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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
OZONE DEPLETION: UV RADIATION & ITS IMPACTS
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.
(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).
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.
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.)
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.
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
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