Liverworts put down first roots on Earth

A BOTANICAL mystery surrounding the emergence of the first aquatic plants to colonise the land nearly 500m years ago has been solved by scientists.

Liverworts - an unassuming group of moss-like plants that thrive in damp, out-of-the-way places - have won the accolade of being the oldest terrestrial plants in the world.

A genetic analysis of more than 352 different species of terrestrial flora has concluded that liverworts were the first plants to make the transition from sea to land. The first evidence of plants colonising the land comes from spores dating back 476m years to the mid-Ordovician period, but botanists have disagreed over which group of plants could have produced these spores.

Jeffrey Palmer a biologist from Indiana University in Bloomington, Indiana, tackled the problem by looking for common genetic characteristics in the four main groups of living plants. The scientists found that nearly all of them, including the ferns, mosses and seed-producing plants, shared certain features within their genes called introns - which are like extra- large spaces in the genetic code.

The same spaces were absent in liverworts and also absent in more primitive life forms such as green algae.

The scientists, who report their finding in the journal Nature, said the results indicate that liverworts are the earliest land plants and that the genetic trait common to all other land plants must have arisen in a common ancestor after liverworts had colonised the land.