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World’s Largest Plant – Posidonia Australis


The world’s largest plant has recently been discovered off the West Coast of Australia: a seagrass 180 km in length.


GS III- Environment and Ecology

Dimensions of the Article:

  1. About Ribbon weed or Posidonia australis
  2. So how remarkable is this plant’s size?
  3. How did it grow, and survive for, so long?
  4. Significance of Seagrass

About Ribbon weed or Posidonia australis

  • The ribbon weed, or Posidonia australis, has been discovered in Shark Bay by a group of researchers from Flinders University and The University of Western Australia.
  • These researchers have also found that the plant is 4,500 years old, is sterile, has double the number of chromosomes than other similar plants, and has managed to survive the volatile atmosphere of the shallow Shark Bay.

So how remarkable is this plant’s size?

  • The ribbon weed covers an area of 20,000 hectares.
  • The next on the podium, the second largest plant, is the clonal colony of a quaking Aspen tree in Utah, which covers 43.6 hectares.
  • The largest tree in India, the Great Banyan in Howrah’s Botanical Garden, covers 1.41 hectares.

How did it grow, and survive for, so long?

  • Sometime in the Harappan era, a plant took root in the Shark Bay.
  • Then it kept spreading through its rhizomes, overcoming everything in its way, and here we are today.
  • Ribbon weed rhizomes can usually grow to around 35cm per year.
  • The researchers found that the ribbon weed cannot spread its seeds, something that helps plants overcome environmental threats.
  • Also, Shark Bay sees fluctuations in temperature and salinity and gets a lot of light, conditions challenging for any plant.
  • Yet the ribbon weed has managed to survive, and a part of the reason may be that it is a polyploid – instead of taking half-half genome from both parents, it took 100 per cent, something not unheard of in plants. Therefore, this ribbon weed has twice the number of chromosomes other plants of the same variety have.

Significance of Seagrass

  • Because seagrass performs a vital role in the environment, and if some of it is hardy, it is good news for everyone in a world threatened by climate change.
  • In India, seagrass is found in many coastal areas, most notably in Gulf of Mannar and Palk Strait.
  • Apart from being home to a variety of small organisms, seagrass trap sediments and prevent water from getting muddy, absorb carbon from the atmosphere, and prevent coastal erosion.

-Source: Indian Express

December 2023