Sparganium longifolium was reported as a hybrid between S. emersum and S. gramineum based on its intermediate type or the common characteristics of its parent species. Its hybrid origin needs to be confirmed using molecular technology. We investigated the origin of S. longifolium based on 10 populations of S. emersum, S. gramineum and S. longifolium from five lakes in European Russia, using sequences of six nuclear loci and one chloroplast DNA fragment. Haplotype network, principal coordinate analysis and genetic clustering based on data of nuclear loci confirmed that S. longifolium is the hybrid between S. emersum and S. gramineum. We found that the natural hybridization between S. emersum and S. gramineum is bidirectional but asymmetrical, and the latter mainly acts as maternal species. We also found that all samples of S. longifolium were F1 generations, and thus hypothesized that S. emersum and S. gramineum could likely maintain their species boundary through the post-zygote reproductive isolation mechanism of F1 generation sterility.

Freshwater macrophytes shape not only the morphological “architecture” of shallow-water ecosystems but also their chemical milieu via low-molecular-weight organic compounds (LMWOCs) that may regulate phytoplankton, periphyton, and the microbiome within the leaf/shoot diffusive boundary layer and the surrounding water column. In this study, GC–MS (gas chromatography–mass spectrometry) was used to identify major LMWOCs of the low-molecular-weight metabolome (LMWM) in 11 widely distributed macrophyte species (Myriophyllum spicatum L., Sparganium emersum Rehm., Sparganium gramineum Georgi, the hybrid Sparganium × foliosum A. A. Bobrov, Volkova, Mochalova et Chemeris, Persicaria amphibia (L.) Delarbre, Potamogeton perfoliatus L., Nuphar lutea (L.) Sibth. & Sm., Potamogeton pectinatus L., Potamogeton natans L., Lobelia dortmanna L., and Ceratophyllum demersum L.). Compounds contributing more than 1% to the total LMWOCs pool were considered major, increasing the ecological realism of interpretations by focusing on metabolites more likely to reach effective concentrations in the plant microenvironment. For interspecific comparisons, the maximum recorded values of relative abundance and concentrations were used to estimate species “potential”. In total, 137 major LMWOCs were detected (four remained unidentified), and their numbers varied markedly among taxa (from 11 in N. lutea to 71 in P. perfoliatus). Similarity analyses (Jaccard, Sørensen–Czekanowski, Morisita–Horn) indicated that similarity based on compound lists and similarity based on dominance structure may diverge, reflecting differences between the “LMWOCs set” and the quantitative architecture of LMWOCs within the LMWM. Fatty acids formed the core of the major fraction in all species: they were among the top three compounds in all 11 macrophytes and ranked first or second in 10 of 11, highlighting the lipid module as a universal “structure–signaling–defense/allelopathy” hub in aquatic plants. Also, an analysis of the ecological-biochemical role of the main major LMWOCs in the studied aquatic macrophytes is presented. Overall, the data offer a comparable, ecologically oriented framework for interpreting chemical regulation of communities in macrophyte-dominated habitats and for selecting target compounds/species for subsequent bioassay and field studies.

The effect of a patented alcoholic solution of algicide based on gallic, tetradecanoic, heptane, and octane organic acids on seed germination and the development of seedlings of three species of helophytes, Sparganium emersum, S. glomeratum, and Schoenoplectus lacustris, has been studied for the first time. Significant differences are found in the effect of different algicide concentrations (0.1, 1.0, and 10.0 mg/L) on seed germination and the initial stages of seedling development of three species of helophytes. We observe the stimulation of germination of Sparganium emersum seeds at a concentration of 10.0 mg/L and the inhibition of this process in S. glomeratum at concentrations of 1.0 and 0.1 mg/L. No significant effect of algicide on the germination of Schoenoplectus lacustris seeds is found. According to the degree of increase in the resistance of morphological parameters of plants to the effect of different algicide concentrations, seedlings of three species of helophytes are arranged in the following series: Schoenoplectus lacustris > Sparganium glomeratum > S. emersum.

Freshwater macrophytes shape not only the morphological “architecture” of shallow-water ecosystems but also their chemical milieu via low-molecular-weight organic compounds (LMWOCs) that may regulate phytoplankton, periphyton, and the microbiome within the leaf/shoot diffusive boundary layer and the surrounding water column. In this study, GC–MS (gas chromatography–mass spectrometry) was used to identify major LMWOCs of the low-molecular-weight metabolome (LMWM) in 11 widely distributed macrophyte species (Myriophyllum spicatum L., Sparganium emersum Rehm., Sparganium gramineum Georgi, the hybrid Sparganium × foliosum A. A. Bobrov, Volkova, Mochalova et Chemeris, Persicaria amphibia (L.) Delarbre, Potamogeton perfoliatus L., Nuphar lutea (L.) Sibth. & Sm., Potamogeton pectinatus L., Potamogeton natans L., Lobelia dortmanna L., and Ceratophyllum demersum L.). Compounds contributing more than 1% to the total LMWOCs pool were considered major, increasing the ecological realism of interpretations by focusing on metabolites more likely to reach effective concentrations in the plant microenvironment. For interspecific comparisons, the maximum recorded values of relative abundance and concentrations were used to estimate species “potential”. In total, 137 major LMWOCs were detected (four remained unidentified), and their numbers varied markedly among taxa (from 11 in Nuphar lutea to 71 in P. perfoliatus). Similarity analyses (Jaccard, Sørensen–Czekanowski, Morisita–Horn) indicated that similarity based on compound lists and similarity based on dominance structure may diverge, reflecting differences between the “LMWOCs set” and the quantitative architecture of LMWOCs within the LMWM. Fatty acids formed the core of the major fraction in all species: they were among the top three compounds in all 11 macrophytes and ranked first or second in 10 of 11, highlighting the lipid module as a universal “structure–signaling–defense/allelopathy” hub in aquatic plants. Also, an analysis of the ecological-biochemical role of the main major LMWOCs in the studied aquatic macrophytes is presented. Overall, the data offer a comparable, ecologically oriented framework for interpreting chemical regulation of communities in macrophyte-dominated habitats and for selecting target compounds/species for subsequent bioassay and field studies.

Pseudovivipary is an extremely rare and poorly studied form of reproduction among angiosperms, including aquatic and riparian plants. In this paper, for the first time, based on the results of our own research and an analysis of numerous foreign and domestic studies, a list of the world’s flora of aquatic plants (74 species from 13 families) exhibiting pseudovivipary has been presented. Special attention is given to the types of viviparous structures and their morphological features, as well as the possible reasons for their formation in various species of aquatic plants. It has been shown that the most common form of pseudoviviparous structures are plantlets, found in 62 species of plants, tubers in 6 species, and turions and bulbils in 3 species. There is a clear gap in knowledge regarding this form of asexual reproduction in aquatic and coastal-aquatic plants, which undoubtedly requires further field observations and experimental work.