Canadensis Plants Research Articles

Conyza canadensis, a new host of Tobacco leaf curl Yunnan virus in China

AbstractIn April 2023, leaf curl, crinkling symptoms were found on Conyza canadensis plants around tobacco fields located at Yuxi, Yunan province, China. PCR detection with genus‐specific primers showed that symptomatic C. canadensis plants was infected by begomovirus. The full‐length viral components and satellite molecules from the diseased C. canadensis (YN‐2023) were obtained by enrichment of circular DNA with rolling circle amplification, restriction enzyme digestion, cloning, and DNA sequencing. The viral component (2, 750 nt, OR509733) shared the highest nt identity at 92.4% to tobacco leaf curl Yunnan virus isolate YN5741 (TbLCYNV‐YN5741 [CN:Yn:Age:16], MN218671). A satellite molecule (1, 339 nt, OR509734) shared the highest nt identity at 86.5% to tobacco curly shoot betasatellite isolate Y115 (TbCSB‐Y115 [CN:Yn:03], AJ457822). Another satellite molecule (1, 357 nt, OR509735) shared the highest nt identity at 94.2% to ageratum yellow vein Singapore alphasatellite (AYVSGA‐[Singapore:1998], NC003414). Based on the threshold for classification of Begomovirus, Betasatellite, Alphasatellite, YN‐2023 was a new strain of TbLCYNV and associated with TbCSB and AYVSGA. To our best knowledge, this is the first report that C. canadensis is a natural host of TbLCYNV.

Facile extraction of berberine from different plants, separation, and identification by thin-layer chromatography, high-performance liquid chromatography, and biological evaluation against Leishmaniosis.

The extraction of berberine was carried out from Berberis vulgaris, Berberis aquifolium, and Hydrastis canadensis plants using ethanol and water (70:30, v/v). The extracted berberine was characterized by ultraviolet-visible and Fourier-transform infrared spectroscopy. The purity of berberine was ascertained by thin-layer chromatography using n-propanol-formic acid-water (95:1:4) and (90:1:9) solvents. hRf values were in the range of 44-49 with compact spots (diameter 0.2-0.4cm). HPLC was carried out using ammonium acetate buffer and acetonitrile in gradient mode with Zodiac (4.6×150mm, 3μm) column. The flow rate was 1.0mL/min and detection was at 220nm. The values of separation and resolution factors of the standard and the extracted berberine were in the range of 1.13-1.16 and 1.40-1.71, respectively. A comparison has shown that both thin-layer chromatography and high-performance liquid chromatography (HPLC) methods found applications in different situations and requirements. The extracted berberine samples were used to treat Leishmaniosis and the results showed better activity of berberine in comparison to the standard drug Amphotericin B. Briefly, the reported research is a novel and may be used to extract berberine from plants, separation and identification of berberine by thin layer chromatography and HPLC and to treat Leishmaniosis.

Bioherbicidal Activity of Albifimbria verrucaria (Formerly Myrothecium verrucaria) on Glyphosate-Resistant Conyza canadensis.

The effects of the bioherbicidal activity of the fungal phytopathogen, Albifimbria verrucaria (AV), formerly Myrothecium verrucaria, on glyphosate-resistant and -susceptible Conyza canadensis (horseweed) were examined in greenhouse and field studies. Spray applications of mycelial formulations of AV infected both glyphosate-resistant and -susceptible C. canadensis plants at various growth stages. Young plants in the rosette leaf stage of growth were controlled more efficaciously than were older plants that had bolted or that were in the inflorescence stage; nevertheless, severe injury and mortality also occurred in mature plants. The results indicate that this bioherbicidal fungus can infect and control C. canadensis, thereby demonstrating the potential of this fungus as a bioherbicidal agent against this troublesome weed, which has become resistant to various herbicides.

Assessment of The Use of Artemisia Dracunculus L and Erigeron Canadensis in The Remediation of Heavy Metal Contaminated Soils and Their Ability to Phytoextraction and Biomass Yield.

Different hyperaccumulator plants growing in the same contaminated soil may have excessive accumulation of different metals or produce biomass. Therefore, it is important to determine the ability of the plant to improve the soil under natural conditions in the improvement of heavy metal-contaminated lands with hyperaccumulator plants. This study focused on the phytoremediation and biomass production capabilities of Artemisa Dracunculus L. and Erigeron Canadensis plants. Considering this fact, Erigeron Canadensis was determined to have the highest phytoextraction potential between the two plants, as it produces more biomass (96%) and mineral content (169%) than Artemisa Dracunculus L. This shows that Erigeron Canadensis has more phytoremediation potential than Artemisa Dracunculus L. and that Erigeron Canadensis plant is one of the alternative hyperaccumulator plant candidates and is more effective for soil reclamation. In addition, when the plants were categorized according to their BAF values, accumulator (1

Angiosperms distribution under the influence of microclimatic factors across a polluted ecosystem

Plant species represent the hierarchical expression of vegetation as it is affected by different ecological, environmental factors and pollution variables. This study assesses the impact of a different hidden treasure or factors on angiosperm plants in the marble waste polluted environment. Quadrat quantitative ecological techniques were adapted for sampling of vegetation. Size of the quadrats was kept 1 × 1m, 5 × 5m and 10 × 10m for herbs, shrubs and tree species, respectively. Soil physicochemical properties were carried out using standard protocols. All the collected data were put in MS Excel for analysis in PCORD, CANOCO, STATA and SPSS software's. The degrees of relationship among variables and with abundant plants were measured using Pearson correlation and regression analysis. The structural relationship between environmental variables and abundant angiosperms was determined through Structural Equation Modeling to examine the admired dignity of diverse environmental factors. A total of one hundred two plant species belong to ninety-five genera and forty-eight families were reported from a marble waste polluted environment. Cluster Analysis via Jaccard distance measurement and ward linkage methods gave rise to three plant communities i.e. (i) Populus alba-Arundo donax-Erigeron canadensis plants community, (ii) Morus alba- Rosa webbiana- Centaurium tenuiflorum plants community and (iii) Dalbergia sissoo- Dodonaea viscosa- Panicum antidotale plants community. Among all the measured environmental variables, the dominant plants of the first plant community comprehend positive and significant relationships with soil pH, potassium and negative plus significant relationship with electrical conductivity and organic matter. The abundant plants of 2nd plant community were under the influence of higher potassium concentration and lower soil pH as compared to other communities. Third community exhibits a negative and significant relationship with soil pH in conjunction with higher electrical conductivity in the region. The aforementioned techniques could be used to find out the relationship between plant species distribution and microclimatic variables.

Integrative physiological and transcriptome analyses provide insights into the Cadmium (Cd) tolerance of a Cd accumulator: Erigeron canadensis

Cadmium (Cd) is a highly toxic pollutant in soil and water that severely hampers the growth and reproduction of plants. Phytoremediation has been presented as a cost-effective and eco-friendly method for addressing heavy metal pollution. However, phytoremediation is restricted by the limited number of accumulators and the unknown mechanisms underlying heavy metal tolerance. In this study, we demonstrated that Erigeron canadensis (Asteraceae), with its strong adaptability, is tolerant to intense Cd stress (2 mmol/L CdCl2 solution). Moreover, E. canadensis exhibited a strong ability to accumulate Cd2+ when treated with CdCl2 solution. The activity of some antioxidant enzymes, as well as the malondialdehyde (MDA) level, was significantly increased when E. canadensis was treated with different CdCl2 solutions (0.5, 1, 2 mmol/L CdCl2). We found high levels of superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities under 1 mmol/L CdCl2 treatment. Comparative transcriptomic analysis identified 5,284 differentially expressed genes (DEGs) in the roots and 3,815 DEGs in the shoots after E. canadensis plants were exposed to 0.5 mM Cd. Functional annotation of key DEGs indicated that signal transduction, hormone response, and reactive oxygen species (ROS) metabolism responded significantly to Cd. In particular, the DEGs involved in auxin (IAA) and ethylene (ETH) signal transduction were overrepresented in shoots, indicating that these genes are mainly involved in regulating plant growth and thus likely responsible for the Cd tolerance. Overall, these results not only determined that E. canadensis can be used as a potential accumulator of Cd but also provided some clues regarding the mechanisms underlying heavy metal tolerance.

Molecular characterization of a novel Conyza canadensis-infecting begomovirus in China

A novel monopartite begomovirus was found in naturally infected Conyza canadensis plants exhibiting typical begomovirus-induced yellow vein symptoms in Yunnan Province of China. Analysis of two obtained full-length viral genome sequences showed that they shared 99.8% nucleotide (nt) sequence similarity, and both consisted of 2733 nts (GenBank accession no. OK120264 and OK120266, respectively). Further analysis showed that these two sequences shared the highest nt sequence similarity (78.9%) with tomato yellow leaf curl Vietnam virus (TYLCVV) (EU189150). In the assayed C. canadensis plants, a betasatellite of 1,341 nts (Accession no. OK120265 and OK120267, respectively) was also found, and it shared 98.1% sequence similarity with malvastrum yellow vein betasatellite (MaYVB) (JX679254). Based on the current classification criteria for begomoviruses, we consider that the two obtained viral isolates are a novel begomovirus, and named it as conyza yellow vein virus (CoYVV). Our further analysis result showed that CoYVV is likely originated from a recombination event between tomato yellow leaf curl Yunnan virus (TYLCYnV) and tomato yellow leaf curl China virus (TYLCCNV). To investigate the effect of CoYVV infection in plant, we constructed two infectious clones (i.e., pCoYVV and pMaYVB), and inoculated them individually or together to Nicotiana benthamiana plants through agro-infiltration. The result showed that the plants co-inoculated with CoYVV and MaYVB developed yellow vein and downward leaf-curling symptoms, whereas the plants inoculated with CoYVV alone showed no clear virus-like symptoms. Virus infection in the inoculated N. benthamiana plants was confirmed through polymerase chain reaction (PCR). The result of quantitative PCR (qPCR) showed that in the presence of MaYVB, the accumulation level of CoYVV DNA was significantly increased compared to that in the plants infected with CoYVV alone.

Solidago canadensis, a Flower or Weed?

Figure 1. Flowers or weeds? S. canadensis is one of the worst exotic weeds in China (A). Yet, farmers grow it as a cut flower (B). Because diploid cytotypes grow faster and flower earlier than other polyploids, all cultivated S. canadensis cytotypes for cut flowers are diploids. We found that diploids are sterile under hot-summer temperature south of 24°C-isotherm range and cultivation of S. canadensis will not lead to naturalization. However, the risk for naturalization increases in regions north of 20ºC-isotherm range. Photo credit: Sheng Qiang. Figure 2. Population of Solidago canadensis in native and introduced range in North America and China, respectively. S. canadensis plants are significantly taller and denser in the introduced range in China (Jiangsu) (A) than in their native range of North America (Pennsylvania, USA) (B). S. canadensis plants often outcompete native plants in invasive habitats and essentially become monoculture-type communities. Photo credit: Sheng Qiang. Figure 3. Dramatic difference in height of Solidago canadensis between native and invasive populations. S. canadensis plants can often be over 4m in height in China (Nanjing) (A), but are usually below 2m in North America (Ottawa, Canada) (B). Photo credit: Sheng Qiang. Figure 4. Field sampling site diagram. At each site, sampling plots were separated by at least 10 m to minimize the probability of sampling multiple ramets from individual genets. Photo credit: Guoqi Chen. Figure 5. Pollen germination and pollen tube growth on a stigma. (A) Pollen germination; (B) pollen tube growth; (C) penetration of pollen tubes into an ovary. Photo credit: Beibei Yao. These photographs illustrate the article “Solidago canadensis, a flower or weed?” by Sheng Qiang, Jiliang Cheng, Guoqi Chen, Beibei Yao published in Ecological Monographs. https://doi.org/10.1002/ecm.1445.

Shading may alter the colonization pattern and dominance between two invasive submerged aquatic plant species

Egeria densa and Elodea canadensis are two common invasive submerged macrophytes in streams and rivers worldwide. We conducted a six-week growth experiment with monocultures of E. densa and E. canadensis and mixed communities of the two species under five different shade levels (35%, 63%, 79%, 90% and 95%). Our aim was to test the effect of shade and competition on colonization of vegetative propagules of these species in flowing waters. We found that biomass accrual in both species was greatly reduced at high shade (≥ 79%) and that E. densa individuals accrued more biomass than E. canadensis individuals at all shade levels. At the least shade level (35%), interspecific competition with E. densa stimulated biomass accrual of E. canadensis individuals, compared to those within an E. canadensis monoculture. At higher shade (≥ 63%), this facilitation response disappeared, although E. canadensis plants continued to have longer stem length and a greater degree of branching than E. densa plants at ≤ 79% shade. At the highest shade level, competition with E. canadensis reduced biomass accrual of E. densa. Hence, shade influenced the competitive interactions between these two species. At low shade, the competitiveness of E. canadensis was enhanced, but in the field E. densa appears to be the dominant species in streams, especially those with higher levels of shade and less frequent disturbance by flushing flow events.

Invasive Solidago canadensis versus its new and old neighbors: Their competitive tolerance depends on soil microbial guilds

An important hypothesis in invasion ecology is that new neighbors in an invaded range should be more susceptible (i.e., low tolerance to competitors) to invaders than old neighbors in a home range. To test this hypothesis in the context of different soil microbes, we conducted a pairwise competition experiment with five Chinese native species, five North American native species, and Solidago canadensis (an invader from North America into China), in which all the species combinations were subject to regular soil, fungicided soil, and autoclaved soil. In the absence of S. canadensis, the average growth of Chinese natives was similar to that of North American natives; in the presence of S. canadensis, Chinese natives grew bigger and had a lower competitive response than North American natives. Solidago canadensis plants grown alone grew larger from China than from North America; in contrast, S. canadensis plants grew smaller when they were grown with Chinese natives than when they were grown with North American natives. Fungicide decreased the growth of species from China and North America whereas autoclaving increased their growth in the presence of S. canadensis; fungicide and autoclaving decreased the growth of S. canadensis grown with neighbors. These findings suggest that new neighbors may have a stronger competitive tolerance to S. canadensis than old neighbors and this tolerance may depend on soil microbial guilds, thereby altering the interactions between S. canadensis and its neighbors.

Conyza canadensis (L.) Extract Analysis of ingredients and anti-inflammatory anti-obesity activity

In this study, I measured the Anti-inflammatory and anti-obesity effect of the wild Conyza Canadensis plants native to Korea extracted from 70% ethanol in order to develop functional foods. I experiments with HEPG2 cells for figure out General ingredient & inhibitory effect of fat, 3T3-L1 cell for Adipogenesis inhibitory effect and anti-inflammatory effect with RAW264 cell, cytotoxicity test with HACAT cells. As a result, the contents of carbohydrates were 46.4%, 30.8% for crude fiber, 26.5% for crude protein, 16.3% for moisture, 9.5% for crude Ash and 1.2% for crude lipid so Carbohydrates content was the highest. In physiological activity, The highest effect is that Raw264.7 cells showed the 40% nitric oxide (NO) inhibitory effect at 25 ppm and 15% fat accumulation inhibitory effect at 50 ppm in HepG2 cells. In the case of 3T3-L1 cells, 25% inhibiting effect of lipid precursor cells was observed at 100 ppm. As shown in the results, the wild Conyza Canadensis extract is expected to have a high potential as a new functional material because it has abundant nutrients, anti-inflammatory activity and inhibitory activity of adipocyte.

Spatial dynamics of pollination in dioecious Shepherdia canadensis (Elaeagnaceae)

The immobility of plants and the need for third-party vectors to enact pollen transfer render pollination an inherently spatial process. Little is known about the spatial scales over which pollen transfer and plant reproductive success are dependent on mate availability in natural plant populations. Dioecious plants provide useful study systems for examining the dependence of reproductive success on spatial patterns of mate availability because potential pollen donors and recipients are unambiguous. We examined the spatial dynamics of pollination in the dioecious shrub Shepherdia canadensis (L.) Nutt. (Elaeagnaceae) at a range of spatial scales in Ivvavik National Park, Canada. On average, males occurred at higher frequencies than females across ten study sites with at least 60 S. canadensis plants per site. Although we detected substantial variation in sex ratios across sites, there was no association between sex ratio and fruit set. Instead, patterns of fruit set were significantly correlated with male density within sites, over distances of 4–6 m. The density of females and males was spatially cross correlated. Therefore, density effects appear to be driven by pollinator responses to the overall density of shrubs. A pollinator exclusion experiment indicated that syrphid flies (Family: Syrphidae) were the most important pollinators in these populations. This study demonstrates that female reproductive success in S. canadensis is limited by plant density over small spatial scales, corresponding with the short foraging distances characteristic of its fly pollinators.

Antibacterial activity of northern Ontario medicinal plant extracts

Hassan, H. M., Jiang, Z.-H., Asmussen, C., McDonald, E. and Qin, W. 2014. Antibacterial activity of northern Ontario medicinal plant extracts. Can. J. Plant Sci. 94: 417–424. In the present study, the antibacterial activity (in vitro) of the leaf and/or flower crude extracts of Anaphalis margaritacea (L.) Benth & Hook.f., Grindelia squarrosa (Pursh) Dunal, Apocynum androsaemifolium L., Arctostaphylos uva-ursi (L.) Spreng, Cornus canadensis L. and Xanthium strumarium L. medicinal plants was analyzed through the hole-plate diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays against Escherichia coli, Aeromonas caviae, Paenibacillus alvei, Micrococcus luteus, Mycobacterium avium subsp. avium and Bacillus cereus bacteria. In addition, the time-kill dynamic processes of these extracts against A. caviae, B. cereus, P. alvei, and M. luteus bacteria were also tested. The leaf and flower extracts of Anap. margaritacea and G. squarrosa possess significant antibacterial activity against all the bacteria tested, with inhibition of A. caviae, P. alvei and M. luteus within 1–12 h of incubation at MBC. Particularly, at higher concentrations of the Anap. margaritacea flower crude extract (2–3×MBC), inhibition of A. caviae, B. cereus, P. alvei, and M. luteus bacteria is achieved between 0.5 and 4 h of incubation. In addition, these extracts exhibit high inhibition diameters (majority > 18 mm) and low MIC and/or MBCs (majority=1.25 mg mL−1). In contrast, the leaf extracts of Arct. uva-ursi, X. strumarium, Apoc. androsaemifolium and C. canadensis plants demonstrate moderate to low activity. These results indicate that extracts from Anap. margaritacea and G. squarrosa could be a source of novel antimicrobial scaffolds, compounds or pharmacophores with implications in the pharmaceutical industry and medicine.

Calcium-mediated enhancement of copper tolerance in Elodea canadensis

The alleviative effects of exogenous calcium on copper phytotoxicity were investigated in Elodea canadensis plants. There was a significant accumulation of Cu in the plants after their exposure to 0.01 mM Cu accompanied by many symptoms of toxicity. Increased uptake of Cu severely reduced content of photosynthetic pigments, soluble proteins, and free proline. The total antioxidant capacity (T-AOC), reduced glutathione (GSH), and non-protein thiol (NP-SH) were severely suppressed in Cu-stressed plants resulting in a rapid increase in content of superoxide anion (O2 .-), hydrogen peroxide, lipid peroxidation, and cell death. Simultaneous application of Ca markedly increased the content of photosynthetic pigments, soluble proteins, free proline, T-AOC, GSH, and NP-SH, and reduced oxidative damage as indicated by lowered content of MDA, O2 .-, and H2O2; and decreased cell death. Furthermore, application of Ca reduced Cu uptake and effectively reversed the Cu-induced nutrient imbalance.

Goldenseal (Hydrastis canadensisL.) Extracts Synergistically Enhance the Antibacterial Activity of Berberine via Efflux Pump Inhibition

Goldenseal (Hydrastis canadensis L.) is used to combat inflammation and infection. Its antibacterial activity in vitRO has been attributed to its alkaloids, the most abundant of which is berberine. The goal of these studies was to compare the composition, antibacterial activity, and efflux pump inhibitory activity of ethanolic extracts prepared from roots and aerial portions of H. canadensis. Ethanolic extracts were prepared separately from roots and aerial portions of six H. canadensis plants. Extracts were analyzed for alkaloid concentration using LC-MS and tested for antimicrobial activity against Staphylococcus aureus (NCTC 8325-4) and for inhibition of ethidium bromide efflux. Synergistic antibacterial activity was observed between the aerial extract (FIC 0.375) and to a lesser extent the root extract (FIC 0.750) and berberine. The aerial extract inhibited ethidium bromide efflux from wild-type S. aureus but had no effect on the expulsion of this compound from an isogenic derivative deleted for norA. Our studies indicate that the roots of H. canadensis contain higher levels of alkaloids than the aerial portions, but the aerial portions synergize with berberine more significantly than the roots. Furthermore, extracts from the aerial portions of H. canadensis contain efflux pump inhibitors, while efflux pump inhibitory activity was not observed for the root extract. The three most abundant H. canadensis alkaloids, berberine, hydrastine, and canadine, are not responsible for the efflux pump inhibitory activity of the extracts from H. canadensis aerial portions.

Evidence for Enhanced Mutualism Hypothesis: Solidago canadensis Plants from Regular Soils Perform Better

The important roles of plant-soil microbe interactions have been documented in exotic plant invasion, but we know very little about how soil mutualists enhance this process (i.e. enhanced mutualism hypothesis). To test this hypothesis we conducted two greenhouse experiments with Solidago canadensis (hereafter Solidago), an invasive forb from North America, and Stipa bungeana (hereafter Stipa), a native Chinese grass. In a germination experiment, we found soil microbes from the rhizospheres of Solidago and Stipa exhibited much stronger facilitative effects on emergence of Solidago than that of Stipa. In a growth and competition experiment, we found that soil microbes strongly facilitated Solidago to outgrow Stipa, and greatly increased the competitive effects of Solidago on Stipa but decreased the competitive effects of Stipa on Solidago. These findings from two experiments suggest that in situ soil microbes enhance the recruitment potential of Solidago and its ability to outcompete native plants, thereby providing strong evidence for the enhanced mutualism hypothesis. On the other hand, to some extent this outperformance of Solidago in the presence of soil microbes seems to be unbeneficial to control its rapid expansion, particularly in some ranges where this enhanced mutualism dominates over other mechanisms.

First Report of Southern Blight on Canadian Goldenrod (Solidago canadensis) Caused by Sclerotium rolfsii in China.

Canadian goldenrod (Solidago canadensis L., Asteraceae) is a rhizomatous perennial plant native to North America that has invaded eastern China and continues to spread northward and westward. It is quite common on field borders, roadsides, and in undeveloped areas, posing a serious threat to native ecosystems and their biodiversity. During the late summers of 2007 and 2008, wilted Canadian goldenrod plants were occasionally found in invasive populations in the suburb of Nanjing city. Wilted plants were transplanted and maintained in a greenhouse at Nanjing Agricultural University. A white mass of fungal hyphae, which grew on the soil surface around the stem of the symptomatic S. canadesis plants and eventually covered the stem, was observed. Initially, the base of the stem became yellow, turned brown, and the light brown discoloration extended up the stem to a height of 3 to 7 cm. The leaves then collapsed, starting from the top until the entire plant wilted. The fungus produced numerous, small, roundish sclerotia of uniform size (0.7 to 2.0 mm in diameter), which were white at first and then became brown to dark brown. The fungus grew into the stems and downward into the rhizome area, but no sclerotia were detected inside the stem or root. Diseased tissue with sclerotia was disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar amended with 100 mg/liter of streptomycin sulfate. On the basis of sclerotia morphology and the presence of clamp connections at hyphal septa, the fungus was identified as Sclerotium rolfsii. Pathogenicity of the isolate was confirmed by inoculating 1-year-old S. canadensis plants (average 1.5 m high) grown in pots. The inoculum consisted of cottonseed hulls infested with mycelium and sclerotia of the pathogen and was placed on the soil surface around the base of each unwounded plant. Noninoculated plants served as controls. The pathogenicity test was conducted twice. After inoculation, the plants were maintained at high humidity and 30°C for 3 days and then transferred to a greenhouse. All inoculated plants developed symptoms of southern blight. Inoculated plants developed symptoms of wilting 5 to 7 days after inoculation and were completely wilted within 15 to 20 days. Symptoms of wilting were soon followed by the appearance of white-to-light brown sclerotia on the collar region. Control plants remained symptomless and Sclerotium rolfsii was reisolated from inoculated plants. To our knowledge, this is the first report of southern blight of Canadian goldenrod caused by Sclerotium rolfsii in China.

Differential Susceptibility to Glyphosate among the Conyza Weed Species in Spain

Greenhouse and laboratory experiments were conducted to investigate differences in glyphosate susceptibility among three species of the genus Conyza introduced as weeds in Spain: tall fleabane (Conyza sumatrensis), hairy fleabane (Conyza bonariensis), and horseweed (Conyza canadensis). Plant material was obtained from seeds collected in weed populations growing in olive groves and citrus orchards in southern Spain, with no previous history of glyphosate application. Dose-response curves displayed ED(50) values of 2.9, 15.7, and 34.9 g ai ha(-1), respectively, for C. sumatrensis, C. bonariensis, and C. canadensis plants at the rosette stage (6-8 leaves). Significant differences were found among the three species in the glyphosate retention on leaves as well as the leaf contact angle. The species order according to glyphosate retention was C. sumatrensis > C. bonariensis > C. canadensis, while the mean contact angles of glyphosate droplets were 59.2, 65.5, and 72.9 degrees , respectively. There were no significant differences among species in the absorption of [(14)C]glyphosate (ranged from 37.4% for C. canadensis to 52.4% for C. sumatrensis), but the order among species was the same as glyphosate retention. The amount of radioactivity translocated from treated leaves was lower in C. canadensis as compared to the other two species (C. sumatrensis > C. bonariensis > C. canadensis). Combined, all of the studied parameters identified differential susceptibility to glyphosate among the Conyza species. Each species accumulated shikimate in leaf tissues following application of glyphosate at 200 g ai ha(-1). However, C. canadensis exhibited lower shikimate levels than the other two species at 168 h after herbicide application. For hairy fleabane, a greenhouse study explored its susceptibility to glyphosate at three developmental stages: rosette, bolting (stem height, 10-15 cm), and flowering. The ED(50) was lower at the rosette stage (15.7 g ai ha(-1)) as compared to bolting (86.6 g ai ha(-1)), with the highest ED(50) values occurring at flowering (117.5 g ai ha(-1)); plants at the earlier developmental stage retained more glyphosate. These results agree with field observations that plants at early developmental stages are more sensitive to glyphosate.

Morphological and Chemical Changes Induced by Herbivory in Three Common Aquatic Macrophytes

AbstractThe Dry Matter Content (DMC), the total phenolic content, the production of new branches and the plant fragmentation were compared in three macrophyte species (Elodea canadensis, Elodea nuttallii and Myriophyllum spicatum) exposed or not to snail herbivory. Grazing significantly reduced the DMC of M. spicatum and E. canadensis, but had no effect on the DMC of E. nuttallii. The phenolic contents of Elodea species were not modified by snail herbivory, whereas that of M. spicatum significantly increased when exposed to grazers. The number of new branches produced by M. spicatum and E. canadensis plants, and the fragmentation of E. canadensis also increased in response to herbivory.Chemical defences are therefore probably constitutive in Elodea and induced in M. spicatum, and morphological changes can be related to species growth form and synthesis of phenolic compounds. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

PERFORMANCE OF TRIRHABDA VIRGATA (COLEOPTERA: CHRYSOMELIDAE) ON THREE POTENTIAL HOSTS

AbstractThe suitability of three potential host plants, Solidago canadensis L. var. canadensis (Asteraceae), Solidago graminifolia (L.) Salisb., and Aster lateriflorus L. (Asteraceae), for the goldenrod beetle, Trirhabda virgata LeConte was determined by measuring several fitness components during the T. virgata life cycle. Neonate larvae were collected from S. canadensis plants and transplanted onto S. canadensis, S. graminifolia, and A. lateriflorus and maintained in field enclosures until the last instar was reached. Once brought into the laboratory, larvae were fed their assigned host plant until pupation. Following emergence, adults were weighed and separated into mating pairs to record oviposition and longevity. Eggs were kept in the laboratory until the following spring, when first instar larvae were taken into the field and re-established on their assigned host, and the experiment was repeated for 2 years. Larval survival and rate of development was not affected by the host plant. Mean weight of adults at emergence was greater on S. canadensis than on either S. graminifolia or A. lateriflorus. Two components of adult fitness, postmating longevity and realized fecundity, were measured. Longevity of adult female T. virgata was not affected by the host plant. Fecundity of T. virgata reared on A. lateriflorus and S. graminifolia was lower than the fecundity of females reared on S. canadensis. These results are consistent with the hypothesis that both intrinsic plant quality and the mobility of the foraging stage are important in the evolution of host range in T. virgata. These experiments were repeated over a 3-year period, using offspring from the survivors of the previous year for the 2nd and 3rd years. Over this time, individuals experienced "laboratory adaptation," and both accepted and increased their performance on previously unacceptable food plants.