Methodology for comprehensive evaluation of UV-B tolerance in trees

Decreasing stratospheric ozone concentrations have led to concern for an enhanced UV-B radiation (wavelength range of 280-315 nm) reaching the earth's surface. An understanding of the mechanism of UV-B radiation tolerance and sensitivity may improve our ability to assess the potential effects of changes in solar UV-B radiation on plant species. The purpose of this research was to conduct an assessment of tolerance of southern trees to future enhanced UV-B radiation. This paper describes the systematic approach developed for such an assessment and the preliminary results associated with thirty-five broadleaf tree species in the south studied during two growing seasons. Results indicated that the diverse trees in the south possessed various biological characteristics in defense of UV-B damage. It is suggested that the approach to comprehensive evaluation of UV-B tolerance in diverse trees should focus on leaf optical properties, mainly depth of light penetration into leaves, leaf anatomical and morphological changes, and concentration of leaf UV-B absorbing compounds during leaf development.