UV-B radiation - How burning is it for plants?

In the last twenty years a bulk of papers studying the influence of UW-B radiation on plants was published. The majority of them are the reports on short term experiments, performed mainly under controlled indoor environment; in laboratories, greenhouses and growth chambers. The comparison with outdoor experiments revealed that the damage caused by UV-B appeared to be much higher under indoor conditions, than in field studies. The main reason is that under natural environment all acclimations e.i. changed optical properties of the leaves, accumulation of UV-B absorbing compounds, repair of DNA damage and ability of scavenging of radicals are much more expressed than in indoor experiments. Different authors claim that above all PAR/UV-A/UV-B ratio is of major importance, not only because of photorepair mechanisms, but also because of the costs of other protective mechanisms including synthesis of secondary substances. UV-B radiation will affect the structure and function of the ecosystems. Reliable estimation of the influence of UV-B radiation on ecosystems must base on the long-term outdoor experiments. Agricultural plants appears to be more sensitive since in the past breeding efforts were directed mainly into an increase of the yield of certain cultivar. The potential of these plants to cope with elevated UV-B radiation is still unclear.