树的慢心跳

夜里，在完全静止的环境中，科学家把激光对准一排排树，然后等待。他们发现的东西不像植物，更像一只睡着的动物：一种缓慢而稳定的脉动，每隔几个小时起伏一次，同时穿过整棵树。

At night, in complete stillness, scientists pointed lasers at rows of trees and waited. What they found looked less like a plant and more like a sleeping animal: a slow, steady pulse, rising and falling every few hours, moving through the entire tree at once.

树枝有节奏地上下移动，幅度大约一厘米，像整棵树在轻轻呼吸。研究者现在认为，树干本身可能在主动挤压，帮着把水沿体内叫作木质部的管道往上推，而不只是被动地吸收。人的心跳每分钟大约七八十次，树的脉动却可能要好几个小时才走完一个周期。

Branches shifted up and down by roughly a centimetre, rhythmically, as if the whole tree were gently breathing. Researchers now believe the trunk itself may be actively squeezing, helping push water up through internal tubes called xylem rather than simply relying on passive absorption. Unlike a human heartbeat, which repeats around seventy or eighty times a minute, a tree's pulse can take several hours to complete a single cycle.

这是个很奇怪的念头：一整座长满树的园子，每一棵都按自己那份私密而极慢的节奏搏动着，除非你正好在黑暗里用对了仪器观察，否则完全看不见。

It is a strange thought: a garden full of trees, each one quietly pulsing on its own private, extremely slow schedule, completely invisible unless you happen to be watching in the dark with the right kind of instrument.