1 . 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.

2 . 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.

2. How does the circadian clock affect plants?

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.

3. Why does the author write the text?

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.

4. What is the best title for the text?

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