[The effect of medium-wave UV-radiation on the photosynthetic apparatus and the productivity of higher plants].

In laboratory and field experiments, the effect of medium-wave (290-320 nm) UV-radiation (UV-B) on the build-up of photosynthetic pigments, growth and productivity of higher plants was investigated. It was found that UV-B of 5-9 W/m2 in intensity applied daily (at a daily dose of 15-20 kJ/m2) or singly (at a daily dose of 24 or 36 kJ/m2) inhibited the formation of chloroplast pigments. The pattern and magnitude of changes depended on the plant species and leaf age. The degree of photosynthetic changes and plant resistance to UV-radiation were closely correlated. In field experiments (daily irradiation with 0.6 W/m2 at a dose of 12-13 kJ/m2/day), UV-B suppressed the growth and yield of cotton and soybean plants. This exposure modified chloroplasts of soybean plants and inhibited their growth to a greater extent than that of cotton plants. The factors responsible for the species-related specificity of UV-B resistance of higher plants are discussed and approaches to its evaluation based on the pigment apparatus of photosynthesis are described.