茎), it looks like a tree once growing tall enough. Besides occasional watering and a bright window, the jade plant has few other requirements. A good challenge for ambitious owners is to regularly cut off its heavy leaves to reduce weight.
Christmas Cactus
This is a succulent with eye-catching flowers that appear in winter. You might assume it a picky plant, but nothing could be further than the truth. It prefers bright, indirect light and grows well in average potting soil. This plant prefers a steady watering schedule, especially in winter. To encourage more growth, plant it in a hanging container that allows its branches to hang down.
Paperwhite
Some people just aren’t interested in keeping houseplants around long-term, and paperwhite flowers are an excellent gift for anyone you know who fits this mould. Paperwhites grow from bulbs (鳞茎) and will produce flowers out of season. The roots need to be kept relatively damp, but once they are blooming (开花), there’s not much that can go wrong. They can be replanted outside after they have run their course.
Corn Plant
The corn plant is forgiving of variable light conditions and watering routines. It grows slowly, but can reach a height of four to six feet, and can make an impressive floor plant. Its leaves turn paler in direct sunlight to reflect the extra light, and darker green in shady conditions to maximize sunlight absorption.
1. Which plant requires practised gardening experience?| A．Jade plant. | B．Christmas cactus. | C．Paperwhite. | D．Corn plant. |
| A．By replanting it outside before blooming. | B．By watering it regularly during blooming. |
| C．By cutting off most of its heavy leaves. | D．By making its branches grow upwards. |
| A．The frequency of watering. | B．Its flowering time. |
| C．Its rate of growing. | D．The amount of sunlight. |
2 . The earth’s climate is largely controlled by how much of the sun’s light and heat is absorbed and reflected. By absorbing the sun’s heat, trees cool the air.
The interaction of this relationship with an area’s topography (地势), latitude (纬度), and altitude, can create microclimates (微气候), just as trees create microclimates almost any place they are by providing a windbreak (风林) and shade. Think about it: On a hot, sunny day, it’s always cooler beneath a shade tree. A city with more tall trees is cooler in the summer than a similar city with fewer trees, which translates into less energy use and lowers cooling costs. Also, in using less energy, less air pollution is created.
The most important role that rural trees and forests play is taking carbon dioxide out of the atmosphere. The living tissue (组织) of a tree is a storage vault (拱顶) for carbon, which would otherwise contribute to the greenhouse effect and to global climate change. To put it most simply, more trees can decrease the rate of climate change and help us withstand its effects, potentially resulting in less intense storms, fewer infectious diseases, a more stable water supply, and fewer wildfires.
Trees, however, are affected by the effects of climate warming. Areas once too cold to support trees now can, and as forests migrate north, harmful insects that were once held at bay (使不能接近) by winter freezes can do damage to native species. Tropical (热带的) vines called lianas (藤本植物) are now growing faster than the trees they climb, causing trees in the Amazon and other rainforests to die at an alarming rate.
Trees and forests can either be the key to slowing climate change and reducing its effects, or they can become its victims. It’s up to us.
1. Trees are believed to create microclimates in that __________.| A．tress can take in large sum of sunlight |
| B．tress can effectively change the weather |
| C．tress can help us save more money on cooling |
| D．tress can stop the strong wind and supply shade |
| A．more types of trees will be endangered |
| B．some rare forest species will grow faster |
| C．tropical vines find their wonderful world |
| D．some harmful insects will be under control |
| A．Make up. | B．Stand up to. |
| C．Think about. | D．Bring out. |
| A．Greenhouse effect is increasing sharply. |
| B．Climate change does great damage to trees. |
| C．Many native species will be frozen to death. |
| D．Forests and climate change influence each other. |
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. |
