原文作者：elena ortiz

sounds like science fiction？ well， it isn't.
　　every year billions of babies are dried and buried， not to be unburied for weeks， months， years or even decades. don't worry. these are not babies like your little brother or sister； these are baby plants， or as you might call them， seeds. why would a mom do such a thing？ to answer this question， imagine you are a plant. you have no legs or wings or fins. you can't move from the place where you are rooted. you can't turn on the heat when it gets cold or the air conditioner when it gets hot. if it doesn't rain near you， you can't go get the water from someplace else. now let's say you're ready to reproduce1）， how could you take care of your babies？ how could you be sure they'd have a good chance at survival？ the answer for mother plants is to pack them up in a special time capsule called a seed.
 　　听上去像科幻小说？不过这不是。wWW.11665.COm
　　每年都有数以十亿计的小宝宝经过脱水后被埋入地下，此后的数周、数月、数年甚至数十年都在不见天日的地下度过。别担心，我说的不是像你的弟弟或妹妹那样的人类宝宝，而是植物宝宝，也许你更习惯叫它们种子。植物妈妈为什么要做这种事呢？要回答这个问题，得先把自己想象成一株植物。没有腿脚、翅膀，也没有鳍，你只能扎根在原地不动，天冷了没法开暖气，天热了也没有空调。如果附近不下雨，你也没法去别的地方找水。现在假设你已经到了该生儿育女的阶段，你怎么照顾自己的小宝宝呢？你怎么确定它们会有良好的存活机会呢？对植物妈妈们来说，解决的办法就是把孩子们装入一种特殊的时间胶囊——种子。
 　　how is a seed like a time capsule？  [论文网]
　　为什么说种子像时间胶囊？
　　like a chicken egg， a seed is a package containing the plant embryo2） and food for the baby plant. the package is then covered in a protective hard shell called the seed coat. but unlike chicken eggs， most seeds can remain dormant3） for weeks or years， waiting for the conditions to be right. when the time is right the seed germinates4） and the new plant starts to grow.
 　　与鸡蛋类似，一颗种子里面包含着植物的胚胎和供植物幼体消耗的养分，外面还包裹着一层叫做种皮的硬壳，能够起到保护作用。不过，与鸡蛋不同的是，大多数种子都能休眠数周甚至数年，以等待合适的条件生根发芽。当时机来临，种子就会发芽，长成新的植株。
 　　what conditions do seeds need to start growing？
　　种子开始生长需要哪些条件？
　　sometimes seeds only need water. but other seeds get clues from their environment that tell them the time is right. what kind of clues do seeds need from their surroundings？ well， that depends on the seed. seeds of annual plants in the desert wait until it has rained a lot and then germinate. some seeds on the forest floor wait for a tree to fall and sunlight to hit them. the seeds of the california chaparral5） plants wait for the plants above them to burn. other seeds need to travel through an animal's gut6） and get scarred7） by the digestive acids in order to germinate.
 　　有时候种子只需要有水就可以生长。但是有些种子需要从外界的环境中获得某种信号，告诉它们生长时机已到。种子需要从它们周围的环境中获得什么样的信号呢？关于这一点，不同的种子情况不同。生长在沙漠中的一年生植物，其种子要等到大量降雨之后才会发芽。有些落在森林地表的种子需要等待旁边的大树倒下，阳光照射到它们的时候才会发芽。加利福尼亚沙巴拉灌木群落里某些植物的种子则要等到野火把原有的植被烧为灰烬后才发芽。还有些种子需要经过动物的消化道，种皮被动物体内的酸性消化液腐蚀后才能发芽。

　what kind of information does the seed get from these clues？
　　种子从这些信号中获得了什么样的信息？
　　these clues let the seed know that it's time to grow. let's say you're a plant that needs a lot of sunlight to grow well. if yo

u reproduce and spread your seeds all over the forest， a lot of your babies end up underneath other plants where they get too much shade. but remember， a seed is like a time capsule， it can wait， dormant， for a long time. one day the plant that is shading you dies. light hits you for the first time since you left your mom， and that is the clue you've been waiting for. now you can germinate， grow big and strong and make new babies of your own.
 　　the seeds of some plants get buried over time. these seeds can't respond to sunlight. they get their clue when the temperature in the soil changes. when the soil warms up， they start growing.
 　　here's another example. ever wonder why some seeds won't germinate until after they've been chilled for a few weeks？ this cold temperature is a clue about the time of year. that's right. it tells them it's winter. but why do they need to know when winter has passed？ well， these plants come from places where the mildest times of the year are spring and fall； these are the times of the year when it's not too cold or too hot. in these places， winters can be so cold that plants die. the seeds need to start growing in the spring so they have enough time to grow up and make their own seeds before winter comes. these seeds won't germinate until it has been cold in the winter and then warm again in the spring.
 　　sometimes seeds get tricked into growing at the wrong time. for example， when there is long warm spell8） in the middle of winter. they start growing during the warm spell. then the winter weather returns and the plants die. other seeds avoid growing at the wrong time by sensing changes in the length of days. in summer days are longer. days get shorter as the winter approaches. seeds that need warm weather and longer days will almost always germinate at the right time.
 　　seeds are actually very amazing time travelers. just how long they can remain dormant and still germinate is part of an ongoing experiment that began in 1880 by a scientist named william james beal. this experiment continues even today along with other studies of seeds that show some seeds have been time traveling for even longer—3000 years to be exact.
 　　这些信号让种子知道，生长的时间到了。假设你是一株需要大量阳光照射才能健康生长的植物，当你开始繁殖并把种子播撒到森林各处，它们中有许多最终会落到其他植物下方，得不到多少光照。不过别忘了，种子就像时间胶囊，可以等待、休眠很长时间。总有一天，挡着你的那棵植物会死去。自从离开母体后，阳光第一次照在你身上，而这就是你一直在等待的信号。现在你可以发芽、茁壮成长并繁育自己的后代了。
 　　有些植物的种子则会随着时间的推移被渐渐掩埋。这些种子无法对阳光产生反应，它们要从周围土壤温度的改变中得到自己的生长信号。当土壤的温度升高时，它们就会开始生长。
 　　再举一个例子。有没有想过为什么有些种子要在受冻几周后才能发芽呢？低温是提示季节的信号。没错，它让种子知道自己身处冬季。但是，这些种子为什么需要知道冬季何时结束呢？原因是，在这些植物的产地，一年中气候最温和的时期是春季和秋季，这两个季节正是这一年中既不太冷也不太热的时候。在这些地区，冬季太过于寒冷，导致这些植物无法存活。因此，它们的种子需要在春天开始生长，以保证在冬季到来前能有足够的时间成熟结籽。这些种子要经历寒冷的冬天然后迎来温暖的春天时才会发芽。
 　　有时，种子也会受骗，在错误的时间开始生长。比如，如果冬季持续出现较长时间的小阳春天气时，就会发生这种情况。种子在小阳春天气中开始生长，然后随着冬季回归、气温下降，它们长成的植株就会被冻死。有些种子通过感知白天时长的变化来避免在错误的时间生长。夏季白天较长，而当冬季临近时，白天会缩短。那些需要温暖天气和较长日照时间的种子几乎总能在正确的时间发芽。
 　　种子确实是非常了不起的时间旅行者。一位名叫威廉·詹姆斯·比尔的科学家在1880年开始了一项不间断的实验，目的