• Researchers have located the largest plant in the world in the shallow, sun-drenched waters of the World Heritage Area of Shark Bay in Western Australia.

• It is larger than the cloned Pando quaking Aspen trees in Utah that cover 106 acres.

• Researchers from the University of Western Australia and Flinders University have identified the sprawling seagrass, a marine flowering plant known as Posidonia australis.

• The seagrass is Poseidon’s ribbon weed, also known as fibre-ball weed. It is commonly found along the southern coastlines of Australia.

• It is an ancient and incredibly resilient seagrass stretching across 180 km that is estimated to be at least 4,500 years old.

• Earlier, Pando, a network of quaking aspen (Populus tremuloides) growing in the Wasatch Mountains of Utah in the US was considered the world’s most massive plant. Pando is an aspen clone that originated from a single seed and spreads by sending up new shoots from the expanding root system. The clone spreads over 106 acres, consisting of over 40,000 individual trees. 

Posidonia australis

• Posidonia australis has large, bright green, strap-like leaves.

• As much as 90 per cent of the mass of the plant may be in the roots. They can be found in large meadows at shallow depths in estuaries, coastal lakes and sheltered coastal waters.

• As one of the slower growing species of seagrass, Posidonia australis can be particularly slow to recover from damage.

• It can form large, dense stands (called meadows), and is also often found mixed with other species of seagrass such as Zostera (eelgrass) and Halophila (paddleweed).

How was the study conducted? 

• The plant is so large because it clones itself, creating genetically identical offshoots. 

• The team sampled seagrass shoots from across Shark Bay’s variable environments and generated a ‘fingerprint’ using 18,000 genetic markers.

• They were able to sequence DNA from the seagrass samples, which revealed that it was a single plant.

• The ribbon weed meadows appear to have expanded from a single, colonising seedling.

• The plant has been able to continue growing through vegetative growth — extending its rhizomes (rootstalks) outwards — the way a buffalo grass would in the back garden, extending runners outwards. The only difference is that the seagrass rhizomes are under a sandy seafloor so you don’t see them, just the shoots within the water column.

• Another interesting point is it has double the number of chromosomes than in other populations we had been studying. It has 40, not the usual 20.

• Whole genome duplication through polyploidy – doubling the number of chromosomes – occurs when diploid ‘parent’ plants hybridise. The new seedling contains 100 per cent of the genome from each parent, rather than sharing the usual 50 per cent.

• Polyploid plants often reside in places with extreme environmental conditions, are often sterile, but can continue to grow if left undisturbed, and this giant seagrass has done just that

• The study suggested that reproducing via cloning helped the seagrass meadow adapt to habitat conditions that were more extreme than where seagrass is usually found — saltier water, high levels of light and wide temperature fluctuations.

• Even without successful flowering and seed production, it appears to be really resilient, experiencing a wide range of temperatures and salinities plus extreme high light conditions, which together would typically be highly stressful for most plants.

Shark Bay

• On the Indian Ocean coast at the most westerly point of Australia, Shark Bay’s waters, islands and peninsulas covering a large area of some 2.2 million hectares (of which about 70 per cent are marine waters) have a number of exceptional natural features, including one of the largest and most diverse seagrass beds in the world. 

• The site is most renowned for its stromatolites (colonies of microbial mats that form hard, dome-shaped deposits which are said to be the oldest life forms on earth). 

• It is also famous for its rich marine life including a large population of dugongs (sea cows), and provides a refuge for a number of other globally threatened species.

Manorama Yearbook app is now available on Google Play Store and iOS App Store