Disruption of plant microtubules induced by enhanced UV-B radiation is accompanied by cell shrinkage, chromatin condensation, and cytoplasmic vacuolation in both interphase and the mitotic phase (Lytvyn et al., 2010).
Therefore, the mechanism of UV-B radiation-enhanced chromosomal aberrations probably involves injury to microtubule arrays (Gao et al., 2010; Guo et al., 2010).
Thus, periods of prolonged cloudiness and severe smoke pollution could play a role in initiating avian and other influenza outbreaks by attenuating the solar UV-B that might otherwise suppress influenza viruses in outdoor air exposed to sunlight.
Significant reduction in UV-B caused by smoke from biomass burning in Brazil.
The increased penetration of UV-B radiation and resulting harm to microorganisms can thus create a positive feedback, accelerating the removal of DOC.
The present study reports that two additional factors, in addition to increased UV-B from ozone depletion, have reduced DOC in boreal lakes during the 20-year study period: climate warming and acidification have caused declines in DOC, allowing increased penetration of UV-B.
Of those 10, he found that the three with the best ability to repair or resist UV-B radiation were the Pacific tree frog, the Western toad and the Cascades frog.
But each had up to 25 percent more hatchlings when their eggs were shielded with a filter that blocked UV-B radiation.
Perhaps UV-B is being blocked by industrial haze or an increase in cloud cover.
"Why not measure directly the thing that worries you, which is UV-B at the surface, not just reductions in stratospheric ozone?" he asks.
Only a small fraction of previous research on UV-B effects has examined plant reproduction, notes study coauthor Stephan D.
In the test, exposure to UV-B radiation significantly reduced germination in only five species, yet it slowed tube growth in a wide variety of others.
Scientists expect increasing UV-B levels to reach Earth's surface as human-made chlorine chemicals thin the stratospheric ozone layer, which normally absorbs most UV-B.
John DeLuisi of the National Oceanic and Atmospheric Administration in Boulder, Colo., contends the meter was not designed to measure long-term trends in UV-B and says those who use it have yet to prove the device can sustain its accuracy over many years.
UV-B's most important threat to agriculture is that it can inhibit photosynthesis.
