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.

關于葉子，有一件事是科學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，當談到葉子的大小時，植物有著一個簡單的重復: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，澳大利亞科學家在自然數(shù)學中發(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——結冰的風險和過熱的風險——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?

當然，大自然設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.

葉子的設計必須足夠開放，以捕獲陽光，進行至關重要的光合作用。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嚴實實。

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計樹葉，以完全適應其所處的環(huán)境。低于這個標準就意味著工廠的終結。

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