题记：大海是美丽的，其拥有的生命也是多样和神奇的。生长在西澳大利亚的鲨鱼湾的海草更是令人惊叹！其单株海草的生长无论是在空间，还是在时间上都创造了星球的奇迹， 它居然有4500岁了，且在海洋中跨过了180公里；堪称世界之最是毋庸置疑的。一棵海草竟然有如此神奇和顽强的生命力，令科学家们为之着迷。“这些水下海草草地以两种方式生长：通过有性繁殖，帮助它们产生新的基因组合和遗传多样性，也通过延长根状茎繁殖，根状茎是生出根和芽的地下茎。”看来，是繁殖的多样成就了这种海草的生长奇迹。当然，还有它特殊的基因：抗干扰、适应性强等。

Scientists Blown Away by World’s Largest Plant – Stretching 112 Miles in Western Australia’s Shark Bay

科学家们被世界上最大的植物惊呆了：在西澳大利亚的鲨鱼湾延伸了112 英里

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Ribbon weed, Posidonia australis, meadow in Shark Bay, Western Australia. Credit: Rachel Austin, University of Western Australia

带状海草，Posidonia australis，西澳大利亚鲨鱼湾的草甸。 图片来源：西澳大利亚大学的 Rachel Austin

Scientists were investigating meadows of ribbon weed seagrass using DNA analysis. The shocking results blew them away; the 18,000 DNA markers they analyzed in Shark Bay World Heritage Area, in Western Australia showed a single plant expanded to stretch 112 miles. This makes it the world’s largest known plant.

科学家们正在使用 DNA 分析研究带状海草的草地。 令人震惊的结果让他们大吃一惊； 他们在西澳大利亚的鲨鱼湾世界遗产区分析了 18,000 个 DNA 标记，结果显示，一株植物已扩展到 112 英里。 这使它成为世界上最大的已知植物。

Somehow this single seedling grew to cover an area of 77 square miles, stretching through waters that are quite different in temperature and salinity. Based on its size and growth rate, the researchers estimate that it is 4,500 years old.

不知何故，这棵单苗长过了 77 平方英里的区域，穿过温度和盐度完全不同的水域。 根据其规模和增长率，研究人员估计它已有 4,500 岁了。

Next time you go diving or snorkeling, have a close look at those wondrously long, bright green ribbons, waving with the ebb and flow of water. They are seagrasses – marine plants which produce flowers, fruit, and seedlings annually, like their land-based relatives.

下次你去潜水或浮潜的时候，仔细看看那些长长的且明亮的绿色丝带，随着水的涨落而摇曳。它们是海草——海洋植物，每年都开花、结果实并长出新的幼苗，就像它们的陆地亲戚一样。

These underwater seagrass meadows grow in two ways: by sexual reproduction, which helps them generate new gene combinations and genetic diversity, and also by extending their rhizomes, the underground stems from which roots and shoots emerge.

这些水下海草草地以两种方式生长：通过有性繁殖，帮助它们产生新的基因组合和遗传多样性，也通过延长根状茎繁殖，根状茎是生出根和芽的地下茎。

To find out how many different individual plants are growing in a seagrass meadow, you have to test their DNA. We did this for meadows of ribbon weed seagrass called Posidonia australis in the shallow sun-drenched waters of the Shark Bay World Heritage Area, in Western Australia.

要了解在海草草地上生长了多少种不同的植物，必须测试它们的 DNA。我们在西澳大利亚鲨鱼湾世界遗产区阳光普照的浅水水域中为名为 POSIDONIA AUSTRALIS 的带状海草草地做了DNA测试。

The result blew us away: it was all one plant. One single plant has expanded over a stretch of 180 km (112 miles) making it the largest known plant on Earth.

结果让我们大吃一惊：都是一株植物，单株植物已经扩展了 180 公里(112 英里), 使其成为地球上已知的最大植物.

We collected shoot samples from ten seagrass meadows from across Shark Bay, in waters where the salt levels range from normal ocean salinity to almost twice as salty. In all samples, we studied 18,000 genetic markers to show that 200 km² (77 miles²) of ribbon weed meadows expanded from a single, colonizing seedling.

我们从鲨鱼湾对面的十个海草草地采集了芽样本，这些水域的盐度范围从正常海洋盐度到几乎是两倍的盐度。 在所有样本中，我们研究了 18,000 个基因标记，表明 200 平方公里（77 英里²）的带状海草草地是从单个定植幼苗扩展而形成的。

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Sampling Posidonia. Credit: Rachel Austin

采样Posidonia 图片来源：Rachel Austin

How did it evolve?
What makes this seagrass plant unique from others, other than its enormous size, is that it has twice as many chromosomes as its relatives. This makes it what scientists call a “polyploid.”

它是如何演变的？

除了巨大的体型之外，这种海草植物的独特之处在于它的染色体数量是其亲属的两倍。 这使它成为科学家所说的“多倍体”。

Most of the time, a seagrass seedling will inherit half the genome of each of its parents. Polyploids, however, carry the entire genome of each of their parents.

大多数情况下，海草幼苗将继承其每个亲本的一半基因组。然而，多倍体携带每个父母的整个基因组。

There are many polyploid plant species, such as potatoes, canola, and bananas. In nature, they often reside in places with extreme environmental conditions.

有许多多倍体植物物种，例如马铃薯、油菜和香蕉。在自然界中，它们通常居住在环境条件极端的地方。

Polyploids are often sterile, but can continue to grow indefinitely if left undisturbed. This seagrass has done just that.

多倍体通常是不育的，但如果不受干扰，可以无限期地继续生长。这种海草就做到了这一点。

How old is this plant?
The sandy dunes of Shark Bay flooded some 8,500 years ago, when the sea level rose after the last ice age. Over the following millennia, the expanding seagrass meadows made shallow coastal banks and sills through creating and capturing sediment, which made the water saltier.

There is also a lot of light in the waters of Shark Bay, as well as low levels of nutrients and large temperature fluctuations. Despite this hostile environment, the plant has been able to thrive and adapt.

这株植物几岁了？

大约 8500 年前，鲨鱼湾的沙丘被洪水淹没，当时海平面在上一个冰河时代后上升。在接下来的几千年里，不断扩大的海草草地通过创造和捕获沉积物形成了浅浅的海堤和岸台，使海水变得更咸。

鲨鱼湾的水域光线也很充足，营养物质含量低，温度波动大。尽管环境恶劣，但植物仍然能够茁壮成长并适应环境。