Abstract
A UVB exposure and monitoring system has been established at the Oak Ridge National Laboratory's Global Climate Change Research Facility. The system consists of a power supply, and data acquisition and exposure equipment to accomplish controlled, elevated exposure of terrestrial plants to UVB. Plant biomass, selected compounds that absorb UV radiation, and DNA integrity/damage were measured for two soybean cultivars [Glycine max (L.) Merr.] Forrest and Essex exposed to elevated UVB (32% above ambient) in this system. The biomass of each major plant organ was observed to be less in soybean cultivar Forrest upon exposure to enhanced UVB with the greatest response in seed pods and stems. In contrast, soybean cultivar Essex showed no biomass response to elevated UVB. Enhanced UVB caused significant (P < 0.1) changes in concentrations of UV-absorbing compounds in both soybean cultivars. The Essex cultivar had an increase in UV-absorbing compounds, whereas a decline was observed for soybean Forrest. There was a decrease in the integrity of DNA, as measured by strand breaks, from both cultivars at 30 and 52 days to exposure. DNA pyrimidine dimers in isolated plant DNA were measured with Micrococcus luteus UV endonuclease. DNA from soybean Forrest exposed to UVB and sampled at 30 and 52 days of exposure had significantly greater (P<0.05) pyrimidine dimer concentration (dimer frequency ≈ 1 dimer per 28,000 DNA bases) than either cultivar exposed to UV treatment for 1 day or Essex at days 30-52 (dimer frequencies < /1 per 120,000 bases of DNA). Decrease in DNA integrity and biomass production in Forrest under elevated UVB may be related to the inability to maintain high concentrations of UV-absorbing compounds in leaves. The tolerant cultivar Essex increased the concentratio of UV-absorbing compounds while maintaining biomass production and DNA integrity under elevated UVB.
| Original language | English |
|---|---|
| Pages (from-to) | 347-356 |
| Number of pages | 10 |
| Journal | Environmental and Experimental Botany |
| Volume | 33 |
| Issue number | 3 |
| DOIs | |
| State | Published - Jul 1993 |
Funding
In conclusion, exposure of two cultivars of soybean plants was accomplished with a UVB exposure apparatus designed to deliver a specified but adjustable level of UVB radiation over an approximately 2-month period during which the plants were actively growing. Within this exposure period several physiological and biochemical parameters were examined and evaluated to determine whether or not UV light was penetrating the plant tissue and interacting or intert~ring with cellular processes. Changes in biomass and UV-absorbing compounds as well as potentially deleterious damaging events to the DNA were documented. Although enhanced UVB radiation exposure (32%) was simulated for the year 2020 based on current calculations of the rate of stratospheric ozone loss,/~2/ it should be noted that recent reports indicate that the loss of stratospheric ozone is occurring at a faster rate than anticipated and the degree of UVB enhancement simulated in this study may be reached by the turn of the century./4/ Acknowledgments This project was funded by the Oak Ridge National Laboratory (ORNL) Director's R & D Program and sponsored in part by an appointment of the senior author to the U.S. Department of Energy Laboratory Cooperative Postgraduate Research Training Program administered by the Oak Ridge Institute for Science and Education. The Oak Ridge National Laboratory is operated by Martin Marietta Energy Systems under contract DE-AC05-84OR21400 with the U.S. Department of Energy. We thank Kelly Roy, Denise Kay, David Morgan, and Kitty McCracken for technical assistance in data collection and analysis. This is Environmental Sciences Division Publication No. 4078.
Keywords
- DNA damage
- UV-absorbing compounds
- UVB radiation
- biomass
- soybean