Breakthrough discovery reveals how thirsty trees pull water to their canopies
A scientific mystery about how trees pull water from the ground to their top branches has been solved by an international team of researchers from the University of Leicester and the Queensland University of Technology, Australia.
The team, led by Dr Adrian Boatwright, who conducted the research while at the University of Leicester's Department of Chemistry, has examined the phenomenon of water being pulled to the top of tree branches, when scientific theory says that the maximum height water can be pulled up is 33 feet due to gravity -- known as the barometric limit.
Adrian Boatwright博士是这个团队的领导,其就职于莱斯特大学化学系期间开展了此项研究。在科学理论认为由于重力的存在水最高可以被运输到33英尺(即我们所知的气压限制)的情况下,该团队仔细研究了水被运输到树枝顶端这一现象。
The researchers have discovered that water can in fact be held in a vacuum for almost indefinite periods of time and even under significant tension without forming bubbles or breaking apart, which helps to explain how trees siphon water to their highest points.
The team also found that water can be pulled up to as much as 45 feet -- well above the barometric limit, overturning the theory proposed by seventeenth century Italian physicist and mathematician Evangelista Torricelli which has stood for the last 400 years.
该团队还发现水可以被拉高到足足45英尺处,已经远远超过了气压限制。这一事实推翻了17世纪意大利物理学家、数学家埃万杰利斯塔·托里拆利(Evangelista Torricelli)提出的一个已经被拥护了400年之久的理论。
Dr Boatwright said: "How is it that trees can pull water up to the top most branches? This question has troubled both botanists and physicists for many years with various mechanisms used to describe this process -- ranging from capillary action to osmotic pressure.
"By siphoning water up to as much as 45 feet we have managed to 'break' the barometric limit and show that the maximum height is limited only by the strength of bonds in the water."
While the widespread view has been that siphons work because of atmospheric pressure, recent research has shown that cohesion and gravity, and not atmospheric pressure is the driving principle.Dr Stephen Hughes, Senior Lecturer in the Science and Engineering Faculty at Queensland University of Technology added: "The first recorded use of siphons was in ancient Egypt circa 1430 BC. Our experiment, conducted over 3,400 years later, is the first report published in the scientific literature of a siphon operating over the barometric limit. How siphons work has been quite controversial. This experiment is a clear demonstration that siphons work through gravity and not atmospheric pressure as is commonly supposed."
尽管人们普遍认为虹吸作用的产生是因为大气压力,但最近的研究已经证明内聚力和重力才是主要的驱动因素。昆士兰科技大学科学与工程学院的高级讲师Stephen Hughes博士补充道:“最早有记录的虹吸管出现在大约公元前1430年的古埃及时期,而3400年之后,我们的实验首先在关于虹吸发挥作用超过气压限制的科学文献中被报道。虹吸管如何工作一直都有很大的争议,这个实验清楚地证明了虹吸管通过重力而非人们通常认为的大气压力发挥作用。”