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 |
When people think of plants, they usually think of gardens, parks, or even jungles. One place that does not usually come to mind is the desert. However, some deserts contain many plants that are able to grow and survive under difficult conditions.
Deserts can reach temperatures of 50 degrees or more in the daytime and can also drop below 0 degrees at night. This is a huge temperature difference under which desert plants have to live. Besides the high and low temperatures, all deserts receive very little water in the form of rain; sometimes it doesn’t rain for months. So, how do desert plants get water when there is no rain?
There are three main ways plants survive in the desert. First, some desert plants grow without leaves. Others have developed special ways of storing whatever water they can find, such as growing a waxy leaf covering that helps keep water inside the leaf. These plants can survive for weeks or months on the water collected from just one rainfall.
A second way desert plants survive even in the most difficult conditions is by growing very long roots. These roots spread out and search for any water they can find. Once they find water, the roots suck up as much as they can and then hold it, only allowing the plant above the ground to have small amounts at a time.
The third way plants survive in the desert is by “sleeping”. Some plants can turn off almost all their processes and just remain inactive, almost as if dead, while they wait for rain. When the rain does come, they quickly drink up every drop they possibly can and burst back into activity.
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