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树叶在秋天变色的原因

你一定听说过落叶乔木为叶子在秋天会变色

You’re probably heard that leaves of deciduous trees change color in autumn

因为之们失去了绿色的叶绿素分子

because they lose their green chlorophyll molecules,

从而露出了一下层的黄橙色色素

allowing the underlying yellow-orange pigments to shine through.

但这并没有解释为什么叶子到秋天先会变色

However, this doesn't explain why sue leaves change color in the first place

落叶乔木每年落叶是为了降低冬天防冻的消耗

Deciduous trees drop their leaves each year to avoid the high cost of winterizing them,

但如果树木把它们每年从土壤里辛苦汲取出来的

but this seasonal shed ding would be too wasteful to be word doing

用于长出新叶子的营养全了的话

If the trees lost all of the valuable nutrients they laboriously extracted from the soil

那这种季节性落叶未免大过浪费

to build their leaves earlier in the year.

所以每年秋天落叶乔木会在叶子落下前进行营养回收

So each fall,deciduous trees recycle their leaves before dropping them

也就是说会分解树叶的细胞和光合器官

That means taking apart cells and photosynthetic apparatus form the inside out

来从中回收氮和磷

并将它们储在树枝中等待来年春天

in order to recoup their nitrogen and phosphorus and store it in twigs and branches until next spring.

这个过程非常困难，因为随着分解的开始

This is actually really tricky because as the disassembly starts

叶绿素为了光合作用

the chlorophyll molecules that absorb sunlight for photosynthesis

仍然在收收太阳能

are still absorbing the sun’ energy.

但却不再进行光合作用

But with no photosynthesis happening

最后他们将多余的能量给了氧分子,

They end up passing the unused energy along to oxygen molecules

此时氧分子一旦被激发会变得非常危险

which become dangerously reactive when energized.

这些氧分子橫行肆厚，破坏了树叶的部分机能

These molecules wreak havoc damaging the parts of the leaf

阻止它们向树的其他部分回收井输送营养物质

that are in the process of recovering and transporting nutrients back to the rest of the tree.

为了使损失最小化

To keep this destruction to a minimum

树叶会把叶绿素变成低危险的分子

Leaves break down their chlorophyll into less dangerous molecules

他们通常是透明的，也有些是黄色的

that are typically transparent,though sometimes yellow.

无论如何 亮绿色的分子消失了

Ether way, with the bright green molecules gone

一直默默帮助光合作用的黄色和橙色色素

yellow and orange pigments that were there all along helping with photosynthesis

就都显现了出来

are no longer overshadowed,and ta-da!

于是就有了黄色和橙色的叶子

Yellow and orange leaves.

有些树木还有一套额外的秋季预防挡施来防止叶绿素引发的破坏

Some trees take an extra autumnal precaution against chlorophyll-induced-destruction,

随着树叶开始分解

as the leaf dismantling starts

它们会形成新的特殊色素来遮挡阳光

they build new special pigments to shade chlorophyll from sunlight

直到叶绿臻柀分解

until it can be broken down.

这些新色素通常是红色或紫色

These new pigments tend to be red or purple to color

所以这些树的叶子看上去就是红色的了

so trees that use them have red leaves in the Fall,

有时也会是鲜红色

sometimes insanely bright red.

最终这些美丽的金色和黄褐色树叶

In the end, these exquisite gold and russet displays

帮助落叶乔木回收了

help deciduous trees recover

旧叶中多达50%的氮和磷

as much as 50% of the nitrogen and phosphorus from their old leaves

让大树可以在春天焕发新绿

to help grow fresh new green ones in the spring.

它们大概是世上最漂亮的回收站

They are perhaps the world’s prettiest recycling plants.

苏州金桥翻译社汇总

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