Search Results (11)

Root length is increasingly used as a rapid endpoint in duckweed ecotoxicology, yet biologically distinct assays are often treated as equivalent. Two 72 h root-length tests are now in use: root re-growth after excision in mature Lemna aequinoctialis fronds, and root development during germination of rootless Spirodela polyrhiza turions exposed directly to the test solution. Both begin from zero initial root length, but for different biological reasons. We asked whether they produce comparable herbicide responses. Thirteen herbicides were drawn from a screening campaign in which both assays were run under matched exposure conditions. Nine compounds returned quantified EC₅₀ estimates (with the L. aequinoctialis coefficient of variation below 40%) and formed the primary comparison. EC₅₀ ratios (S. polyrhiza/L. aequinoctialis) ranged from 0.75 to 430 (median 2.76). Five compounds agreed within about three-fold, whereas four compounds spanning several target-site classes diverged by 74- to 430-fold, and potency rankings were not significantly correlated (Spearman ρ = 0.43, p = 0.24). For the common reference toxicant, the two assays differed by only about two-fold, and in the opposite direction; comparable reference-toxicant performance therefore did not predict comparable herbicide responses. The two assays should not be treated as interchangeable root-length tests. However, they differ not only in the biological origin of the measured root but also in species and developmental starting condition, and the present design cannot separate these factors; the observed differences therefore demonstrate assay-level non-equivalence without identifying its biological cause. Full article

Duckweed-associated plant growth-promoting bacteria have attracted attention for their potential to enhance duckweed biomass production. However, the mechanisms underlying isolate-specific growth promotion are unclear. This study compared the effects of two duckweed-associated bacterial isolates, Terrimicrobium sp. PS02 and Aeromicrobium sp. PS05, on the growth, biomass composition, colonization behavior, and transcriptomic responses of Spirodela polyrhiza. Biomass composition and transcriptome analyses were performed to characterize the host responses. Both isolates enhanced duckweed biomass; PS02 increased it 1.2-fold, whereas PS05 induced a significant 1.4-fold increase compared to the uninoculated control. PS05 established bacterial populations approximately one order of magnitude higher than those of PS02 and formed dense extracellular polymeric substance-mediated microcolonies on the surface. Transcriptome analysis revealed that PS05 induced 1108 differentially expressed genes, compared with 454 in PS02, indicating greater host transcriptomic reprogramming. Functional enrichment of transcriptome responses showed that PS05 preferentially regulates carbohydrate biosynthesis, central carbon metabolism, and starch biosynthesis, significantly enhancing starch accumulation and turion formation without reducing protein or photosynthetic pigment content. This study provides evidence linking bacterial colonization, host transcriptomic regulation, carbon allocation, and biomass production in duckweed, offering a basis for engineering high-performance duckweed–microbiome systems for sustainable biomass production. Full article

Turions (overwintering buds) as modified shoot apices constitute specialized vegetative structures that enable many aquatic vascular plants to withstand adverse environmental conditions such as low temperature, desiccation, or limited light availability. Turions serve as major storage sites for organic reserves, including sugars, proteins, fatty acids, and polyamines. Owing to their high content of energy-rich and nutritionally valuable compounds, turions represent a potential renewable resource for applications in biofuel production, animal feed, and the food industry. We investigated whether arabinogalactan proteins (AGPs) occur in aquatic plant turions and localized these compounds within specific tissues or cell types. This work was designed to evaluate whether stress-resistant storage organs may constitute a practical reservoir of AGPs. Considering the central role of AGPs in plant responses to abiotic stress, we hypothesized that turions, which routinely encounter cold, anoxia, and intermittent dehydration, would exhibit particularly high AGP accumulation. Mature turions of aquatic species (Aldrovanda vesiculosa, Utricularia australis, U. intermedia, and Caldesia parnassifolia) were used. Immunofluorescent labeling with AGP-specific antibodies (JIM8, JIM13, JIM14, LM2, MAC207) and confocal laser scanning microscopy were employed. In Aldrovanda vesiculosa and Caldesia parnassifolia, AGP epitopes were abundantly presented in cytoplasmic compartments. AGP epitopes occurred in secretory structures in turions of all examined species (trichomes of Aldrovanda and Utricularia, secretory ducts of Caldesia). In analyzing turions of four different species, we identified Aldrovanda vesiculosa turions as the most promising potential source of AGPs, also noting their high reserve potential for use in animal feed or the food industry. Full article

Duckweeds are widely distributed small, simply constructed aquatic higher plants (the Lemnaceae) found on quiet freshwater surfaces. Species inhabiting temperate climates may have to cope with long periods of severe cold during the winter season. Several duckweeds form compact resting structures from the assimilatory fronds of the growing season that can bridge inhospitable conditions in a quiescent state. Of these, turions separate from the mother fronds and overwinter on the water body bottom in a dormant state. They can surface, germinate, and sprout to resume active growth upon warming in the spring. The turions of the largest duckweed, Spirodela polyrhiza, have been intensively examined as to ultrastructure, the factors governing their formation and release from dormancy, and the signals driving their germination and sprouting and the accompanying starch degradation. Comparative transcriptomics of assimilatory fronds and dormant turions are revealing the molecular features of this developmental cycle. The results illustrate an elegant sequence of reactions that ensures aquatic survival of even severe winters by frost avoidance in a vegetative mode. Since little is known about other duckweed resting fronds, the S. polyrhiza turion developmental cycle cannot be considered to be representative of duckweed resting fronds in general but can serve as a reference for corresponding investigations. Full article

Background: Fatty acids are essential for human health. Currently, there is a search for alternative sources of fatty acids that could supplement such sources as staple crops or fishes. Turions of aquatic plants accumulate a variety of substances such as starch, free sugars, amino acids, reserve proteins and lipids. Our aim is to see if turions can be a valuable source of fatty acids. Methods: Overwintering shoots and turions of aquatic carnivorous plants were collected. The plant material was extracted with hexane. The oils were analyzed using a gas chromatograph with mass spectrometer. Results: The dominant compound in all samples was linolenic acid. The oil content was different in turions and shoots. The oil content of the shoots was higher than that of the turions, but the proportion of fatty acids in the oils from the shoots was low in contrast to the oils from the turions. The turions of Utricularia species were shown to be composed of about 50% fatty acids. Conclusions: The turions of Utricularia species can be used to obtain oil with unsaturated fatty acids. In addition, the high fatty acid content of turions may explain their ability to survive at low temperatures. Full article

Duckweeds (Lemnaceae) are small, simply constructed aquatic higher plants that grow on or just below the surface of quiet waters. They consist primarily of leaf-like assimilatory organs, or fronds, that reproduce mainly by vegetative replication. Despite their diminutive size and inornate habit, duckweeds have been able to colonize and maintain themselves in almost all of the world’s climate zones. They are thereby subject to multiple adverse influences during the growing season, such as high temperatures, extremes of light intensity and pH, nutrient shortage, damage by microorganisms and herbivores, the presence of harmful substances in the water, and competition from other aquatic plants, and they must also be able to withstand winter cold and drought that can be lethal to the fronds. This review discusses the means by which duckweeds come to grips with these adverse influences to ensure their survival. Important duckweed attributes in this regard are a pronounced potential for rapid growth and frond replication, a juvenile developmental status facilitating adventitious organ formation, and clonal diversity. Duckweeds have specific features at their disposal for coping with particular environmental difficulties and can also cooperate with other organisms of their surroundings to improve their survival chances. Full article

The European Habitats Directive was adopted to halt the rapid loss of biodiversity and has become an important instrument for protecting biodiversity in the European Union. Three aquatic plant species protected under the European Habitats Directive have so far been found in Lithuania: Aldrovanda vesiculosa, Caldesia parnassifolia, and Najas flexilis. Our aim in this study was to evaluate the former and current distribution and the status of conservation of the target species. Screening for the above-mentioned protected aquatic plant species was performed in 73 natural lakes throughout Lithuania in 2019–2021. We confirmed extant populations of Aldrovanda vesiculosa in four lakes, Caldesia parnassifolia in two lakes, and Najas flexilis in four lakes in the northeastern part of the country. We studied Aldrovanda vesiculosa populations three times (2015, 2019, and 2022) in Lake Rūžas and once each in Lake Apvardai and Lake Dysnai (2020). The population density of Aldrovanda vesiculosa ranged from 193.4 ± 159.7 to 224.0 ± 211.0 individuals/m², the mean length of plants ranged from 12.5 ± 2.1 to 14.3 ± 2.7 cm, and the mean number of apices ranged from 2.0 ± 0.7 to 2.2 ± 0.9 per individual. The habitat of Aldrovanda vesiculosa in Lake Rūžas covered an area of about 3 ha. The number of generative individuals of Caldesia parnassifolia widely varied between years in Lake Rūžas. All populations of Najas flexilis were small, although the potential habitats in the studied lakes cover relatively large areas. We propose designating all lakes with populations of Aldrovanda vesiculosa, Caldesia parnassifolia, and Najas flexilis as special areas of conservation, as well as developing and implementing action plans for the conservation of these species and their habitats. Full article

Aldrovanda vesiculosa is a rare and critically endangered carnivorous plant species. Its populations have declined worldwide, so there is a need to protect the species from extinction. The research was conducted to establish an effective method of in vitro propagation of the species in order to obtain plants for reintroduction in the wild. The procedures included disinfection, multiplication, and acclimatization of plants. Contamination-free in vitro cultures were established using shoots and turions, which were disinfected with 0.25% sodium hypochlorite. The shoots were first defoliated. The explants regenerated better in liquid 1/5 MS medium than in solidified one. The optimum medium for the multiplication phase contained MS macro- and microelements diluted to 1/10. Plants cultivated in that medium were of good quality, long, and branched. The advantageous effect of medium was also confirmed by the content of photosynthetic pigments in the plant material. The content of chlorophyll a was highest in plants cultivated in 1/5 or 1/10 MS medium. The plants obtained were acclimatized to ex vitro conditions and reintroduced in the wild. Full article

Growth-regulating factors (GRFs) are plant-specific transcription factors that play essential roles in regulating plant growth and stress response. The GRF gene families have been described in several terrestrial plants, but a comprehensive analysis of these genes in diverse aquatic species has not been reported yet. In this study, we identified 130 GRF genes in 13 aquatic plants, including floating plants (Azolla filiculoides, Wolffia australiana, Lemna minuta, Spirodela intermedia, and Spirodela polyrhiza), floating-leaved plants (Nymphaea colorata and Euryale ferox), submersed plants (Zostera marina, Ceratophyllum demersum, Aldrovanda vesiculosa, and Utricularia gibba), an emergent plant (Nelumbo nucifera), and an amphibious plant (Cladopus chinensis). The gene structures, motifs, and cis-acting regulatory elements of these genes were analyzed. Phylogenetic analysis divided these GRFs into five clusters, and ABRE cis-elements were highly enriched in the promoter region of the GRFs in floating plants. We found that abscisic acid (ABA) is efficient at inducing the turion of Spirodela polyrhiza (giant duckweed), accompanied by the fluctuated expression of SpGRF genes in their fronds. Our results provide information about the GRF gene family in aquatic species and lay the foundation for future studies on the functions of these genes. Full article

Carnivorous plants from the Lentibulariaceae form a variety of standard and novel vegetative organs and survive unfavorable environmental conditions. Within Genlisea, only G. tuberosa, from the Brazilian Cerrado, formed tubers, while Utricularia menziesii is the only member of the genus to form seasonally dormant tubers. We aimed to examine and compare the tuber structure of two taxonomically and phylogenetically divergent terrestrial carnivorous plants: Genlisea tuberosa and Utricularia menziesii. Additionally, we analyzed tubers of U. mannii. We constructed phylogenetic trees using chloroplast genes matK/trnK and rbcL and used studied characters for ancestral state reconstruction. All examined species contained mainly starch as histologically observable reserves. The ancestral state reconstruction showed that specialized organs such as turions evolved once and tubers at least 12 times from stolons in Lentibulariaceae. Different from other clades, tubers probably evolved from thick stolons for sect. Orchidioides and both structures are primarily water storage structures. In contrast to species from section Orchidioides, G. tuberosa, U. menziesii and U. mannii form starchy tubers. In G. tuberosa and U. menziesii, underground tubers provide a perennating bud bank that protects the species in their fire-prone and seasonally desiccating environments. Full article

The aim of the research was to establish the density of specimens and shoots as well as the reproductive effort of Hydrocharis morsus-ranae during the whole vegetative period in a Polish oxbow lake. The following specimen features were examined: plant diameter, total length, the number of buds, flowers, young fruit, ripe fruit, turions and leaves and also dry total mass, vegetative mass, generative mass, the bud mass, the flower mass, young fruit mass and ripe fruit mass. The density of Hydrocharis morsus-ranae specimens per square metre ranged from 10 to 170 while the density of shoots ranged from 10 to 545. From one square metre overgrown with Hydrocharis morsus-ranae, a maximum of 389 turions, 50 fruit and 4000 seeds are produced. The maximum of reproductive effort is 97.8% of vegetative mass and 2.2% of generative mass in September 2010. The factors which best explain changeability of the Hydrocharis morsus-ranae population in time are the length and the diameter of the specimens in the population. Fruiting of Hydrocharis morsus-ranae in Poland is higher than in Canada, where it is an invasive taxon. Hydrocharis morsus-ranae is well adapted to the environment in oxbow lakes of the River Vistula and represents the S-R strategy. Full article