They were all built for life in the tropics, where it's always warm, water is always liquid, and leaves are safe year round without fear of frost.

它們只適合生長在熱帶地區，很溫暖、有液態水、終年不落葉、不用擔心結霜。

If you took a tropical tree, whether ancient or modern, and transported it to Siberia or Patagonia in winter, its water would freeze into sharp-edged ice crystals, fatally puncturing the living cells in all of its leaves.

如果你把一棵熱帶樹種(無論古代或現代)運送到冬天的西伯利亞或巴塔哥尼亞，水分會凝固成邊緣鋒利的冰晶，致命刺穿所有葉片內的活細胞。

The same thing that happens to lettuce and spinach when it freezes.

就和萵苣和菠菜結凍時會發生的狀況一樣。

Cold weather also means that water in the tree's plumbing system freezes, and dangerous bubbles form in the ice from air that was previously dissolved in the liquid water.

寒冷的天氣也意味著樹的水管系統內水分會結凍，先前溶解於液態水中的空氣成為冰中危險的氣泡。

The ice itself doesn't cause much harm, but when it thaws, the bubbles remain, which is a problem because the whole plumbing system relies on the inter-molecular attraction of water molecules pulling each other upward against gravity.

冰本身並不會造成太多傷害，但當它融化，氣泡會留下，這就造成問題了，因為整個水管系統是依靠水分子間的作用力，將每個水分子抵抗重力向上拉。

Air bubbles break the chain of molecules, essentially shutting off the flow of water.

氣泡會中斷這一串分子鏈，本質上阻斷了水的流動 。

So to survive in cold weather, trees need to avoid two things: bubbles in their pipes and direct damage to living cells due to ice crystals.

所以要在寒冬存活，樹必須避免兩件事：導管內的氣泡和冰晶對活細胞的直接傷害。

Tree solved the first problem before ever leaving hot climates, because air bubbles are also a problem during drought.

早在離開炎熱氣候前它們便解決了第一個問題，因為氣泡在乾旱時也是一個問題。

When plants work harder to get water from the soil, their water-conducting pipes can accidentally suck in tiny pockets of air from the surrounding tissue.

當植物更努力地從土壤中吸取水分，它們的輸水管道可能從周圍組織意外吸入微小氣泡。

To combat this, trees in the dry tropics developed skinnier pipes, which thanks to the counterintuitive physics of bubbles and water, develop fewer bubble blockages than the wide, high-capacity pipes of their wet-tropical cousins.

為了避免，乾燥地區的樹發展出更細的管柱，由於氣泡和水有違常理的性質，這些管柱的氣泡阻礙比起它們在濕熱地區的親戚所擁有的大容積管柱要少。

So the plumbing of ancestral drought-adapted trees was accidentally pre-adapted to the cold as well, well before they began to spread beyond the tropics.

所以古老的適應乾旱樹種的水管也偶然地預先適應了寒冷，早在它們開始散播出熱帶地區之前。

Upon arriving in cold places, trees then evolved two techniques they still use to avoid frozen leaves.

一旦到了寒冷地區，樹木便演化出兩種他們現在仍然使用的防止樹葉結凍的方法。

One is to fill living leaf cells with concentrated sugary sap, a biological version of anti-freeze.

一個是將活的葉片細胞填滿濃縮糖液，也就是生物學版本的防凍劑。

Some trees, mostly evergreen conifers like pines or spruce, use solely this technique and keep their needle-like leaves unfrozen year-round with a super strong anti-freeze.

有些樹種，多為常綠針葉樹，例如松樹或雲杉，只用這個方法就能讓它們的針狀葉終年不結凍，靠的是一個超強防凍劑。

But other species, like maples and birches and larches, combine a less extreme level of sugar in their leaves with the practice of going leafless during the winter to avoid foliar frostbite.

但其他樹種，像是楓樹、樺樹、落葉松，結合葉片中不那麼高的糖份以及在冬天落葉的方法以避免樹葉凍傷。

These techniques are uniquely cold-beating adaptations.

這些方法是獨特的抗寒措施。

Well, they were, until descendants of leaf-dropping trees made it back to the dry tropics, where their strategy helps them deal with the extended seasonal droughts that occur in monsoonal climates.

這個嘛，它們曾經是，直到後來的落葉樹種成功回到乾燥熱帶地區，在那兒它們的策略幫助它們面對季風氣候中延長的季節性乾旱。

As far as we know, sugary sap remains the only adaptation that's only useful in cold places, which is why you have to come to the north if you want to tap into the sweet, sweet, anti-freeze that might just help you survive the winter

目前就我們所知，糖液依然是寒冷地區唯一有用的適應方式，這也就是為什麼你必須來到北方才能一嘗這甜蜜的、 可能助你活過冬天的防凍劑。

We call it maple syrup.

我們稱之為楓糖漿。