From: Tom Marshall, Planet Earth On Line
Published May 23, 2012 06:48 AM

Study links fungi to early vascular plants

Cooperating with fungi didn't just help the earliest plants spread across a barren, rocky landscape; it also played a decisive role in the rise of more complex plants with roots and leaves that make up most of today's flora.

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That's the conclusion of a recent study, which used experiments on closely-related plants that are still around today to investigate how major environmental changes around 400 million years ago gave more complex new 'vascular' arrivals the edge over older, simpler 'non-vascular' plants like liverworts.

A sudden plunge in atmospheric CO2 made these simpler plants' cooperative fungal networks far less capable of supplying them with enough nutrients to grow, compared to a corresponding improvement for their vascular rivals. Adding to the problem, the upstarts were starting to outcompete them for light.

Also known as 'higher plants', vascular plants are far more anatomically complex than non-vascular ones, and their appearance saw the birth of innovations like leaves, stems and roots. The new conditions didn't just reward such novelties; they pushed evolutionary lineages further down the path towards complexity, helping shape the rich plant life we see today.

'The liverworts and other non-vascular plants were getting shaded out by plants with roots, leaves and stems, and they were faced with a huge drop in CO2 levels that made their fungal networks far less effective,' says Dr Katie Field, a plant scientist at the University of Sheffield and lead author of the paper, which appears in Nature Communications. 'They really were up against it.' They quickly lost the top spot; and have never regained it since, though their relations are still around today.

Thalloid liverwort with gemma cups, via Shutterstock.

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