科学美国人60秒 SSS Birch Trees Droop at Night with No Rays in Sight
时间：2018-12-24 作者：英语课 分类：2016年Scientific American(九)月
It’s easy to see that some plants change from day to night—flowers open and close, and even turn to face the sun. In 1880 Darwin noted 1 that the leaves and seedlings 2 of various plants appeared to engage in nighttime changes that he called sleep. But there’s now evidence that some entire trees may have their own version of sleep, which lets them recharge for the following day. That’s according to a study in the journal Frontiers in Plant Science. [Eetu Puttonen et al., Quantification of Overnight Movement of Birch (Betula pendula) Branches and Foliage 3 with Short Interval 4 Terrestrial Laser Scanning]
Researchers used lasers to scan birch trees in both Finland and Austria. They found that the branches drooped 5 by as much as four inches at night compared with daytime.
And exposure to the elements was not responsible—the trees were surveyed from sunset to sunrise over enough time to rule out the changes being caused by wind or other external environmental factors.
The researchers have a couple of ideas about what’s causing the branches to slouch. One is that the fluid pressure inside the tree decreases—something like dehydration 6.
The other proposal is that the trees are actually engaged in a botanical version of sleep. During the daylight hours the leaves perk 7 upwards 8 to get more sun, but with no chance to catch rays at night, they relax. And even before the sun rose, some branches were found to be returning to their daytime position—as the researchers say, perhaps governed by their internal circadian clock in preparation for a new day of light gathering 9.
But unlike us, there’s no evidence that trees sleep in on the weekend.
—Erika Beras
- The local hotel is noted for its good table.当地的那家酒店以餐食精美而著称。
- Jim is noted for arriving late for work.吉姆上班迟到出了名。
- Ninety-five per cent of the new seedlings have survived. 新栽的树苗95%都已成活。 来自《现代汉英综合大词典》
- In such wet weather we must prevent the seedlings from rotting. 这样的阴雨天要防止烂秧。 来自《现代汉英综合大词典》
- The path was completely covered by the dense foliage.小路被树叶厚厚地盖了一层。
- Dark foliage clothes the hills.浓密的树叶覆盖着群山。
- The interval between the two trees measures 40 feet.这两棵树的间隔是40英尺。
- There was a long interval before he anwsered the telephone.隔了好久他才回了电话。
- Her eyelids drooped as if she were on the verge of sleep. 她眼睑低垂好像快要睡着的样子。
- The flowers drooped in the heat of the sun. 花儿晒蔫了。
- He died from severe dehydration.他死于严重脱水。
- The eyes are often retracted from dehydration.眼睛常因脱水而凹陷。
- His perks include a car provided by the firm.他的额外津贴包括公司提供的一辆汽车。
- And the money is,of course,a perk.当然钱是额外津贴。