Bryophyte Tissues Research Articles

Bryophytes enhance nitrogen content in decaying wood via biological interactions

AbstractAn increase in the nitrogen (N) content in coarse woody debris (CWD) facilitates its decomposition, affecting the cycling of N and other nutrients in forest ecosystems. Bryophytes may increase the N content by transferring the N in bryophyte tissues to the underlying CWD. This study examined whether and how bryophytes increase N content in the underlying CWD using N‐stable isotope ratios (δ15N) as tracers for N sources. The N content and δ15N values in CWD with bryophytes were significantly higher than those in CWD without bryophytes. However, the δ15N values in CWD with bryophytes differed significantly from those in bryophytes on CWD, demonstrating that the N in bryophytes did not cause the increase in N content in CWD. The analyses using δ15N further indicated that the high N content in CWD with bryophytes may be attributed to increased N supply from wood‐decomposing fungi and N‐fixing bacteria. This increase in N content may result from the enhanced moisture content in CWD beneath bryophytes, which facilitates the activity of wood‐decomposing fungi and N‐fixing bacteria. Notably, the influence of bryophytes on the N content in CWD differed between bryophyte life forms: bryophytes that form dense mats increased the N content in CWD, whereas those with loose mats decreased the N content. This difference can be explained by the greater humidity experienced by CWD with bryophytes forming dense mats than that experienced by CWD with bryophytes forming loose mats. Given that the N content in CWD affects the decay processes, the results highlight the importance of biological interactions associated with bryophytes in forest ecosystems.

Potentially toxic element accumulation of bryophyte taxa in contaminated soils at Tak Province, Thailand

Three sampling locations, Mae Sot National Forest, Pha Daeng waterfall, and agricultural land in Pha De, were representative locations in contaminated areas for determining bryophyte communities and their potentially toxic element (PTE) accumulation capacity. A total of 18 bryophyte taxa from 10 genera and 10 families were recorded. Fissidentaceae is the dominant family in the study area. Pollution load index (PLI) indicated that anthropogenic activities, particularly zinc (Zn) mining activities were key causes of PTE pollution in soils, particularly cadmium (Cd) and Zn. The order of Cd and Zn concentrations in bryophyte tissue as a function of sampling location was: agricultural area > waterfall > forest, where PTEs in bryophyte tissue were in the order Zn > Cd. Bryum coronatum showed significant Zn accumulation (>300,000 mg kg−1), while Philonotis thwaitessii had substantial Cd accumulation (50 mg kg−1). Principal component analysis (PCA) indicated that P. thwaitessii and Fissidens involutus had high correlation with Cd and Zn, which might be used as bioindicators in the Cd and Zn co-contaminated area. According to X-ray fluorescence analysis, the order of atomic percentage elemental composition in plant tissue was: Al > Fe > Pb > Cd > Zn > Cu > Ni > Cr > Mn. When taking Cd contents in phyllidium surfaces of bryophyte taxa into account, P. thwaitessii, Notothylas javanica and Splachnobryum oorschotii may serve as phytoremediators of Cd because their percentage atomic Cd values were>10 %, and whole plant tissues had Cd concentrations exceeding 10 mg kg−1. In light of its capacity for Cd phytoremediation and biomonitoring, P. thwaitessii may be the most suitable bryophyte taxon in the Mae Tao River Basin.

Auxin Biology in Bryophyta: A Simple Platform with Versatile Functions.

Bryophytes, including liverworts, mosses, and hornworts, are gametophyte-dominant land plants that are derived from a common ancestor and underwent independent evolution from the sporophyte-dominant vascular plants since their divergence. The plant hormone auxin has been shown to play pleiotropic roles in the haploid bodies of bryophytes. Pharmacological and chemical studies identified conserved auxin molecules, their inactivated forms, and auxin transport in bryophyte tissues. Recent genomic and molecular biological studies show deep conservation of components and their functions in auxin biosynthesis, inactivation, transport, and signaling in land plants. Low genetic redundancy in model bryophytes enable unique assays, which are elucidating the design principles of the auxin signaling pathway. In this article, the physiological roles of auxin and regulatory mechanisms of gene expression and development by auxin in Bryophyta are reviewed.

Ecological stoichiometry of the epiphyte community in a subtropical forest canopy.

Epiphytes in tree canopies make a considerable contribution to the species diversity, aboveground biomass, and nutrient pools in forest ecosystems. However, the nutrient status of epiphytes and their possible adaptations to nutrient deficiencies in the forest canopy remain unclear. Therefore, we analyzed the stoichiometry of five macroelements (C, N, P, K, and Ca) in four taxonomic groups (lichens, bryophytes, ferns, and spermatophytes) to investigate this issue in a subtropical montane moist evergreen broad‐leaved forest in Southwest China. We found that the interspecific variations in element concentrations and mass ratios were generally greater than the intraspecific variations. And there were significant stoichiometric differences among functional groups. Allometric relationships between N and P across the epiphyte community indicated that P might be in greater demand than N with an increase in nutrients. Although canopy nutrients were deficient, most epiphytes could still maintain high N and P concentrations and low N:P ratios. Moreover, ferns and spermatophytes allocated more limited nutrients to leaves than to stems and roots. To alleviate frequent drought stress in the forest canopy, vascular epiphytes maintained several times higher K concentrations in their leaves than in the tissues of lichens and bryophytes. Our results suggest that epiphytes may have evolved specific nutrient characteristics and adaptations, so that they can distribute in heterogeneous canopy habitats and maintain the stability of nutrient metabolism.

Evolution of phytolith deposition in modern bryophytes, and implications for the fossil record and influence on silica cycle in early land plant evolution.

Anecdotal evidence indicating substantial silica accumulation in tissues of bryophytes suggests that silica (phytolith) deposition evolved early on in embryophytes. To test this hypothesis, we conducted the first survey of phytolith content representing the major liverwort, moss and hornwort clades. We also assessed the diagnostic value of bryophyte phytoliths. Silica extracted from bryophyte material through wet-ashing was described, focusing on abundance, classifying taxa as nonproducers, light producers and higher producers; and phytolith morphotypes. Ancestral state reconstruction of these characters was performed for mosses and liverworts using published phylogenies. Phytoliths are present in multiple subclades within liverworts, mosses and hornworts, but these phyla were not ancestrally high silica-producers. Higher deposition occurs in liverworts and mosses with specialized water-conducting cells. We hypothesize that active, high silica accumulation was not ancestral for embryophytes, but became possible in clades with increased water conductance. Phytoliths of diagnostic structures (e.g. pegged rhizoids) could help track bryophyte clades or water conductance evolution in the fossil record.

Evolutionary conservation of structure and function of the UVR8 photoreceptor from the liverwort Marchantia polymorpha and the moss Physcomitrella patens.

The ultraviolet-B (UV-B) photoreceptor UV RESISTANCE LOCUS 8 (UVR8) mediates photomorphogenic responses to UV-B in Arabidopsis through differential gene expression, but little is known about UVR8 in other species. Bryophyte lineages were the earliest diverging embryophytes, thus being the first plants facing the UV-B regime typical of land. We therefore examined whether liverwort and moss species have functional UVR8 proteins and whether they are regulated similarly to Arabidopsis UVR8. We examined the expression, dimer/monomer status, cellular localisation and function of Marchantia polymorpha and Physcomitrella patens UVR8 in experiments with bryophyte tissue and expression of green fluorescent protein (GFP)-UVR8 fusions in Nicotiana leaves and transgenic Arabidopsis. P. patens expresses two UVR8 genes that encode functional proteins, whereas the single M.polymorpha UVR8 gene expresses two transcripts by alternative splicing that encode functional UVR8 variants. P.patens UVR8 proteins form dimers that monomerise and accumulate in the nucleus following UV-B exposure, similar to Arabidopsis UVR8, but M.polymorpha UVR8 has weaker dimers and the proteins appear more constitutively nuclear. We conclude that liverwort and moss species produce functional UVR8 proteins. Although there are differences in expression and regulation of P.patens and M.polymorpha UVR8, the mechanism of UVR8 action is strongly conserved in evolution.

An optimised clearing protocol for the quantitative assessment of sub-epidermal ovule tissues within whole cereal pistils

BackgroundSeed development in the angiosperms requires the production of a female gametophyte (embryo sac) within the ovule. Many aspects of female reproductive development in cereal crops are yet to be described, largely due to the technical difficulty in obtaining phenotypic information at the cellular or sub-cellular level. Hoyer’s solution is currently well established as a solution for clearing thin tissues samples, such as sections or whole tissues of bryophytes, mycorrhizal fungi, and small model organisms (e.g. Arabidopsis thaliana).ResultsHere we report a Hoyer’s solution-based clearing method to facilitate clearing of the whole barley pistil, with high reproducibility. The clearing process takes 10 days from fixation to visualisation, whereupon tissue is sufficiently clear to obtain multiple phenotypic measurements from sub-epidermal tissues and cells within the ovule.ConclusionVisualisation of cereal ovules that have not been dissected from the pistil allows an unprecedented capability to collect quantitative morphological information from the developing ovule, integument, nucellus and embryo sac. This will enable comparisons with genetic data to reveal the contribution of pre-fertilisation ovule tissues towards downstream seed development.

Effects of heavy metals on protonemal growth and bud formation in the moss Hydrogonium arcuatum

The present study was conducted to investigate the toxic effects of cadmium and lead salts on protonemal growth and bud formation. For this purpose bryophyte tissue were acclimated to the laboratory conditions by culturing on Nitsch’s basal medium supplemented with various salts of heavy metals (Cadmium and Lead) in the specific concentration range 10-8 – 10-4 M to assess physiological stress- response. Rounding of protonemal cells and formation of brood cells like structures were observed and Bud formation was adversely affected. The present study thus confirmed the morphological changes by mosses can be used to detect heavy metal pollution.

Organic nitrogen uptake is a significant contributor to nitrogen economy of subtropical epiphytic bryophytes.

Without any root contact with the soil, epiphytic bryophytes must experience and explore poor, patchy, and heterogeneous habitats; while, the nitrogen (N) uptake and use strategies of these organisms remain uncharacterized, which obscures their roles in the N cycle. To investigate the N sources, N preferences, and responses to enhanced N deposition in epiphytic bryophytes, we carried out an in situ manipulation experiment via the 15N labelling technique in an Asian cloud forest. Epiphytic bryophytes obtained more N from air deposition than from the bark, but the contribution of N from the bark was non-negligible. Glycine accounted for 28.4% to 44.5% of the total N in bryophyte tissue, which implies that organic N might serve as an important N source. Increased N deposition increased the total N uptake, but did not alter the N preference of the epiphytic bryophytes. This study provides sound evidence that epiphytic bryophytes could take up N from the bark and wet deposition in both organic and inorganic N forms. It is thus important to consider organic N and bark N sources, which were usually neglected, when estimating the role of epiphytic bryophytes in N cycling and the impacts of N deposition on epiphytic bryophytes in cloud forests.

Dead or alive? Testing the use of C:N ratios and chlorophyll fluorescence in vertical shoot profiles to determine depth of vitality and point of senescence in populations of bryophytes.

Bryophytes with indeterminate growth rarely exhibit clearly identifiable modules or age segments, but can be vertically divided into different physiologically active zones, since physiological activity normally declines vertically along the shoot profile depth. The aim of this study was to investigate whether it is possible to use C:N ratios (C/N) and/or parameters from chlorophyll fluorescence measurements (e.g. Fv/Fm, Fm or qN) to determine if bryophyte tissue is alive, senescent or dead, and at what distance along the shoot segment profile the moss tissue cease to live. Variation in C:N ratios and chlorophyll fluorescence between sites was also examined. This study shows that it is possible to separate alive, senescing and dead parts of the moss shoots in Pleurozium schreberi, and that chlorophyll fluorescence is a good method to use, whereas C/N varies between sites and species (for Hylcomium splendens and Racomitrium lanuginosum) and does not seem to reflect physiological activity to the same degree.

Diversity of endophytic fungi associated with bryophyte in the maritime Antarctic (King George Island)

Bryophytes comprise one of the richest microfungal microhabitats in the Antarctic environment. The maritime Antarctic is very vulnerable to rapid environmental change caused by global warming. The aim of this study was to investigate the importance of bryophytes as a microhabitat for fungal species in the maritime Antarctic by surveying endophytic fungal diversity from several bryophytes including Andreaea sp., Barbilophozia hatcheri, Chorisodontium aciphyllum, Polytrichum alpinum, Polytrichumstrictum, Sanionia uncinata, and Warnstorfia sarmentosa. We collected 13 bryophyte samples at four localities on Barton Peninsula, King George Island. In total, 31 endophytic fungi morphotypes were isolated from bryophyte tissues by a thorough surface sterilization method. Using internal transcribed spacer sequence analysis, 16 endophytic fungal strains belonging to Ascomycota (12), Basidiomycota (1), Oomycota (1), and Zygomycota (2) phyla were obtained. Our results suggest the presence of a diverse range of fungal species even in a very limited area, and those bryophytes play an important role in conserving fungal diversity in this harsh environment. Growth rate measurements at a wide range of temperatures confirmed that most of the fungal strains were both mesophilic and psychrotolerant. This is the first report of endophytic fungi in Antarctic moss tissue by fluorescence in situ hybridization.

Regeneration of Little Ice Age bryophytes emerging from a polar glacier with implications of totipotency in extreme environments.

Across the Canadian Arctic Archipelago, widespread ice retreat during the 20th century has sharply accelerated since 2004. In Sverdrup Pass, central Ellesmere Island, rapid glacier retreat is exposing intact plant communities whose radiocarbon dates demonstrate entombment during the Little Ice Age (1550-1850 AD). The exhumed bryophyte assemblages have exceptional structural integrity (i.e., setae, stem structures, leaf hair points) and have remarkable species richness (60 of 144 extant taxa in Sverdrup Pass). Although the populations are often discolored (blackened), some have developed green stem apices or lateral branches suggesting in vivo regrowth. To test their biological viability, Little Ice Age populations emerging from the ice margin were collected for in vitro growth experiments. Our results include a unique successful regeneration of subglacial bryophytes following 400 y of ice entombment. This finding demonstrates the totipotent capacity of bryophytes, the ability of a cell to dedifferentiate into a meristematic state (analogous to stem cells) and develop a new plant. In polar ecosystems, regrowth of bryophyte tissue buried by ice for 400 y significantly expands our understanding of their role in recolonization of polar landscapes (past or present). Regeneration of subglacial bryophytes broadens the concept of Ice Age refugia, traditionally confined to survival of land plants to sites above and beyond glacier margins. Our results emphasize the unrecognized resilience of bryophytes, which are commonly overlooked vis-a-vis their contribution to the establishment, colonization, and maintenance of polar terrestrial ecosystems.

Role of selected dark septate endophyte species and other hyphomycetes as saprobes on moss gametophytes

Dark septate endophytes (DSEs) live asymptomatically in the roots of vascular plants, are common in arctic and alpine areas, and are thought to play a quasimycorrhizal role. It is not known, however, whether they precede or arrive with their hosts. Previously reported enzymatic abilities of Phialocephala fortinii suggest that DSEs can live on organic debris in the soil, but there is little direct or experimental evidence for this. Phialocephala fortinii , Leptodontidium orchidicola , Cadophora melinii , Cadophora luteo-olivacea , and Lecythophora sp. were inoculated onto autoclaved Hylocomium splendens gametophytes and incubated for 3 months to determine if they degrade this organic material based on observations made using light and scanning electron microscopy. All fungi were able to colonize the bryophyte tissue to some extent. Lecythophora sp. and L. orchidicola penetrated cells by forming bore holes. Cadophora luteo-olivacea and P. fortinii were also observed inside cells, but bore holes through bryophyte cell walls were not observed. Cadophora melinii sporulated and grew abundantly on the surface of gametophytes but did not appear to penetrate cell walls. Phialocephala fortinii and L. orchidicola formed sclerotia in the gametophytes similar to those formed in roots. These results suggest that DSE fungi can persist and produce propagules, i.e., sclerotia and conidia, in the absence of host roots. These observations support the hypothesis that DSE fungi are able to precede their hosts during primary succession events.

Bryophytes attenuate anthropogenic nitrogen inputs in boreal forests

Productivity in boreal ecosystems is primarily limited by available soil nitrogen (N), and there is substantial interest in understanding whether deposition of anthropogenically derived reactive nitrogen (Nr) results in greater N availability to woody vegetation, which could result in greater carbon (C) sequestration. One factor that may limit the acquisition of Nr by woody plants is the presence of bryophytes, which are a significant C and N pool, and a location where associative cyanobacterial N-fixation occurs. Using a replicated stand-scale N-addition experiment (five levels: 0, 3, 6, 12, and 50 kg N ha−1 yr−1; n=6) in the boreal zone of northern Sweden, we tested the hypothesis that sequestration of Nr into bryophyte tissues, and downregulation of N-fixation would attenuate Nr inputs, and thereby limit anthropogenic Nr acquisition by woody plants. Our data showed that N-fixation per unit moss mass and per unit area sharply decreased with increasing N addition. Additionally, the tissue N concentrations of Pleuorzium schreberi increased and its biomass decreased with increasing N addition. This response to increasing N addition caused the P. schreberi N pool to be stable at all but the highest N addition rate, where it significantly decreased. The combined effects of changed N-fixation and P. schreberi biomass N accounted for 56.7% of cumulative Nr additions at the lowest Nr addition rate, but only a minor fraction for all other treatments. This ‘bryophyte effect’ can in part explain why soil inorganic N availability and acquisition by woody plants (indicated by their δ15N signatures) remained unchanged up to N addition rates of 12 kg ha−1 yr−1 or greater. Finally, we demonstrate that approximately 71.8% of the boreal forest experiences Nr deposition rates at or below 3 kg ha−1 yr−1, suggesting that bryophytes likely limit woody plant acquisition of ambient anthropogenic Nr inputs throughout a majority of the boreal forest.

Desiccation tolerance and natural cold acclimation allow cryopreservation of bryophytes without pretreatment or use of cryoprotectants

Biodiversity of threatened species can be preserved in cryopreservation repositories, allowing storage of biological information and future re-introduction to the wild. The success of ex situ programs for species conservation relies on using simple and efficient cryopreservation techniques. Bryophytes may be classified as stress-tolerant plants, but a large fraction worldwide is nevertheless threatened by extinction to various degrees. The aims of this study were to investigate how to exploit natural stress tolerance of bryophytes in the development of simple cryopreservation protocols without the use of cryoprotectants or pretreatment. We studied regeneration capacity of bryophytes found at different moisture and light conditions in vivo (reflecting varying levels of plant desiccation tolerance), both sampled from herbarium specimens of varying ages and also collected in situ during winter season and thus naturally cold acclimated. Furthermore, to identify optimal samples for direct cryopreservation we investigated how the ability to regenerate corresponds to the fragment size. We show that young samples (≤ 7 yrs) of the most desiccation tolerant species regenerate via protonemata, where shoot tips regenerate better than small plant fragments. Herbaria can therefore represent a source of samples for direct cryopreservation when using desiccation tolerant species, stored for a limited time. Conversely, all species sampled in situ regenerated, mainly through budding. In these plants, the number of regenerated samples is positively correlated to desiccation tolerance, and they show a higher frost tolerance than previously reported. Cryopreservation without pretreatment or cryoprotectants of cold acclimated bryophytes can therefore be used as a simple and efficient method for storage of bryophyte tissue.

Historical nitrogen content of bryophyte tissue as an indicator of increased nitrogen deposition in the Cape Metropolitan Area, South Africa

Information on changes in precipitation chemistry in the rapidly expanding Cape Metropolitan Area (CMA) of South Africa is scarce. To obtain a long-term record of N deposition we investigated changes in moss foliar N, C:N ratios and nitrogen isotope values that might reflect precipitation chemistry. Tissue from 9 species was obtained from herbarium specimens collected between 1875 and 2000 while field samples were collected in 2001/2002. There is a strong trend of increasing foliar N content in all mosses collected over the past century (1.32–1.69 %N). Differences exist between ectohydric mosses which have higher foliar N than the mixohydric group. C:N ratios declined while foliar δ 15N values showed no distinct pattern. From relationships between moss tissue N and N deposition rates we estimated an increase of 6–13 kg N ha −1 a −1 since 1950. Enhanced N deposition rates of this magnitude could lead to biodiversity losses in native ecosystems.

The effects of low levels of nitrogen deposition and grazing on dune grassland

Coastal sand dunes are considered to be threatened by the atmospheric deposition of nitrogen (N); however, experimental investigations of the effects of N deposition on dune vegetation and soil using realistic N loads and sites with low background deposition are scarce. This study reports the effects of low levels of fertilisation with N and phosphorus (P) on the vegetation, above-ground biomass, plant tissue chemistry and soil chemistry of fixed dune grasslands. In addition, the impacts of grazing management and its potential to mitigate adverse effects of N fertilisation were examined. Four N treatments (unwatered control, watered control, + 7.5 kg ha − 1 year − 1 , + 15 kg ha − 1 year − 1 ) were combined with three grazing treatments (ungrazed, rabbit grazed, rabbit and pony grazed). In a separate experiment, effects of fertilisation with both N (15 kg ha − 1 year − 1 ) and P (20 kg ha − 1 year − 1 ) were investigated. Vegetation composition was assessed using the point quadrat method. Above-ground biomass, sward heights, tissue N and P concentrations and soil chemical parameters were also measured. After two years, N addition resulted in greater amounts of total above-ground biomass, bryophyte biomass and changes in bryophyte tissue chemistry. No effects on vegetation composition, sward height or soil parameters occurred. Fertilisation with both nutrients had a greater impact on above-ground biomass, sward heights and sward structure than N addition alone. The grazing treatments differed in their species composition. The changes observed after only two years of fertilisation may lead to community changes over longer time scales. Effects were observed even under heavy grazing with phosphorus limitation. Therefore, the upper critical load for N for dune grasslands may be below the previously proposed 20 kg ha − 1 year − 1 and grazing may not mitigate all negative effects of N deposition.

Cadmium and Zinc Accumulation in Aquatic Bryophytes Immersed in the Arkansas River, Colorado: Comparison of Fall versus Spring

ABSTRACT A bryophyte, Hygrohypnum ochraceum, was used as an indicator of heavy metals in the upper Arkansas River below the historical mining district at Leadville, Colorado. Plants were immersed in the river at nine sites near Leadville for 10 days during fall 2000 and spring 2001. Cadmium and zinc tissue-metals in plants were higher in the fall than in spring. The plants showed site-to-site differences in concentrations of cadmium and zinc in the Arkansas River, and metals were markedly higher in California Gulch, a contaminated tributary draining the mining district of Leadville, Colorado. There were strong correlations between total cadmium in Arkansas River water and cadmium in bryophyte tissues and between dissolved and total zinc in the Arkansas River water and zinc in the bryophytes. Our study suggests that bryophytes could potentially be valuable monitoring organisms for assessing site and seasonal bioavailability of metals.

From axenic spore germination to molecular farming

The first bryophyte tissue culture techniques were established almost a century ago. All of the techniques that have been developed for tissue culture of seed plants have also been adapted for bryophytes, and these range from mere axenic culture to molecular farming. However, specific characteristics of bryophyte biology--for example, a unique regeneration capacity--have also resulted in the development of methodologies and techniques different than those used for seed plants. In this review we provide an overview of the application of in vitro techniques to bryophytes, emphasising the differences as well as the similarities between bryophytes and seed plants. These are discussed within the framework of physiological and developmental processes as well as with respect to potential applications in plant biotechnology.

Response of two Antarctic bryophytes to stratospheric ozone depletion

AbstractWe report a study which measured changes to the radiative environment arising from stratospheric O3 depletion at Rothera Point on the western Antarctic Peninsula (67°S, 68°W) and subsequent associations between these changes and the pigmentation and maximum quantum yield of photochemistry (Fv/Fm) of two Antarctic bryophytes, the liverwort Cephaloziella varians and the moss Sanionia uncinata. We found a strong relationship between O3 column depth and the ratio of UV‐B to PAR irradiance (FUV‐B/FPAR) recorded at ground level. Weaker, but significant, associations were also found between O3 column depth and noon irradiances and daily doses of unweighted and biologically effective UV‐B radiation received at ground level. Regression analyses indicated that FUV‐B/FPAR and daily dose of unweighted UV‐B were best predictors for concentrations of total carotenoids and UV‐B screening pigments extracted from bryophyte tissues. Concentrations of these pigments were loosely but significantly positively associated with O3‐dependent irradiance parameters. HPLC analyses of carotenoids also suggested that both species increased the synthesis of neoxanthin during periods of O3 depletion. Violaxanthin, lutein, zeaxanthin and b,bββ‐carotene concentrations were also apparently influenced by O3 reduction, but not consistently across both bryophyte species. Concentrations of chlorophylls a and b were apparently unaffected by O3 depletion.No direct associations between Fv/Fm and O3‐dependent irradiance parameters were found. However stepwise multiple regression analyses suggested that the production of UV‐B screening pigments conferred protection from elevated FUV‐B/FPAR on Fv/Fm in both species and that carotenoids conferred protection on Fv/Fm in Sanionia. Our data suggest that changes to the radiative environment associated with stratospheric O3 depletion influence the pigmentation of two Antarctic bryophytes, but that Fv/Fm is unaffected, at least in part because of rapid synthesis of protective pigments.