In natural ecosystems plants commonly enter into a symbiosis with bacteria or fungi. These relationships generally provide shelter or nutrients to one or both of the partners, but the role of mutualistic fungi in plant environmental adaptation has been unclear. In November 22 Science, Regina Redman and colleagues at the University of Washington, Seattle, USA, show that one such symbiosis can generate plant thermotolerance (Science, 298, 1581, November 22, 2002).

Redman et al. used with Dichanthelium lanuginosum plants collected from geothermal soils in the Lassen Volcanic and Yellowstone National Parks. These plants were grown in the lab in either symbiotic (with Curvularia sp. fungi) or nonsymbiotic conditions. They observed that in the absence of thermal stress, symbiotic and nonsymbiotic plants showed no measurable growth or developmental differences. But when root zones were heated with thermal tape, nonsymbiotic plants (45/45) became shriveled and chlorotic at 50°C. In...