However, this doesn’t explain why the leaves change color in the first place.

然而 ，這並沒有解釋起初這些葉子變色的原因。

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

落葉樹木每年落下葉子是為了避免冬天時的大損失，

but this seasonal shedding would be too wasteful to be worth doing if the trees lost all of the valuable nutrients they laboriously extracted from the soil to build their leaves earlier in the year.

但是這樣季節性的落葉實在太浪費而不值得，因為會讓它們失去原本辛苦從土壤中吸收，用來製造葉片的那些珍貴的營養素。

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

所以每當秋天到來時，落葉樹木會在落葉前回收利用它們的樹葉。

That means taking apart cells and photosynthetic apparatus from the inside out in order to recoup their nitrogen and phosphorus and store it in twigs and branches until next spring.

便是從裡到外的拆解細胞與光合作用來收回它們的氮和磷，並儲存在枝幹和細枝裡直到下個春天到來。

This is actually really tricky, because as the disassembly starts, the chlorophyll molecules that absorb sunlight for photosynthesis are still absorbing the sun’s energy.

不過事實上這很麻煩， 因為當拆解工作開始時，吸收陽光來進行光合作用的葉綠素仍然在持續吸收太陽能。

But with no photosynthesis happening, they end up passing the unused energy along to oxygen molecules, which become dangerously reactive when energized.

但是若光合作用沒有發生，它們最後就會將未使用的能量傳遞給氧分子 ，而當這些氧分子被激活後就會產生危險反應。

These molecules wreak havoc, damaging the parts of the leaf that are in the process of recovering and transporting nutrients back to the rest of the tree.

分子將大肆破壞，回收並運輸營養素回到樹木的一部分葉片將被摧毀。

To keep this destruction to a minimum, leaves break down their chlorophyll into less dangerous molecules that are typically transparent, though sometimes yellow.

為了讓傷害降至最低，葉子把葉綠素分解成危險較低的分子，這些分子通常是透明的，有時是黃色。

Either way, with the bright green molecules gone, yellow and orange pigments that were there all along (helping with photosynthesis), are no longer overshadowed, and ta-da! Yellow and orange leaves.

無論哪種，隨著葉綠素的消失，一直在那幫助光合作用進行的橘黃色素將不再被遮蔽 ，於是登登！就會變成橘黃色的樹葉。

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

有些樹木在秋季採取額外的預防措施防止葉綠素導致的破壞。

As the leaf dismantling starts, they build new, special pigments to shade chlorophyll from sunlight until it can be broken down.

當葉片拆解開始，他們製造新的特殊色素來遮蔽陽光照到葉綠素，直到它被分解。

These new pigments tend to be red or purple in color, so trees that use them have red leaves in the fall, sometimes insanely bright red.

這些新色素偏紫色或紅色，所以這些樹木在秋季時有紅色的葉子，有時會是鮮亮的紅色。

In the end, these exquisite gold and russet displays help deciduous trees recover as much as 50% of the nitrogen and phosphorus from their old leaves to help grow fresh new green ones in the spring.

最後這些美妙的金色和棕褐色落葉幫助樹木從舊樹葉中回收最多50%的氮與磷 ，幫忙在來年春天時長出新的樹葉。

They are perhaps the world’s prettiest recycling plants.

它們可能是世界上最漂亮的回收廠 。