[Plant reaction to elevated ultraviolet irradiation: potential impacts of stratospheric ozone depletion]

The ozone layer depletion evokes the increase of solar UV-B radiation intensity and corresponding reductions of growth (height, leaf area, fresh and dry weight), photosynthetic activity and flowering in higher plants. Competitive interactions also may be altered indirectly by differential growth responses. The UV-B-sensitivity of plants varies both among species and among cultivars of a given species. Photosynthetic activity may be reduced by direct effects on the photosynthetic process or metabolic pathways, or indirectly through effects on photosynthetic pigments or stomatal function. Plants may also respond by accumulating UV-absorbing compounds in their outer tissue layers, which presumably protect sensitive target from UV-damage. The key enzymes in the biosynthetic pathways of these compounds are specifically induced by UV-B irradiation via gene activation. The effects of UV-B radiation on plants can be modified by prevailing microclimatic conditions. Plants tend to be less sensitive to UV-B under drought or mineral deficiency, while sensitivity increases under low levels of visible light. Prognoses of agricultural yield reduction and economic loss for different scenarious of stratospheric ozone depletion are presented.