Search Results (51)

Rocky outcrops are harsh habitats that support specialized organisms and communities, including biocrusts, which play roles in soil stabilization, water retention, and nutrient cycling. Despite their importance, tropical biocrusts, particularly in granite-gneiss formations, remain underexplored. This study examines biocrust composition in a granite-gneiss outcrop in a rural landscape in Southeastern Brazil, identifying microhabitats and analyzing co-occurrence patterns and community structure. We recorded eleven bryophyte species and one diatom species, while six cyanobacteria, three charophytes, and two chlorophytes were identified at the genus level. They were found in shallow depressions, though termite mounds also served as an important microhabitat. The cyanobacterium Scytonema was the most prevalent taxon. The liverwort Riccia weinionis had the highest number of positive co-occurrences, associating with cyanobacteria and algae. Network analysis based on co-occurrence revealed that Scytonema and the mosses Anomobryum conicum and Bryum argenteum were the most connected taxa, crucial for ecological network stability. The moss Bryum atenense acted as a key intermediary, with the highest betweenness centrality—a measure of its role in linking taxa. These findings provide insights into tropical rocky outcrop biocrusts, shedding light on their composition and interactions. Furthermore, the co-occurrence patterns and key taxa connectivity uncovered provide insights into ecosystem stability and can guide ecological restoration strategies. Full article

The composition and diversity of the sensitive benthic Charophyta were examined in 13 lakes and 1 pond located in the Kaçkar Mountains National Park during the summer and autumn months of 2020. While a total of 78 taxa were identified, Cosmarium became the main genus of the flora with 33 species. In the flora, the filamentous members of the Charophyta (12 species) were also noteworthy. Intraspecies variability is very high, with a Subspecies/Species index of 1.11, which reflects the sensitivity of the identified charophyte flora as an indicator of conservation efficiency. The physico-chemical analysis results and bioindicator species indicate that the investigated waters are fresh, with low salinity and a circumneutral or slightly alkaline pH, and are not organically polluted. Comparative statistics and RDA divide the studied lakes into two clusters (northern and southern in the park territory) and reveal the complex factors related to salinity and oxygen saturation as regulators of species abundance in communities. Full article

Softwater lakes with specific, rare, and protected aquatic plant vegetation are very sensitive to increased trophic and water chemical changes, especially alkalization. These changes might be reflected in the stable carbon and nitrogen isotopes of the organic matter (OM) of those plants (δ¹³C_ORG and δ¹⁵N_ORG) and sediments (δ¹³C_ORG and δ¹⁵N_TN) which they cocreated. To recognize the relationship between OM in the aquatic plants of softwater lakes and the cocreated sediments, we analyzed the plants δ¹³C_ORG and δ¹⁵N_ORG in light of four ecological groups (as well as the sediments δ¹³C_ORG and δ¹⁵N_TN in which these plants thrived). Studies were performed in July 2020 on 14 softwater lakes in northern Poland with varying pH gradients from 4.86 to 9.20. For each lake, a single stand was examined for each species detected. The goal was to investigate each species at 10 sites, but this target was not reached for several species. Among the investigated ecological groups, isoetids and mosses showed the least variation in obtained values. In contrast, elodeids exhibited the highest variation in δ¹³C results due to their diverse carbon uptake strategies, involving both CO₂ and HCO₃⁻ forms. Moreover, the δ¹³C values of charophytes and elodeids were highly related to the increasing pH of water. The slight differences between the δ¹³C results of plants and sediments in isoetid stands further support this finding. Furthermore, we noticed an increase in sediment δ¹³C_ORG values along the alkalization gradient, suggesting that macrophytes were the primary source of OM for the sediments. The positive correlation between the δ¹³C values of plants and sediments (r = 0.69, p < 0.05) might also confirm that the macrophytes were a significant source of OM in sediments. Regarding δ¹⁵N values, we did not find significant differentiation between plants and sediments across ecological groups. However, sediment consistently exhibited ¹⁵N-enrichment compared to plant material. This enrichment is likely attributed to the accumulation of ¹⁵N during the decomposition of the deposited material. This study confirms the possibility of tracking changes in the aquatic vegetation of softwater lakes based primarily on the sediment δ¹³C_ORG values along the alkalization gradient. Full article

The identification of a charophyte population found in a rice field in Ferrara, North Italy, collected in 1999 and initially identified as Nitella translucens, has been reevaluated. Detailed morphological observations here reported have suggested that the specimen displays characteristics more akin to Nitella axillaris, particularly in the structure of its bicellular dactyls and axillary heads. Additional examinations, including scanning electron microscopy (SEM) of oospores and analyses of herbarium specimens—encompassing original materials of N. axillaris, N. axillaris f. tenuoir, and N. translucens f. confervoides—support this reclassification. Notably, the Ferrara specimens exhibit reticulate oospores and specific morphological traits that align well with N. axillaris. However, a syntype of N. axillaris housed at the BM Herbarium presents an anomaly, as it features granulate rather than the expected reticulate oospores. This discrepancy indicates a need for further studies, given that the lectotype of N. axillaris lacks oospores altogether. For now, the charophyte population from Ferrara can be provisionally assigned to N. axillaris “sensu Auctores”. Additionally, it appears to be an alien species introduced into the rice fields of Northern Italy, highlighting the need for further investigation into its taxonomy and distribution. Full article

Background: The plant hormone cytokinin is a conserved regulator of plant development. LONELY GUY (LOG) proteins are pivotal in cytokinin biosynthesis. However, their origin, evolutionary history, and enzymatic characteristics remain largely uncharacterized. Methods: To elucidate LOG family evolution history and protein motif composition, we conducted phylogenetic and motif analyses encompassing representative species across the whole green plant lineage. Catalytic activity and structure analysis were conducted to thoroughly characterize the LOG proteins. Results: Our phylogeny showed that LOG proteins could be divided into five groups and revealed three major duplication events giving rise to four distinct groups of vascular LOG proteins. LOG proteins share a conserved structure characterized by a canonical motif arrangement comprising motifs 1, 2, 3, 4, 5, 6, and 7. Two significant changes in LOG motif composition occurred during the transition to land plants: the emergence of motif 3 in charophyte LOG sequences and the subsequent acquisition of motif 8 at the C-terminus of LOG proteins. Enzymatic assays demonstrated that LOG proteins can be classified into two groups based on their enzyme activity. One group act as cytokinin riboside 5′-monophosphate phosphoribohydrolase and primarily convert iPRMP to iP, while the other group act as 5′-ribonucleotide phosphohydrolase, and preferentially produce iPR from the same substrates. TaLOG5-4A1, TaLOG5-4A2, TaLOG5-5B2, and TaLOG5-D1 shared conserved residues in the critical motif and were predicted to have similar protein structures, but displayed distinct enzymatic activities. Conclusions: Our findings provide a comprehensive overview of LOG protein phylogeny and lay a foundation for further investigations into their functional diversification. Full article

High-mountain lakes (HMLs) are remote, extreme, and sensitive ecosystems recognized as sentinels of global change. Lakes El Sol and La Luna are very close to each other inside the crater of the Nevado de Toluca volcano, but they differ morphometrically and limnologically. This study aimed to identify the seasonal fluctuation of the phytoplankton communities of these two tropical HMLs. El Sol phytoplankton comprised 50 taxa (chlorophytes, diatoms, charophytes) and La Luna 28 taxa (diatoms, euglenoids). The abundance of phytoplankton in El Sol was three times higher than in La Luna, and the biomass in El Sol was five times higher than in La Luna. Tropical seasonality was reflected differently in each lake. In El Sol, the highest phytoplankton abundance occurred in the rainy season, while the highest biomass was recorded in the dry/warm season. Conversely, in La Luna, abundance and biomass were more prominent in the dry/cold season. The study found that no meteorological or limnological factors could explain the seasonal dynamics of the taxonomic richness, abundance, or biomass of the phytoplankton communities in both lakes. The differences between the lakes are likely due to the more extreme conditions of La Luna, such as lower pH, ultra-oligotrophy, and increased exposure to ultraviolet radiation (UVR). Additionally, the introduction of rainbow trout into El Sol in the 1950s may have also contributed to the differences. Full article

Most of the aquatic vegetation produces organic substances via the C3 photosynthetic pathway (mosses, isoetids—Lobelia dortmanna L., Luronium natans (L.) Raf., and vascular plants) or Crassulacean acid metabolism (CAM, e.g., Littorella uniflora (L.) Asch. and Isoëtes lacustris L.) or by their ability to use HCO₃⁻ via carbon concentration mechanisms (CCMs—some elodeids and charophytes). Differentiating these predominant photosynthetic pathways in aquatic vegetation based on their organic matter (OM) carbon stable isotopes (δ¹³C_ORG) is a complex task, in contrast to terrestrial plants. This study investigates the OM deposition, characterized by δ¹³C_ORG values in 10 macrophyte species with different photosynthetic pathways (C3, CAM, and CCM) collected from 14 softwater Lobelia lakes in northern Poland. The higher δ¹³C_ORG values distinguish the CCM group, indicating their use of ¹³C-enriched HCO₃¯ in photosynthesis. CAM species show slightly higher δ¹³C_ORG values than C3, particularly in lower pH lakes. Principal component analysis of isotopic and environmental data did not yield clear distinctions by the groups, but still, they significantly differ in light of analyzed parameters and isotopic signals (PRMANOVA = 5.08, p < 0.01; K-W H = 27.01, p < 0.001). The first two PCA dimensions showed that the water pH and Ca²⁺ concentration positively influenced δ¹³C values. The influence of light conditions on δ¹³C_ORG values revealed by third PCA components seems to also be important. In summary, northern Polish Lobelia lakes serve as a key differentiation point between vegetation employing CCMs and those relying on C3/CAM photosynthesis without HCO₃⁻ utilization, providing insights into transitions in plant communities within these ecosystems. Full article

Because their resistant, sporopolleninous walls preserve a record of morphogenetic change during spore formation, fossil cryptospores provide a direct physical record of the evolution of sporogenesis during the algal–plant transition. That transition itself is a story of the evolution of development—it is not about phylogeny. Here, we review the fossil record of terrestrially derived spore/cryptospore assemblages and attempt to place these microfossils in their evolutionary context with respect to the origin of complex multicellularity in plants. Cambrian cryptospores show features related to karyokinesis seen in extant charophytes, but they also possess ultrastructure similar to that seen in liverworts today. Dyadospora, a cryptospore dyad recovered from sporangia of Devonian embryophytes, first occurs in the earliest Ordovician. Tetrahedraletes, a likely precursor to the trilete spore, first occurs in the Middle Ordovician. These fossils correspond to evolutionary novelties that were acquired during a period of genome assembly prior to the existence of upright, axial sporophytes. The cryptospore/spore fossil record provides a temporal scaffold for the acquisition of novel characters relating to the evolution of plant sporogenesis during the Cambrian–Silurian interval. Full article

PsbS is one of the key photoprotective proteins, ensuring the tolerance of the photosynthetic apparatus (PSA) of a plant to abrupt changes in irradiance. Being a component of photosystem II, it provides the formation of quenching centers for excited states of chlorophyll in the photosynthetic antenna with an excess of light energy. The signal for “turning on” the photoprotective function of the protein is an excessive decrease in pH in the thylakoid lumen occurring when all the absorbed light energy (stored in the form of transmembrane proton potential) cannot be used for carbon assimilation. Hence, lumen-exposed protonatable amino acid residues that could serve as pH sensors are the essential components of PsbS-dependent photoprotection, and their pK_a values are necessary to describe it. Previously, calculations of the lumen-exposed protonatable residue pK_a values in PsbS from spinach were described in the literature. However, it has recently become clear that PsbS, although typical of higher plants and charophytes, can also provide photoprotection in green algae. Namely, the stress-induced expression of PsbS was recently shown for two green microalgae species: Chlamydomonas reinhardtii and Lobosphaera incisa. Therefore, we determined the amino acid sequence and modeled the three-dimensional structure of the PsbS from L. incisa, as well as calculated the pK_a values of its lumen-exposed protonatable residues. Despite significant differences in amino acid sequence, proteins from L. incisa and Spinacia oleracea have similar three-dimensional structures. Along with the other differences, one of the two pH-sensing glutamates in PsbS from S. oleracea (namely, Glu-173) has no analogue in L. incisa protein. Moreover, there are only four glutamate residues in the lumenal region of the L. incisa protein, while there are eight glutamates in S. oleracea. However, our calculations show that, despite the relative deficiency in protonatable residues, at least two residues of L. incisa PsbS can be considered probable pH sensors: Glu-87 and Lys-196. Full article

Charophytes are amongst the most endangered primary producers in freshwater and coastal ecosystems. In spite of the extensive research on the group and its ecological and conservational relevance, scarce information is available on Mediterranean environments, especially rivers and small water reservoirs, where charophytes face challenging summer droughts and changes in hydrological regimes, as well as pervasive anthropogenic pressures. This research aimed, through repeated field observations, detailed analyses of population traits, and extensive characterization of the colonized environments, to foster an understanding of the distribution, biodiversity, and ecology of charophytes in an area of exceptional environmental value and that is still uninvestigated in relation to its charophyte flora, the southern Campania region (Italy). Overall, 17 populations were discovered, belonging to 4 taxa of the Chara genus: C. globularis, C. gymnophylla, C. vulgaris, and C. vulgaris var. papillata, reduced to 12 populations and to the first 3 taxa by the end of the study. The species occupied different ecological niches and colonized environments such as rivers and small ponds, with environment-dependent morphotypes. The occurrence of few taxa with a wide distribution, often forming ephemeral populations, suggests ongoing constraints on charophyte biodiversity in the area, favoring opportunistic species that are able to benefit from temporary refugia. Full article

Within the northeastern part of the Black Sea, the vegetation of charophytes was studied using the Braun-Blanquet approach. For the first time, five communities are described, including three associations and two subassociations from the alliance Charion canescentis Krausch 1964, the order Charetalia intermediae Sauer 1937, and the class Charetea intermediae F. Fukarek 1961. Diagnoses of the described syntaxa are given. A comparison with the Baltic and Mediterranean communities of charophytes is made. It is shown that all northeastern Black Sea communities with the dominance of charophytes, in contrast to Western European ones, include Lamprothamnium papulosum with high constancy. At the same time, the investigated communities are characterized by a lower occurrence and abundance of higher aquatic plants (except for Nanozostera noltei) and a slightly higher occurrence of red and green algae. An indirect ordination analysis showed the ecological isolation of the described phytocenoses and revealed two main factors influencing the floristic composition of communities—the granulometric composition of bottom sediments and water eutrophication. Full article

The charophytes in many regions of the world are still poorly understood. This hampers the synthesis of distributional and ecological datasets at worldwide and continental scales, as well as complicates the generalization of species concepts for widely distributed and local taxa. To fill in the blanks for charophytes in the Caucasus and to improve our knowledge of species distribution areas in Eurasia, a field survey and study of available specimens from Dagestan (North Caucasus, Russia) was conducted based on morphological observation using light and scanning electron microscopy and molecular genetic analyses allowing for the precise identification and testing of the presence of cryptic and undescribed taxa. Nineteen new localities for seven Chara species and one Tolypella species, seven new species, and one new genus were identified in the studied region, and one new species in the Caspian Sea region was found. Some species records changed the outline or filled in the gaps in species distribution data. The presence of species distributed mainly in central Eurasia (C. globata, C. neglecta) with mainly Mediterranean–Middle Eastern species (C. gymnophylla) is notable for this region, as well as for other studied regions of the Caucasus characterized by a mixture combination of species with different distribution patterns. Chara gymnophylla was frequent in Dagestan, similar to the Mediterranean and Middle Eastern regions. Small brackish waterbodies on the coast of the Caspian Sea, freshwater mountain rivers, small associated waterbodies, and water reservoirs are the main habitats of charophytes in the studied region. Based on habitat preference and distribution in the Caucasus, recommendations for the protection of some species were suggested. The lack of endemic species among charophytes from Dagestan and Caucasus contrasts with the flora of terrestrial magnoliophytes that is rich in species endemism. Full article

Plant primary cell walls are composite structures surrounding the protoplast and containing pectins, hemicelluloses, and cellulose polysaccharides, as well as proteins. Their composition changed during the evolution of the green lineage from algae to terrestrial plants, i.e., from an aquatic to a terrestrial environment. The constraints of life in terrestrial environments have generated new requirements for the organisms, necessitating adaptations, such as cell wall modifications. We have studied the cell wall polysaccharide composition of thalli of Marchantia polymorpha, a bryophyte belonging to one of the first land plant genera. Using a collection of specific antibodies raised against different cell wall polysaccharide epitopes, we were able to identify in polysaccharide-enriched fractions: pectins, including low-methylesterified homogalacturonans; rhamnogalacturonan I with arabinan side-chains; and hemicelluloses, such as xyloglucans with XXLG and XXXG modules, mannans, including galactomannans, and xylans. We could also show the even distribution of XXLG xyloglucans and galactomannans in the cell walls of thalli by immunocytochemistry. These results are discussed with regard to the cell wall proteome composition and in the context of the evolution of the green lineage. The cell wall polysaccharides of M. polymorpha illustrate the transition from the charophyte ancestors of terrestrial plants containing xyloglucans, xylans and mannans as hemicelluloses, and embryophytes which do not exhibit mannans as major primary cell wall polysaccharides. Full article

In Serbia, almost all charophyte species belong to one of the IUCN categories. This study aimed to gather more knowledge about their floristic richness, distribution and ecology. During the survey, 262 localities were investigated in the Vojvodina province, northern Serbia. Seventeen charophyte species were found, out of which 16 were included in the analyses. The environmental matrix included 38 localities, each characterized by habitat type and 35 environmental parameters. The canonical correspondence analysis (CCA) showed six parameters as being statistically significant: substrate, altitude, depth, water temperature, temperature annual range and precipitation of the driest month. Together, these explain the 32.34% variability in the species composition and abundance data. Altitude and substrate contributed the most to this. Two main types of habitats were outlined by the analysis. Small and shallow temporary habitats in the river floodplains, at lower altitudes, with muddy and clayish substrate, belong to one type. These areas are inhabited by either very tolerant species, such as Chara vulgaris and C. globularis, or the so-called “spring” species of the genera Tolypella and Nitella. Habitats which are located at higher altitudes, when deeper and more permanent with a sandy substrate, such as sandpits and river habitats, belong to the second one. These areas are inhabited by species like Chara papillosa, C. hispida, and Nitellopsis obtusa. Full article