The surprising scent of the world’s largest flower - Daniel Nickrent

翻译人员: 芷扬 朱 校对人员: Sophia Ye

Deep inside the Sumatran rainforest, a carrion fly descends,

在苏门答腊雨林深处，

一只腐肉苍蝇正循着它最喜欢 产卵的地方的气味飞去，

guided by the scent of its favorite place to lay eggs:

dead and rotting animal carcasses.

那是死去或腐烂的动物尸体的味道。

But when it lands, it isn’t on liquefying flesh,

然而，当它着陆时， 并不是在溶解的肉上，

but instead on the world’s biggest, and perhaps strangest, flower—

而是落在世界上最大、 也许是最奇怪的花朵——

Rafflesia arnoldii.

大王花上。

Rafflesia is a genus of over 30 species

大王花是分布在东南亚热带森林中的 30 多个物种的属。

found across the tropical forests of Southeast Asia.

While its smallest representative has a flower only a few centimeters wide,

虽然其中最小的花只有几厘米宽，

its biggest weighs seven kilograms and spans over a meter wide.

但最大的花重达七千克，宽度超过一米。

And its putrid aroma isn’t the only thing that sets these plants apart—

而且它散发出的腐烂气味， 并不是这些植物与众不同的唯一特点——

all Rafflesia are parasites.

所有的大王花都是寄生植物。

For most of its life, the Rafflesia plant exists as an endophyte,

在大部分时间里， 大王花以内生植物的方式存在，

a single thin strand of almost uniform cells beneath the bark of its host.

是宿主树皮下的一条 由几乎均匀的细胞组成的细链。

It strictly infects Tetrastigma,

它只感染崖爬藤属，

a genus of large vines related to the grape.

一种葡萄科的大型藤本植物属。

Like typical leafy plants, the host Tetrastigma’s cells contain chloroplasts.

像典型的多叶植物一样， 宿主崖爬藤属的细胞也含有叶绿体。

These organelles convert sunlight into energy

这些细胞器将阳光转化为能量，

and are each equipped with their own DNA.

并且每个细胞器都有自己的DNA。

Rafflesia’s plastids, on the other hand, appear to have lost their DNA,

然而，大王花的细胞器似乎 已经失去了其DNA，

and with it the ability to photosynthesize.

随之失去了光合作用的能力。

This sort of loss is incredibly rare.

这种损失非常罕见。

With no roots and no ability to produce its own food,

由于没有根，也没有能力自己生产食物，

Rafflesia is completely dependent on its host,

大王花完全依赖它的宿主，

抽走崖爬藤属植物的水和营养物质 来推动其自身的生长。

siphoning the Tetrastigma’s water and nutrients to fuel its own growth.

And Rafflesia’s propensity for theft doesn’t end there.

而且，大王花的盗窃习性还不止于此。

Using a process known as horizontal gene transfer, or HGT,

通过使用一种被称为水平基因转移， 又称HGT的过程，

Rafflesia has stolen quite a bit of genetic material from its host

大王花从其宿主和同栖息地的其他植物中 窃取了大量遗传物质。

and other plants in its habitat.

While HGT is well known in bacteria,

尽管 HGT 在细菌领域广为人知，

it has only recently been documented in parasitic plants.

但直到最近才在寄生植物中被记录在案。

And scientists are still trying to understand

科学家们仍在努力了解 这种DNA转移到底是如何发生的。

exactly how this DNA transfer happens.

Rafflesia appears to utilize several of these stolen sequences

大王花似乎利用了其中几个被盗序列，

as if they were their own,

就好像这是它们自己的序列一样，

transcribing the DNA into RNA and then translating it into proteins,

将DNA转录成RNA，

然后将其转化成蛋白质， 用于关键的细胞过程。

which are used in key cellular processes.

After living some time embedded in the host vine,

在寄主葡萄树中生活了一段时间后，

Rafflesia emerges as a single bud,

大王花会以单芽的形式出现，

which then takes several months, or even a year, to reach full size.

然后需要几个月， 甚至一年的时间才能完全长成。

When it opens, its fleshy maroon petals

当它打开时，它的肉质红褐色花瓣

emit several foul-smelling sulfur-containing compounds.

会释放出几种难闻的含硫化合物。

The evolutionary reason for this odor is relatively straightforward:

演化出这种气味的原因相对简单：

to attract pollinators.

吸引传粉者。

For most species of Rafflesia, single flowers are either male or female.

在大王花的大多数种类中，

一朵花要么是雄花，要么是雌花。

So, to produce a seed,

因此，要产生种子，

pollen must be transferred from one flower to the next.

必须将花粉从一朵花转移到另一朵花。

The rotten stench is ideal for attracting corpse-loving carrion flies,

腐烂的恶臭非常适合吸引喜爱 尸体的腐肉苍蝇，

and the massive size of the flower may help broadcast it

而花朵的巨大尺寸

可能有助于这种气味 在流通性差的热带雨林空气中传播。

through the stagnant rainforest air.

A deceived fly will explore the flower’s interior,

一只受骗的苍蝇将飞进花朵的内部，

laying thousands of ill-fated eggs.

产下成千上万个不幸的虫卵。

But during the fly’s visit,

而在苍蝇来访期间，

the male Rafflesia’s liquid pollen may end up on the fly’s back where it dries.

雄花的液体花粉可能会落在 苍蝇背部干燥的地方。

If the fly encounters an open female Rafflesia flower,

如果苍蝇遇到一朵开着的雌性大王花，

the pollen will rehydrate when rubbed against the flower’s damp stigma,

花粉在花朵潮湿的柱头上摩擦后 会重新补充水份，

completing cross-pollination.

从而完成异花授粉。

A pollinated Rafflesia flower gradually withers and turns black,

被授粉后的大王花会逐渐枯萎并变黑，

but this doesn't mean it's dead.

但这并不意味着它已经死亡。

Over several months, a fruit forms which contains thousands of tiny seeds.

在几个月的时间里，它会形成一种含有 数千个微小种子的水果。

But what disperses these seeds is still debated,

然而，是什么散播了这些种子仍有争议，

with hypotheses ranging from elephants to rodents to ants.

有着从大象到啮齿动物再到 蚂蚁的各种假设。

We do know that the seeds have an oily appendage called an elaiosome,

我们确实知道这些种子有一种 叫做油质体的油性附属物，

a structure ants often feed to their larvae.

这是蚂蚁经常喂给幼虫的物质。

And scientists have even observed ants carrying Rafflesia seeds.

科学家甚至观察到 蚂蚁携带大王花的种子，

But what happens to the Rafflesia seeds once inside the ant nest remains unclear.

但是，进入蚂蚁巢后， 大王花种子发生了什么尚不清楚。

In any case, nobody has seen Rafflesia seeds germinate,

无论如何，没有人看到大王花籽发芽，

or attach to and infect a host root.

或附着并感染宿主的根部。

Because this crucial step of their development is still not fully understood,

由于其生长的这一关 键步骤仍未被完全理解，

cultivation of Rafflesia is difficult.

所以种植大王花很困难。

Despite many attempts, botanists from around the globe

尽管进行了多次尝试，

但来自世界各地的植物学家

have been largely unsuccessful at growing Rafflesia

在利用自然栖息地之外的种子 种植大王花方面基本上没有成功。

from seeds outside its natural habitat.

As these tropical forests are under threat,

由于这些热带森林受到威胁，

we’re at risk of losing Rafflesia,

我们正在失去大王花 和解开剩下的许多秘密的可能性。

and our ability to unravel some of its many remaining secrets.