Fungus: ally of desert, wetland plants.

Mycorrhizal fungi and plants practice the "you scratch my back, I'll scratch yours" approach to life. The fungi attach themselves to the roots of plants and feed on their hosts' store of carbohydrates. But they give back more than they take, as they tap hard-to-reach nutrients and water in the soil and share their finds with the plants.

Many mycorrhizal plants and fungi exist throughout the world, in salt marshes, deserts, and pine forests (SN: 9/23/95, p.198)--but not in wetlands, or so scientists had thought.

Now, Carl F. Friese of the University of Dayton in Ohio and his colleagues report that more than 50 percent of the plants growing in southwestern Ohio's large Beaver Creek watershed are mycorrhizal.

Other researchers may have missed mycorrhizal inhabitants of wetlands because they failed to look at the right species of plants or looked at the wrong time of year, he explains.

These results, which Friese and his colleagues are now preparing for publication, show that ecologists should protect existing mycorrhizal fungi or introduce new spores to ensure that wetlands function properly.

Protecting or introducing mycorrhizal fungi may also prove more important to preventing desertification than previously thought, Friese says.

Earlier investigations showed that almost 90 percent of the 61 plant families growing in arid regions worldwide have mycorrhizal members. However, none of those studies included South America, home of some unique plant species, Friese says. So he and his coworkers undertook two surveys of Chile.

They started with parkland near the northern Chilean town of La Serena, where they examined 38 common and rare plant species from 19 different families. More than 90 percent of the species formed symbiotic relationships with mycorrhizal fungi, report Friese, Shivcharn S. Dhillion, now at the University of Oslo in Norway, and their colleagues in the September/October Mycorrhiza.

In another, not yet published study of northern Chile's Atacama desert, one of the driest regions in the world, Friese and his coworkers report that the area's dominant shrubs, members of the genus Atriplex, are mycorrhizal. Atriplex species growing elsewhere in the world are not mycorrhizal, other studies have shown.