Ozone depletion and UVB radiation: Impact on plant DNA damage in southern South America

ROUSSEAUX, M. C.; BALLARE, C. L.; GIORDANO, C. V.; SCOPEL, A.L.; ZIMA, A. M.; SZWARBERG-BRACCHITTA, M.; SEARLES, P.S; CALDWELL, M.M.; DIAZ, S. B.

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA

NATL ACAD SCIENCES

Año: 1999 vol. 96 p. 15310 - 15315

0027-8424

The primary motivation behind the considerable effort in studyingstratospheric ozone depletion is the potential for biological consequencesof increased solar UVB (280–315 nm) radiation. Yet,direct links between ozone depletion and biological impacts havebeen established only for organisms of Antarctic waters under theinfluence of the ozone ‘‘hole;’’ no direct evidence exists thatozone-related variations in UVB affect ecosystems of temperatelatitudes. Indeed, calculations based on laboratory studies withplants suggest that the biological impact of ozone depletion(measured by the formation of cyclobutane pyrimidine dimers inDNA) is likely to be less marked than previously thought, becauseUVA quanta (315–400 nm) may also cause significant damage, andUVA is unaffected by ozone depletion. Herein, we show that thetemperate ecosystems of southern South America have beensubjected to increasingly high levels of ozone depletion during thelast decade. We found that in the spring of 1997, despite frequentcloud cover, the passages of the ozone hole over Tierra del Fuego(55° S) caused concomitant increases in solar UV and that theenhanced ground-level UV led to significant increases in DNAdamage in the native plant Gunnera magellanica. The fluctuationsin solar UV explained a large proportion of the variation in DNAdamage (up to 68%), particularly when the solar UV was weightedfor biological effectiveness according to action spectra that assumea sharp decline in quantum efficiency with increasing wavelengthfrom the UVB into the UVA regions of the spectrum.cyclobutane pyrimidine dimer u global change u Gunnera u Tierra