Trees Are So Weird · Kurzgesagt – In a Nutshell
揭秘树木如何在极端环境中生存，了解它们的结构与进化策略。适合练习自然、科技和成长类词汇。
Every tree you have ever seen is dead.
你所见过的每一棵树其实都已经“死”了（即它们已经不再生长）。
It turns out the alive part of a tree is just a tiny, paper thin strip of cells,
原来，树木中具有生命的部分其实只是一条极其细小、薄如纸片的细胞带而已。
trapped between a dead skeleton and dead outsides.
被困在一只干枯的骷髅与一片死寂的外壳之间……
Trees are some of the most extreme
树木堪称自然界中最“极端”的生物之一（即它们能够在极其恶劣的环境中生存）。
beings on earth with one of the most unique strategies in nature – on top of being mostly dead stuff,
地球上的这些生物拥有自然界中最独特的生存策略之一；尽管它们的大部分身体其实都是“死物质”（即无法进行新陈代谢的有机组织）。
they forge their body out of thin air, they mercilessly crush rocks with acid, and they have an internal negative pressure that would kill you instantly.
它们能凭空“制造”出自己的身体；它们会用酸液无情地侵蚀岩石；同时，它们体内存在着极高的负压——这种压力足以瞬间杀死任何生物。
So, how do trees actually work?
那么，树木究竟是如何运作的呢？
Let’s go back…to the beginning.
让我们回到起点吧。
The Ancient Battle for the Sky For over a billion years the ancestors of plants only inhabited the sun drenched surfaces of the oceans.
这场关于“天空控制权”的古老战争： 在超过十亿年的时间里，植物的祖先仅生活在被阳光照射到的海洋表面。
Their bodies were thin and delicate and absorbed water straight through their surfaces, getting their energy through photosynthesis.
它们的身体纤细而脆弱，能够直接通过体表吸收水分，并通过光合作用获取能量。
Forging sunlight, carbon dioxide and water into sugar.
将阳光、二氧化碳和水转化为糖。
But about 470 million years ago they decided to conquer a hostile alien planet: the land.
但大约4.7亿年前，它们决定征服一颗充满敌意的外星行星——地球。
Like green rugs with ambition these plant ancestors began clinging to the ground wherever it was wet and damp.
这些植物的祖先就像那些充满野心的“绿色地毯”一样，开始在任何潮湿的地方扎根生长。
But now, with solid ground beneath and no ability to float around a new dimension became a place of intense warfare: up.
但现在，由于脚下有了坚实的地面，且不再具备在新的维度中“漂浮”的能力，这个地方便变成了激烈战斗的战场——向上突进便是主要的战斗方向。
The higher they grew, the more sun they would get, while starving their competition below.
它们长得越高，就能接收到越多的阳光；与此同时，它们会压制那些位于较低位置的竞争对手（使其无法获得足够的阳光）。
Height became a deadly weapon.
身高变成了一种致命的“武器”。
The battle for the sky had begun.
争夺天空的战斗已经打响了。
Until now, plants were built mostly from cellulose, which was great for shape, but not for strength, which limited how tall they could grow.
直到现在，植物主要由纤维素构成。纤维素确实有助于植物保持良好的形态，但其强度较低，这限制了植物的生长高度。
Over dozens of millions of years of evolutionary warfare, a group of plants developed one of life's greatest breakthroughs: lignin.
在长达数千万年的进化过程中，某些植物发展出了生命史上最重要的突破之一——木质素。
Lignin is a macromolecule made of ring-shaped structures.
木质素是一种由环状结构组成的高分子化合物。
It is rigid, tough, waterproof, and incredibly hard to break down.
这种材料非常坚硬、耐用、防水，且极难被分解。
Concrete in a world made of jelly.
在一个由“果冻”构成的世界里，混凝土依然存在……
It filled gaps between cellulose threads, stiffening and locking everything into place.
这种物质填充了纤维素纤维之间的空隙，使整个结构变得更为坚固，并将其固定到位。
Lignin gave plants the strength to grow taller and claim the sun for themselves.
木质素赋予植物足够的强度，使它们能够长得更高，并从而获得更多的阳光。
But of course now they were competing with each other, which must have been really annoying for them.
不过现在他们当然是在互相竞争，这对他们来说肯定非常烦人。
So as more millions of years passed, some plants just went all in on lignin and produced more and more of it,
随着数百万年的流逝，一些植物开始大量合成木质素，并且其产量持续增加。
becoming stiffer, harder and stronger.
变得越来越坚硬、更结实、更耐用。
Until one day, around 385 million years ago they got the biological equivalent of steel reinforced concrete: wood.
直到大约3.85亿年前的一天，它们获得了生物学意义上的“钢筋混凝土”：木材。
More on it later, but with this magic material the first trees emerged.
稍后会有更多关于这方面的内容。正是由于这种神奇的材料，第一棵树才得以诞生。
Almost immediately they became the largest living beings alive, shooting up to 20 meters high into the sky – and they only got bigger from here.
几乎立刻，它们就成为了地球上最大的生物：它们能够长到20米高，并且此后体型还在继续增大。
But this enormous size created extremely hard problems: How do you get water from the ground up to the green parts that do the actual photosynthesis?
然而，这种巨大的体型却带来了极其棘手的问题：如何将水从地下输送到那些负责进行光合作用的绿色植物部位呢？
And how do you get the sugar they produce down to the cells that keep you up there?
那么，他们产生的糖分究竟是如何被输送到那些维持人体正常功能的细胞中的呢？
On the scale of a cell a
在细胞这个尺度上……
distance of a few meters is like you’re working in Britain while your lunch box is in Egypt and your drink in New York.
即使距离只有几米，也相当于你在英国工作，而你的午餐盒却在埃及，饮料则在纽约……
How do you not die?
你怎么才能不死呢？
So trees came up with one of the most amazing ways any organism grows, and became nearly immortal by accident.
树木进化出了所有生物中最令人惊叹的生长方式之一，从而意外地获得了近乎“永生”的能力。
A Conveyor Belt of Death Let us slice an ancient tree in half and get to the heart running it all:
一条“死亡传送带”…… 让我们将这棵古老的树木切成两半，从而找到其核心——也就是驱动这一切运转的根源。
the cambium, a razor-thin, circular zone, just a few stem cells wide.
形成层（cambium）是一个极其薄且呈环状的区域，宽度仅相当于几个干细胞的体积。
These stem cells grow inward and outwards, turning into two groups of specialists.
这些干细胞会向内和向外生长，最终分化成两类具有特定功能的细胞（即两类“专家型”细胞）。
The inward specialists are on a conveyor belt of death, the xylem.
那些专门负责植物内部结构的专家们，其实正处在一条通往死亡的“传送带上”——那就是植物的木质部（xylem）。