It follows from negative plant growth response that the solar UV-B wavelengths that penetrate the ozone layer
(≥286 nm), in contrast to those absorbed (< 286 nm), must leave growth inhibition fingerprints on plants.
These fingerprints are expected from the growth of the Sphagnum genus, which are dominant in boreal and
subarctic peatlands and have increased sensitivity to ambient UV-B. To test this hypothesis, we analysed the
response of the daily growth rates of Sphagnum riparium measured over four years to solar UV radiation of
200–310 nm wavelengths recorded outside the Earth's atmosphere by SORCE satellite. We found that only
wavelengths longer than 286 nm inhibit Sphagnum growth, while shorter wavelengths do not affect growth
process. The data precisely correspond to the physical data on the specific wavelengths reaching the Earth’s
surface. Based on the universal UVR8-dependent mechanism of UV-B perception in plants, we concluded that
plants with increased UV sensitivity have indicator potential for the evaluation of the penetration of the shortest
solar UV wavelengths through the ozone layer.