Conifer tree pollen from 250 million years ago show the same mutations as those of modern pines hit by fallout from the Chernobyl nuclear power plant disaster, a new study has found.

The prehistoric mutations probably occurred after gas and dust from massive volcanic eruptions damaged Earth's ozone layer, resulting in a torrent of damaging ultra-violet radiation from the sun, according to Dr Clinton Foster, of Geoscience Australia, who presented the findings at a recent conference at Utrecht, Netherlands.

"An extreme change in the environment resulted and that caused conifers to produce mutant pollen," Foster told ABC Science Online. "The fascinating thing is that modern conifers show just these sorts of mutations in response to stress, such as extreme cold, dryness, or the Chernobyl fallout."

The pollen date from about the time of the Permian-Triassic mass extinction event, which killed off more than 90% of the world's animals, but evidence of its impact on living things has been largely from marine environments: the new discovery is among the first to reveal how a major group of land plants reacted, Foster says.

Working with Dr Sergey Afonin, of the Paleontological Institute, Moscow, and Professor Xiaofeng Wang, of the Centre for Stratigraphy & Palaeontology, Yichang, Dr Foster found the mutant pollen trapped in ancient lake-bed sediments at sites as far apart as Urumqi, about 2200 kilometres west of Beijing in China, and Nedubrovo, about 800 kilometres north-east of Moscow.

"About 250 million years ago the world was an alien place, with what is now Russia and China separated by thousands of kilometres and an immense ocean," Foster says. "The only thing that linked the two land masses was the atmosphere.

"Sudden and drastic changes in the atmosphere, such as those caused by massive volcanic eruptions, would have released huge amounts of dust and gases into the air. The ozone layer would have been damaged and there would have been a subsequent increase in ultra-violet B light."

Weird wings
Normal conifer pollen grains have a central body, holding the plant's male genetic material, and a pair of wing-like inflated sacks that help the pollen to drift through the air.

But those produced by trees under stress can have no sacks, or one, three or even more, Dr Afonin said. Scientists now routinely use such pollen mutations to monitor the impacts of environmental change of plants, including the 1986 Chernobyl disaster, but this is the first time they have been used to interpret such ancient pollen.

With the collaboration of Professor Ian Metcalfe of the University of New England in Australia, the team studied thousands of fossil pollen grains trapped in the Permian-Triassic rocks and discovered that they showed the same mutations in the sack structures as stressed modern conifer species do.

By sorting them into groups, the team was able to show that the pollens were not from a diverse variety of prehistoric tree species, as previously thought. Many were simply mutations of the same species of extinct trees.

Although genetic analysis was not possible because the genes in the central pollen body have degraded, the consistent characteristic shape and structure of those bodies was enough to show that they were from the same species of trees, Foster says.

He predicts that similar evidence of mutant pollens and spores will be found in sediments laid down at the time of other mass-extinction events, such as the one that wiped out the dinosaurs about 65 million years ago.

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