Solidago Species Research Articles

The promoting effects of soil microplastics on alien plant invasion depend on microplastic shape and concentration

Both alien plant invasions and soil microplastic pollution have become a concerning threat for terrestrial ecosystems, with consequences on the human well-being. However, our current knowledge of microplastic effects on the successful invasion of plants remains limited, despite numerous studies demonstrating the direct and indirect impacts of microplastics on plant performance. To address this knowledge gap, we conducted a greenhouse experiment involving the mixtures of soil and low-density polyethylene (LDPE) microplastic pellets and fragments at the concentrations of 0, 0.5 % and 2.0 %. Additionally, we included Solidago decurrens (native plant) and S. canadensis (alien invasive plant) as the target plants. Each pot contained an individual of either species, after six-month cultivation, plant biomass and antioxidant enzymes, as well as soil properties including soil moisture, pH, available nutrient, and microbial biomass were measured. Our results indicated that microplastic effects on soil properties and plant growth indices depended on the Solidago species, microplastic shapes and concentrations. For example, microplastics exerted positive effects on soil moisture of the soil with native species but negative effects with invasive species, which were impacted by microplastic shapes and concentrations, respectively. Microplastics significantly impacted catalase (P < 0.05) and superoxide dismutase (P < 0.01), aboveground biomass (P < 0.01), and belowground/aboveground biomass (P < 0.01) of the native species depending on microplastic shapes, but no significant effects on those of the invasive species. Furthermore, microplastics effects on soil properties, nutrient, nutrient ratio, and plant antioxidant enzyme activities contributed to plant biomass differently among these two species. These results suggested that the microplastics exerted a more pronounced impact on native Solidago plants than the invasive ones. This implies that the alien invasive species displays greater resistance to microplastic pollution, potentially promoting their invasion. Overall, our study contributes to a better understanding of the promoting effects of microplastic pollution on plant invasion.

Effect of litter decomposition on mowing and plant composition change during Solidago stand restoration

Decomposition of organic matter supports important soil ecosystem services. The rate of decomposition depends mostly on the type of plant material being decomposed and the abundance and diversity of organisms that process the organic matter. Consequently, any disturbance to the soil ecosystem will affect the decomposition process. Invasive plants, such as Solidago species, pose a serious ecological threat to natural habitats, so effective and environmentally safe methods of controlling their occurrence should be developed. In this study, decomposition rates were used as indicators of soil health during grassland restoration after Solidago invasion. Different seed mixtures (grasses, grasses with legumes, seeds collected from a seminatural meadow; use of fresh hay and no seeds) were sown during a field experiment and different mowing frequencies (1, 2 and 3 times per year) were established. Two hypotheses were tested: (1) plant species composition used in the restoration process affects litter decomposition rates, and (2) mowing regimes affect litter decomposition rates. It was found that decomposition rates were higher in plots with the highest species diversity. This indicates that an increase in species diversity has a positive effect on soil processes. Secondly, mowing two and three times per season has a positive effect on the decomposition process. In conclusion, decomposition rates can be used as a tool to identify adequate grassland management.

Five invasive alien plant powders, Norway spruce (Picea abies [L.] H. Karst.) wood ash and diatomaceous earth against Sitophilus oryzae (L.) adults: are they closer to guns or roses?

We tested the insecticidal efficacy of different powders as surface treatment against the rice weevil (Sitophilus oryzae) adults. We have applied dusts from five invasive alien plant species (Solidago canadensis, Solidago gigantea, Amorpha fruticosa, Rhus typhina, Ailanthus altissima) and two inert dusts, i.e. wood ash from Norway Spruce (Picea abies) and commercial product SilicoSec® (as diatomaceous earth). Mortality was evaluated from 1st till 7th day after exposure, at 20 and 25 °C, two values of relative humidity and two doses (20 and 40 g/m2). After Day 7, alive beetles were placed into clean Petri dishes, and mortality counts were measured from 8th till 14th day. In general, we have detected poor efficacy of plant powders against S. oryzae. SilicoSec® at 20 g/m2 caused 100 % mortality at 25 °C and 55% RH, after seven days. Wood ash (13.46% SiO2) was less effective in comparison to SilicoSec® (79.48% SiO2), as approx. 60% mortality was recorded at the same conditions. We have detected that leaves of A. altissima and flowers od S. gigantea are rich with polyphenols (like catechin hydrate), on average almost 17 mg/g in S. gigantea flowers. Flowers and leaves of Solidago species are also rich with essential oil, like beta-copaene. The results of our research indicate that the powders of invasive plants are closer to fragrant roses in controlling S. oryzae adults, while the gun for this pest is only diatomaceous earth. To improve the effectiveness of invasive plant products, we suggest testing their independent effectiveness in liquid form as well as combinations of their essential oils with inert dusts.

Comparative Analysis of Root Phenolic Profiles and Antioxidant Activity of Five Native and Invasive Solidago L. Species.

The high environmental importance of invasive goldenrod has prompted research to find potential benefits that can be derived from these species. This study aimed to identify differences in root phenolic profiles among five Solidago species, thus providing valuable information on their potential applications and the botanical origin of the raw material. The roots of native S. virgaurea L., two alien species S. gigantea Aiton and S. canadensis L. and their hybrids S. ×niederederi Khek and S. ×snarskisii Gudž. & Žaln. were sampled from mixed-species stands in Lithuania. A complex of twelve phenolic acids and their derivatives was identified and quantified in methanol-water root extracts using the HPLC-PDA and LC/MS systems. The radical-scavenging capacities of the extracts were assessed by ABTS. The chemical content of the roots of S. virgaurea, S. gigantea and S. ×niederederi were statistically similar, while the roots of S. canadensis and S. ×snarskisii contained lower amounts of compounds than the other species. The PCA score-plot models of the phenolic profiles only partially confirmed the identification of S. ×niederederi and S. ×snarskisii as crosses between native and alien species. The findings from the phenolic profiles and the observed radical-scavenging activity of root extracts of Solidago species provide valuable insights into their potential applications in various fields.

Contrasting invasion patterns of two closely related Solidago alien species

AbstractAimNew areas are often simultaneously invaded by closely related alien species; however, between‐species differences in the course of their invasive spreading due to diverse ecological preferences have rarely been investigated. Here, we aim to study the species‐specific spatio‐temporal invasion patterns of Solidago canadensis and S. gigantea.LocationSlovakia—the Western Carpathian and adjacent Pannonian regions.TaxonInvasive alien Solidago canadensis and S. gigantea.MethodsOur study was based on revised herbarium specimens, a recent field survey which included gathering abundance and habitat data, and environmental data from GIS layers. We characterised the environmental niche differentiation between S. canadensis and S. gigantea. Generalised additive models were then used to identify the key drivers of the species' occurrences and to assess their potential current and future distributions.ResultsBoth species began to spread in Slovakia in the 1850s; in the first 100 years, the number of S. gigantea sites increased exponentially, while that of S. canadensis remained low. Currently, S. canadensis is more widespread in the region. The species have similar habitat preferences. Their environmental niches overlap, but are not identical. The core distribution of S. canadensis is in foothills and valleys that experience lower annual mean temperatures, while that of S. gigantea is in lowlands with higher annual mean temperatures. A large part of their potential distribution areas seems to be already invaded. Possible future climate change could stimulate the spreading of S. canadensis into higher altitudes and S. gigantea farther into lowlands and Carpathian foothills.Main conclusionsThe studied invasive Solidago species differed considerably in the early stages of invasion. Their environmental niches, current realised and potential distribution patterns are different. In the studied region, further spreading, with an increase in the number and size of populations, is likely unless effective measures are undertaken.

Effects of extracts from various parts of invasive Solidago species on the germination and growth of native grassland plant species.

Allelopathy is an important factor influencing whether an invasive plant species can become successfully established in a new range through disrupting the germination and growth of native plant species. Goldenrods (Solidago species) are one of the most widespread invasive taxa in Central Europe of North American origin. Owing to their high environmental impact and wide distribution range, invasive Solidago species should be controlled in Europe, and the areas invaded by them should be restored. Numerous studies have reported the allelopathic effects of Solidago gigantea and Solidago canadensis, but the results are inconsistent regarding differences in the allelopathic effects of particular plant parts and in the sensitivity to Solidago allelopathic effects among native species as well as between the two invasive species themselves. In this study, we aimed to analyse the effect of water extracts from S. canadensis and S. gigantea parts (roots, rhizomes, stems, leaves, and inflorescences) on the germination and initial growth of seedlings of 13 grassland species that typically grow in Central Europe. The tested grassland species differed in susceptibility to Solidago allelopathy, with the most resistant species being Schedonorus pratensis, Lolium perenne, Trifolium pratense, Daucus carota and Leucanthemum vulgare. The inhibitory effect of 10% water extracts from leaves and flowers were stronger than those from rhizomes, roots, and stems without leaves, regardless of the Solidago species. Our study results imply that reducing the allelopathic effect of Solidago during habitat restoration requires removal of the aboveground parts, including fallen leaves. The allelopathic effects of roots and rhizomes seem to be of secondary importance.

Analytical and chromatographic parameters used to quantify flavonols and chlorogenic acid in Solidago raw extracts

Species in the Solidago genus are used worldwide due to the therapeutic activities of their flavonoids and terpenoids. Its anti-inflammatory, vulnerary, antirheumatic, analgesic, diuretic, aquaretic, wound-healing properties, as well as its ability to relieve the burn and insect bites, allow use in a variety of therapeutic applications. This study was carried out to determine the comparative chemical profile, the content of flavonoids (FLV) and chlorogenic acid (CA) in the inflorescence extracts of Solidago chilensis and Solidago canadensis, as well as the biological potential of these species, regarding other Solidago species used in North America and Europe. S. chilensis was cultivated in Itaipava, Tapera Quilombo’s (Rio de Janeiro/Itaboraí Forum - FIT/Fiocruz) and in the Agroecological Platform of Phytomedicines (PAF/Farmanguinhos/Fiocruz). S. canadensis was acquired in Rio de Janeiro, in a popular market. The inflorescences polar extracts were evaluated and standardized by HPLC analytical methodology about the levels of the flavonoids reference standards and CA content and expressed in µg/mL for quantification, using the selectivity analytical parameters, linearity, limit of detection, accuracy, precision, and robustness as defined by national health surveillance agency in Brazil. The HPLC-UV-PDA revealed mainly flavonols (FLV) such as quercetin, glycosides as well as CA. S. canadensis presented the highest concentrations of quercetin (114.46 ± 0.114 µg/mL) and quercitrin (54.40 ± 2.014 µg/mL) but did not present isoquercitrin. However, the S. chilensis (TT0116 extract) presented the highest amount of CA (96.06 ± 2.365 µg/mL) and isoquercitrin (143.88 ± 4.219 µg/mL), and the samples of TB0116 extract presented the highest amount of hyperoside (227.79 ± 3.333 µg/mL and 153.49 ± 4.200 µg/mL). The presented data in this study indicate qualitative similarities and quantitative differences in the CA and FLV contents in the crude extracts of the two Solidago species. These differences are essential to assess the biological activity of each species, confirm its antioxidant and anti-inflammatory actions, and perform quality control of species occurring in Brazil.

Goldenrod herbariomics: Hybrid-sequence capture reveals the phylogeny of Solidago.

The phylogenetic relationships among the ca. 138 species of goldenrods (Solidago; Asteraceae) have been difficult to infer due to species richness, and shallow interspecific genetic divergences. This study aims to overcome these obstacles by combining extensive sampling of goldenrod herbarium specimens with the use of a custom Solidago hybrid-sequence capture probe set. A set of tissues from herbarium samples comprising ca. 90% of Solidago species was assembled and DNA was extracted. A custom hybrid-sequence capture probe set was designed, and data from 854 nuclear regions were obtained and analyzed from 209 specimens. Maximum likelihood and coalescent approaches were used to estimate the genus phylogeny for 157 diploid samples. Although DNAs from older specimens were both more fragmented and produced fewer sequencing reads, there was no relationship between specimen age and our ability to obtain sufficient data at the target loci. The Solidago phylogeny was generally well-supported, with 88/155 (57%) nodes receiving ≥95% bootstrap support. Solidago was supported as monophyletic, with Chrysoma pauciflosculosa identified as sister. A clade comprising Solidago ericameriodes, Solidago odora, and Solidago chapmanii was identified as the earliest diverging Solidago lineage. The previously segregated genera Brintonia and Oligoneuron were identified as placed well within Solidago. These and other phylogenetic results were used to establish four subgenera and fifteen sections within the genus. The combination of expansive herbarium sampling and hybrid-sequence capture data allowed us to quickly and rigorously establish the evolutionary relationships within this difficult, species-rich group.

Soil phosphorus form affects the advantages that arbuscular mycorrhizal fungi confer on the invasive plant species, Solidago canadensis, over its congener.

Interactions between plants and arbuscular mycorrhizal fungi (AMF) are strongly affected by soil phosphorus (P) availability. However, how P forms impact rhizosphere AMF diversity, community composition, and the co-occurrence network associated with native and invasive plants, and whether these changes in turn influence the invasiveness of alien species remain unclear. In this work, we performed a greenhouse experiment with the invasive species Solidago canadensis and its native congener S. decurrens to investigate how different forms of P altered the AMF community and evaluate how these changes were linked with the growth advantage of S. canadensis relative to S. decurrens. Plants were subjected to five different P treatments: no P addition (control), simple inorganic P (sodium dihydrogen phosphate, NaP), complex inorganic P (hydroxyapatite, CaP), simple organic P (adenosine monophosphate, AMP) and complex organic P (myo-inositol hexakisphosphate, PA). Overall, invasive S. canadensis grew larger than native S. decurrens across all P treatments, and this growth advantage was strengthened when these species were grown in CaP and AMP treatments. The two Solidago species harbored divergent AMF communities, and soil P treatments significantly shifted AMF community composition. In particular, the differences in AMF diversity, community composition, topological features and keystone taxa of the co-occurrence networks between S. canadensis and S. decurrens were amplified when the dominant form of soil P was altered. Despite significant correlations between AMF alpha diversity, community structure, co-occurrence network composition and plant performance, we found that alpha diversity and keystone taxa of the AMF co-occurrence networks were the primary factors influencing plant growth and the growth advantage of invasive S. canadensis between soil P treatments. These results suggest that AMF could confer invasive plants with greater advantages over native congeners, depending on the forms of P in the soil, and emphasize the important roles of multiple AMF traits in plant invasion.

Allelopathic Activity of Canadian Goldenrod (Solidago canadensis L.) Extracts on Seed Germination and Growth of Lettuce (Lactuca sativa L.) and Garden Pepper Cress (Lepidium sativum L.).

Native to N. America, Canadian goldenrod (Solidago canadensis L.) was introduced to Europe as an ornamental plant and quickly spread here and in other parts of the world. The rapid spread of the plant is due to several reasons: phenotypic plasticity, broad climatic tolerance, propagation via underground rhizomes and seeds that mature in large numbers, etc. Additionally, the success of Canadian goldenrod's invasion is determined by its allelochemicals that affect seed germination, root formation and whole growth of nearby plants. Allelopathy of various extracts and essential oils (EOs) of S. canadensis on seed germination and growth of lettuce (Lactuca sativa L.) and garden pepper cress (Lepidium sativum L.) was evaluated and compared with other Solidago species (S. virgaurea, S. × niederederi) collected from the same growing locality in Lithuania. Soil characteristics (conductivity, pH and major elements) of the collecting site were determined. Aqueous flower extracts of all studied Solidago species showed the highest inhibitory effect on model plants. Canadian goldenrod leaf water/diethyl ether extract showed highest inhibitory effect in all relative concentrations (1.0; 0.1; 0.01) suppressing growth of L. sativa (from 0 to 2.3 mm compared with 22.7 mm for control samples) and L. sativum (from 0.5 to 16.8 mm compared with 35.3 mm in control). It was noticed that garden pepper cress was more susceptible to Solidago spp. inhibitory effects than lettuce. S. canadensis root EOs comprised mainly of limonene (35.0%) and β-pinene (26.2%) and inflorescence oils containing α-pinene (21.6%), germacrene D (15.1%), limonene (10.2%) and lupenyl acetate (9.8%) exhibited the highest inhibitory effect on lettuce and garden pepper cress growth. Relative germination and vigor index of model plants was conducted. Chemical composition of extracts and EOs was determined by HPLC/DAD/TOF and GC/MS techniques.

&lt;i&gt;Solidago psammophila&lt;/i&gt; (Asteraceae: Astereae), a New Sand Dune Endemic Goldenrod from Northern Michigan, U.S.A.

Solidago psammophila is described as a new species from open dune habitats along the southern shore of Lake Superior in Michigan’s Upper Peninsula. Field and herbarium studies revealed that it is endemic to the state of Michigan, restricted to an approximately 100 km section of shoreline from Grand Sable Dunes in the west to Whitefish Point in the east. This goldenrod is ecologically similar to S. gillmanii (A. Gray) Steele in Solidago subsect. Humiles (Rydb.) Semple, sharing apparent adaptations to the sand dune environment. However, it differs from S. gillmanii and other members of subsect. Humiles in its vegetative pubescence and lack of glutinosity. It is morphologically most similar to the widespread S. hispida Muhl. in subsect. Erectae (G. Don) Semple &amp; J.B. Beck. DNA ploidy determinations from flow cytometry revealed that this newly described species is tetraploid, whereas S. hispida has been shown to be uniformly diploid across its range. Solidago psammophila appears to be an example of the interplay of polyploidy and habitat specialization leading to ecological speciation in the recently glaciated Great Lakes region. A brief discussion of the other Great Lakes region endemic goldenrods and a revised key to all Michigan Solidago species are included.

The impact of restoration methods for Solidago-invaded land on soil invertebrates

The belowground community structure of soil biota depends on plant composition and may be affected by invasive plant species. We hypothesized that the type of land restoration method applied affects the abundance and composition of soil invertebrates. Our field experiment centred on Solidago species control using different seed mixtures and methods of seed introduction (sowing mixtures: grasses, grasses with legumes, seeds from a seminatural meadow, and application of fresh hay) and different frequencies of mowing (one, two, or three times per year). Soil invertebrates were identified to the taxa, using light microscopes. Richness and diversity indices were calculated, and a redundancy analysis was conducted. Generally, mowing intensity negatively influenced soil organisms, although increased mowing frequency positively affected the abundance of some taxa (Symphyla, Hemiptera). Mowing twice per year decreased the abundance of soil invertebrates, but not their diversity. Soil invertebrate taxa had the greatest abundance in the plots sown with a seed mixture containing grasses with legumes. Among the restoration methods studied, mowing once a year and introducing grasses with legumes represented the least harmful strategy with regard to soil invertebrate abundance. Further studies are needed to investigate the dynamics of soil mesofauna exposed to long-term mowing and changes in vegetation characteristics.

Restoration of ecologically valuable grassland on sites degraded by invasive Solidago: lessons from a 6‐year experiment

AbstractMost semi‐natural grasslands are threatened by invasive alien plants, which have also overgrown abandoned fields. We conducted a 6‐year experiment testing different methods of eliminating invasive Solidago species and adding seed to restore valuable species‐rich grassland. Three removal treatments (herbicide spraying, rototilling, turf stripping) and two seed addition methods (direct sowing of a fast‐growing grass species mixture, spreading of fresh hay collected from a semi‐natural meadow) were examined alongside control treatments (no removal, no seed addition). The experimental plots were mowed twice a year, and the vegetation composition, biomass production, hay chemical composition, and fodder quality were assessed. Mowing twice a year significantly reduced Solidago cover. Although significant differences were observed in the invaders' cover between the removal treatments and between the seed addition methods early in the study, the differences lessened over time, especially for the removal treatments. By the end of the 6‐year study period, the Solidago cover was reduced to 25% of the initial complete coverage. Spreading fresh hay greatly reduced Solidago biomass and yielded the highest characteristic species cover. Herbicide treatment was no more efficient than the more environmentally friendly methods over the study period. The results suggest that fresh hay is good method of seed addition for restoring old fields overgrown by invasive Solidago. With mowing of the restored area twice a year for several years, Solidago removal by turf striping (scalping) followed by the spreading of fresh hay is recommended for grassland restoration given its environmental impact, cost, and hay quality.

Distribution Patterns of Essential Oil Terpenes in Native and Invasive Solidago Species and Their Comparative Assessment.

The importance of invasive Solidago L. species to the environment creates a new approach to controlling their spread through the use of potentially high value raw materials. The aim of this study was to assess the distribution patterns of volatile compounds in the four Solidago spp., by identifying common and species-specific compounds with their potentials, and to confirm the origin of the spontaneous hybrid Solidago × niederederi on the basis of comparative assessment of essential oil (EO) profiles. Plant material in the flowering phase was collected in mixed populations from six different sites. The EOs were isolated separately from the leaf and the inflorescence samples by hydrodistillation for 3 h. The chemical analysis was performed by gas chromatography—mass spectrometry. Multivariate data analysis was employed to explain the interspecies relationships among Solidago spp. The results revealed the similarity among Solidago spp. EO profiles, which were dominated by monoterpenes and oxygenated compound fractions. Solidago spp. differed in species distinctive terpenes and their distribution between accessions and plant parts. Volatile compound patterns confirmed the origin of Solidago × niederederi between Solidago canadensis and Solidago virgaurea, with the higher contribution of alien species than native ones. Correct taxonomic identification of species is highly essential for the targeted collection of raw material from the wild for different applications. Solidago spp. can be considered to be underutilized sources of bioactive secondary metabolites.

High-performance thin-layer chromatography–direct bioautography combined with chemometrics for the distinction of goldenrod species

Thirteen root extract samples of four goldenrod (Solidago) species present in Europe were investigated by hyphenated high-performance thin-layer chromatography (HPTLC). Only S. virgaurea is native, whereas S. gigantea, S. canadensis, and S. graminifolia have been introduced from North America. The bioactive zones in the Aliivibrio fischeri bioautogram were identified as polyacetylenes, labdane diterpenes, or clerodane diterpenes by HPTLC coupled to high-resolution mass spectrometry, exploiting the two interfaces, heated electrospray ionization, and direct analysis in real time. Principal component analysis of the obtained bioprofiles enabled the discrimination of the Solidago species. Furthermore, chemometrics pointed to the discriminative components, the main bioactive markers of the species: Z,Z-matricaria ester from S. virgaurea, solidagenone from S. canadensis, solidagoic acid A, and a dialdehyde clerodane diterpene from S. gigantea, and Z-dehydromatricaria ester from S. graminifolia.

Self-Renewal of Invasive Goldenrods (Solidago spp.) as a Result of Different Mechanical Management of Fallow

The spread of invasive plants is one of the most significant causes of biodiversity loss in natural, semi-natural, and anthropogenic habitats in Poland. This two-year study aimed to assess the rate of self-renewal of Canadian goldenrod (Solidago canadensis L.) and giant goldenrod (S. gigantea Aiton), and the possibility of achieving full generative development on fallow land restored to agricultural use with mechanical treatments. The following research objects were examined: the control (no mechanical treatments); one-time mowing; two-time mowing; one-time mowing plus one-time rotary tilling; and one-time mowing plus two-time rotary tilling. The phenological development of Solidago spp. was observed every 14 days from June to September each year. In October of each growing season, the aboveground parts of goldenrods’ biomass were measured, and selected morphological parameters were assessed. Two-time mowing and one-time mowing with two-time rotary tilling resulted in the highest reductions in the share of goldenrods in the generative stages of development, of 64.0% and 51.7% compared to the control, respectively. The two-time mowing treatment was the most effective at inhibiting goldenrods’ biomass accumulation, with a 57.7–77.0% decrease in biomass compared to the control. This treatment also reduced the number of flowering shoots and inflorescence lengths of both Solidago species.

Chemical Composition and Antiproliferative Effect of Essential Oils of Four Solidago Species (S. canadensis, S. gigantea, S. virgaurea and S.×niederederi).

There is a growing interest in the research of natural products with potent activity in the prevention and treatment of diseases. Thereby, essential oil phytochemicals have demonstrated broad bioactivities. This study highlights the chemical composition of essential oils obtained from the leaves and inflorescences of diverse species of the genus Solidago (Solidago canadensis, Solidago gigantea, Solidago virgaurea and Solidago×niederederi), also known as Goldenrod, through GC/MS analysis, and their antiproliferative activity on three human tumor cell lines (MDA-MB 231, A375 and HCT116) by the MTT assay. The most represented chemical classes in the essential oils were oxygenated sesquiterpenes, sesquiterpene hydrocarbons, oxygenated monoterpenes and monoterpene hydrocarbons, with a remarkable contribution of compounds such as germacrene D (3.89-19.51 %), α-pinene (3.59-18.82 %), bornyl acetate (3.30-12.73 %) and caryophyllene oxide (3.07-9.18 %). Chemical quali- and quantitative differences were noticed between the leaves and flowers of the same species, as well as between the studied species. The MTT assay showed that the essential oils from the leaves were more active than those from the flower ones. The essential oil having the highest impact on cell viability was that from S.×niederederi (IC50 =12.93, 6.72, and 6.82 μg/ml), followed by S. virgaurea (IC50 =13.39, 7.96, and 8.36 μg/ml) and finally S. gigantea (IC50 =18.04, 5.94, and 8.10 μg/ml) on MDA-MB 231, A375 and HCT116 cell lines, respectively. The essential oil from S. canadensis showed the lowest activity (IC50 =29.33, 12.63, and 18.03 μg/ml, respectively). Taken together, these findings highlight the Solidago species as good sources of cytotoxic compounds. Further studies are encouraged on the in vivo effects and safety of these products.

Morpho-histological studies of three Romanian Solidago species

Morpho-histological studies of three Romanian Solidago species

Seed germination traits in the rare sandstone rockhouse endemic Solidago albopilosa (Asteraceae)

Understanding how temperature and other environmental cues influence germination traits can aid in the conservation and management of rare plant species. We examined the germination niche of the narrow endemic Solidago albopilosa, a perennial herb restricted to sandstone rockhouses in the southeastern United States. We experimentally subjected seeds to varying lengths of cold stratification, incubation temperatures, photoperiods, and seasonal temperature cycles that simulated current ambient temperatures and a climate warming scenario. Seeds exhibited conditional physiological dormancy and germinated at greater proportions following chilling than when fresh in all temperatures and light regimes tested. In seasonal temperature cycles that simulate those after seed dispersal in late autumn, seeds began germinating after 9 wk in late-winter temperatures (February), with peak germination occurring in early spring (March). Germination timing shifted 1 wk earlier in the spring with climate warming, but germination proportions did not differ among treatments. Buried seeds did not persist to the second germination season (spring), suggesting minimal carryover among years. Seed viability declined in the smallest (< 50 stems) populations but varied less among sites with different levels of human disturbance. A germination niche defined by conditional physiological dormancy, a minimal chilling requirement, dark germination, seasonal germination cueing, and low persistence in the soil is consistent with the expectation of a perennial herb from a stable habitat, but diverges in some aspects from seed traits found in Solidago species of grasslands and open habitats. These results suggest that dormancy or germination do not limit seed regeneration in most natural populations nor contribute to S. albopilosa's rarity.

Does an invader have a bright side? Floral reward in two Solidago species

The knowledge of nectar secretion and pollen production is important for understanding the biology of invasive species. In the present paper, the floral reward in Solidago canadensis and S. gigantea (Asteraceae), two invasive plant species in Europe, were investigated. Flowers of Solidago species are protandrous. The floral nectar was found to be rich in hexose (sucrose/fructose/glucose – 13.8/32.7/53.5% in S. canadensis and 18.3/35.1/46.6% in S. gigantea). The per-flower rewards (sugars/pollen) in the Solidago species were not abundant; however, due to the formation of dense populations and massive floral display, high amounts of resources were produced at the community level. The mean sugar output was 482.3 kg/ha in S. canadensis and 121.6 kg/ha in S. gigantea. The mean pollen yield was 30.7 kg/ha (S. canadensis) and 6.5 kg/ha (S. gigantea). In the landscape with limited floral resources, the nectar and pollen available in Solidago flowers are important and can provide additional (or even exclusive) food resources for pollinators during summer/late summer. In particular, areas invaded by Solidago species may be attractive to beekeepers, as >80.0% of visits were performed by Apis mellifera. However, a broad spectrum of wild insect visitors (including Bombus spp., Vespula spp., Diptera, Lepidoptera, Coleoptera) deserves further studies to assess the impact of mass flowering in Solidago species on the native plant species-insect interactions.