SENSITIVITY TO UV-B OF PLANTS GROWING IN DIFFERENT ALTITUDES IN THE ALPS

The purpose of our investigations was to elucidate whether different s pecies of the same genus growing preferentially in different altitudes have a genetically fixed different sensitivity to ultraviolet B (UV-B , 280-320 nn), possibly by selection, and/or whether they have a diffe rent ability to adapt to UV-B. Plants from species pairs or triplets o f 5 genera were grown from seeds without or with additional UV-B. Sens itivity was tested in a growth chamber with UV-B-irradiation in additi on to white light by estimation of visible injury. Content and accumul ation of UV-absorbing compounds were measured from leaf extracts. In p lants grown without UV-B to a cushion there were marked differences in the sensitivity to UV-B between different genera. Different species o f the same genus showed only slight differences in sensitivity but in 2 genera the alpine species exhibited a better adaptation after UV-B p re-irradiation. UV-B enhanced the accumulation of UV-absorbing substan ces to different amounts. Marked differences in the sensitivity to UV- B between different genera may lead to a change in ecosystems should t he natural UV-B-radiation increase.