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All one: seaweed in Shark Bay
Photo: Rachel Austin/UWA
They wanted to prepare a marine reserve, but came across a record in botany: researchers from the University of Western Australia accidentally discovered what they say is the largest plant on the planet.
Seagrass of the species Posidonia australis covers an area of around 200 square kilometers in the UNESCO World Heritage protected Shark Bay off Australia's west coast, the university said on Wednesday - and the whole meadow should be regarded as a single plant.
Evolutionary biologist Elizabeth Sinclair said the team took samples to determine which plants would be suitable for reclamation projects.
»We are often asked how many different plants grow in seagrass beds.
This time we used genetic tools to answer that."
Shoots were collected from different parts of the bay and a kind of genetic fingerprinting with 18,000 markers was taken, explained student assistant Jane Edgeloe, who is now lead author of a study published in the journal Proceedings of the Royal Society B.
"We were blown away by the answer," says Edgeloe.
All shoots are genetically identical.
'It was only one.
A single plant has spread over 180 kilometers in Shark Bay, making it the largest known plant on earth.”
Apparently the whole meadow was created from a seedling.
For this to happen, the seagrass must have been growing for at least 4,500 years.
It is not unusual for seagrass plants to form such clones, i.e. genetically identical offshoots.
But the plant in the shallow, salty water of Shark Bay has another special feature in addition to its sheer size: it is polyploid, meaning it has more than two sets of chromosomes in its cells - unlike its relatives in the ocean.
Polyploidy can arise when diploid plants - i.e. those with two pairs of chromosomes - cross.
Then the new seedling takes over the entire genetic material of both parent plants instead of half each.
The phenomenon usually occurs only temporarily.
"Polyploid plants often settle in places with extreme environmental conditions," said Elizabeth Sinclair.
"They are often sterile, but can always continue to grow if they are not disturbed." Shark Bay's "really hardy" seagrass seems to have succeeded in doing this.
The plant can withstand a wide range of temperature and salinity, as well as intense light.
"All of this would put most plants under a lot of stress." With further experiments, the researchers now want to find out why the seagrass copes so well under these conditions.
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