FUTURE WORK

1. Fungi Plant Soil Mycorrhiza REFERENCES Bécard, G. and J.A. Fortin. 1988. Early events of vesicular-arbuscular mycorrhiza formation on Ri T-DNA transformed roots. New Phytologist. 108:211-218. Blackwell. M. 2000. Terrestrial Life - Fungal from the Start? Science. 289:1884-1885. Burns, B. 1997. Vegetation change along a geothermal stress gradient at the Te Kopia steamfield. Journal of The Royal Society of New Zealand. 27:279-294. Christiansen, R.L. 1984. Yellowstone magmatic evolution: Its bearing on understanding large-volume explosive volcanism. Explosive Volcanism, Its Inception, Evolution and Hazards. Washington, D.C.: National Academy of Sciences. 84-95. Giovannetti, M., C. Sbrana, L. Avio, A.S. Citernesi, and C. Logi. 1993. Differential hyphal morphogenesis in arbuscular mycorrhizal fungi during pre-infection stages. New Phytologist. 125:587-593. Heppell, K.B., D.L. Shumway, and R.T. Koide. 1998. The effect of mycorrhizal infection of Abutilon theophrasti on competitiveness of offspring. Functional Ecology. 12:171-175. Johansen, A., I. Jakobsen, and E.S. Jensen. 1993. External hyphae of vesicular-arbuscular mycorrhizal fungi associated with Triolium subterraneum L. 3. Hyphal transport of 32P and 15N. New Phytologist. 124:61-68. Johnson, N.C. 1993. Can fertilization of soil select less mutualistic mycorrhizae? Ecological Applications. 3:749-757. Johnson, N.C., J.H. Graham, and F.A. Smith. 1997. Functioning of mycorrhizal associations along the mutualism-parasitism continuum. New Phytologist. 135:575-585. McGonigle, T.P., M.H. Miller, D.G. Evans, G.L. Fairchild, and J.A. Swan. 1990. A new method which gives an objective measure of colonization of roots by vesicular-arbuscular mycorrhizal fungi. New Phytologist. 115:495-501. Newsham, K.K., A.H. Fitter, and A.R. Watkinson. 1995. Multi-functionality and biodiversity in arbuscular mycorrhizas. Trends in Ecology and Evolution. 10:407-411. Peng, S., D.M. Eissenstat, J.H. Graham, K. Williams, and N.C. Hodge. 1993. Growth depression in mycorrhizal citrus at high-phosphorus supply. Plant Physiology. 101:1063-1071. Phillips, J.M. and D.S. Hayman. 1970. Improved procedures for clearing roots and staining parasitic and vesicular-arbuscular mycorrhizal fungi for rapid assessment of infection. Transactions of the British Mycological Society. 55:158-161. Redecker, D., J.B. Morton, and T.D. Bruns. 2000. Molecular phylogeny of the arbuscular mycorrhizal fungi Glomus sinuosum and Sclerocystis coremioides. Mycologia. 92:282-285. Remy, W., T.N. Taylor, H. Hass, and H. Kerp. 1994. Four hundred-million-year-old vesicular arbuscular mycorrhizae. Proceedings of the National Academy of Sciences. 91:11841-11843. Smith, S.E. and D.J. Read. 1997. Mycorrhizal Symbiosis, 2nd Edition. Academic Press, San Diego. Stahl, P.D., G.E. Schuman, S.M. Frost, and S.E. Williams. 1998. Influence of arbuscular mycorrhiza and plant age on water stress tolerance of big sagebrush seedlings. Soil Science Society of America Journal. 62:1309-13. Stanley, M.R., R.T. Koide, and D.L. Shumway. 1993. Mycorrhizal symbiosis increases growth, reproduction and recruitment of Abutilon theophrasti Medic. in the field. Oecologia. 94: 30-35. Stout, R.G., M.L. Summers, T. Kerstetter, and T.R. McDermott. 1997. Heat- and acid-tolerance of a grass commonly found in geothermal areas of Yellowstone National Park. Plant Science. 130:1-9. Subramanian, K.S. and C. Charest. 1999. Acquisition of N by external hyphae of an arbuscular mycorrhizal fungus and its impact on physiological responses in maize under drought-stressed and well-watered conditions. Mycorrhiza. 9:69-75. Zabinski, C. and R. A. Bunn. In review. Arbuscular Mycorrhizae in Hydrothermal-Influenced Soils in Yellowstone National Park. Western North American Naturalist. • SUMMARY • Mycorrhizae resulted in a decreased plant biomass at ambient temperatures, under the low nutrient conditions. • In elevated temperatures, D. lanuginosum biomass was equal in the mycorrhizal and microbial wash plants (ME~1). • With the previous exception, plants receiving a microbial wash (without mycorrhizal propagules) had the greatest biomass and the mycorrhizal plants had the smallest. • Mycorrhizal plants had significantly lower root to total biomass ratios, especially at elevated temperatures; in contrast, the microbial wash treatment did not affect root to total biomass mass ratio, which remained consistent across sterilized and wash treatments. • CONCLUSIONS • The depression in biomass of mycorrhizal seedlings (ME<1) is an indication of the cost of mycorrhizae (Peng et al. 1993). However, at elevated soil temperatures, the mycorrhizal D. lanuginosum maintained total biomass (ME~1) and increased shoot biomass relative to non-mycorrhizal plants. Increasing shoot biomass without sacrificing total biomass might ultimately increase plant fitness. The mycorrhizal symbiosis appeared mutualistic for D. lanuginosum growing in elevated temperatures. • The mycorrhizae was parasitic for A. scabra under both ambient and elevated temperatures. However, because the A. scabra seed was from a non-thermal area, the data from that species are difficult to interpret. The results may be confounded by species-specific interactions (thermal fungus and non-thermal plant), species' differences (A. scabra vs. D. lanuginosum), or ecotypic variation(thermal A. scabra vs. non-thermal A. scabra). • The benefits of the microbial wash may be attributed to non-mycorrhizal microorganisms (smaller than 8 μm) or hormones present in the soil. • Mycorrhizal plants shifted their carbon allocation pattern, forming significantly shorter and and less massive roots. This phenomenon was more pronounced at elevated temperatures. It is possible that mycorrhizal associations compensate for reduced root mass and, as environmental conditions restrict root growth, (elevated temperatures) this benefit is more valuable. Mycorrhizal D. lanuginosum produced greater shoot biomass in elevated temperatures, which may ultimately increase plant fitness over a period longer than this experiment. Non-mycorrhizal A. scabra Mycorrhizal A. scabra Arbuscules in fine root FUTURE WORK During Summer 2001 we are sampling AM colonization levels across the season, and gathering detailed soil chemistry data at eleven sites in Yellowstone’s Rabbit Creek Basin. The soil pH at these sites varies from 3.5 to 9.4 (1:1 soil:water), and soil temperatures range from 21 to 64ºC. Subsequent analysis will provide concentrations of key elements and nutrients at these sites. The information will enable us to select field sites for subsequent experiments, and appropriate locations for soil and AM fungi collection. We will continue to explore the ecology of mycorrhizae in thermal areas by examining each component of the mycorrhizal symbiosis: • Soil – Measure ME across soil temperatures and chemistry • Fungi - Evaluate AM fungal species diversity in thermal sites • Plant and Fungi - Assess species and ecotypic differences in mycorrhizal functioning for both AM fungi and host plants • Plant and Fungi - Elucidate AM mechanisms in stressful environments ACKNOWLEDGEMENTS Figure 3. Scanning electron microscope (SEM) photograph of a fine root with the tip’s cortical tissue stripped away. Fungal hyphae are visible along the surface of the root. Coupling Energy Dispersive X-ray Spectrometry (EDX) with SEM would allow us to investigate mechanisms of plant tolerance to toxic elements. Figure 4. ME is dependent on soil parameters and plant and fungal ecotypes or species. Thermal Biology Institute Montana Space Grant Consortium Ann McCauley, Emily Davies, Tamara Sperber, Abby Ward, and Sara Zimmerley