Meeting Abstract
Plants have mechanisms to sense dangerous ultraviolet radiation and regulate their responses to changes in their light environment. In particular, plants exposed to UV-B (280 to 315 nm), which includes photons of the highest energy levels found in sunlight, display unique responses such as inhibited growth and production of UV-protecting pigments. These responses may be permanent or transitory. Persistence of plant responses to a reduction in UV radiation in field setting was studied as follows. Texas grasses were placed, in full sunlight, under two filters: aclar, which is UV transparent, and cellulose acetate, which blocks almost all energy at wavelengths shorter than 300nm. The immediate and long-term effects of high energy UV-B radiation on plant function were tested using UV absorbance spectra taken from leaf pigment extracts and reflectance spectrophotometry of leaves. Both spectra were taken three times for each test plot, once at the beginning of the experiment, once after the treatment period, and once after two weeks of recovery. Results from rural and urban field sites in addition to greenhouse studies support that exposure to UV radiation sometimes leads to changes in leaf structure and composition that can persist after treatment concludes. However, this result is not identical across species or field sites. For instance, the Bandera county sideoats grama (Bouteloua curtipendula) extracts exhibited lower absorption in the 300-320 nm band after treatment than before treatment, but for Travis county sideoats grama there were no differences between initial, treatment, and recovery absorbance readings. These results indicate that under different circumstances as yet unidentified, grasses of even the same species exhibit different responses to UV-B radiation.
