Copper and lead trigger distinct responses in two Brazilian mosses

Abstract Metal contamination, particularly by copper (Cu) and lead (Pb), is a persistent environmental threat, yet the adaptive responses of Neotropical bryophytes to such stressors remain largely unexplored. This study evaluated biomass production, photosynthetic performance, and metal accumulation in two native Brazilian mosses ( Campylopus savannarum (Müll.Hal.) Mitt. and Polytrichum juniperinum Willd. ex Hedw.) exposed to increasing concentrations of Cu and Pb under controlled laboratory conditions. We hypothesized that their contrasting morpho-anatomical traits, especially differences in lamellae structure, photosynthetic surface organization, and the presence of conduction tissues, would lead to distinct physiological strategies of metal tolerance. At the end of 240 days, biomass and maximum quantum efficiency of PSII ( Fv/Fm ) were assessed, and tissue metal concentrations were quantified. The moss P. juniperinum exhibited remarkable tolerance, maintaining stable biomass and photosynthetic capacity across all treatments, while C. savannarum presented pronounced declines, especially under high Pb exposure. Both species displayed dose-dependent metal accumulation but with distinct patterns: C. savannarum accumulated nearly 196-fold more Cu at the highest treatment compared to the control, whereas P. juniperinum stored about 44-fold more Pb than the control. These contrasting responses likely reflect species-specific strategies of metal tolerance. These results position Neotropical mosses as valuable bioindicators and potential agents for generating genomic data to improve our understanding of metal tolerance in bryophytes. Future research should investigate tissue-concentration metal partitioning and the molecular mechanisms underlying tolerance in native Brazilian bryophytes.