為什么樹葉的形狀如此不同?

為什么樹葉的形狀如此不同?

There’s one thing about leaves that science has long agreed upon: They only grow so big as available water allows — but not so big that the whole plant overheats.

關(guān)于葉子，有一件事是科學(xué)界長期以來一致同意的:葉子只能在可利用的水分允許的情況下長得那么大，但又不能大到讓整個植物過熱。

Every leaf tells a story — not just about the plant, but also its environment. Claudio Divizia/Shutterstock

The water part makes sense. We all need water to grow. And the sun? Leaves collect those rays and, through photosynthesis, convert them into food.

水的部分是有意義的。我們都需要水來成長。那太陽呢?樹葉收集這些光線，通過光合作用把它們轉(zhuǎn)化為食物。

Too much direct sunlight and that photosynthetic engine spins hot and risks burning out.

如果陽光直射太多，光合作用引擎就會轉(zhuǎn)得很熱，有燒壞的危險。

A plant's leaves are perfectly designed to capture sunlight and carbon dioxide — and thanks to the marvel that is photosynthesis — turning them into food. GiroScience/Shutterstock

So, when it comes to the size of leaves, plants sing a simple refrain: Water grows. Sunshine restrains. And somewhere in the middle, there’s a happy balance of a leaf that grows just the right size under its own unique set of circumstances.

所以，當(dāng)談到葉子的大小時，植物有著一個簡單的重復(fù):水生長。陽光抑制。而在中間的某個地方，一片葉子有著良好的平衡，在它自己獨特的環(huán)境下，它能長到合適的大小。

But recently, after studying some 7,000 plants from around the world, Australian scientists found a new variable in nature’s math.

但是最近，在研究了世界各地的7000種植物后，澳大利亞科學(xué)家在自然數(shù)學(xué)中發(fā)現(xiàn)了一個新的變量。

It’s not just the risk of overheating that keeps leaves in check, but also the cold that comes creeping at night.

這不僅是過熱的風(fēng)險，還有寒冷來襲的夜晚。

"You put these two ingredients together — the risk of freezing and the risk of overheating — and this helps understand the pattern of leaf sizes you see across the entire world,” Ian Wright of Sydney’s Macquarie University, told the BBC.

“你把這兩種成分放在一起——結(jié)冰的風(fēng)險和過熱的風(fēng)險——這有助于理解你在全世界看到的葉子大小的模式，”悉尼麥考瑞大學(xué)的伊恩·賴特告訴BBC。

In fact, plants may be much more wary of catching a chill than too many rays.

事實上，比起過多的光線，植物可能更擔(dān)心受到寒冷的侵襲。

But don't all leaves do the same thing?

但所有的樹葉不都是一樣的嗎?

Leaves from a common fig tree (left) couldn't look more different from those of a fern. Pavel Vakhrushev/COLOA Studio/Shutterstock

What science seems far less sure about is why leaves look the way they do.

科學(xué)似乎遠不能確定的是樹葉為什么是這樣的。

Why is a fig tree’s foliage so wildly different-looking than that of, say, a fern?

為什么無花果樹的葉子和蕨類植物的葉子看起來如此不同?

Surely, nature didn’t design this swirling kaleidoscope of colors and patterns just to keep humans in a state of awe and wonder?

當(dāng)然，大自然設(shè)計出這五彩繽紛的萬花筒，不是為了讓人類保持敬畏和驚奇嗎?

In other words, a species develops a kind of leaf — whether that’s the simple, openness of a banana leaf or the moisture-retaining spindle that is the hardy pine needle.

換句話說，一個物種進化出了一種葉子——不管是簡單的、開放的芭蕉葉，還是保持水分的梭形——耐寒的松針。

The pine needle is also a kind of leaf — one specially designed to retain moisture and rebuff extreme cold. Oleksandr Kostiuchenko/Shutterstock

Right plant, right place (and right leaf)

正確的植物，正確的地方(和正確的葉子)

The angles in leaves, for example, may play a role in how sunlight is intercepted. Sharp angles, the study notes, may reduce the amount of light that the leaf intercepts during the blaring midday sun. In effect, a sharp-angled leaf can shade itself.

例如，樹葉的角度可能在陽光被攔截的過程中起作用。研究指出，尖銳的角度可能會減少葉子在正午耀眼的陽光下截取的光線。實際上，尖角的葉子可以遮蔭。

Conversely, rounder leaves have “greater daily light interception and potentially greater carbon gain."

相反，圓葉有“更大的日常光截獲和潛在更大的碳獲取。”

The tropical pine leaf is angled in such a way that it can shade itself from too much sun. Eduardo Lopez/Shutterstock

Of course, there are a few basic rules that keep plants from coloring too far out of nature’s lines.

當(dāng)然，有一些基本的規(guī)則可以防止植物的顏色偏離自然的線條太遠。

A leaf’s design must be open enough to capture sunlight for all-important photosynthesis. It also needs to make sure a leaf is shaped in a way that ensures the pores — called stomatae — can soak up enough carbon dioxide, which helps fuel that process.

葉子的設(shè)計必須足夠開放，以捕獲陽光，進行至關(guān)重要的光合作用。它還需要確保葉子的形狀能夠確保氣孔能夠吸收足夠的二氧化碳，從而為這個過程提供燃料。

Leaves have pores that help them breathe in carbon dioxide, a key requirement for photosynthesis. phanthit.malisuwan/Shutterstock

And that’s where size plays a key role. Like solar panels, big leaves harvest as much sunlight as they can. Smaller leaves shun too much sun and focus on keeping bundled tight in the cold.

這就是規(guī)模發(fā)揮關(guān)鍵作用的地方。就像太陽能電池板一樣，大樹葉可以收集盡可能多的陽光。小葉子會避開過多的陽光，在寒冷的天氣里會把葉子裹得嚴(yán)嚴(yán)實實。

Every species designs its foliage differently to be perfectly suited to its environment. Anything less than that spells the end of the plant.

每一種植物都以不同的方式設(shè)計樹葉，以完全適應(yīng)其所處的環(huán)境。低于這個標(biāo)準(zhǔn)就意味著工廠的終結(jié)。

Ultimately, something as crucial to a plant’s survival can’t afford to be anything less than perfect. Beauty just happens to be a side-product of that functional perfection.

最終，對植物生存至關(guān)重要的東西是不完美的。美麗只是完美功能的副產(chǎn)品。