360 million-year-old fossilized tree has oldest known defense mechanism

By Mark Waghorn via SWNS

A 360 million-year-old fossilized tree from Ireland has the oldest known defense mechanism protecting it from disease, scientists believe.

The tree had balloon-like swellings, called tyloses, which researchers say are the first evidence of plant self-defense in wood.

They prevented infection and water loss by blocking bacterial and fungal bugs - shedding fresh light on early evolution.

An international team identified the strange structures in an extinct species called Archaeopteris - the world's first real tree.

They were imprinted on rocks unearthed at Hook Head - a long, narrow peninsula on the coast of Wexford in the southeast corner.

The plants, known as progymnosperms, had a large woody trunk, branches - and complex root systems.

They lived long before the age of the dinosaurs - or even flying insects.

They formed the first primeval forests when plants ruled the continents, accompanied by microorganisms, fungi and early relatives of spiders, millipedes and centipedes.

Lead author Dr. Carla Harper, of Trinity College Dublin, said: "Fossil wood is an example of an anatomically preserved fossil. Plant remains that have been infiltrated by a water rich in minerals, preserving their tissues in three dimensions.

"These fossils allow us to study very fine details of extinct plant anatomy, down to the cellular level. This type of preservation, in general, is rare but occurs in certain fossil deposits in Ireland."

They reveal these primitive trees were also able to protect themselves by forming tyloses - seen in many of their descendants today.

Ireland is one of the few places on the planet where such details can be observed in plants from this remote time period.

Harper said: "Continuing fieldwork in Irish Devonian localities will yield new fossils that will increase our understanding of the diversity and biology of extinct plants.

"Overall, Ireland's rich plant fossil history - an untapped resource - plays a key role in answering exciting research questions and raises many more."

Hundreds of millions of years ago the land that makes up Ireland existed on two continents - named Laurentia and Gondwana.

The southern part was located on the latter - to the south of the equator.

Added Harper: "By studying these fossil plants and their past environments, we can get powerful insights into the history of plant physiological processes that still occur today, and into both current and future ecosystems of Ireland and the world."

Archaeopteris, like its modern counterparts, had a critical influence on life on Earth.

It helped filter out high levels of greenhouse gas in the atmosphere - helping organisms thrive.

Trunks reaching almost 18 inches in diameter sprouted branches and buds. Each tree could survive for up to 50 years.

The study is in the journal Nature Plants.