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Watch out – don’t step on a Hydatellaceae!

Each time you leave Perth airport, you fly over a tiny swamp containing Trithuria submersa – ancient plants that grow no more than five centimetres tall. Photo: R. Tuckett
Each time you leave Perth airport, you fly over a swamp containing Trithuria submersa – one of the oldest oldest lineage flowering plants on Earth
Photo: R. Tuckett
    Research on Hydatellaceae encompassed many other aquatic species, including those that grow in gnammas – temporary pools that form on granite outcrops across south Western Australia. Photo: R. Tuckett
Research on the plant family Hydatellaceae encompassed many other aquatic species, including those that grow in gnammas – temporary pools that form on granite outcrops across south Western Australia
Photo: R. Tuckett

Look closely next time you visit a Western Australian swamp, and you may be lucky enough to find one of the oldest lineage flowering plants on Earth.

The group of plants is from the plant family Hydatellaceae. Long thought to be unremarkable, they have recently been recognised as sister to the ancient water lily plant family, Nymphaeales. These native Western Australian plants date back some 130 million years!

South-west Western Australia is the hotspot for this group of tiny red annuals, which grow no larger than five centimetres high. Five of the 11 species occurs in the region, with four species being endemic, and three species occurring in the Perth metropolitan area.

Hydatellaceae live in temporary wetland claypans and rock pools, and are most visible on the edges when the water is receding. The seeds germinate in May/June and grow, flower and reproduce before November, when they die. The seeds are left to bake in the soil over the hot summer months before germinating the following year.

Research under the partnership between Kings Park and Botanic Garden and the Millennium Seed Bank discovered that these ancient seeds possess a new type of dormancy, previously unknown to science. Remarkably, during the germination process the undeveloped embryos emerge from the protective seed coat to develop into a shoot and root outside of the seed. The aquatic environment is thought to enable the unprotected embryo to develop in this way.

The Hydatellaceae group is now of exceptional conservation value. So, if you are lucky enough to see one or two of these unique plants when you’re out and about – make sure you just observe to conserve!