時(shí)差N小時(shí):植物的自我防御 Plant Self-defense
植物在饑餓的咀齒動(dòng)物面前似乎毫無(wú)防御，然而許多植物已經(jīng)進(jìn)化出了有趣的自我保護(hù)體系。
Coarse meadow grasses are a good example.
粗糙的藍(lán)草是一個(gè)很好的例子。
If you run your finger along a blade of coarsegrass,you just might cut yourself.
當(dāng)你的手指滑過(guò)它的葉子，很可能將自己劃傷。
What makes it so sharp?
它為什么如此鋒利呢?
A row of microscopic silica blades lines thegrass like tiny teeth, and most grasses have silicainside as well.
因?yàn)樵谒{(lán)草葉片邊緣有一排細(xì)小的像牙齒似的硅片，并且大部分藍(lán)草體內(nèi)也含有硅。
Although the silica doesn’tprevent animals from feasting on the grass, it is hard enough to weardown the animals'teethover time.
雖然這些硅質(zhì)不能阻止動(dòng)物的盡情咀嚼，但它的硬度很高，長(zhǎng)期食用會(huì)磨損動(dòng)物的牙齒。
Imagine trying to chomp that tough meadow grass with dull, worn teeth, you wouldn’tgettoo far!
試想一下，用又老又鈍的牙齒咀嚼那樣的牧草，顯然不會(huì)逍遙很久。
The grasses must have evolved this bristling defense fairly early in their relationship withgrazinganimals, because the anatomy of the animals'mouths has changed in response.
藍(lán)草一定很早以前就在與草食動(dòng)物的“對(duì)抗”中進(jìn)化出這種密集的齒狀硅片。因?yàn)閯?dòng)物的口腔結(jié)構(gòu)發(fā)生了相應(yīng)的變化。
The teeth ofmost mammals stop growing in adulthood.
大多數(shù)哺乳類動(dòng)物的牙齒在成年以后就停止了生長(zhǎng)。
But, the teeth of grazing animals like horses and cowshave evolved in a different way.
但是馬和牛等食草動(dòng)物的牙齒，卻產(chǎn)生了不同的進(jìn)化。
They continue to grow from the roots over the course of theanimals'lives.
它們從牙根不斷生長(zhǎng)，貫穿動(dòng)物的整個(gè)生命周期。
As the grasses'silica blades wear away the teeth, continuous growth from the rootsat leastpartially compensates for the loss.
由于藍(lán)草的硅片磨損牙齒，從牙根不斷生長(zhǎng)的牙至少部分彌補(bǔ)了磨損。
If an animal’s diet consists mostly of coarse meadowgrasses with silica blades, the animal stillcould develop extensive wearing and damage to its teeth.
如果食草動(dòng)物的食物以這種粗糙藍(lán)草為主，那么磨損仍會(huì)加劇并對(duì)牙齒造成傷害。
