Atrichum Undulatum Research Articles

Exploring In Vitro Immunomodulatory Properties of Moss Atrichum undulatum Extracts.

Bryophytes are rich sources of diverse secondary metabolites with a wide range of biological activities, including anti-inflammatory, antitumor and antimicrobial effects. The aim of this study was to investigate the chemical composition of extracts from two different genotypes (Serbian and Hungarian) of the axenic moss Atrichum undulatum and evaluate the immunomodulatory potential of the prepared extracts in vitro. Both genotypes of moss samples were cultivated in vitro and subsequently extracted in a Soxhlet apparatus with methanol or ethyl acetate. The highest concentration of total phenolic compounds was found in the methanolic extract of the Serbian genotype (54.25 mg GAE/g extract), while the ethyl acetate extract of the Hungarian genotype showed the highest concentration of phenolic acids (163.20 mg CAE/extract), flavonoids (35.57 mg QE/extract), and flavonols (2.25 mg QE/extract). The extracts showed anti-neuroinflammatory properties by reducing the production of reactive oxygen species, nitric oxide, and tumor necrosis factor alpha by lipopolysaccharide-stimulated microglial cells. Moreover, they mitigated the cytotoxic effects of the pro-inflammatory mediators produced by activated microglia on neurons. The data obtained suggest that extracts from A. undulatum moss have promising anti-neuroinflammatory and neuroprotective properties, making them interesting candidates for further research to combat neuroinflammation.

Interspecific competition affects spore germination and gametophore development of mosses

Background Interactions between moss species in their earliest growth stages have received little attention. To what extent interspecific competition or priority effects influence spore germination, protonemal development and gametophore emergence is unknown. We evaluated such effects in pairwise interaction between six common bryophyte species: Atrichum undulatum, Bryum argenteum, Ceratodon purpureus, Funaria hygrometrica, Hypnum cupressiforme, Leptobryum pyriforme Methods Interspecific interactions were assessed in vitro. Spores were sterilized and sown on agar plates in three treatments: 1) as single species cultures (controls), 2) as pairwise species cultures inoculated simultaneously, and 3) with a time lag of 20 days between species. Data on time needed for spore germination, germination rate, the time needed for gametophore differentiation, number of gametophores per germinated spore and average diameter of colonies were collected. We also performed spore germination tests in single-species cultures at the start and end of the study, as well as tests for density-dependency at spore germination and gametophore formation. Results We observed strong pairwise interactive effects when sowing spores of different species simultaneously or with a delay of 20 days. The results indicate that spore germination is often inhibited by interspecific competition. The first species has an advantage as compared to the later colonizing species, i.e., an apparent priority effect. Interspecific interactions were also evident during gametophore development and included both inhibition and facilitation. Conclusion We found pronounced differences in the relative performance of species in interaction with other species during spore germination and gametophore formation. Allelopathic effects are the most probable explanation for these observations. Our results under sterile lab conditions are likely to reflect processes that occur in the wild, governing biotic filtering and bryophyte community assembly during primary and secondary colonization.

Effects of Cesium on Physiological Traits of the Catherine's Moss Atrichum undulatum Hedw.

Mosses are proven bioindicators of living environments. It is known that mosses accumulate pollutants from precipitates and, to some lesser extent, from the substrate. In this study, the effects of cesium (Cs) on the physiological traits of acrocarp polytrichaceous Catherine's moss (Atrichum undulatum Hedw.) were studied under controlled, in vitro conditions. Cesium can be found in the environment in a stable form (133Cs) and as a radioactive isotope (134Cs and 137Cs). Belonging to the same group of elements, Cs and potassium (K) share various similarities, due to which Cs can interfere with this essential element and thus possibly alter the plant's metabolism. Results have shown that Cs affects the measured physiological characteristics of A. undulatum, although the changes to antioxidative enzyme activities were not drastic following Cs treatments. Therefore, the activities of antioxidative enzymes at lower pH values are more the consequence of pH effects on enzymatic conformation than simply the harmful effects of Cs. Moreover, Cs did not affect the survival of plants grown on the solid substrate nor plants grown in conditions of light and heavy rain simulation using Cs with variable pH, indicating that Cs is not harmful in this form for the studied species A. undulatum.

The content of phenols and activity of polyphenol oxidase in the hametophyte of dominant mosses in forest ecosystems of the Ukrainian Roztochia

Bryophytes are indicators of the state of forest ecosystems. Dominant species of forest mosses are sensitive to the influence of abiotic factors and demonstrate adaptive reactions different from vascular plants, which are decisive for the prediction of changes in the natural environment. We have analyzed the changes in the content of water-soluble phenols and the activity of polyphenol oxidase n the hametophyte of dominant epigean forest mosses depending on changes in the intensity of insolation, the water and temperature regime of soils and air in experimental localities of forest ecosystems of the Ukrainian Roztochia. The highest content of water-soluble phenolic compounds was found in the resistant mosses Polytrichum formosum and Atrichum undulatum on the territory of protected beech forest under conditions of low light intensity and sufficient humidity of local vegetation. The maximum indicators of the content of phenolic compounds were found in A. undulatum (199.5±9.8 μg/g of dry matter mass), and the lowest – in Plagiomnium affine (54.7±2.6 μg/g of dry matter mass) that is sensitive to changes in the ecological conditions of local vegetation in all studied areas. A significant decrease in the content of phenolic compounds in areas of disturbed ecosystems may indicate the active participation of phenols in the adaptation of mosses to the effects of high light intensity, elevated temperatures and moisture deficit. The highest indicators of polyphenol oxidase activity were determined in P. affine (120.4±6.1 relative units/g of dry matter mass*s) and P. formosum (41.8±2.1 relative units/g of dry matter mass*s) from local vegetation under unfavorable conditions on the territory of stationary recreation. A direct correlation between the content of phenolic compounds and the activity of polyphenol oxidase was not established. The higher activity of this enzyme under conditions of high light intensity than in shaded local plants may indicate a relationship between polyphenol oxidase and photosynthesis. An increase in the activity of polyphenol oxidase contributes to the significant formation of quinones, which, accumulating in cell walls, reduce the processes of lipid peroxidation, regulate their permeability and ensure better moisture storage in the moss turfs.

Interspecific competition affects spore germination and gametophore development of mosses.

Interactions between moss species in their earliest growth stages have received little attention. To what extent interspecific competition or priority effects influence spore germination, protonemal development and gametophore emergence is unknown. We evaluated such effects in pairwise interaction between six common bryophyte species: Atrichum undulatum, Bryum argenteum, Ceratodon purpureus, Funaria hygrometrica, Hypnum cupressiforme, Leptobryum pyriforme. Interspecific interactions were assessed in vitro. Spores were sterilized and sown on agar plates in three treatments: 1) as single species cultures (controls), 2) as pairwise species cultures inoculated simultaneously, and 3) with a time lag of 20 days between species. Data on time needed for spore germination, germination rate, the time needed for gametophore differentiation, number of gametophores per germinated spore and average diameter of colonies were collected. We also performed spore germination tests in single-species cultures at the start and end of the study, as well as tests for density-dependency at spore germination and gametophore formation. We observed strong pairwise interactive effects when sowing spores of different species simultaneously or with a delay of 20 days. The results indicate that spore germination is often inhibited by interspecific competition. The first species has an advantage as compared to the later colonizing species, i.e., an apparent priority effect. Interspecific interactions were also evident during gametophore development and included both inhibition and facilitation. We found pronounced differences in the relative performance of species in interaction with other species during spore germination and gametophore formation. Allelopathic effects are the most probable explanation for these observations. Our results under sterile lab conditions are likely to reflect processes that occur in the wild, governing biotic filtering and bryophyte community assembly during primary and secondary colonization.

Antifungal activity, phytochemical analysis and mode of action of Atrichum undulatum (Hedw.) P. Beauv.

Antifungal activity, phytochemical analysis and mode of action of Atrichum undulatum (Hedw.) P. Beauv.

Floristic composition of bryophytes in disturbed habitats of two different elevations in Chandragiri Hill, central Nepal

Bryophytes are small, photosynthetic plants, capable of growing on variety of habitats, so are pioneer of ecological succession. In Nepal bryophytes have been studied floristically in different parts of the country, but the impact of disturbance on floristic composition was lacking. Therefore, present study aimed to determine floristic composition of bryophytes especially on disturbed habitat generated by recently established Cable Car facility in Chandragiri hill, Kathmandu. The study area, highly disturbed at the base (1550-1600 m asl) and top of the hill (2400-2450 m asl), were selected for the collection of bryophytes. Altogether, 17 species of bryophytes including 5 liverworts, 11 mosses and 1 hornwort were recorded from the disturbed habitats. Among the 5 classes, Bryopsida was the most dominant class followed by the class Marchantiopsida, Polytrichopsida, Jungermanniopsida and Anthocerotopsida. Impact of elevation on diversity of bryophytes was observed in both sites of disturbed habitats. The diversity of bryophyte was found higher (13 species) at the base of the hill as compared to the top (8 species). Among the 17 species of bryophytes, 5 taxa (Aerobryidium filamentosum, Anomobryum auratum, Atrichum undulatum var. subserratum, Chiloscyphus profundus and Plagiomnium ellipticum) that have not been enumerated from the study site so far were also documented.

Influence estimation of recreation pressure on the forest trail "Buchyna" NNP "Skolivski Beskydy"

Complex studies of the impact of recreational pressure on the forest trail "Buchina" of NNP "Skolivski Beskydy" were carried out. It was found that the air microclimatic parameters across the all transects were shown to fluctuate. The air temperature was stable, as well as the humidity changed very slightly. The wind force gradually decreased from the middle of the forest trail to the margins. The difference in the illumination of the soil surface on the trail and adjacent areas is the most noticeable. The impact of recreational activities on the microclimatic parameters of soils is more significant than this in the air. The temperature and humidity of the soil was decreased and the density of the structure was increased towards the center of the trail. Changes in water-physical parameters of soils let us identify the initial stages of digression in the studied recreational-pressed forest ecosystems. Brioindication studies have shown that the forest area on both sides of the route, which does not experience recreational pressure, is characterized by extremely weak development of moss cover. It was represented by 5 species of mosses such as Atrichum undulatum, Polytrichum formosum, Plagiomnium undulatum, Eurhynchium angustirete and E. striatum. Those species were represented by toll turf, dendroides and rough carpet growth forms. Species diversity at the trail edges were doubled. There were founded 10 spesies of bryobionta: A. undulatum, P. formosum, Plagiomnium cuspidatum, P. ellipticum, P. undulatum, E. angustirete, Pseudoscleropodium purum, Thuidium delicatulum, T. tamariscinum, Calliergonella cuspidatа, were represented by toll turf, dendroides, rough mats and weft growth forms. In the zone of intensive trampling on the forest trail, the moss cover was completely absent. Bryophytes, which were recorded in trail margins, marked the initial stages of recreational digression (I-II) and were belonging to the group of sensitive forest species. The strongest pressure was recorded on the central part of the forest trail. However, the density of the soil structure, even in this area, didn't overtop the indicator rate for the category of "very loose soils". Our study suggests that the organization of recreational activities for the planning of permanent tourist routes (so-called "ecological trails'') in the areas of spruce-beech forests haven't cause extremely pressure on the park ecosystems (equally for soil and vegetation cover) in NNP "Skolivski Beskydy". As a preventive measure, we recommend regulating the number of visitors to reduce the mechanical trampling on the forest trails and the arrangement of different fences, decks, etc.

Seasonal changes in the content of plastid pigments in the hametophyte of dominant mosses in forest ecosystems of Ukrainian Roztochchya

Poikilohydric mosses, as one of the most sensitive groups of plants to the influence of habitat conditions, responding to environmental factors, demonstrate adaptations, which differ from vascular plants, for the prediction of changes in the natural environment. The changes in the content of photosynthesis pigments and their ratio in dominant deciduous epigeal species of mosses depending on changes in stand crowns, insolation intensity, water-temperature regime of soil and air in local ecosystems of Ukrainian Roztochchya were analyzed. Due to the significant projective cover and closed crowns in the area of ancient forests, the 30-50% lower indicators of light intensity, 8-12% of substrate temperature under moss turf, and 43-50% higher indicators of its humidity compared to pine plantations were identified. Anthropogenic impact in the area of stationary recreation was conditioned by the intensive trampling, which led to a decrease in the closure of the tree crowns (up to 0,4-0,5), an increase in light intensity by 2,5 times, and a decrease in soil moisture under moss turf by 2-4 times. The shade-tolerant Polytrichastrum formosum, Atrichum undulatum and Plagiomnium affine mosses compensated the limited amount of light energy available for growth by intensively increasing of the content of pigments (chlorophylls a and b), light-harvesting complexes and reducing of the chlorophylls a/b ratio to 1,6-2,1. A significant variability in the ratio of chlorophylls to carotenoids from 5 to 9 was found. Significant limits of variation in the content of carotenoids and the ratio of chlorophylls to carotenoids served as an indicator for assessing the edapho-climatic changes in the living conditions of bryophytes in forest ecosystems. Significant variability in the ratio of chlorophylls a/b (2,35-4,25) in autumn in comparison with such indicators in summer is associated with increased illumination of the experimental areas and the activity of the reactions of mutual transformations of chlorophylls a and b. The increase in the values of the ratio of chlorophylls a/b caused by the activation of pigment metabolism indicates their adaptation to both light and shadow. In autumn, the decrease in the ratio of chlorophylls to carotenoids (in the range of 4,31-5,08) is associated with the intensity of synthesis and decomposition of chlorophylls a and b, and carotenoids, which can be used as an important indicator of plant adaptation ability to the changes in light intensity, humidity, and temperature.

PARTICIPATION OF THE POLYTRICHACEAE FAMILY IN THE FORMATION OF THE MOSSON COVER OF THE FOREST-STEPPE OF UKRAINE

The participation of species of the family Polytrichaceae in the formation of bryocenoses of the Forest-Steppe of Ukraine is analyzed in the article. The part of the syntaxonomic scheme of moss vegetation of Ukraine, in the syntaxons of which the species of the studied family take part, is given. In the bryoflora of the Forest-Steppe of Ukraine we (Gapon S., 2011) found 10 species, namely: Atrichum tenellum, A. undulatum, Pogonatum urnigerum, Polytrichum commune, R. formosum, P. juniperinum, P. longisetum, P. perigoniale, R. piliferum, P. strictum.According to the results of our research, it is established that the epigeal bryogroups of the region include 6 species of the family, each of which has a different coenotic role. Epigeous bryogroups with species of the family Polytrichaceae are represented by four classes, five orders, 7 unions, two sub-unions, 11 associations, four sub-associations and 5 rankless groups.In the bryocenoses of the associations Racomitrio-Polytrichetum piliferi ceratodontetosum purpurei, Polytrichetum juniperini and the rankless group Atrichum undulatum – somm. classes Seratodonto purpurei-Polytrichétea piliferi, Cladonio digitatae-Lepidozietea reptantis species Polytrichum piliferum, Polytrichum juniperinum, Atrichum undulatum are edificators and are diagnostic species. In the composition of other syntaxons of epigeal groups of classes Seratodonto purpurei-Polytrichétea piliferi, Cladonio digitatae-Lepidozietea reptantis, Pleurochaeto squarrosae-Abietinelletea abietinae, Hylocomietea splendentis, these and other species: Рolytrichum commune, P. formosum, P. longisetum, P. strictum detected infrequently and sporadically.

Investigation of the flora of epigean bryobionta of the Olexandria Dendrological Park

Species composition of epigeic bryophytes of the Olexandria Dendrological Park, located in the northeast of the Right-Bank forest-steppe of Ukraine, was studied. The research was conducted in 2017–2019. As a result, 40 species of 25 genera, 14 families, 7 orders, 2 classes, and 1 division were registered. A taxonomic analysis showed that the orders Hypnales (14 species), Pottiales (9 species) and Bryales (9 species) are represented best. The main families were as follows: Pottiaceae (9 species), Brachytheciaceae (7 species), Bryaceae (5 species), Amblystegiaceae and Mniaceae (4 species each). The most speciose were the genera Bryum (5 species), Brachythecium (4 species), Tortula (4 species) and Plagiomnium (3 species). Among the identified taxa, two species, (Barbula сonvoluta and Bryum rubens) are regionally rare in the Forest-Steppe zone of Ukraine. In the historical part of Olexandria, five species Ceratodon purpureus, Oxyrrhynchium hians, Hypnum cupressiforme, Atrichum undulatum, and Bryum moravicum were the most common epigean bryophytes. In the western part of the Dendropark, the prevalent species were Atrichum undulatum, Bryum moravicum, Oxyrrhynchium hians, Hypnum cupressiforme, Brachytheciastrum velutinum, and Hygroamblystegium varium, in the central part – Bryum moravicum, Hypnum cupressiforme, Ceratodon purpureus, and in the eastern part – Fissidens taxifolius, Fissidens viridulus, and Brachythecium rutabulum. Twenty species (50 % of the identified taxa) were obligate epigees while the other 20 species belonged to the facultative epigees. In 2018, a new species to the Dendropark’s bryoflora, Ephemerum minutissimum, was found in an oakery (locality 14). It grew there together with Dicranella heteromalla, Bryum rubens, Barbula convoluta, Ceratodon purpureus, Tortula acaulon, and Weissia brachycarpa. This is the second record of E. minutissimum from Ukraine. The highest number of epigeic moss species was registered in the central part of Olexandria (29 taxa). At present, the epigeic bryoflora of the Dendropark’s historical part comprises 44 % of its whole bryoflora (90 species).

Evaluation of Atrichum undulatum as an effective indicator of lead pollution in soil

Aim: The aim of this study was to evaluate the sensitivity of Atrichum undulatum to soil Pb contamination and check its affectivity as an indicator of Pb pollution indicator. Methodology: Soil and plant samples were collected and characterized. Plants were grown in different levels of Pb contaminated soil (35, 70,140 and 280 mg kg-1, respectively). After 35 days, the plant samples were cut and ground to determine physiological and biochemical parameters. Results: Soil available Pb accounted for approximately 15–24% of total Pb, and the ratio of available Pb decreased with increase in treatment concentration. All the above mentioned parameters were closely related to soil Pb stress, especially when soil Pb concentration was higher than 140 mg kg-1. A. undulatum had a low tolerance to Pb and distinct responses to soil Pb pollution, with visible symptoms such as damaged sporophytes and gametophytes. When soil Pb concentration was in low concentration (70 and 140 mg kg-1), the leaves turned yellow and brown. When soil Pb concentration increased to 280 mg kg-1, the seta softened and kinked and eventually, the plants withered and died. Interpretation: Changes in physiological and biochemical parameters of tested plants such as chlorophyll, soluble protein and MDA content were related to soil Pb stress, especially to soil bioavailable Pb content, and corresponded well to changes in soil Pb pollution level. The results suggest that A. undulatum can be used as indicators to monitor and evaluate Pb pollution in soil.

The toxic metal stress in two mosses of different growth forms under axenic and controlled conditions

Bryophytes are widely used in monitoring environmental changes and various types of pollution. Features such as longevity and direct intake by the whole body make them very good models for bioindication. However, there is a considerable lack of knowledge on the coping, resistance and tolerance mechanisms to toxic elements within representatives of this second largest group of terrestrial plants. We tested two different growth form mosses, acrocarpous Atrichum undulatum and pleurocarpous Hypnum cupressiforme in axenic in vitro fully controlled laboratory conditions, thus eliminating additional side, antagonistic or synergistic effects. These mosses were exposed to three concentrations (including control) of zinc-, copper- or cadmium-acetate for a short and long period, and their growth, development and biochemical parameters were recorded. The results showed that reactions to stress are both species and metal-specific. Also, the short and long-term exposure times and the level of toxic elements played a role in species response and showed the differences between the two moss growth forms and species. Among the investigated parameters considered in the two mosses tested, the multiplication index proved to be the most useful and sensitive in detecting the metal pollution effects. On the other hand, the concentration of chl a seemed to vary over a rather small range between the stressed moss species. Overall, copper was shown to be quite toxic compared to the other two metals at lower applied concentration. However, the studied mosses demonstrated decreased viability according to all of the parameters tested in the media enriched with high concentrations of cadmium when compared with copper and zinc. These results suggest that species studies related to different metals/pollutants in small scale controlled conditions are urgently needed before application in broad areas monitored by mosses.

Determination of plant communities based on bryophytes: The combined use of Kohonen artificial neural network and indicator species analysis

Abstract Mosses and liverworts are good bioindicators, not only of environmental pollution and the substrates on which they develop, but also of the plant communities in which they grow. The present study classifies bryological releves and identifies epigeic species significantly associated with three forest phytocoenoses important for Central Poland: Tilio-Carpinetum with Abies alba, Abietetum polonicum and managed forests; importantly, the study takes an approach using a Kohonen artificial neural network (i.e. self-organising map, SOM), its first use in bryological studies, together with Indicator Species Analysis based on IndVal index. The number of species significantly associated with natural forests was found to be 2–3 times higher than in managed forests, which reflected the differences in the quality of forest habitats. Additionally, the approach not only confirmed that some taxa play a diagnostic role (e.g.: Pleurozium schreberi, Dicranum polysetum, Dicranum scoparium, Thuidium tamariscinum, Atrichum undulatum, Eurhynchium angustirete) but also indicated new species which may have diagnostic potential for the studied communities. Our findings demonstrate that the epigeic bryophyte layer can play an important role in separating the studied phytocoenoses, and thus in the syntaxonomy of forest communities.

Metal accumulation in the acrocarp moss Atrichum undulatum under controlled conditions

Mosses are frequently used to monitor atmospheric metal contamination but few studies on metal adsorption under controlled conditions are available. Here, the accumulation of the heavy metals copper and zinc was studied in the acrocarp moss Atrichum undulatum. An in vitro culture of A. undulatum was established and the same line, size and equally old remets were exposed to six different treatments representing various metal exposure times and washing scenarios as rain simulation. The metal treatments were done in copper and zinc salts (Cu-acetate, CuSO4, ZnSO4 and ZnCl2, respectively). Energy-Dispersive X-ray microanalysis (EDX) was employed to detect bound heavy metals on the moss plantlets. Element distribution in stems and leaves was measured separately. The aqueous solution of metal salts facilitated an adsorption of both elements in the moss tissue as compared to solid medium. Furthermore, A. undulatum can tolerate pollution of zinc and copper in a distinctive extent; our data point towards a higher zinc tolerance whereas copper is rather harmful. However, semi-quantitatively, less zinc was detected within the moss tissue compared to copper. Interestingly, a strong positive correlation between the accumulation of copper/zinc and iron, and a strong negative correlation between copper/zinc and magnesium, respectively, was documented.

Effects of zinc and copper on development and survival of the moss Atrichum undulatum in controlled conditions

Effects of zinc and copper on development and survival of the moss Atrichum undulatum in controlled conditions

In vitro assessment of antimicrobial activity of aqueous and alcoholic extracts of moss Atrichum undulatum (Hedw.) P. Beauv.

Bryophytes, the shade loving plants, have tremendous medicinal properties. The aqueous and alcoholic extracts of Atrichum undulatum (Hedw.) P. Beauv. were analysed for antimicrobial properties against the fungi Aspergillus fumigatus and Fusarium oxysporum and the bacteria Escherichia coli, Bacillus mycoides, Proteus mirabilis, Staphylococcus aureus and Salmonella typhi. The study is an attempt to investigate the medicinal properties of Atrichum undulatum (Hedw.) P.Beauv. using disc-diffusion method. No inhibition was observed against A. fumigatus and P. mirabilis. For bacteria S. typhi and E. coli (20 and 15mm), aqueous and alcoholic extracts of Atrichum showed significant inhibition. However, alcoholic extract was found remarkably effective against bacteria rather than aqueous extract.

Mosses inhibit germination of vascular plants on an extensive green roof

Mosses are capable of tolerating harsh conditions, and are commonly found on both conventional bare roofs and engineered green roofs. Intentional planting of mosses on green roofs has shown that mosses can improve ecosystem services such as stormwater retention and microclimate cooling. Past studies of moss interactions with vascular plants on green roofs and in other habitats demonstrate both positive and negative effects on juvenile and adult tracheophytes. Moss can aid vascular plants by buffering environmental extremes, facilitating seed establishment, and improving nutrient and water availability. Conversely, moss can also hinder young seedling germination by blocking access to the soil column and/or light. In the green roof context, few studies have examined the relationship between moss and vascular plant germination. Since mosses commonly colonize green roofs it is important to understand the effects of established moss colonies on incoming plant propagules. The purpose of this study was to examine how four moss species, Atrichum undulatum (Hedw.) P. Beauv., Polytrichum commune Hedw., Polytrichum piliferum Hedw., and Racomitrium lanuginosum (Hedw.) Brid. affected the germination of weedy and native vascular plant seeds in a green roof system. Seeds were added to six pre-established moss treatments: monocultures of each moss species, a mixture which included all four moss species, and a substrate only control in pots on a rooftop. Overall, the control (moss-free) treatment resulted the highest germination rates for the majority of seeded species examined, an indication that for these vascular plants, mosses tend to inhibit germination of incoming seeds.

Dehydration-responsive features of Atrichum undulatum.

Drought is an increasingly important limitation on plant productivity worldwide. Understanding the mechanisms of drought tolerance in plants can lead to new strategies for developing drought-tolerant crops. Many moss species are able to survive desiccation—a more severe state of dehydration than drought. Research into the mechanisms and evolution of desiccation tolerance in basal land plants is of particular significance to both biology and agriculture. In this study, we conducted morphological, cytological, and physiological analyses of gametophytes of the highly desiccation-tolerant bryophyte Atrichum undulatum (Hedw.) P. Beauv during dehydration and rehydration. Our results suggested that the mechanisms underlying the dehydration–recovery cycle in A. undulatum gametophytes include maintenance of membrane stability, cellular structure protection, prevention of reactive oxygen species (ROS) generation, elimination of ROS, protection against ROS-induced damage, and repair of ROS-induced damage. Our data also indicate that this dehydration–recovery cycle consists not only of the physical removal and addition of water, but also involves a highly organized series of cytological, physiological, and biochemical changes. These attributes are similar to those reported for other drought- and desiccation-tolerant plant species. Our findings provide major insights into the mechanisms of dehydration-tolerance in the moss A. undulatum.

Hybridization is associated with changes in sexual system in the bryophyte genus Atrichum.

Over 50% of bryophytes have separate sexes, and numerous transitions have occurred between combined and separate sexes. Polyploidy and hybridization is one proximate mechanism hypothesized to cause evolutionary transitions to hermaphroditism in bryophytes because sex is expressed at the haploid stage and in nonpolyploid dioecious species males have a single V chromosome and females a U. Hermaphroditism can arise if gametophytes of allopolyploids have both U and V chromosomes. We examined the association between polyploidy and hermaphroditism in the bryophyte genus Atrichum, which has species where gametophytes can be haploid, diploid, or triploid, and some species have hermaphroditic individuals. We generated phylogenies of Atrichum from sequences of three plastid regions (rbcL, rps4, and trnL-trnF) and the second intron for the nuclear gene Leafy/Floricaula to further understand the relationships among haploid, diploid, and triploid species, and those with combined or separate sexes. The existence of multiple sequences of Leafy/Floricaula in diploid and triploid, but not haploid, individuals is consistent with independent allopolyploid origins of the diploid and triploid species. Allopolyploidy was associated with a likely gain in hermaphroditism in triploid Atrichum undulatum and possibly diploid A. altecristatum, but not in the allopolyploid A. crispulum (diploid at the gametophyte level). These results highlight a role for hybridization and polyploidy in sexual system evolution, but the presence of diploid (allopolyploid) dioecious species suggest that other factors may influence the maintenance of sexual systems after an evolutionary transition.