Many animals depend upon sound to find food or communicate with one another. These species understandably suffer when loud motorways cut through their habitats. Scientists have long documented the ecological damage caused by noise pollution. It has always been assumed, however, that noise is a problem unique to animals. But a new study by Ali Akbar Ghotbi-Ravandi, a botanist in Tehran, has revealed that plants fell victim to it too.
Working with a team of colleagues, Dr Ghotbi-Ravandi grew two species in his lab that are commonly found in urban environments. The plants were grown from seed and allowed to mature for two months in the same space before they were divided into two groups. One group was exposed to 73 decibels of traffic noise recorded from a busy motorway in Tehran for 16 hours a day. The other group was left to grow in silence. After 15 days had passed, samples were taken from the youngest fully expanded leaves on every plant in the experiment and studied.
Analysis of their leaves revealed that the chemicals which are indicators of stress in plants were found at much higher levels in the species exposed to the traffic noise. The team also found that certain chemicals normally associated with healthy growth in plants were present at significantly reduced levels in the plants exposed to the noise. Even the weight of the freshly-cut leaves differed — leaves from plants exposed to noise consistently weighed less than those from plants grown in silence.
Dr Ghotbi-Ravandi’s findings make it clear that, though plants lack ears, the vibrations (震动) generated by the noise of traffic still bothers them enough to cause strong stress responses that are not much different to those that would be found in plants exposed to extreme conditions.
The next question is whether all noise pollution affects all species in the same way. The natural world is by no means silent. Whether some plant species have evolved to adapt to the noisy environment, which might one day be collected and transplanted in urban areas, is a mystery worth exploring.
【小题1】What does the author stress in paragraph 1?| A．The influence of noise on plants. | B．Effects motorways have on animals. |
| C．The importance of sound for animals. | D．Problems plants have surviving in nature. |
| A．By choosing two rare plant species. | B．By collecting samples from old leaves. |
| C．By making plants grow along motorways. | D．By studying plants grown in different conditions. |
| A．Plants exposed to noise were less stressful. |
| B．Changes of chemicals in leaves were unclear. |
| C．Leaves of plants grown in silence weighed more. |
| D．Plants grew more slowly when grown in silence. |
| A．To improve the adapting ability of plants. | B．To develop new species with high survival rate. |
| C．To set more restrictions on urban traffic noise. | D．To find plants suitable for noisy urban areas. |
