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Lolium perenne (cv. AberDart) was grown at 14 locations along a latitudinal gradient across Europe (37-68°N) to study the impact of ultraviolet radiation (UV) and climate on aboveground growth and foliar UV-B absorbing compounds. At each location, plants were grown outdoors for 5 weeks in a replicated UV-B filtration experiment consisting of open, UV-B transparent (cellulose diacetate) and UV-B opaque (polyester) environments. Fourier transform-infrared spectroscopy was used to compare plant metabolite profiles in relation to treatment and location. UV radiation and climatic parameters were determined for each location from online sources and the data were assessed using a combination of anova and multiple regression analyses. Most of the variation in growth between the locations was attributable to the combination of climatic parameters, with minimum temperature identified as an important growth constraint. However, no single environmental parameter could consistently account for the variability in plant growth. Concentrations of foliar UV-B absorbing compounds showed a positive trend with solar UV across the latitudinal gradient; however, this relationship was not consistent in all treatments. The most striking experimental outcome from this study was the effect of presence or absence of filtration frames on UV-absorbing compounds. Overall, the study demonstrates the value of an European approach in studying the impacts of natural UV across a large latitudinal gradient. We have shown the feasibility of coordinated UV filtration at multiple sites but have also highlighted the need for open controls and careful interpretation of plant responses., (Copyright © Physiologia Plantarum 2012.)

UV-B radiation and elevated CO₂ may impact rhizosphere processes through altered below-ground plant resource allocation and root exudation, changes that may have implications for nutrient acquisition. As nutrients limit plant growth in many habitats, their supply may dictate plant response under elevated CO₂. This study investigated UV-B exposure and elevated CO₂ effects, including interactions, on plant growth, tissue chemistry and rooting responses relating to P acquisition. The sub-arctic grass Calamagrostis purpurea was subjected to UV-B (0 or 3.04 kJ m⁻² day⁻¹) and CO₂ (ambient 380 or 650 ppmv) treatments in a factorial glasshouse experiment, with sparingly soluble P (0 or 0.152 mg P per plant as FePO₄) a further factor. It was hypothesized that UV-B exposure and elevated CO₂would change plant resource allocation, with CO₂ mitigating adverse responses to UV-B exposure and aiding P uptake. Plant biomass and morphology, tissue composition and rhizosphere leachate properties were measured. UV-B directly affected chemical composition of shoots and interacted with CO₂ to give a greater root biomass. Elevated CO₂ altered the composition of both shoots and roots and increased shoot biomass and secondary root length, while leachate pH decreased. Below-ground responses to CO₂ did not affect P acquisition although P limitation progressively reduced leachate pH and increased secondary root length. Although direct plant growth, foliar composition and below-ground nutrient acquisition responses were dominated by CO₂ treatments, UV-B modified these CO₂ responses significantly. These interactions have implications for plant responses to future atmospheric conditions., (Copyright © Physiologia Plantarum 2012.)