Graphene-based materials (GBMs) are currently under careful examination due to their potential impact on health and environment. Over the last few years, ecotoxicology has started to analyze all the potential issues related to GBMs and their possible consequences on living organisms. These topics are critically considered in this comprehensive review along with some considerations about future perspectives. RECEIVED

This study investigates how hydration during light and dark periods influences growth in two epiphytic old forest lichens, the green algal Lobaria pulmonaria and the cyanobacterial L. scrobiculata. The lichens were cultivated in growth chambers for 14 days (200 μmol m(-1) s(-2); 12 h photoperiod) at four temperature regimes (25/20 °C, 21/16 °C, 13/8 °C, and 6/1 °C; day/night temperatures) and two hydration regimes (12 h day-time hydration; 12 h day-time + 12 h night-time hydration). Growth was highly dynamic, showing that short-term growth experiments in growth cabinets have a high, but largely unexplored potential in functional lichen studies. The highest measured growth rates were not far from the maximal dry matter gain estimated from published net photosynthetic CO2 uptake data. For the entire data set, photobiont type, temperature, hydration regime and specific thallus mass accounted for 46.6 % of the variation in relative growth rate (RGR). Both species showed substantially higher relative growth rates based on both biomass (RGR) and thallus area (RTAGR) when they were hydrated day and night compared to hydration in light only. Chronic photoinhibition was substantial in thalli hydrated only during the day time and kept at the highest and lowest temperature regimes, resulting in exponential increases in RGR with increasing maximal PSII efficiency (F v/F m) in both species. However, the depression in F v/F m was stronger for the cyanolichen than for the cephalolichen at extreme temperatures. The growth-stimulating effect of night-time hydration suggests that nocturnal metabolic activity improves recovery of photoinhibition and/or enhances the conversion rate of photosynthates into thallus extension.

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We investigated altitudinal variation (550–1650 m) in relative growth rates (RGR) and carbon-based secondary compounds (CBSC) in the cephalolichen Lobaria pulmonaria (L.) Hoffm. and the chlorolichen Hypogymnia occidentalis L. H. Pike transplanted for 14 months in a U-shaped valley in inland southern British Columbia. Prior to transplantation, half of the thalli were treated with phosphorus (P) to examine effects of P on carbon allocation. Growth in L. pulmonaria was substantially higher in the toe-slope position, corresponding to much higher bark pH. Sixty-four percent of the variation in RGR was accounted for by positive pH effects and adverse effects of direct light exposure in the best subset multiple regression model. For H. occidentalis, 57% of the variation in RGR was accounted for by positive and negative effects of indirect and direct light, respectively. Neither altitude nor P had a noticeable effect on RGR, the former possibly reflecting a trade-off between orographic precipitation and inversion-boosted nocturnal dew in valley bottom localities. Neither was there any correlation between altitude and CBSCs, although treatment with P did significantly trigger secondary metabolism in L. pulmonaria, but not in H. occidentalis. No significant intraspecific relationship between growth and CBSC investments was noted.

Relative growth rates (RGR) and carbon-based secondary compounds (CBSCs) were quantified in four dominant terricolous arctic-alpine mat-forming lichens with different preferences for snow cover. The aim was to evaluate the effects of snow depth, and thus snow cover duration, on lichen growth and performance. The species,Alectoria ochroleuca,Flavocetraria nivalis,Cladonia mitisandCetrariella delisei, are associated with increasing snow depth, respectively. They were transplanted for one year at five snow depths (0, 60, 120, 160 and 200 cm measured in early May) along each of four natural ridge to snow bed gradient transects in oceanic-alpine sites (western Norway). Snow slightly thicker than in source habitats caused negative RGR in the ridge top-dependentA. ochroleucaand the co-occurringF. nivaliswith somewhat higher snow tolerance. OnlyC. mitiswith the broadest ecological niche had positive RGR along most of the gradients (0–160 cm), even outside its natural range. The most snow-tolerant species,C. delisei, tolerant also to temporal inundation in water, had the lowest RGR. Nevertheless, it performed as well in places with little or no snow as in places where it grows naturally. Snow depth significantly affected total concentrations of CBSCs mainly inA. ochroleuca, which experienced substantial mass loss under snow. There was a highly significant increase in usnic acid concentration with increasing mass loss inA. ochroleuca, probably because usnic acid decays more slowly than other components. In conclusion, snow reduced lichen RGR, but in species-specific ways. Therefore, increasing snow depthper sealong spatial and/or temporal scales likely reduces abundance and distribution of dominant mat-forming lichens in the alpine ecosystems of Scandinavia.