SSS 2008-06-12
时间：2019-01-08 作者：英语课 分类：Scientific American(六)月
This is Scientific American's 60-Second Science, I'm Karen Hopkin. This'll just take a minute.
With temperatures approaching 100 degrees in the eastern U.S. this week, it’s amazing that the leaves on the trees don’t simply burst into flames. Maybe one reason they don’t is that no matter how hot or cold it gets, leaves tend to maintain themselves at a nice, climate-controlled 70 degrees. That’s according to a report in the online issue of the journal Nature. Scientists had always assumed that the temperature of a leaf was the same as the surrounding air. And why wouldn’t they? It’s not like trees are warm-blooded. But University of Pennsylvania researchers examined leaves from 39 tree species in 25 different locations, ranging from inside the Arctic circle to the island of Puerto Rico. And they found that no matter where the leaf comes from, its average temperature is the same. The explanation: leaves from the tropics have evolved mechanisms 1 for keeping cool, say by angling themselves away from the sun. And trees in polar regions have come up with ways to heat their leaves, by putting out more leaves per branch, for example, so they can essentially 2 huddle 3 for warmth. After all, what choice does a tree have in bad weather? It can’t just pack up its trunk and leaf.
Thanks for the minute for Scientific American's 60-Second Science, I'm Karen Hopkin.
- The research will provide direct insight into molecular mechanisms. 这项研究将使人能够直接地了解分子的机理。 来自《简明英汉词典》
- He explained how the two mechanisms worked. 他解释这两台机械装置是如何工作的。 来自《简明英汉词典》
- Really great men are essentially modest.真正的伟人大都很谦虚。
- She is an essentially selfish person.她本质上是个自私自利的人。