HEAT-TOLERANCE AND ACID-TOLERANCE OF A GRASS COMMONLY FOUND IN GEOTHERMAL AREAS WITHIN YELLOWSTONE-NATIONAL-PARK

Surveys of geothermally-heated environments in Yellowstone National Pa rk have revealed an exceptionally heat-resistant grass Dichanthelium l anuginosum. Individuals of this species were able to withstand rhizosp here temperatures ranging from 40 to 57 degrees C. Long-term (July and August, 1996) rhizosphere temperature measurements at three sites con firmed that geothermal heat maintained high soil temperatures during t he night. Plants grown in the lab from field-collected seed display si gnificantly higher shoot fresh weight when grown at soil temperatures of 35-41 degrees C vs. 23-27 degrees C. Though there is no difference in root fresh weight of plants grown at these two temperature regimes, the roots from the warmer soils are significantly shorter and more hi ghly branched compared with plants grown in the cooler soils. This spe cies also displays acid tolerance both in the field, with rhizosphere pH < 3, measured at several sites, and when grown in the lab. In respo nse to increased temperature, individual D. lanuginosum plants, either grown in the lab or collected in the field, expressed a low molecular weight protein that cross-reacted with heat shock protein antibodies. (C) 1997 Elsevier Science Ireland Ltd.