The Effects of Solar UV-B Radiation (280–315 nm) on Higher Plants: Implications of Stratospheric Ozone Reduction

Summary

For each 1% reduction in the atmospheric ozone column there would be a predictable increase of approximately 2% in solar UV-B radiation weighted for biological effectiveness, UV-B_BE. Yet, physiological manifestations reflecting the net unrepaired damage to higher plants would not necessarily increase as a linear function of the UV-B_BE enhancement. Recent evidence shows that for impairment of photosynthetic capacity, the response to UV-B_BE was quite nonlinear. There was, however, no apparent threshold of UV-B_BE to which the plants must be exposed before photosynthetic damage ensued and reciprocity in the response to UV-B applied over a considerable period of time. If the accumulative mode of damage to the photosynthetic apparatus is generally applicable to higher plants, even moderately UV-B resistant species may be affected by small increases in UV-B radiation, if such species possess long-lived leaves which are exposed to full sunlight. Because higher plant species appear to be differentially sensitive to UV-B radiation, the ecological significance of ozone reduction may lie more in changes in the competitive balance of species rather than in reduced primary productivity per se. The differential UV-B sensitivity of higher plant species may be related to the optical properties of tissues covering physiological targets and the efficacy of repair mechanisms.