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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999

FROM VOLUME 9, NUMBER 9, SEPTEMBER 1996

PROFESSIONAL PUBLICATIONS...
OZONE DEPLETION: UV RADIATION & ITS IMPACTS

Item #d96sep39

"Accumulated Effect of Elevated Ultraviolet-B Radiation over Multiple Generations of the Arid-Environment Annual Dimporphotheca sinuata DC. (Asteraceae)," C.F. Musil (Natl. Botanical Inst., X7, Claremont 7735, Cape Town, S. Africa), Plant, Cell & Environ., 19(9), 1017-1027, Sep. 1996.

Two populations from the same seed batch were cultured under ambient and enhanced UV-B radiation for two generations and subsequently grown an additional generation under both UV influences at different alignments. Overall, D. sinuata performance deteriorated after multiple generations of enhanced UV-B. Results suggest a progressive decline in plant growth and reproduction capacity, which projected over 100 years for stratospheric ozone depletion should have a greater impact on natural communities with relatively short life spans. Plant responses to UV-B reflect existing exposures, but also the exposure of previous generations.

Item #d96sep40

"UV-B Increases (1979-1992) from Decreases in Total Ozone," J.R. Herman (Code 916, NASA-Goddard, Greenbelt MD 20771), P.K. Bhartia et al., Geophys. Res. Lett., 23(16), 2117-2120, Aug. 1, 1996.

Applied several refinements to data from the Nimbus-7 satellite TOMS (Total Ozone Mapping Spectrometer), including a new calibration and correction for reflection of UV by atmospheric clouds and aerosols, to estimate the trend of UV-B over the period. The linear trend of UV determined for various latitude bands is significantly positive poleward of about 40° latitude in both hemispheres, but somewhat moreso in the Southern Hemisphere due to Antarctic ozone depletion. Estimates corresponding values for UV biological impact on DNA, plants, and erythema (skin reddening). For example, the respective trends in exposure values at 45° N in April are 8.6%, 9.8%, and 5.1% per decade. Erythemal UV increases obtained here disagree with previous estimates of a decrease based on ground measurements (Scotto et al., 1988).

Item #d96sep41

"Effects of Enhanced UV-B Radiation on Pea (Pisum sativum L.) Grown Under Field Conditions in the U.K.," R. Mepsted, N.D. Paul (Inst. Environ. Sci., Lancaster Univ., Lancaster LA1 4YQ, UK; e-mail: N.Paul@ lancaster.ac.uk) et al., Global Change Biology, 2(4), 325-334, Aug. 1996.

A new modulated lamp system has successfully provided a UV-B supplement in proportion to ambient levels, and has been used to simulate the environment resulting from an annual mean reduction of stratospheric ozone of 15% under U.K. field conditions. The results, consistent with previous controlled environment experiments, suggest that reduction in yield may be from direct effects of UV-B on plant growth rather than a decrease in photosynthetic capacity.

Item #d96sep42

"Ultraviolet-B Photodestruction of a Light-Harvesting Complex," K. Lao, A.N. Glazer (Dept. Molecular Biol., 229 Stanley Hall, MC 3206, Univ. California, Berkeley CA 94720), Proc. Natl. Acad. Sci., 93(11), 5258-5263, May 1996.

For cyanobacteria, calculations show that light harvesting proteins (phycobiliproteins and chlorophyll proteins) account for >99% of the UV-B absorbed. Presents data on UV-B induced damage to the major cyanobacterial photosynthetic light harvesting complex (the phycobilisome) and to its constituent phycobiliproteins. In photosynthetic organisms, UV-B damage to light harvesting complexes may significantly exceed that to DNA. The laboratory technique used here could provide a field test for UV-B damage to organisms. (See Science, pp. 38-39, July 5, 1996.)

Item #d96sep43

"Atmospheric Modification and Vegetation Responses to Environmental Stress," R.F. Sage (Dept. Botany, Univ. Toronto, Toronto ON M5S 3B2, Can.), Global Change Biol., 2(2), 79-83, Apr. 1996.

Summarizes an international workshop (May 1995, Lake Tahoe, Calif.) with 31 presentations on the current understanding of the interacting effects on plants and soils of: rising CO₂ and drought, salinity, temperature, nutrient deficiency, and ozone and UV-B stress. Consensus statements were formulated on a number of questions, separately by one working group composed of agricultural researchers, and by another consisting of natural systems specialists. Both agreed that increasing land use by humans could easily obscure direct responses of ecosystems to changing atmospheric conditions, and that this factor must be incorporated into estimates of global change impacts.

Item #d96sep44

"Effects of Growth Under Elevated UV-B on Photosynthesis and Isoprene Emission in Quercus gambelii and Mucuna pruriens," P. Harley (NCAR, POB 3000, Boulder CO 80307), G. Deem et al., Global Change Biology, 2(2), 149-154, Apr. 1996.

Describes a preliminary study of possible interactions between elevated UV-B and ground-level ozone production through vegetative production of volatile organic compounds, particularly isoprene. Gambel oak and velvet bean were treated in the field with supplemental UV-B to simulate a 30% ozone depletion. The oak showed significantly greater photosynthesis and isoprene emission in the elevated UV-B treatments when expressed on a leaf area, but not leaf mass, basis. Velvet bean showed no significant effect of UV-B on photosynthesis or isoprene emission.