Enhanced UV-B radiation under field conditions increases anthocyanin and reduces the risk of photoinhibition but does not affect growth in the carnivorous plant Pinguicula vulgaris

The effects of enhanced UV-B radiation were investigated in the carnivorous plant Pinguicula vulgaris in a field experiment performed in Abisko, North Sweden (68° 21« N, 18° 49« E, 380 m above sea level). Potted plants were exposed to either ambient or ambient plus supplemental UV-B radiation, simulating a 15% ozone depletion. No effect was observed on either the epicuticular (external) or cellular (internal) UV absorbing capacity of the leaves. However, the anthocyanin content was more than doubled by supplemental UV-B radiation. In laboratory experiments, the anthocyanin rich, UV-B treated leaves were less susceptible to a low temperature}high light photoinhibitory treatment, as judged by in vivo chlorophyll fluorescence measurements. Yet, this potential benefit did not considerably affect the growth of the plant in the field (leaf area and dry mass, reproductive dry mass, flowering frequency, senescence rates, dry mass of winter buds). However, there was a marginally significant increase in root dry mass and in the root to shoot ratio, which may underlie the significant increase in the nitrogen content of the leaves. We suggest that P. vulgaris is resistant against UV-B radiation damage and that the possible negative effects of additional UV-B radiation on the growth of these plants may have been effectively counterbalanced by the lower risk of photoinhibition, due to the concomitant increase in anthocyanins.