ASU SoLS Faculty: Tad Day

Professor Day came to Arizona State University in 1995. Prior to that he held appointments as Assistant Professor of Biology at West Virginia University and staff scientist at the U.S. Department of Agriculture. He received his Ph.D. from Colorado State University and completed postdoctoral studies at the University of Illinois in physiological plant ecology.

Research

In our research we use physiological and ecological approaches to determine how environmental factors influence the performance and distribution of plants. Environmental factors which we have recently addressed include high levels of ultraviolet (UV) and visible light, extreme temperatures and water stress. Our investigations typically contain field work where we assess the importance of these factors in limiting plant performance under natural conditions, and are complimented with a strong laboratory component where we investigate the underlying mechanisms responsible for limitations. We focus on how these factors alter key processes in plants such as photosynthesis, respiration, growth and reproduction.

One area of our research examines how plants respond to enhanced levels of UV light associated with stratospheric ozone depletion. Using techniques such as microscopic fiber-optic light sensors which we can insert into leaves to measure light levels, we have found that plants vary tremendously in their abilities to screen out or filter UV before it reaches sensitive tissue inside their leaves. Some of our current work aims at determining why species are so different in their UV screening abilities, their various adaptations to UV, and what the implications are in terms of performance under enhanced UV found during ozone depletion events. At a more ecological level we have ongoing studies assessing how enhanced ultraviolet levels, as well as global warming, affect terrestrial plants in Antarctica.

Another area of our research assesses the significance of UV-induced blue-green fluorescence in leaves. Certain compounds in leaves absorb UV and release or emit some of this energy inside the leaf as blue-green light. Our preliminary evidence suggests that this blue-green light may improve or drive photosynthesis. We are currently studying the prevalence and variability of this blue-green fluorescence in leaves and quantifying its contribution to photosynthesis.

A third area of our research examines differences in the microclimate of different urban and residential land use patches in central Arizona, and assesses how these differences in microclimate influence the performance of desert plants. Specifically, we are interested in how the temperature regimes of residential patch types such well-watered lawns, desert xeriscapes, asphalt and concrete vary, and how these differences in temperature regime in turn affect photosynthesis, respiration and growth of associated plants in these patches.

Selected Publications

Day, TA & PJ Neale. 2002. Effects of UV-B radiation on terrestrial and aquatic primary producers. Annual Review of Ecology and Systematics 33:371-396.

Convey, P, PJA Pugh, C Jackson, AW Murray, CT Ruhland, FS Xiong & TA Day. 2002. Response of Antarctic terrestrial microarthropods to long-term climate manipulations. Ecology 83:3130-3140.

Day, TA, P Gober, FS Xiong & EA Wentz. 2002. Temporal patterns in near-surface CO2 concentrations over contrasting vegetation types in the Phoenix metropolitan area. Agricultural and Forest Meteorology 110:229-245.

Wentz, EA, P Gober, RC Balling & TA Day. 2002. Spatial patterns and determinants of winter atmospheric carbon dioxide concentrations in an urban environment. Annals of the Association of American Geographers 92:15-28.

Xiong, FS, Ruhland, CT & TA Day. 2002. Effect of springtime ultraviolet-B radiation on growth of Colobanthus quitensis at Palmer Station, Antarctica. Global Change Biology 8:1146-1155.

Morse, LJ, TA Day & SH Faeth. 2002. Effect of Neotyphodium endophyte infection on growth and leaf gas exchange of Arizona fescue under contrasting water availability regimes. Environmental and Experimental Botany 48:257-268.

Johnson, GA & TA Day. 2002. Enhancement of photosynthesis in Sorghum bicolor by ultraviolet radiation. Physiologia Plantarum 116:554-562.

Xiong, F & TA Day. 2001. Effect of solar ultraviolet-B radiation during springtime ozone depletion on photosynthesis and biomass production of Antarctic vascular plants. Plant Physiology 125:738-751.

Day, TA. 2001. Ultraviolet radiation and plant ecosystems. pp 80-117 In: Ecosystems, evolution and ultraviolet radiation. CS Cockell and AR Blaustein (editors). Springer-Verlag, NY.

Ruhland, CT & TA Day. 2001. Size and longevity of seedbanks in Antarctica and the influence of ultraviolet-B radiation on survivorship, growth and pigment concentrations of Colobanthus quitensis seedlings. Environmental and Experimental Botany 45:143-154.

Mantha, SV, GA Johnson & TA Day. 2001. Evidence from action and fluorescence spectra that UV-induced violet-blue-green fluorescence enhances leaf photosynthesis. Photochemistry and Photobiology 73:249-256.

Day, TA, CT Ruhland, & F Xiong. 2001. Influence of solar ultraviolet-B radiation on Antarctic terrestrial plants: results from a 4-year field study. Journal of Photochemistry and Photobiology B: Biology 62:78-87.

Day, TA. 2001. Multiple trophic levels in UV-B assessments - completing the ecosystem. New Phytologist 152:183-186.