Impacts of long-term enhanced UV-B radiation on bryophytes in two sub-Arctic heathlands of contrasting water availability

• Published in: Annals of Botany
• Main Authors: Arróniz-Crespo, M., Gwynn-Jones, D., Callaghan, T.V., Núñez-Olivera, E., Martínez-Abaigar, J., Horton, P., Phoenix, G.K.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2011
• Subjects: chlorophyll fluorescence; Enhanced long-term UV-B; sporophytes; sub-Arctic bryophytes; water availability; xanthophylls; Arctic
• Online Access: https://investigacion.unirioja.es/documentos/5bbc697bb750603269e81bf0; https://doi.org/10.1093/AOB/MCR178

Background and Aims: Anthropogenic depletion of stratospheric ozone in Arctic latitudes has resulted in an increase of ultraviolet-B radiation (UV-B) reaching the biosphere. UV-B exposure is known to reduce above-ground biomass and plant height, to increase DNA damage and cause accumulation of UV-absorbing compounds in polar plants. However, many studies on Arctic mosses tended to be inconclusive. The importance of different water availability in influencing UV-B impacts on lower plants in the Arctic has been poorly explored and might partially explain the observed wide variation of responses, given the importance of water in controlling bryophyte physiology. This study aimed to assess the long-term responses of three common sub-Arctic bryophytes to enhanced UV-B radiation (+UV-B) and to elucidate the influence of water supply on those responses. Methods: Responses of three sub-Arctic bryophytes (the mosses Hylocomium splendens and Polytrichum commune and the liverwort Barbilophozia lycopodioides) to +UV-B for 15 and 13 years were studied in two field experiments using lamps for UV-B enhancement with identical design and located in neighbouring areas with contrasting water availability (naturally mesic and drier sites). Responses evaluated included bryophyte abundance, growth, sporophyte production and sclerophylly; cellular protection by accumulation of UV-absorbing compounds, -carotene, xanthophylls and development of non-photochemical quenching (NPQ); and impacts on photosynthesis performance by maximum quantum yield (F v/F m) and electron transport rate (ETR) through photosystem II (PSII) and chlorophyll concentrations. Results: Responses were species specific: H. splendens responded most to +UV-B, with reduction in both annual growth (-22%) and sporophyte production (-44%), together with increased -carotene, violaxanthin, total chlorophyll and NPQ, and decreased zeaxanthin and de-epoxidation of the xanthophyll cycle pool (DES). Barbilophozia lycopodioides responded less to +UV-B, showing increased -carotene ...