POTENTIAL EFFECTS OF UV-B ON PHOTOSYNTHESIS AND PHOTOSYNTHETIC PRODUCTIVITY OF HIGHER PLANTS

摘要

The effects of UV-B radiation on photosynthesis and photosynthetic productivity of higher plants are reviewed. When plants were exposed to large UV-B doses in a glasshouse in order to study the mechanistic basis of UV-B-induced inhibition of photosynthesis, direct effects on stomata and on Calvin cycle enzymes (i.e. large decreases in ribulose-1,5-bisphosphate carboxylase/oxygenase and in sedoheptulose-1,7-bisphosphate) without any significant effect on photosystem II were observed. When plants were continuously grown and developed under UV-B in a glasshouse, exposure to UV-B only decreased adaxial stomatal conductance (g_s) of the leaves and consequently increased the stomatal limitation of CO_2 uptake. Furthermore, field studies using realistic UV-B levels (i.e. a predicted 30% increase in this radiation) demonstrate a lack of UV-B effects on photosynthesis or on plant biomass. It is concluded that any predicted future increase in UV-B irradiation is unlikely to have a significant impact on the photosynthetic characteristics and productivity of higher plants.