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Potamogetonaceae are aquatic plants divided into six genera. The largest genus in the family is Potamogeton, which is morphologically diverse with many hybrids and polyploids. Potamogetonaceae plastomes were conserved in genome size (155,863 bp–156,669 bp), gene contents (113 genes in total, comprising 79 protein-coding genes and 30 tRNA and 4 rRNA genes), and GC content (36.5%). However, we detected a duplication of the trnH gene in the IR region of the Potamogeton crispus and P. maakianus plastomes. A comparative analysis of Alismatales indicated that the plastomes of Potamogetonaceae, Cymodaceae, and Ruppiaceae have experienced a 6-kb inversion of the rbcL-trnV region and the ndh complex has been lost in the Najas flexilis plastome. Five divergent hotspots (rps16-trnQ, atpF intron, rpoB-trnC, trnC-psbM, and ndhF-rpl32) were identified among the Potamogeton plastomes, which will be useful for species identification. Phylogenetic analyses showed that the family Potamogetonaceae is a well-defined with 100% bootstrap support and divided into two different clades, Potamogeton and Stuckenia. Compared to the nucleotide substitution rates among Alismatales, we found neutral selection in all plastid genes of Potamogeton species. Our results reveal the complete plastome sequences of Potamogeton species, and will be helpful for taxonomic identification, the elucidation of phylogenetic relationships, and the plastome structural analysis of aquatic plants. [ABSTRACT FROM AUTHOR]

Applicability of ITS1–ITS2 primary structure for species attribution of representatives of the genus Stuckenia was experimentally tested. Analysis of the ITS1–ITS2 region sequences of S. vaginata and S. pectinata from public databases showed that they differed by insertions/deletions and single or double nucleotide substitutions. Besides, the ITS1–ITS2 region of S. pectinata was shown to be represented by two haplotype groups designated as S. pectinata type A and S. pectinata type B with good bootstrap support in phylogenetic reconstructions. In 28 samples identified as S. pectinata, S. vaginata, S. macrocarpa and S. chakassiensis on the basis of morphology, the ITS1–ITS2 region was sequenced in this study. Three groups of samples with good bootstrap support were revealed to be corresponding to S. vaginata, S. pectinata type A and S. pectinata type B. The S. vaginata group was formed by the samples identified on the basis of morphology as S. vaginata, and the S. pectinata type A group was formed by the samples identified on the basis of morphology as S. pectinata. The S. pectinata type B group was further divided into two subgroups, S. pectinata type B subgroup and S. chakassiensis subgroup. The S. chakassiensis subgroup included mainly the samples identified as such on the basis of morphology. The S. pectinata type B subgroup included samples identified on the basis of morphology as S. pectinata, S. vaginata and S. macrocarpa. We suppose that these samples were S. pectinata type B, S. macrocarpa and their hybrids.

Aquatic plant species are often widespread, even across continents. They pose a challenge to species delimitation and taxonomy due to their reduced morphology and high phenotypic plasticity. These difficulties are even more pronounced in the case of interspecific hybridization. We investigate the aquatic plant genus Stuckenia for the first time on a worldwide scale. Expert species determination is aided by sequencing of nuclear ribosomal ITS and 5S-NTS regions and the plastid intergenic spacers rpl20-5'rps12 and trnT-trnL. Nuclear markers are used to infer hybridization, and the maternal origin of hybrids is addressed with plastid markers. Pure species are subjected to phylogenetic analyses. Two main Stuckenia lineages are found: one consists of S. amblyphylla, S. filiformis, S. pamirica, and S. vaginata, the other includes S. pectinata and S. striata. The widespread species S. pectinata, S. filiformis, and S. vaginata show intraspecific genetic variation, which is structured geographically. Many intraspecific hybrids, which are usually fertile, occur between those genotypes. Interspecific hybrids, which are consistently sterile, are detected among all widespread species; some are reported for the first time in several countries and regions. They originated multiple times from reciprocal crosses and reflect the geographical origins of parental genotypes. Intraspecific genetic variation can be higher than interspecific differences between closely related species. Comparison of phenotypic variation in the field and in cultivation with genotypic variation shows that numerous conspicuous forms have been overestimated taxonomically. These are resolved as phenotypes responding to unusual environments, have recurrently evolved adaptations, or represent extreme forms of continuous variation of the recognized species. However, some specific regional lineages, which have evolved from variable species, may be interpreted as early steps of the speciation process. Hybridization has been underestimated in some regions as a source of Stuckenia diversity, and the respective hybrid plants have been misidentified as intraspecific taxa or even as separate species. Many erroneous entries in sequence databases are detected and summarized. This work provides a sound basis for species delimitation and hybrid recognition in this difficult genus. [ABSTRACT FROM AUTHOR]

Lanthanum-modified bentonite (LMB) combined with submerged macrophytes (SM) has been a conventional means of eutrophication management in lakes in recent years, and is one of the most important methods for P removal. However, trends in nutrients and sediment enzymes at the water-sediment interface during this process have not been systematically assessed, and there are still some gaps in how abiotic properties drive changes in enzyme activity. Here, we show changes in aquatic environmental conditions under the action of different ratios of modified bentonite (0, 10%, 20%, and 30%) in combination with SM (Vallisneria natans, Potamogeton lucens, and Hydrilla verticillate) and quantify their effects on sediment enzyme activities. The results showed that the nutrient cycling at the water-sediment interface was facilitated by the combined effect of SM and LMB, which effectively reduced the overlying water nutrient concentration, increased the sediment enzyme activity and enhanced the N cycling process. Partial least squares structural equation model (PLS-SEM) showed that sediment parameters strongly influenced changes in enzyme activity, with NO 3 -N as the main controlling factors. Our study fills in the process of changing environmental conditions in lake water under geoengineered materials combined with macrophyte measures, especially the changes in biological properties enzyme activities, which contributes to a clearer understanding of nutrient fluxes during the management of eutrophication in lakes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Aquatic plant species are often widespread, even across continents. They pose a challenge to species delimitation and taxonomy due to their reduced morphology and high phenotypic plasticity. These difficulties are even more pronounced in the case of interspecific hybridization. We investigate the aquatic plant genus Stuckenia for the first time on a worldwide scale. Expert species determination is aided by sequencing of nuclear ribosomal ITS and 5S-NTS regions and the plastid intergenic spacers rpl20-5’rps12 and trnT–trnL. Nuclear markers are used to infer hybridization, and the maternal origin of hybrids is addressed with plastid markers. Pure species are subjected to phylogenetic analyses. Two main Stuckenia lineages are found: one consists of S. amblyphylla, S. filiformis, S. pamirica, and S. vaginata, the other includes S. pectinata and S. striata. The widespread species S. pectinata, S. filiformis, and S. vaginata show intraspecific genetic variation, which is structured geographically. Many intraspecific hybrids, which are usually fertile, occur between those genotypes. Interspecific hybrids, which are consistently sterile, are detected among all widespread species; some are reported for the first time in several countries and regions. They originated multiple times from reciprocal crosses and reflect the geographical origins of parental genotypes. Intraspecific genetic variation can be higher than interspecific differences between closely related species. Comparison of phenotypic variation in the field and in cultivation with genotypic variation shows that numerous conspicuous forms have been overestimated taxonomically. These are resolved as phenotypes responding to unusual environments, have recurrently evolved adaptations, or represent extreme forms of continuous variation of the recognized species. However, some specific regional lineages, which have evolved from variable species, may be interpreted as early steps of the speciation process. Hybridization has been underestimated in some regions as a source of Stuckenia diversity, and the respective hybrid plants have been misidentified as intraspecific taxa or even as separate species. Many erroneous entries in sequence databases are detected and summarized. This work provides a sound basis for species delimitation and hybrid recognition in this difficult genus.

Premise: The sporoderm of seed‐plant pollen grains typically has apertures in which the outer sporopollenin‐bearing layer is relatively sparse. The apertures allow regulation of the internal volume of the pollen grain during desiccation and rehydration (harmomegathy) and also serve as sites of pollen germination. A small fraction of angiosperms undergo pollination in water or at the water surface, where desiccation is unlikely. Their pollen grains commonly lack apertures, though with some notable exceptions. We tested a hypothesis that in some angiosperm aquatics that inhabit water of unstable salinity, the pollen apertures accommodate osmotic effects that occur during pollination in such conditions. Methods: Pollen grains of the tepaloid clade of the monocot order Alismatales, which contains ecologically diverse aquatic and marshy plants, were examined using light microscopy and scanning electron microscopy. We used Ruppia as a model to test pollen grain response in water of various salinities. Pollen aperture evolution was also analyzed using molecular tree topologies. Results: Phylogenetic optimizations demonstrated an evolutionary loss and two subsequent regains of the aperturate condition in the tepaloid clade of Alismatales. Both of the taxa that have reverted to aperturate pollen (Ruppia, Ruppiaceae; Althenia, Potamogetonaceae) are adapted to changeable water salinity. Direct experiments with Ruppia showed that the pollen apertures have a role in a harmomegathic response to differences in water salinity. Conclusions: Our results showed that the inferred regain of pollen apertures represents an adaptation to changeable water salinity. We invoke a loss‐and‐regain scenario, prompting questions that are testable using developmental genetics and plant physiology. [ABSTRACT FROM AUTHOR]

Clasping-leaved Potamogeton L. species growing in Turkey are P. praelongus Wulfen and P. perfoliatus L. There exists no detailed study about distribution, habitat requirements, and anatomical properties of the Turkish populations of the two species. Potamogeton perfoliatus is widespread throughout the country but P. praelongus was recorded only from a single locality. Therefore, P. praelongus is rare and endangered in Turkey. In this study, we recorded presence of P. perfoliatus in 54 wetlands based on examination of 86 herbarium specimens. Physical and chemical parameters of the water bodies where the two species occur were measured from 24 sites for P. perfoliatus and from one site for P. praelongus. According to our findings, P. praelongus grows in an alpine lake with oligotrophic, calcareous and alkaline water. Potamogeton perfoliatus occupies diverse habitats but prefers deep lentic water bodies with high pH and low salinity levels. Stem anatomy of the species were studied based on three individuals for P. praelongus and 35 individuals for P. perfoliatus. Morphological features of the species were also investigated and descriptions based on Turkish material were prepared. We provided the distinguishing anatomical and morphological characters between the species. Our anatomical findings showed that P. praelongus specimens have eight vascular bundles in contrast to previous reports on the species. Our results can be used for future monitoring of the two submerged Potamogeton species as we provide detailed information about their current distribution pattern and habitat features.

Zannichellia L. (Potamogetonaceae) is a widespread aquatic genus that is distributed in temperate and subtropical aquatic ecosystems worldwide. Because the biogeographical location of Iran includes mountain ranges and deserts that may cause different habitat types, it was assumed that these Zannichellia populations would be stronger differentiated than observed in Zannichellia from temperate regions. The present study aimed to test whether Z. palustris would demonstrate high levels of genetic differentiation over long distances and across mountain ranges. The genetic structure of the populations of Zannichellia was investigated using inter simple sequence repeats (ISSR) and sequence-related amplified polymorphism (SRAP) as molecular markers. The results demonstrated overall high levels of genetic differentiation among populations (GST = 0.53) and isolation by distance. Bayesian assignment analysis at the population level grouped individuals into eight genetic clusters (K = 8) that largely correspond to the topographic barriers. Alongside the same mountain ridge, the freshwater and saltwater habitat differences corresponded to Z. palustris var. palustris and Z. palustris var. pedicellata, respectively. Our results support the hypothesis of isolation by distance. This high level of genetic differentiation argues for a conservation strategy to maintain a diversity of populations of Zannichellia in mountainous regions. [ABSTRACT FROM AUTHOR]

Antimony (Sb) is increasingly released and poses a risk to the environment and human health. Antimonite (Sb(III)) oxidation can decrease Sb toxicity, but the current knowledge regarding the effects of Sb(III) and antimonate (Sb(V)) exposure is limited to wetland plants, especially the Sb speciation in plants. In this study, Phragmites australis and Potamogeton crispus were exposed to 10 and 30 mg/L Sb(III) or Sb(V) for 20 days. The total concentration, subcellular distribution, and concentration in the iron plaque of Sb were determined. The Sb speciation in plants was analyzed by HPLC-ICP-MS. It illustrated that Sb(III) exposure led to more Sb accumulation in plants than Sb(V) treatments, with the highest Sb concentration of 405.35 and 3218 mg/kg in Phragmites australis and Potamogeton crispus, respectively. In the subcellular distribution of Sb, accumulation of Sb mainly occurred in cell walls and cell cytosol. In Phragmites australis, the transport factor in the Sb(V) treatments was about 3 times higher than the Sb(III) treatments, however, it was lower in the Sb(V) treatments than Sb(III) treatments for Potamogeton crispus. Sb(V) was detected in the plants of Sb(III) treatments with different Sb(V)-total Sb vitro (Phragmites australis: 34 % and, Potamogeton crispus: 15 %), moreover, Sb(V) was also detected in the nutrient solution of Sb(III) treatments. Antimony exposure caused a reduction of the iron plaque formation, at the same time, the root aerenchyma formation was disrupted, and this phenomenon is more pronounced in the Sb(III) treatments. Moreover, the iron plaque has a higher sorption potential to Sb under Sb(III) exposure than that under Sb(V) exposure. The results can fill the gap for antinomy speciation in wetland plants and expand the current knowledge regarding the Sb translocation in wetland systems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The influence of macrophytes on the optical environment of the littoral zone was assessed by studying the effect of monospecific Potamogeton perfoliatus on the quantitative and qualitative properties of light and the response of plants to this altered environment. P. perfoliatus was shown to alter the optical environment and consequently its own architecture: in high-density pondweed patches, 67 percent of incident light was absorbed in the top 10 cm, while spectral properties of light was significantly altered. Leaf morphology and photophysiology adapted to these changes, with photosynthetically active biomass concentrated in the upper water layer and stem biomass increasing in the basal parts due to self-shading. This study highlights the importance of submerged macrophytes in shaping the optical environment and ecological dynamics of littoral zones. Not only do pondweed plants from different sites show very similar vertical patterns of morphological and physiological parameters, but they also contribute to similar vertical spatial variability in water optics, thus increasing habitat complexity. This added optical heterogeneity not only increases the diversity of the littoral zone, but also enriches the entire aquatic ecosystem of shallow lakes by providing additional optical ecological niches., (© 2024. The Author(s).)

Research on the toxicity effects of nano-plastics on submerged macrophytes has been increasing over the past several years. However, how the endophytic bacteria of submerged macrophytes respond to nano-plastics remains unknown, although they have been widely shown to help terrestrial plants cope with various environmental stressors. Here, a microcosm experiment was performed to unravel the effects of high concentration of nano-plastics (20 mg/L) on three submerged macrophyte (Vallisneria natans, Potamogeton maackianus, Myriophyllum spicatum) and their endophytic bacterial communities. Results indicated that nano-plastics induced antioxidative stress in plants, but significantly reduction in relative growth rate (RGR) only occurred in V. natans (from 0.0034 to -0.0029 day -1 ), accompanied by change in the stem/leaves endophyte community composition. Further analysis suggested nano-plastics caused a reduction in environmental nutrient availability and the proportion of positive interactions between endophyte communities (43%), resulting in the lowest RGR of V. natans. In contrast, endophytes may help P. maackianus and M. spicatum cope with nano-plastic stress by increasing the proportion of positive correlations among communities (70% and 75%), leaving their RGR unaffected. Collectively, our study elucidates the species-specific response strategies of submerged macrophyte-endophyte to nano-plastics, which helps to reveal the different phytoremediation potential of submerged macrophytes against nano-plastic pollution., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Abstract Oxygen availability in water is considered one of the most important factors for growth and productivity in aquatic submerged macrophytes. In the present study, the growth, stress responses, and metabolic changes in Potamogeton anguillanus Koidz. (Potamogetonaceae) were assessed after a 21-day exposure to low (hypoxia; dissolved oxygen, DO < 1 mg/L) or null (anoxia) oxygen concentrations in water. High growth rates and an increased indole acetic acid (IAA) content in P. anguillanus were observed under the hypoxic conditions (4-fold to control) compared to the anoxic conditions. In addition, the activation of glycolysis and fermentation processes was further recorded, given the increase in alcohol dehydrogenase activity and pyruvate concentration on the studied plants that were exposed to low oxygen concentrations. Moreover, the positive correlations of antioxidative enzyme activities, catalase (CAT) and guaiacol peroxidase (POD) with hydrogen peroxide (H 2 O 2) confirmed the species ability to scavenge excess H 2 O 2 under low oxygen stress. The capillary electrophoresis–mass spectrometry (CE-MS) analysis of the metabolome identified metabolite accumulations (e.g., glutamate, glutamine, aspartate, asparagine, valine, malate, lactate, citrate, isocitrate, proline and γ-amino butyric acid) in response to the anoxia. [ABSTRACT FROM AUTHOR]

Montezuma Well is a geothermal limnocrene spring within Montezuma Castle National Monument, Yavapai County, Arizona, U.S.A. The Well's unusual geological qualities, water chemistry, and a history of aquatic plant collecting are discussed. Evidence to support the fact that a unique species of Potamogeton has likely grown in this location for thousands of years and is now recognized as the seventh apparent autochthonous endemic species from this small area is presented. Although this new species shares a few superficial characters with P. illinoensis Morong, it is easily distinguished by its massive height (7-8 m tall), lack of floating leaves, long acuminate leaf apices of its submerged leaves, and bright translucent green leaf color. A complete description with drawing and photographs is provided. [ABSTRACT FROM AUTHOR]

A classical biological control programme against Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae) was initiated in South Africa following the discovery of extensive mats in Jozini Dam in northern KwaZulu-Natal (KZN) in 2006. However, in mid-2008, high densities of a phytophagous insect, Parapoynx diminutalis Snellen (Lepidoptera: Crambidae) were discovered on the H. verticillata infestation, causing high levels of defoliation and dieback of the weed. In order to quantify the impact of the moth and to assess the long-term threat of H. verticillata to South African water bodies, a monitoring programme was initiated in 2013. Although P. diminutalis did not demonstrate a preference for H. verticillata over a native aquatic plant, Potamogeton schweinfurthii A. Bennett (Potamogetonaceae), moth populations followed a cyclical pattern of abundance, with rapid population increases coinciding with increases in the abundance of H. verticillata. High damage levels to H. verticillata were associated with high densities of immature P. diminutalis, which consistently led to population crashes of H. verticillata. Parapoynx diminutalis appears to have great potential to contribute to the management of H. verticillata in South Africa. However, the moth's oligophagous habits will probably preclude its intentional introduction into water bodies with H. verticillata where it does not already occur. [ABSTRACT FROM AUTHOR]

The new species Groenlandia pescheri D. Uhl & Poschmann sp. nov., belonging to the family Potamogetonaceae, is described from the Late Oligocene Fossil-Lagerstätte Enspel (Westerwald, Germany). The species is characterized by sub-oppositely arranged leaves without observable stipule-like appendages at the leaf bases and a very thin exocarp (both characteristics of the aquatic genus Groenlandia J. Gay) with a spiked crest (which differs from the only other species included in this genus, the modern Groenlandia densa (L.) Four.). The taxon represents the first pre-Quaternary record of the genus Groenlandia, which is usually regarded as a basal sister group of all other Potamogetonaceae. [ABSTRACT FROM AUTHOR]

Premise of the Study: The detection of environmental DNA (eDNA) using high‐throughput sequencing has rapidly emerged as a method to detect organisms from environmental samples. However, eDNA studies of aquatic biomes have focused on surveillance of animal species with less emphasis on plants. Pondweeds are important bioindicators of freshwater ecosystems, although their diversity is underestimated due to difficulties in morphological identification and monitoring. Methods: A protocol was developed to detect pondweeds in water samples using atpB‐rbcL and ITS2 markers. The water samples were collected from the Grand River within the rare Charitable Research Reserve, Ontario (RARE). Short fragments were amplified using primers targeting pondweeds, sequenced on an Ion Torrent Personal Genome Machine, and assigned to the taxonomy using a local DNA reference library and GenBank. Results: We detected two species earlier documented at the experimental site during ecological surveys (Potamogeton crispus and Stuckenia pectinata) and three species new to the RARE checklist (P. foliosus, S. filiformis, and Zannichellia palustris). Discussion: Our targeted approach to track the species composition of pondweeds in freshwater ecosystems revealed underestimation of their diversity. This result suggests that eDNA is an effective tool for monitoring plant diversity in aquatic habitats. [ABSTRACT FROM AUTHOR]

Aerenchyma tissue presents large air spaces with important physiological and ecological implications. Aerenchyma tissue enables the circulation and storage of gases in response to waterlogging and flooding. Although collapsed cells are usually identified as characteristic of lysigenous aerenchyma, organelles have been found in these cells in other aquatic species. Cell walls have also been implicated in cellular adhesion/separation. Therefore, the formation of a constitutive aerenchyma as in Potamogeton polygonus was investigated based on the glycan distribution and cytological aspects of collapsed cells. The interrelatedness of cell wall properties and aerenchyma formation have given new insights into aerenchyma formation, as a response to different plant habits. We investigated the cytological aspects of these cells via light and electron microscopy. We also performed immunolabeling experiments with a range of glycan-directed monoclonal antibodies to detect possible cell wall polymer changes in this tissue. P. polygonus presents a schizo-radial lysigenous type of aerenchyma in the roots. The lysigeny process did not involve middle lamella degradation. Highly methyl-esterified pectin labeled with LM20 is lost in the cell walls of collapsed cells, which could affect cell adhesion and morphology, leading to the stretching of aerenchyma cells. In contrast, labeling with LM19 (low methyl-esterified pectin) is increased in the anticlinal cell walls and middle lamella of aerenchyma cells. Beyond their known adhesion/separation properties, pectic polysaccharides might play an important role during the stretching of the collapsed cells. The relation of cell wall composition between induced/constitutive aerenchyma and habit indicates different glycan distribution among species. [ABSTRACT FROM AUTHOR]

Many plant species exhibit different leaf morphologies within a single plant, or heterophylly. The molecular mechanisms regulating this phenomenon, however, have remained elusive. In this study, the transcriptomes of submerged and floating leaves of an aquatic heterophyllous plant, Potamogeton octandrus Poir, at different stages of development, were sequenced using high-throughput sequencing (RNA-Seq), in order to aid gene discovery and functional studies of genes involved in heterophylly. A total of 81,103 unigenes were identified in submerged and floating leaves and 6,822 differentially expressed genes (DEGs) were identified by comparing samples at differing time points of development. KEGG pathway enrichment analysis categorized these unigenes into 128 pathways. A total of 24,025 differentially expressed genes were involved in carbon metabolic pathways, biosynthesis of amino acids, ribosomal processes, and plant-pathogen interactions. In particular, KEGG pathway enrichment analysis categorized a total of 70 DEGs into plant hormone signal transduction pathways. The high-throughput transcriptomic results presented here highlight the potential for understanding the molecular mechanisms underlying heterophylly, which is still poorly understood. Further, these data provide a framework to better understand heterophyllous leaf development in P. octandrus via targeted studies utilizing gene cloning and functional analyses. [ABSTRACT FROM AUTHOR]

Although aquatic plants usually are less taxonomically diverse than related terrestrial groups, genetic studies could reveal groups of sibling species and thus increase taxonomic resolution. We hypothesised that different age and environmental diversity of water bodies in southern Siberia caused diversification within Stuckenia pectinata s.l. (Potamogetonaceae). To test this hypothesis we studied nuclear (ITS) and plastid (rpl32-trnL) genetic variation of 37 populations of S . pectinata from eastern Europe, the Russian Far East and southern Siberia with special emphasis on the latter. Plastid DNA variability within S . pectinata s.l. was found to be structured neither geographically nor taxonomically. We revealed strong ITS differentiation within S . pectinata s.l. in southern Siberian water bodies with different combinations of age and salinity. We discuss possible causes of such differentiation. We found a striking contrast between the absence of ITS variability across almost all of Europe colonized by the only ribotype, and relatively high ITS variability in southern Siberia. This contrast could be explained by the different history of young European populations that could have appeared as a result of recent northwards expansion following the Last Glacial Maximum, and the relatively old ones of southern Siberia. The absence of clear correspondence between genetic variation and morphological variability does not sufficiently support delimitation of species within Siberian S . pectinata s.l. (such as S . chakassiensis and S . macrocarpa ). [ABSTRACT FROM AUTHOR]

Seed sources are vital for restoration and conservation of submerged macrophytes. Developing proper storage techniques is important to maintain seed vigor. The present study aimed to investigate the appropriate seed storage methods for species of Hydrocharitaceae ( Ottelia acuminata , O. alismoides , and Valisneria natans ) and Potamogetonaceae ( Potamogeton lucens , P. wrightii , and Stuckenia pectinata ). Seed germination was tested for these six species stored for 30 months in seven conditions (4 °C-Water, 4 °C-Dry, 4 °C-Sand, Ambient-Water, Ambient-Dry, Ambient-Sand, and ambient storage condition: submerged in a pond with lake water). Our results showed that: 1) the three Hydrocharitaceae species had high germination in ambient storage condition; 2) that the germination of these six species was low in ambient temperature storage conditions (Ambient-Water, Ambient-Dry, and Ambient-Sand); 3) that O. acuminata , V. natans , P. wrightii and S. pectinata had higher germination percentage in 4 °C-Dry than in 4 °C-Water. These results suggest that low temperature and dry conditions are favorable to maintain most species seed viability. Natural condition is appropriate for Hydrocharitaceae seed storage. This study will help the conservation and restoration of submerged macrophytes. [ABSTRACT FROM AUTHOR]

Potamogeton pectinatus L. is a widespread aquatic species distributed widely in aquatic ecosystems of Iran. In this study, inter simple sequence repeat (ISSR) markers were used to assess the genetic diversity of 35 accessions and 175 individuals of P. pectinatus collected from different regions of Iran. In total, 123 polymorphic DNA fragments were amplified from five combinations of ISSR primers. The ISSR based principle coordinate analyses (PCoA) demonstrated four different groups mostly corresponding with their geographic origins (North, Kerman/Fars, Centre and Southwest). The most variable populations were found in the central region of Iran possibly as a consequence of the larger number of samples from that region. The result of molecular variance (AMOVA) attributed 11% of the total genetic variation among and 89% within population variation. The results showed high levels of intra-regional and low inter-regional gene flow between clones, although the Northern accessions were clearly differentiated from the others. There was a low correlation between genetic distance and geographic distance of accessions. The results of STRUCTURE analysis suggested the presence of three genetic groups of this species in Iran, mostly adapted to different ecological conditions. Our results cover one of the gaps of different studies worldwide. In addition, our results confirm high levels of genetic diversity of P. pectinatus in Iran. [ABSTRACT FROM AUTHOR]

Due to methodological challenges there are only a few studies that focus on macrophyte dynamics in large lakes despite their notable role in a lake's ecosystem functioning. This study investigates composition and productivity changes of the submerged vegetation of Lake Karakul, Pamir Mountains (Tajikistan), using sedimentary ancient DNA metabarcoding and elemental (C/N) and isotopic (δC, δN) measurements of Stuckenia cf. pamirica (Baagøe) Z. Kaplan (Potamogetonaceae) leaf remains. No Stuckenia cf. pamirica leaf remains were found for 28.7-26.1 cal ka BP, when both Potamogetonaceae and Chara (L.) DNA sequences were recorded, suggesting sparse submerged vegetation at the coring site. This agrees with the inference of a deep lake reached using geochemical proxies. From 26.1 to 17.5 cal ka BP a few macrophyte remains and high numbers of Potamogetonaceae sequences were recovered: lake level was probably low, as suggested by other studies on the lake. Another phase of increased numbers of Chara sequences and the absence of Stuckenia cf. pamirica leaf remains was found between 17.5 and 12.2 cal ka BP, which coincides with a lake-level transgression at Lake Karakul as indicated by paleo-shoreline investigations. Analyses of macrophyte remains reveal intermediate paleo-productivity from 6.9 cal ka BP and high paleo-productivity from 2.2 cal ka BP onwards. From comparisons with other studies, we suggest that lake-level changes are the main driver for the submerged vegetation composition and productivity at the coring site in Lake Karakul and underline our conclusions by depicting the present-day distribution of Stuckenia cf. pamirica and Chara within the lake. [ABSTRACT FROM AUTHOR]

Seagrasses are the only seed plants to have invaded marine environments successfully. Seagrass fossils are both rare and have received scant attention so far. However, among the limited number of plant fossils from marine strata in the Maastrichtian type area, remains of seagrasses are relatively common. The present paper provides a detailed description of the morphology and anatomy of the stems and attached roots of Thalassocharis bosquetii Debey ex Miquel, 1853, mainly on the basis of silicified material. This has enabled an interpretation of features of the abundant imprints (external moulds) among the specimens studied, inclusive of the type material. Contrary to the outcome of earlier studies, the internodes have been found to constitute leaf scars. T. bosquetii is considered to have been a seagrass, but has a complex stem anatomy, including a substantial central stele with numerous sheathed vascular bundles, an inner cortex with many small intercellular cavities, a middle cortex with distinct fibre strands, and an outer cortex with conspicuously thickened vascular bundles, each of which constricts into a thin vascular strand just below a furrow/pit on the leaf scar. The last-named feature underlies the characteristic stem surface pattern seen in Thalassocharis . The stem anatomy of T. bosquetii is clearly more complex than that of extant seagrasses, which, due to prolonged adaptation to their aquatic habitat, show a more or less reduced anatomy. As far as the complexity of the stele is concerned, T. bosquetii reminds more of some non-marine Alismatales, such as the pondweed family Potamogetonaceae and the monotypical peat bog family Scheuchzeriaceae. [ABSTRACT FROM AUTHOR]

In the present study Mg, Al, Si, P, S, Cl, K, Ca, Mn, Fe, Zn, Ag, Sr contents were determined by X-ray fluorescence analysis in sediments and organisms of Contectiana listeri and Potamogeton lucens L. of Lake Ilmenskoe located on the territory of the Ilmen State Reserve (South Ural, Russia). It was shown that microelements-rich sapropels are formed in the Lake Ilmenskoe. The Lake Ilmenskoe is free of anthropogenic impact and may be regarded as models while assessing the lakes under anthropogenic impact. The average element composition of macrophytes, gastropod shells and muscles, sapropel and sandy sediment were compared with the clarkes of elements in the continental crust with a preliminary aluminium rating, aluminium being the least fluent and abiogenic element of the system 'sediment - hydrobiont'. Sapropel was particular rich in microelements in comparison with sandy sediments. Study is shown that most elements are accumulated in aquatic organisms. Contectiana listeri and Potamogeton lucens L. may be considered as geochemical barriers. They can be used as biomonitors. We found out that low-iron, lowcalcium, low-ash sapropel was forming in Lake Ilmenskoe. [ABSTRACT FROM AUTHOR]

The genus Ditylenchus consists of more than 60 species, some of which are plant parasites. In this paper we report on Ditylenchus laurae sp. n. from Poland, a new species associated with the aquatic plant, Potamogeton perfoliatus L. Ditylenchus laurae sp. n. is characterised by a long and slender body with L = 1881 (1523-2095) µm and 1875 (1690-2089) µm, a = 88.8 (72.5-102.5) and 89.7 (71.9-97.9), stylet length = 10.8 (9.6-12.1) µm and 8.3 (7.7-9.0) µm, tail length = 117.2 (103.5-126.7) µm and 102.4 (98.3-113.6) µm in females and males, respectively; four incisures, rounded stylet knobs, long basal bulb (about ten times as long as wide), post-vulval uterine sac from 4.3-5.6 vulval body diam. long, and mucronate tail. Characterisation using the ITS rRNA, COI and hsp90 gene sequences was conducted and a phylogenetic analyses revealed that D. laurae sp. n. belongs to the D. dipsaci complex. [ABSTRACT FROM AUTHOR]

In the present study, a novel seasonal plant collocation system (SPCS), specifically the Potamogeton crispus and Phragmites australis series system, was investigated to enhance the performance of surface flow constructed wetlands (SFCWs) at low temperature. Results of a year-round experiment showed that SPCS conquered the adverse effect of low temperature and achieved sustainable nutrients removal. In addition, during winter, removal efficiencies of NH 4 -N, TP, COD, and TN in SPCS were 18.1%, 17.6%, 10.1% and 5.2% higher than that in the control, respectively. P. crispus and P. australis complemented each other in terms of plant growth and plant uptake during the experiment period. Furthermore, it emerged that P. crispus could increase the quantity of ammonia oxidizing bacteria by 10.2%, due to its high oxygen enrichment ability. It is suggested that seasonal plant collocation has a promising future in SFCWs of areas being affected by climate change, e.g. northern China. [ABSTRACT FROM AUTHOR]

This study focuses on the Potamogetonaceae found in the state of Rio de Janeiro, Southeast Brazil. It is based on a morphological analysis of herbaria collections, as well as on a review of the relevant literature. A total of four species were recorded for the state: Potamogeton illinoensis, P. montevidensis, P. polygonus e P. pusillus, occurring in specific regions of the state (Cabo Frio, Carapebus, Itatiaia, Jacarepaguá, Macaé, São João da Barra and Teresópolis). Identification key, description, habitat data, phenology, and geographic distribution are also provided. [ABSTRACT FROM AUTHOR]

Morphological variation in widely distributed plants may be driven by phenotypic plasticity or underlying genetic differences. In the brackish to fresh open waters of San Francisco Estuary, there are at least two distinct growth forms of a native pondweed in the genus Stuckenia. We determined that all plants collected from throughout the region are S. pectinata by sequencing the nuclear ribosomal internal transcribed spacer (ITS) region. This led us to question if different morphologies result from intraspecific genetic differentiation or differences in water flow, which we explored using microsatellites and a common garden experiment, respectively. As only four of nine microsatellite loci developed in Europe were polymorphic for our samples, there was low resolution to detect differences; however, some multilocus genotypes found only in narrow-leaf samples hinted of within-species variation. Further, while morphological traits were plastic in response to flow manipulation, distinct morphotypes did not converge under the same conditions, implicating genetic differences. Regardless of mechanisms for contrasting growth forms, leaf size and quantity may affect available habitat for ecologically-important invertebrates. We found narrow/dense leaves supported greater invertebrate densities at both a low-salinity, and especially, a brackish site. The latter was dominated by an amphipod that we determined strongly prefers to consume narrower leaves. We conclude that both environmental conditions and genetic differentiation play a role in S. pectinata morphology. That these differences propagate to higher trophic levels calls for further investigation into the genetic basis for, as well as spatial extent of, the two morphotypes. • Stuckenia sp. pondweeds in San Francisco Estuary have unusual morphology. • Genetic data show plants ranging in morphology are all Stuckenia pectinata. • Common garden experiments only partially explain the range of variation in the region. • Within-species genetic variation may play a role in the observed variation. • Herbivory experiments suggest morphological differences affect higher trophic levels. [ABSTRACT FROM AUTHOR]

Water exchange unevenness (WEU) is defined as the coefficient of variation in water exchange intensity over time. Although its influence on aquatic plant characteristics has been recently investigated, there is limited understanding regarding the effects of this hydrodynamic change on submerged vegetation. This study investigated the impacts of WEU on the species dominance and community composition of submerged macrophytes in three bays with different WEU conditions in Erhai Lake, China. Subsequently, a laboratory experiment was conducted to elucidate the mechanisms underlying these effects. The field investigation showed that the dominance values of submerged macrophytes were influenced by WEU. As WEU decreased, the average dominance value decreased for Vallisneria natans (by 34.54 %), Myriophyllum spicatum (16.82 %), and Hydrilla verticillata (12.84 %); showed no significant change for Potamogeton lucens; and increased for Potamogeton maackianus (14.22 %) and Ceratophyllum demersum (17.52 %). The laboratory experiment showed that lower WEU markedly inhibited the growth of V. natans, slightly inhibited that of M. spicatum, and stimulated that of P. maackianus, consistent with the field observations. The inhibitory effect was attributed to a reduced concentration of carbon dioxide in the water; adaptive strategies, i.e., plant height, biomass allocation, and root traits, were more effective for M. spicatum than for V. natans. The stimulated growth of P. maackianus was attributed to increased dissolved oxygen concentration, which promoted root growth and nutrient uptake. Our results indicate that WEU has significant effects on the growth and community characteristics of submerged macrophytes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Special characterization and assembly of epiphytic microbial communities remain unclear in micro-polluted water column during submersed macrophytes restoration. In this study, an in-situ enclosure area sowing with turions of Potamogeton crispus (P. crispus) was conducted in a micro-polluted urban river to investigate the characterization of P. crispus and epiphytic microbial communities and their response to water environment under different water depths. Turions completely germinated in water column with <90 cm water depth and the germination speed decreased with increasing water depth within 18 days. There were obvious differences in morphological characteristics of P. crispus between deep and shallow water layers. P. crispus restoration decreased by 12-32%, 13-36%, 9-43% and 5-36% of COD, NH 4 + -N, TN and TP concentration, respectively, in enclosed overlying water compared to the river (P < 0.05) during 5 months of experiment. Illumina sequencing was employed to explore the epiphytic bacterial and microeukayotic communities at water depth 25-35 cm (shallow area) and 80-90 cm (deep area). A total of 9 bacterial and 12 microeukayotic dominant phyla were obtained in eight samples. It should be noted that the algae abundances were higher in shallow area than deep area but a reverse trend was observed for methanotrophs. Null model analysis revealed that dispersal limitation and undominated process was the most important assembly process, whereas stochastic processes gained more importance in shallow area than deep one. According to cooccurrence analysis (|r| > 0.6, P < 0.05), there were more strongly correlated edges in shallow area (456 edges) than deep area (340 edges). These results highlight that submerged macrophytes restoration can increase microbial diversity and improve water quality, and provide a "summer disease cured in winter" way by using could-resistant P. crispus for water purification in micro-polluted rivers in low-temperature season., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Macrophytes are one of the important indicators used in assessing the anthropic impact on aquatic ecosystems. The structure of macrophyte communities of two rivers were compared by species composition, dominant species and projective cover using statistical methods. It is shown that the influence of storm runoff on these rivers is manifested in the form of a change in the dominant species composition. Based on the statistical analysis carried out, it can be argued that, despite the peculiarities of the flora composition of each of the rivers, the influence of storm runoffs largely neutralizes this specificity, determining the situation in local areas immediately below the runoff. In the area of the effluent discharge the dominance of individual species and an increase in the area overgrown with macrophytes was observed. In the area of stormwater discharge on the Psel River, species were usually present: Nuphar lutea , Ceratophyllum demersum , Myriophyllum spicatum and on the Bystrica River- Glyceria maxima , Sagitaria sagittiformis , Stuckenia pectinata and Potamogeton crispus . The use of the NMDS method has been found to provide good insight into the structural rearrangements in macrophyte communities affected by runoff from stormwater systems., Competing Interests: The authors declare there are no competing interests., (©2023 Babko et al.)