Field testing of biological spectral weighting functions for induction of UV-absorbing compounds in higher plants

Action spectra are typically used as biological spectral weighting functions (BSWF) in biological research on the stratospheric ozone depletion issue. Despite their critical role in determining the amount of UV supplied in experiments, there has been only limited testing of different functions under realistic field conditions. Here, we calculate effective radiation according to five published BSWF and evaluate the appropriateness of these BSWF in representing the induction of UV-absorbing compounds. Experiments were carried out in the field using both ultraviolet-B radiation (280-320 nm) supplementation and selective filtering of solar UV radiation. For the four species tested, BSWF that extend into the ultraviolet-A radiation (320-400 nm) (UV-A) with moderate effectiveness best represented the observed results. When compared with the commonly used generalized plant response, these BSWF suggest that simulations of ozone depletion will require more radiation than in the past experiments. However, they imply lower radiation supplements than a new plant growth BSWF that has a greater emphasis on UV-A wavelengths.