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  • Fossil records tell us that about 250 million years ago, there wasn't a tree on Earth designed

    化石紀錄告訴我們約2億5千萬年前,地球上的樹無法

  • to survive in temperatures below freezing. They were all built for life in the tropics,

    在冰點以下的溫度存活,它們全都適合生長在熱帶地區

  • where it's always warm, water is always liquid, and leaves are safe year round without fear of frost.

    那裡一直都很溫暖,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

    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

  • or Patagonia in winter, its water would freeze into sharp-edged ice crystals,

    或巴塔哥尼亞,水分會凝固成邊緣鋒利的冰晶

  • fatally puncturing the living cells in all of its leaves. The same thing that happens to lettuce and spinach when it freezes.

    致命地刺穿所有葉片內的活細胞,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

    寒冷的天氣也意味著樹的水管系統內水分會結凍

  • bubbles form in the ice from air that was previously dissolved in the liquid water.

    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

    冰本身並不會造成太多傷害,但當它融化,氣泡會留下,這就

  • a problem because the whole plumbing system relies on the inter-molecular attraction of

    造成問題了,因為整個水管系統是依靠水分子間的作用力

  • water molecules pulling each other upward against gravity. Air bubbles break the chain

    將每個水分子抵抗重力向上拉,氣泡會中斷這一串

  • of molecules, essentially shutting off the flow of water.

    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

    所以要在寒冬存活,樹必須避免兩件事:導管內的氣泡

  • and direct damage to living cells due to ice crystals.

    和冰晶對活細胞的直接傷害

  • They solved the first problem before ever leaving hot climates, because air bubbles

    早在離開炎熱氣候前它們便解決了第一個問題,因為氣泡

  • are also a problem during drought. When plants work harder to get water from the soil, their

    在乾旱時也是一個問題,當植物更努力地從土壤中吸取水分,它們的

  • water-conducting pipes can accidentally suck in tiny pockets of air from the surrounding

    輸水管道可能從周圍組織意外吸入微小氣泡

  • tissue. To combat this, trees in the dry tropics developed skinnier pipes, which, thanks to

    為了避免,乾燥地區的樹發展出更細的管柱,由於

  • the counterintuitive physics of bubbles and water, develop fewer bubble blockages than the high-capacity

    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

  • pipes of their wet-tropical cousins. So the plumbing of ancestral drought-adapted trees

    所擁有的大容積管柱要少,所以古老的適應乾旱樹種的水管

  • was accidentally pre-adapted to the cold as well, well before they began to spread beyond

    也偶然地預先適應了寒冷,早在它們開始散播出

  • the tropics.

    熱帶地區之前

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

    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

  • leaves: one is to fill living leaf cells with concentrated sugary sap, a biological version

    的方法: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

  • of anti-freeze. Some trees -- mostly evergreen conifers like pines or spruce -- use solely

    防凍劑。有些樹種--多為常綠針葉樹,例如松樹或雲杉--只用

  • this technique and keep their needle-like leaves unfrozen year-round with a super strong

    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

  • anti-freeze. But other species, like maples and birches and larches, combine a less extreme

    防凍劑。但其他樹種,像是楓樹、樺樹、落葉松,結合較不那麼高

  • level of sugar in their leaves with the practice of going leafless during the winter to avoid

    的葉片中糖份以及在冬天落葉的方法以避免

  • foliar frostbite.

    樹葉凍傷

  • These techniques are uniquely cold-beating adaptations - well, they were, until descendants

    這些方法是獨特的抗寒措施--這個嘛,它們曾經是,直到後來的

  • of leaf-dropping trees made it back to the dry tropics, where their strategy helps them

    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

  • deal with the extended seasonal droughts that occur in monsoonal climates.

    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

    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

  • places, which is why you have to come to the north if you want to tap into the sweet, sweet,

    這也就是為什麼你必須來到北方才能一嘗這甜蜜的、

  • anti-freeze that might just help you survive the winter - we call it maple syrup.

    可能助你活過冬天的防凍劑--我們稱之為楓糖漿

Fossil records tell us that about 250 million years ago, there wasn't a tree on Earth designed

化石紀錄告訴我們約2億5千萬年前,地球上的樹無法

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B1 中級 中文 氣泡 結凍 葉片 熱帶 地區 落葉

樹木如何度過冬天? (How do Trees Survive Winter?)

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    Mark Lin 發佈於 2021 年 01 月 14 日
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