UV-C irradiation effects on young tomato plants: Preliminary results

Ultraviolet-C radiation (UV-C = 100-280 nm) is strongly affected by ozone levels, so that the amount of this radiation reaching the Earth's surface is extremely low. In the future, UV-C radiation is expected to increase as the result of stratospheric ozone depletion due to atmospheric pollution, with strong negative effects on economically important crops. To assess the effect of UV-C irradiation on young tomato plants (Lycopersicon esculentum Mill.; cv Cuore di bue), an experiment was conducted in controlled conditions, using a black chamber equipped with an UV-C lamp. Tomato plants were divided in four groups on the basis of UV-C irradiation time (10, 30, 60, and 120 min), and non-irradiated plants were kept as controls. Plant gas exchange, leaf color and morphologic traits were recorded before and after UV-C treatments. The photosynthetic apparatus was influenced by UV-C treatment, as shown by the strong increase in intracellular CO2, particularly evident in the 120 min treatment (338 μL L–1). This was due both to the stomatal and non-stomatal inhibition of the assimilation activity due to UV-C exposure. In 10 and 30-min treated plants, leaf color, measured immediately after the irradiation, did not statistically change, whereas the 60 and 120-min treatments were characterized by a deep senescence with a general stem and leaf yellowing. The results demonstrate that high UV-C doses determined irreversible damages, both at physiological and morphological levels, that lead plants to death, whereas lower irradiations (up to 60 min) allowed plants to partially recovery their normal physiological status.