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Aims We aimed at assessing the influence of above- and below-ground environmental conditions over the performance of Centaurea jacea L., a drought-resistant grassland forb species. Methods Transpiration rate, CO2 assimilation rate, leaf water potential, instantaneous and intrinsic water use efficiency, temperature, relative humidity, vapor pressure deficit and soil water content in one plant and root length density in four plants, all grown in custom-made columns, were monitored daily for 87 days in the lab. The soil water isotopic composition in eleven depths was recorded daily in a non-destructive manner. The isotopic composition of plant transpiration was inferred from gas chamber measurements. Vertical isotopic gradients in the soil column were created by adding labeled water. Daily root water uptake (RWU) profiles were computed using the multi-source mixing model Stable Isotope Analysis in R (Parnell et al. PLoS ONE 5(3):1–5, 2010). Results RWU occurred mainly in soil layer 0–15 cm, ranging from 79 to 44%, even when water was more easily available in deeper layers. In wet soil, the transpiration rate was driven mainly by vapor pressure deficit and light intensity. Once soil water content was less than 0.12 cm3 cm− 3, the computed canopy conductance declined, which restricted leaf gas exchange. Leaf water potential dropped steeply to around − 3 MPa after soil water content was below 0.10 cm3 cm− 3. Conclusion Our comprehensive data set contributes to a better understanding of the effects of drought on a grassland species and the limits of its acclimation in dry conditions.

In the current report, we studied the possible inhibitors of COVID-19 from bioactive constituents of Centaurea jacea using a threefold approach consisting of quantum chemical, molecular docking and molecular dynamic techniques. Centaurea jacea is a perennial herb often used in folk medicines of dermatological complaints and fever. Moreover, anticancer, antioxidant, antibacterial and antiviral properties of its bioactive compounds are also reported. The Mpro (Main proteases) was docked with different compounds of Centaurea jacea through molecular docking. All the studied compounds including apigenin, axillarin, Centaureidin, Cirsiliol, Eupatorin and Isokaempferide, show suitable binding affinities to the binding site of SARS-CoV-2 main protease with their binding energies -6.7 kcal/mol, -7.4 kcal/mol, -7.0 kcal/mol, -5.8 kcal/mol, -6.2 kcal/mol and -6.8 kcal/mol, respectively. Among all studied compounds, axillarin was found to have maximum inhibitor efficiency followed by Centaureidin, Isokaempferide, Apigenin, Eupatorin and Cirsiliol. Our results suggested that axillarin binds with the most crucial catalytic residues CYS145 and HIS41 of the Mpro, moreover axillarin shows 5 hydrogen bond interactions and 5 hydrophobic interactions with various residues of Mpro. Furthermore, the molecular dynamic calculations over 60 ns (6×106 femtosecond) time scale also shown significant insights into the binding effects of axillarin with Mpro of SARS-CoV-2 by imitating protein like aqueous environment. From molecular dynamic calculations, the RMSD and RMSF computations indicate the stability and dynamics of the best docked complex in aqueous environment. The ADME properties and toxicity prediction analysis of axillarin also recommended it as safe drug candidate. Further, in vivo and in vitro investigations are essential to ensure the anti SARS-CoV-2 activity of all bioactive compounds particularly axillarin to encourage preventive use of Centaurea jacea against COVID-19 infections.

Flower-feeding insects are declining due to the loss of floral resources. The EU Grassland Butterfly Index underlined a decrease in abundance of 39% between 1990 and 2017. In Northwest Europe, land use intensification is the main driver of grassland butterflies' decline. Among the agri-environment schemes in Wallonia (Belgium), wildflower strips are implemented along crops in order to prevent further loss. They provide nectar sources and host plants to butterflies. For more than ten years, butterflies have been monitored in the Walloon flower strips. The strips vegetation was also surveyed to evaluate the larval food potential. In addition, flower visits for nectar were studied in 2020. Between 2010 and 2020, 56 butterfly species (more than 84,000 individuals) were recorded inside the strips and their population showed an overall increase of 82%. We suggest that this increase was due to the strips temporal continuity, combined with a local climate change. Most recorded butterflies belonged to common generalist species but species that are rare, threatened or protected in the region were also observed. Most species had at least one potential host plant inside the strips and we hypothesize that some of the abundant food generalists used them as breeding sites. In 2020, butterflies mainly visited Centaurea jacea, Lotus corniculatus and Medicago sativa for nectar collection. Before the flowering of C. jacea in June, few nectar was available and only a few flower visits were recorded. Thus, flower strips mostly benefit butterflies in summer in terms of nectar supply. Our results highlight that the long term application of wildflower strips can be a good instrument to contribute to butterfly conservation in Wallonia. The study of the potential host plants and effective nectar sources provide additional understanding on how butterflies interact with the flower strips.

Purpose: In a complex soil environment, competitive and environmental factors will interact with individual traits to influence a plant’s root growth patterns and ability to compete for resources. Here, we examine how root growth of a focal plant, Plantago lanceolata L., responds to resource heterogeneity and to presence of two neighbor species, Centaurea jacea L.and Poa pratensis L. Methods: A full factorial experiment tested the effects of nutrient heterogeneity, neighbors, and their interaction on root responses of Plantago. Roots in shared quadrants of a pot were harvested and quantified by qPCR for plants grown alone or with a neighbor, in patchy or even soil. The effects of experimental treatments on Plantago root mass distribution were tested with two-way ANOVA. Results: When soil resources were evenly distributed, Plantago individuals increased root allocation to soil shared with a Centaurea neighbor but not a Poa neighbor. When soil resources were patchy, Plantago responded more strongly to Poa than to Centuarea, and placed more roots in the high-resource patch. Conclusions: These results demonstrate that plants can respond differently to neighbors depending on species and that integrating multiple cues results in non-additive effects on root behavior.

Aims Numerous organisms show range expansions in response to current climate change. Differences in expansion rates, such as between plants and soil biota, may lead to altered interactions in the new compared to the original range. While plant-soil interactions influence plant performance and stress tolerance, the roles of specific soil organisms driving these responses remain unknown. Methods We manipulated the abundances of nematodes and arbuscular mycorrhizal fungi (AMF), collected from original and new range soils, and examined their effects on the biomass of range-expanding Centaurea stoebe and native Centaurea jacea. In the first approach, nematode and AMF communities were extracted from field soils, and inoculated to sterilized soil. In the second approach, the abundance of soil organisms in soil inocula was reduced by wet sieving; at first, plants were grown to condition the soil, and then plant-soil feedback was determined under ambient and drought conditions. Results The origin of soil communities did not influence the biomass production of range-expanding or native plant species, neither by addition nor by (partial) removal. However, after conditioning and under drought, range expanding C. stoebe produced more biomass with soil communities from the original range while C. jacea, native to both ranges, produced more biomass with new range soil communities. Conclusions We show that nematode and AMF communities from original and new range have similar effect on the growth of range expanding C. stoebe. Our results highlight that the effect of soil communities on plant growth increases after soil conditioning and under drought stress.

Nitrogen (N) loading and extreme drought were found to strongly alter biomass production, species composition, carbon and water fluxes of temperate grasslands. Such changes at the community level are often attributed to species and functional group‐specific responses in phenology and/or physiology. In a multifactorial field experiment, we studied the responses of three abundant grassland species (forb Centaurea jacea, grasses Arrhenatherum elatius and Dactylis glomerata) to N loading and extreme drought, focusing on responses in carbon and water relations at the leaf level. We analyzed 1) changes in bulk leaf N (uptake efficiency of additional N), 2) adaptation of plant water status (leaf water potential) and 3) the impact on leaf carbon and water fluxes. We observed more efficient N utilization in both grasses compared to C. jacea. Naturally occurring summer drought impacted the plant water status of all species significantly while extreme drought treatment only affected water status additionally during and after summer drought. C. jacea was able to maintain much lower leaf water potentials compared to grasses during drought. Despite these clear species‐specific responses to N loading and drought in bulk, species were able to maintain homeostasis of leaf carbon and water fluxes. Thus, strong declines in the (community) carbon sequestration observed at this site during the (natural) summer drought were not related to leaf physiological responses in assimilation but driven by phenological adaptions of the species community: The drought sensitive grasses, even though exhibiting a higher N uptake efficiency, responded with a shortened life cycle to severe summer drought.

The introduced meadow knapweed (Centaurea × moncktonii C.E. Britton), a hybrid of black (Centaurea nigra L.) and brown (Centaurea jacea L.) knapweeds, is increasingly common in pastures, meadows, and waste areas across many U.S. states, including New York. We evaluated the effects of temperature, light, seed stratification, scarification, and population on percent germination in four experiments over 2 yr. Percent germination ranged from 3% to 100% across treatment combinations. Higher temperatures (30:20, 25:15, and sometimes 20:10 C day:night regimes compared with 15:5 C) promoted germination, especially when combined with the stimulatory effect of light (14:10 h L:D compared with continuous darkness). Under the three lowest temperature treatments, light increased percent germination by 15% to 86%. Cold-wet seed stratification also increased germination rates, especially at lower germination temperatures, but was not a prerequisite for germination. Scarification did not increase percent germination. Differences between C. × moncktonii populations were generally less significant than differences between temperature, light, and stratification treatments. Taken together, these results indicate that C. × moncktonii is capable of germinating under a broad range of environments, which may have facilitated this species’ range expansion in recent decades. However, C. × moncktonii also shows evidence of germination polymorphism: some seeds will germinate under suboptimal conditions, while others may remain dormant until the abiotic environment improves. Subtle differences in dormancy mechanisms and their relative frequencies may affect phenological traits like the timing of seedling emergence and ultimately shape the sizes and ranges of C. × moncktonii populations.

Root water uptake is a key ecohydrological process for which a physically-based understanding has been developed in the past decades. However, due to methodological constraints, knowledge gaps remain about the plastic response of whole plant root systems to a rapidly changing environment. - We designed a laboratory system for non-destructive monitoring of stable isotopic composition in plant transpiration of an herbaceous species (Centaurea jacea) and of soil water across depths, taking advantage of newly developed in-situ methods. Daily root water uptake profiles were obtained using a statistical Bayesian multi-source mixing model. - Fast shifts in the isotopic composition of both soil and transpiration water could be observed with the setup and translated into dynamic and pronounced shifts of the root water uptake profile, even in well-watered conditions. - The incorporation of plant physiological and soil physical information into statistical modelling improved the model output. A simple exercise of water balance closure underlined the non-unique relationship between root water uptake profile on the one hand, and water content and root distribution profiles on the other, illustrating the continuous adaption of the plant water uptake as a function of its root hydraulic architecture and soil water availability during the experiment

The order of arrival of plant species during assembly can affect the structure and functioning of grassland communities. These so-called priority effects have been extensively studied aboveground, but we still do not know how they affect the vertical distribution of roots in the soil and the rooting depth of plant communities. To test this hypothesis, we manipulated the order of arrival of three plant functional groups (forbs, grasses and legumes) in a rhizobox experiment. Priority effects were created by sowing one functional group 10 days before the other two. Rhizoboxes in which all functional groups were sown simultaneously were used as controls. During the experiment, the mean rooting depth of plant communities was monitored using image analysis and a new methodological approach using deep learning (RootPainter) for root segmentation. At harvest, we measured aboveground (community and species level) and belowground (community level) biomass, and assessed the vertical distribution of the root biomass in different soil layers. At the community level, all scenarios where one functional group was sown before the other two had similar shoot and root productivity. At the species level, two forbs (Achillea millefolium and Centaurea jacea) benefited from arriving early, and one legume (Trifolium pratense) had a disadvantage when it was sown after the grasses. Priority effect treatments also affected the vertical distribution of roots. When grasses were sown first, plant communities rooted more shallowly than when forbs or legumes were sown first,. In addition, roots moved down the soil profile 24% more slowly in grasses-first communities. Our results highlight that plant functional group order of arrival in grassland communities can affect the vertical distribution of roots in the soil and this may have implications for species coexistence.

In the current report, we studied the possible inhibitors of COVID-19 from bioactive constituents of Centaurea jacea using a threefold approach consisting of quantum chemical, molecular docking and molecular dynamic techniques. Centaurea jacea is a perennial herb often used in folk medicines of dermatological complaints and fever. Moreover, anticancer, antioxidant, antibacterial and antiviral properties of its bioactive compounds are also reported. The Mpro (Main proteases) was docked with different compounds of Centaurea jacea through molecular docking. All the studied compounds including apigenin, axillarin, Centaureidin, Cirsiliol, Eupatorin and Isokaempferide, show suitable binding affinities to the binding site of SARS-CoV-2 main protease with their binding energies -6.7 kcal/mol, -7.4 kcal/mol, -7.0 kcal/mol, -5.8 kcal/mol, -6.2 kcal/mol and -6.8 kcal/mol, respectively. Among all studied compounds, axillarin was found to have maximum inhibitor efficiency followed by Centaureidin, Isokaempferide, Apigenin, Eupatorin and Cirsiliol. Our results suggested that axillarin binds with the most crucial catalytic residues CYS145 and HIS41 of the Mpro, moreover axillarin shows 5 hydrogen bond interactions and 5 hydrophobic interactions with various residues of Mpro. Furthermore, the molecular dynamic calculations over 60 ns (6×106 femtosecond) time scale also shown significant insights into the binding effects of axillarin with Mpro of SARS-CoV-2 by imitating protein like aqueous environment. From molecular dynamic calculations, the RMSD and RMSF computations indicate the stability and dynamics of the best docked complex in aqueous environment. The ADME properties and toxicity prediction analysis of axillarin also recommended it as safe drug candidate. Further, in vivo and in vitro investigations are essential to ensure the anti SARS-CoV-2 activity of all bioactive compounds particularly axillarin to encourage preventive use of Centaurea jacea against COVID-19 infections. Resumo No presente relatório, estudamos os possíveis inibidores de Covid-19 de constituintes bioativos de Centaurea jacea usando uma abordagem tripla que consiste em técnicas de química quântica, docking molecular e dinâmica molecular. Centaurea jacea é uma erva perene frequentemente usada em remédios populares de doenças dermatológicas e febre. Além disso, as propriedades anticâncer, antioxidante, antibacteriana e antiviral de seus compostos bioativos também são relatadas. A Mpro (proteases principais) foi acoplada a diferentes compostos de Centaurea jacea por meio de docking molecular. Todos os compostos estudados, incluindo apigenina, axilarina, Centaureidina, Cirsiliol, Eupatorina e Isokaempferide, mostram afinidades de ligação adequadas ao sítio de ligação da protease principal SARS-CoV-2 com suas energias de ligação -6,7 kcal / mol, -7,4 kcal / mol, - 7,0 kcal / mol, -5,8 kcal / mol, -6,2 kcal / mol e -6,8 kcal / mol, respectivamente. Dentre todos os compostos estudados, a axilarina apresentou eficiência máxima de inibidor, seguida pela Centaureidina, Isokaempferida, Apigenina, Eupatorina e Cirsiliol. Nossos resultados sugeriram que a axilarina se liga aos resíduos catalíticos mais cruciais CYS145 e HIS41 do Mpro, além disso a axilarina mostra 5 interações de ligações de hidrogênio e 5 interações hidrofóbicas com vários resíduos de Mpro. Além disso, os cálculos de dinâmica molecular em uma escala de tempo de 60 ns (6 × 106 femtossegundos) também mostraram percepções significativas sobre os efeitos de ligação da axilarina com Mpro de SARS-CoV-2 por imitação de proteínas como o ambiente aquoso. A partir de cálculos de dinâmica molecular, os cálculos RMSD e RMSF indicam a estabilidade e dinâmica do melhor complexo ancorado em ambiente aquoso. As propriedades ADME e a análise de previsão de toxicidade da axilarina também a recomendaram como um candidato a medicamento seguro. Além disso, as investigações in vivo e in vitro são essenciais para garantir a atividade anti-SARS-CoV-2 de todos os compostos bioativos, particularmente a axilarina, para encorajar o uso preventivo de Centaurea jacea contra infecções por Covid-19.

The purpose of this research is to study the antiradical activity of various extracts from the Centaurea scabiosa L. aerial part (wild-growing and cultivated) and Centaurea jacea L. as potential sources of antioxidant herbal remedies. In the study of the antiradical activity of extracts from the aerial part of Centaurea jacea L., Centaurea scabiosa L. wild growing and cultivated, in the reaction with a stable diphenylpicrylhydrazyl radical, it was found that the degree of antiradical activity within each species correlates with the quantitative content of flavonoids. Lower values ​​of the antiradical activity of cultivated Centaurea scabiosa L. extracts compared to wild growing Centaurea scabiosa L. extracts are consistent with a lower content of flavonoids in the latter. The dependence of the Centaurea jacea L. and wild growing Centaurea scabiosa L. extracts antiradical activity on flavonoids quantitative and qualitative composition of these species has been established.

In plants, secondary metabolites provide a unique opportunity to explore seasonal variation and responses to the environment. These include both abiotic and biotic factors. In field experiments, such stress factors occur in combination. This variation alters the plant metabolic profiles in yet uninvestigated ways. This data set contains trait and mass spectrometry data of thirteen grassland species collected at four time points in the growing season in 2017. We collected above-ground vegetative material of seven grass and six herb species that were grown in plant communities with different levels of diversity in the Jena Experiment. For each sample, we recorded visible traits and acquired shoot metabolic profiles on a UPLC-ESI-Qq-TOF-MS. We performed the feature detection, grouping, and annotation in Galaxy-W4M and prepared the data for statistical analysis in R by applying missing data imputation, batch correction, and validity checks on the features. Together with this comprehensive data set, we also provide a detailed tutorial for the processing steps in R.

We explored the total and pathogenic fungi community of sixteen grassland species affiliated to two plant functional groups (grass and forb) grown as monocultures to assess which plant-related predictor, such as plant identity, plant functional group and host phylogeny was better in explaining the variation in fungal richness and community structure among the plants studied. Moreover, we investigated the response of the fungal community to drought. Briefly, the experiment consisted of plant communities comprised of the following plant species: the grasses Agrostis stolonifera, Anthoxanthum odoratum, Arrhenatherum elatius, Briza media, Festuca pratensis, Festuca rubra, Phleum pratense, Trisetum flavescens and forbs Achillea millefolium, Centaurea jacea, Galium mollugo, Leontodon hispidus, Leucanthemum vulgare, Prunella vulgaris, Ranunculus repens, and Sanguisorba officinalis. The plant species were grown in plot of 70 cm x 70 cm, with six replicates for each plant species, leading to a total of 96 plots. These plots were distributed in 3 blocks, which contained 2 plots (2 replicates) of each of the sixteen species per block. In the growing season of the fourth year (10 June -14 July 2017) a drought treatment was set up in half of the replicates using rainout shelters and supplementary watering of control plots.

Set-asides sown to wildflowers are introduced to promote agrobiodiversity. Often, sown seed mixtures have been used to enhance aboveground biodiversity while belowground biodiversity has received less attention. We studied in a 15-year-old set-aside experiment, the impact of seed mixtures (grass vs. meadow) and mowing (mown vs. unmown) on the abundance and diversity of plants, two aboveground invertebrate groups (pollinators and natural enemies of pest species) and one key belowground group, earthworms. We also studied the treatment effects on selected soil chemical properties. In general, a sown meadow seed mixture mostly benefitted aboveground biodiversity, whereas the impacts of late-season mowing were most discernible for earthworms. Plant species richness or coverage did not differ between seed mixtures, but plant coverage showed a positive response to mowing, while the impact on species richness was minor. The meadow seed mixture was dominated by Centaurea jacea. A non-mown meadow treatment supported the highest earthworm density and species richness, while the values were lowest in the mown meadow, where earthworm total mass was also at its lowest. In a grass seed mixture of intermediate density and richness, the mowing had no measurable effect on the earthworm community. Topsoil carbon, nitrogen and soluble phosphorus concentrations showed a typical gradient for non-inverted soils, with the highest concentrations in the 0–2.5 cm layer. The two uppermost soil layers (to 5 cm depth) had higher soluble phosphorus content under grass than under meadow seed mixture. Abundance of natural enemies of pests was not significantly different between the treatments, but for carabids there was a marginally significant positive response to mowing. Bumblebee species richness and the abundance of bumblebees and honeybees were highest in the mown meadow seed mixture plots. Butterfly species richness was marginally significantly higher in mown than in non-mown treatments in both seed mixtures. The results showed the potential of set-asides to promote both aboveground and belowground biodiversity through increased plant diversity.

International audience; Temperate grasslands provide both habitats and flower resources for pollinators in agricultural landscapes. Plant-pollinator networks change according to local and landscape variables, which are important to identify to help conserve pollinators in grasslands. We analysed plant-pollinator networks in 18 grasslands on experimental dairy farms located in three French regions contrasting by their climate, altitude, landscape or management. We combined visual surveys and pollen DNA barcoding. Our objectives were to determine which environmental factors influence pollinator taxa abundance and diversity and differences among the visual plant-pollinator networks in the three farming regions. Flower-visiting insects were trapped in six grasslands per farm during three sessions from mid-April to mid-July along fixed 400 m2 transects. Insects were identified individually to the lowest taxonomic rank possible. Pollen carried by insects was identified using nuclear ribosomal ITS2 sequences belonging to the NCBI nucleotide database. The size and diversity of plant-pollinator networks were much larger and higher in permanent grasslands at the two farms located in lowlands (Mirecourt) and mountains (Marcenat) than those at the farm with temporary grasslands and a crop landscape (Lusignan), but the degree of specialisation (H2′) was relatively similar and low (mean of 0.46). Diptera, especially Empididae and Syrphidae, represented most plant-pollinator interactions in Mirecourt and Marcenat, while Hymenoptera were more abundant at Lusignan. The percentage of semi-natural habitats in 500 m buffers and vegetation height explained 23% of the variance in pollinator abundance. Ranunculus sp. Knautia arvensis, Centaurea jacea and Trifolium repens were key plant species in the networks. DNA metabarcoding of pollen loads identified 114 genera in addition to those identified by visual observations (+34–42 per site), reflecting insects’ floral pathways and differences in the immediate landscape among farms. This study highlighted the importance of Diptera in plant-pollinator networks and the need to conserve permanent grassland diversity to conserve pollinators.

The study of the structure of coenopopulations (CP) is one of the directions in phytocoenology. Analysis of the morphological characteristics of individuals, ontogenetic structure, vitality, effective density allows predicting the dynamics of population development, which is importante for the rational use of both plant resources and territories occupied by different populations. We chose Centaurea jacea L. (meadow cornflower) as the object of our study. It is a perennial short-rhizome herb of the family Asteraceae Dumort., Hemicryptophyte, xeromesophyte, and a frequent component of meadow communities. Using the ecological scales of D.N. Tsyganov, a phytoindication assessment of the habitat conditions of Centaurea jacea L. is given. The values of the realized ecological valence fit into all ranges of the scaes given by D N Tsyganov for this species. This indicates a fairly wide range of tolerance of C. jacea. Coenopopulations of C. jacea are normal. Ontogenetic spectra are single-vertex: in CP 1-centered, in CP 2, 5-right-sided, in CP 3-left-sided. In CP 4 of C. jacea, the spectrum of ontogenetic states is bimodal. According to the “delta-omega” classification by L A Zhivotovsky CPs 1 and 2 of C. jacea, according to the values of efficiency and age indices, are characterized as mature, CPs 3 and 4 are transitional, and CP 5 is aging. The ontogenetic structure and type of spectrum depend on the growth rate of individuals, seed productivity, ecological conditions (soil turf, economic activity and mode of use).

High biodiversity is known to increase many ecosystem functions, but studies investigating biodiversity effects have more rarely looked at multi‐trophic interactions. We studied a tri‐trophic system composed of Centaurea jacea (brown knapweed), its flower head‐infesting tephritid fruit flies and their hymenopteran parasitoids, in a grassland biodiversity experiment. We aimed to disentangle the importance of direct effects of plant diversity (through changes in apparency and resource availability) from indirect effects (mediated by host plant quality and performance). To do this, we compared insect communities in C. jacea transplants, whose growth was influenced by the surrounding plant communities (and where direct and indirect effects can occur), with potted C. jacea plants, which do not compete with the surrounding plant community (and where only direct effects are possible). Tephritid infestation rate and insect load, mainly of the dominant species Chaetorellia jaceae, decreased with increasing plant species and functional group richness. These effects were not seen in the potted plants and are therefore likely to be mediated by changes in host plant performance and quality. Parasitism rates, mainly of the abundant chalcid wasps Eurytoma compressa and Pteromalus albipennis, increased with plant species or functional group richness in both transplants and potted plants, suggesting that direct effects of plant diversity are most important. The differential effects in transplants and potted plants emphasize the importance of plant‐mediated direct and indirect effects for trophic interactions at the community level. The findings also show how plant–plant interactions critically affect results obtained using transplants. More generally, our results indicate that plant biodiversity affects the abundance of higher trophic levels through a variety of different mechanisms.

Aim. To investigate the antibacterial properties of the fl owers of melliferous plants on the cultures isolated from honeycombs affected by foulbrood. Methods. Microbiological, cultural-morphological, biochemical, electron- microscopic, statistical. Results. Antibacterial effect on the Melissococcus pluton 8.1 strain was demonstrated by the fl ower extracts of 14 plant species and that on Bacillusaspecies – by the fl ower extracts of 27 plant spe- cies blossoming in the early spring. Conclusions. To study bee colonies affected by foulbrood, it is possible to use the properties of such nectariferous plants as Lamium album, Acer campestre, Prunus tomentosa, Allium cepa, Tagetes patula, Spiraea japonica, Achillea millefolium, Calluna vulgaris, Mentha piperita, Tilia cordata, Centaurea jacea, Lysimachia nummularia. The results of the experiments on the culture of microorganisms, isolated from the honeycombs of the bee colonies affected by foulbrood, demonstrated that these plants could be effective for the prevention and treatment of bacterial bee diseases.

Butterflies are often considered as opportunistic nectar consumers that visit a range of flower species. The degree of specialisation in foraging behaviour and flower choice may, however, vary considerably at the inter-specific level, from highly specialised to generalist species. In generalist nectar use, there can be intra-specific variation in the availability and use of floral resources (diversity and abundance) among different populations. Knowing the preferences of nectar-feeding butterflies can increase the understanding of ecological relationships and resource use and help in developing better strategies for butterfly conservation. By means of behavioural tracking, we identified foraging patterns of Maniola jurtina butterflies in nectar-rich and nectar-poor grasslands. For both males and females, we showed significant preference for the brown knapweed Centaurea jacea and thistles (Cirsium sp.) in nectar-rich, extensively managed grasslands. In the absence of these preferred species, as is typically the case in nectar-poor intensively managed sites, M. jurtina nectared on Trifolium pratense and Leucanthemum vulgare. Flower visits were on average shorter on T. pratense compared to C. jacea. These observational results were confirmed by a field experiment in which a wild flower nectar array with C. jacea and T. pratense was introduced. In extensively managed grasslands, foraging bouts were generally confined to patches of flowering plants and did not involve long flights between flower visits. In intensively managed meadows, butterflies performed longer flights, and ignored more flowers between two consecutive visits. Despite the variety of flower species visited, M. jurtina showed a significant preference for a few nectar sources in a context-dependent way.

Plant invasions are prime opportunities for studying hybridization and the nature of species boundaries, but hybrids also complicate the taxonomic treatment and management of introduced taxa. In this study, we use population genomics to estimate the extent of genomic admixture and test for its association with morphology and genome size in a hybrid complex of knapweeds invasive to North America: meadow knapweed (Centaurea × moncktonii) and its parental species (C. jacea and C. nigra). We sampled 20 populations from New York and Vermont, USA, and used genotyping by sequencing to identify single nucleotide polymorphisms in order to estimate genome-wide ancestry and classify individuals into hybrid genotype classes. We then tested for association between degree of genomic introgression and variation in a subset of traits diagnostic for the parental taxa, namely capitula morphology and monoploid genome size. Genomic clustering revealed two clearly defined lineages, as well as many admixed individuals forming a continuous gradation of introgression. Individual assignments to hybrid genotype classes revealed many advanced generation intercrosses and backcrosses, suggesting introgression has been extensive and unimpeded by strong reproductive barriers between taxa. Variation in capitula traits between the two unadmixed, presumed parental, lineages exhibited continuous, and in some cases transgressive, segregation among introgressed hybrids. Genome size was also divergent between lineages, although advanced generation hybrids had smaller genomes relative to additive expectations. Our study demonstrates deep introgression between the porous genomes of a hybrid invasive species complex. In addition to strong associations among genomic ancestry, genome size and morphology, hybrids expressed more extreme phenotypic values for capitula traits and genome size, indicating transgressive segregation, as well as a bias towards smaller genomes, possibly due to genomic downsizing. Future studies will apply these results to experimentally test how introgression, transgressive segregation and genome size reduction interact to confer invasiveness., Hybridization is thought to be a primary trigger underlying plant invasiveness, yet identifying hybrids and differentiating them from their parental species presents formidable challenges. Here, we present a multifaceted analysis of the invasive meadow knapweed complex that unravels the genetic make-up of hybrid populations in North America using DNA sequencing to infer the genomic ancestry of individuals, and associating ancestry with variation in floral traits and genome size. We find extensive genomic evidence of hybrids, with significant but incomplete correspondence with floral traits and genome size. Our results highlight the widespread yet often cryptic nature of hybridization in plant invasions.

This paper reports on the phytochemical composition as well as antiradical and anticholinesterase potential of volatile oils isolated from Centaurea alba and Centaurea jacea, from Croatia. The volatile components, obtained by hydrodistillation, were determined by GC and GC-MS analyses. A total of 18 compounds were identified in C. alba volatile oil with hexadecanoic acid, germacrene D and tetradecanoic acid as main compounds. A total of 29 compounds were identified in C. jacea volatile oil, with epi-bicyclosesquiphellandrene, aromadendrene and hexadecanoic acid as a major compounds. The tested volatile oils showed low DPPH inhibition potential as well as low to moderate antiAChE potential and low antiBuChE potential. This work is licensed under a Creative Commons Attribution 4.0 International License.

The data on the phytochemical composition and biological activity for flowering plant extracts of the genus Centaurea (Knapweed)—cornflower (Centaurea cyanus L.), brown knapweed (Centaurea jacea L.), and greater knapweed (Centaurea scabiosa L.), which are typical representatives of the flora in the middle belt of the Russian Federation, were obtained. For the first time, biologically active substances such as pyranone, coumaran (2,3-dihydrobenzofuran), and 5-hydroxymethylfurfural were identified in ethanol and methanol extracts of Centaurea scabiosa L. by gas chromatography–mass spectrometry. Catechol and α-amyrin were the major components of the ethanol extract from Centaurea cyanus L., and flavone was the major component of Centaurea jacea L. flower extract. The greatest antimicrobial activity against phytopathogens was detected in Centaurea scabiosa L. when extracting freshly harvested flower biomass with methyl tert-butyl ether at room temperature: the minimum inhibitory concentrations were 60–120 µg/mL, the minimum fungicidal concentration was 120 µg/mL, and the minimum bactericidal concentration was 250 µg/mL. The low antioxidant activity of the studied plant extracts was established using the maximum values of Centaurea jacea L. Ethanol extract of Centaurea cyanus L. flowers had low antimicrobial and antioxidant activity. The extracts showed no phytotoxicity to garden cress germination but inhibited the growth of juvenile plants, especially roots. The greatest phytotoxic effect was revealed with methyl tert-butyl ether, where the depression of growth indicators was 35% or more.

In plant conservation and ecosystem restoration, plants are often translocated to ensure or enhance plant survival and performance. While the effects of ecotype origin on the performance of translocated plants are increasingly acknowledged among researchers and practitioners, ecotype effects on associated communities and ecosystems have hardly been studied. This is critical because plants also constitute the habitat for a large number of interacting organisms, and many of them might be influenced by plant ecotype characteristics. Here, we studied different ecotypes of Centaurea jacea L., a plant species commonly used in grassland restoration, and their effects on seed herbivores and their parasitoids. We grew eight C. jacea ecotypes originating from different regions in Germany in a common garden and found that the ecotypes differed up to three-fold in the frequencies of seed herbivores. These differences appeared to be mainly driven by ecotype differences in flowering phenology. We also found that there were up to four-fold differences in the frequencies of parasitoids, and even up to nine-fold differences in the abundances of parasitoids among ecotypes. In summary, plants from different origins substantially differed in their effects on interacting organisms, potentially reflecting coevolutionary relationships across trophic levels. The introduction of foreign ecotypes in restoration projects may thus not only affect the plants themselves, but it may also disrupt the balance of their biotic interactions.

Background and aim Arbuscular mycorrhizal fungi (AMF) have an important role in plant-microbe interactions. But, there are few studies in which the combined effect of AMF with a stress factor, such as the presence of a metal, on plant species were assessed. This study investigated the effect of arbuscular mycorrhizal (AM) fungus Rhizophagus intraradices and other soil microbial groups in the presence of copper on three plant species in a microcosm experiment. Methods Two grass species Poa compressa and Festuca rubra and one herb species Centaurea jacea were selected as model plants in a pot-design test in which soils were artificially contaminated with copper. Treatments were bacteria (control), saprophytic fungi, protists, and a combined treatment of saprophytic fungi and protists, all in the presence or absence of the AM fungal species. After sixty days, plants were harvested and the biomass of grass and herb species and microbial respiration were measured. Results The results showed almost equal above- and belowground plant biomass and microbial respiration in the treatments in the presence or absence of R. intraradices. The herb species C. jecea responded significantly to the soil inoculation with AM fungus, while grass species showed inconsistent patterns. Significant effect of AMF and copper and their interactions was observed on plant biomass when comparing contaminated vs. non-contaminated soils. Conclusion Strong effect of AMF on the biomass of herb species and slight changes in plant growth with the presence of this fungal species in copper-spiked test soils indicates the importance of mycorrhizal fungi compared to other soil microorganisms in our experimental microcosms.

Increasing frequency and magnitude of climatic extremes, such as heat waves are expected to enhance abiotic stresses on ecological communities. It has been proposed that ecological communities in disturbed habitats may be most sensitive to climatic extremes, as disturbance may reduce density and diversity of higher trophic level organisms like predators. However, there is little experimental evidence that climatic extremes indeed have stronger impact on functioning of such trophically downgraded ecosystems. Here, we experimentally examine how removal of predators from soil communities affects plant performance under periodic heat waves. We used a native plant species, and a congeneric native that is currently expanding its range because of climate change. We used soil nematode communities as the model system, as these are most abundant soil animals and their communities are trophically diverse. Predatory nematodes were manually removed from intact soil nematode communities (mainly the adults as some juveniles are impossible to manually remove) to create a trophically downgraded soil. Intact nematode communities and communities with reduced predatory nematodes were added separately to soils that were planted with either the native Centaurea jacea or the range-expanding congener Centaurea stoebe. Half the experimental units were exposed periodically to experimental heat waves of 10 °C above the control temperature. Our results show that the C: N and C: N: P ratio of plant shoots in predator-reduced soils became lower when exposed to periodic heat waves, however, only in the native plant C. jacea. The decrease in C: N ratio corresponded with increase of an herbivorous nematode in trophically intact soils of C. jacea independent of warming, whereas this relationships disappeared in warmed and predator-reduced soils. Our results accordingly highlight that periodic heat waves may affect stoichiometry of certain plant species by altering trophic interactions in predator-reduced soils.

Malignant melanoma is a highly aggressive form of skin cancer which has a propensity for metastasis. Epithelial mesenchymal transition (EMT) plays a primordial role in the progression of metastatic disease. Metastatic melanoma is resistant to conventional therapies. Hence, researchers have been exploring alternative approaches, including the utility of bioactive phytochemicals to manage metastatic disease. In the present study, we investigated the potential of cirsiliol, a flavonoid isolated from Centaurea jacea L., in modulating the aggressive behavior of B16F10 metastatic melanoma cells, including EMT, and associated molecular mechanisms of action. Cirsiliol was found to be effective in restraining the colony formation and migration of fibronectin-induced B16F10 metastatic melanoma cells. Cirsiliol inhibited the activity and expression of matrix metalloproteinase-9 (MMP-9). Cirsiliol also suppressed the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (also known as Akt)/nuclear factor-&kappa, B (NF-&kappa, B) signaling pathway which, in turn, caused upregulation of E-cadherin and downregulation of N-cadherin, Snail and Twist. Based on these results, cirsiliol may be considered a promising compound against EMT in the therapeutic management of malignant melanoma.