New α-pyrone derivatives with herbicidal activity from the endophytic fungus Alternaria brassicicola.

Three pairs of undescribed enantiomeric α-pyrone derivatives (1a/1b-3a/3b) and six undescribed congeners (4-9), were obtained from the fungus Alternaria brassicicola that was isolated from the fresh leaves of Siegesbeckia pubescens Makino (Compositae). The structures of these new compounds were characterized by extensive NMR spectroscopic and HRESIMS data, and their absolute configurations were further elucidated by a modified Mosher's method, chemical conversion, single-crystal X-ray diffraction analysis, and ECD calculations. This is the first report of three pairs of enantiomeric α-pyrone derivatives from the fungus A. brassicicola, and these enantiomers were successfully acquired from scalemic mixtures via chiral HPLC. Compounds 1a/1b-3a/3b and 4-9 were evaluated for the herbicidal activity against Echinochloa crusgalli, Setaria viridis, Portulaca oleracea, and Taraxacum mongolicum. At a concentration of 100 µg/mL, compounds 1a and 1b could significantly inhibit the germination of monocotyledon weed seeds (E. crusgalli and S. viridis) with inhibitory ratios ranging from 68.6 ± 6.4% to 84.2 ± 5.1%, which was equivalent to that of the positive control (glyphosate). The potential structure-herbicidal activity relationship of these compounds was also discussed. To a certain extent, the results of this study will attract great interest for the potential practical application of promising fungal metabolites, α-pyrone derivatives, as ecofriendly herbicides.

Evaluation of the Therapeutic Effects of the Hydroethanolic Extract of Portulaca oleracea on Surgical-Induced Peritoneal Adhesion.

OBJECTIVE: Peritoneal adhesion (PA) is an abnormal connective tissue that usually occurs between tissues adjacent to damaged organs during processes such as surgery. In this study, the anti-inflammatory and antioxidant effects of Portulaca oleracea (PO) were investigated against postoperative-induced peritoneal adhesion. METHODS: Thirty healthy male Wistar rats (220 ± 20 g, 6-8 weeks) were randomly divided into four groups: (1) normal, (2) control (induced peritoneal adhesion), and (3) and (4) PO extracts (induced peritoneal adhesion and received 100 or 300 mg/kg/day of PO extract for seven days). Finally, macroscopic and microscopic examinations were performed using different scoring systems and immunoassays in the peritoneal lavage fluid. RESULTS: We found that the levels of adhesion scores and interleukin- (IL-) 1ß, IL-6, IL-10, tumour necrosis factor- (TNF-) α, transforming growth factor- (TGF-) ß 1, vascular endothelial growth factor (VEGF), and malondialdehyde (MDA) were increased in the control group. However, PO extract (100 and 300 mg/kg) notably reduced inflammatory (IL-1ß, IL-6, and TNF-α), fibrosis (TGF-ß 1), angiogenesis (VEGF), and oxidative (MDA) factors, while increased anti-inflammatory cytokine IL-10, antioxidant factor glutathione (GSH), compared to the control group. CONCLUSION: Oral administration of PO improved postoperational-induced PA by alleviating the oxidative factors, fibrosis, inflammatory cytokines, angiogenesis biomarkers, and stimulating antioxidative factors. Hence, PO can be considered a potential herbal medicine to manage postoperative PA. However, further clinical studies are required to approve the effectiveness of PO.

Characterization and Phytotoxicity Assessment of Essential Oils from Plant Byproducts.

The present work describes the chemical characterization and the phytotoxicity assessment of essential oils (EOs) obtained from spent materials or pruning waste of four plant species: Zingiber officinale Roscoe used in the juicing industry, Pistacia vera L. var. Bronte used in the food industry, discarded material of industrial hemp (Cannabis sativa L. var. Futura 75), and pruning waste from Cupressus sempervirens L. The phytochemical profile of the EOs was evaluated by gas chromatographic flame ionization detection (GC-FID) and GC-MS analyses, which highlighted the presence of several compounds with a wide range of biological activities. Among them, application possibilities in agriculture were evaluated by studying the phytotoxic activity in vitro against germination and initial radical growth of several seeds such as Raphanus sativus L., Lepidium sativum L., Lactuca sativa L., Solanum lycopersicum L., Lolium multiflorum Lam., and Portulaca oleracea L.

Responses of Portulaca oleracea Linn. to selenium exposure.

The present study was investigated to evaluate the uptake and accumulation of selenium (Se) by the stem cuttings of Portulaca oleracea L. grown in alfisol amended with various concentrations of Se. P. oleracea accumulated a maximum of 63.4 µg g(-1) dry weight in a short growth period of 42 days. The order of accumulation of Se among the plant parts was leaves (31.5 µg g(-1)) > stems (16.4 µg g(-1)) > roots (15.5 µg g(-1)). The accumulation potential was fourfold higher than the plant available concentration of 15.2 µg g(-1) of Se g(-1) of soil (diethylenetriaminepentaacetic acid extracted). Although the plant was able to accumulate Se in their tissues, increase in Se concentrations in soil caused a concentration-dependent decrease in the growth rate of plants (regeneration of leaves, number of leaves, number of roots, root length, stem length and biomass).

Tolerance of Portulaca grandiflora to individual and combined application of Ni, Pb and Zn.

In the present study, metal accumulation capacity and tolerance of Portulaca grandiflora were investigated. Plants were grown under greenhouse conditions in pots on soil amended with Ni, Pb and Zn to the final concentration of 2 mmol kg(-1) for each metal. Results show considerable accumulating capacity and translocation of Ni and Zn, as well as significant accumulation of Pb in roots. A slight decrease of biomass with Zn and of chlorophyll content with Zn and Ni were observed, as well as an increase of proline content with each of the metals. Combinations of metals revealed mutual interference affecting both the uptake and translocation of the metals and their impact on physiological parameters. Results suggest that Portulaca grandiflora, although not a hyperaccumulator, shows a good tolerance and accumulation capacity for Ni, Pb and Zn, but, for the purposes of remediation, interference of the metals must be taken into account.

Screening of purslane (Portulaca oleracea L.) accessions for high salt tolerance.

Purslane (Portulaca oleracea L.) is an herbaceous leafy vegetable crop, comparatively more salt-tolerant than any other vegetables with high antioxidants, minerals, and vitamins. Salt-tolerant crop variety development is of importance due to inadequate cultivable land and escalating salinity together with population pressure. In this view a total of 25 purslane accessions were initially selected from 45 collected purslane accessions based on better growth performance and subjected to 5 different salinity levels, that is, 0.0, 10.0, 20.0, 30.0, and 40.0 dS m(-1) NaCl. Plant height, number of leaves, number of flowers, and dry matter contents in salt treated purslane accessions were significantly reduced (P ≤ 0.05) and the enormity of reduction increased with increasing salinity stress. Based on dry matter yield reduction, among all 25 purslane accessions 2 accessions were graded as tolerant (Ac7 and Ac9), 6 accessions were moderately tolerant (Ac3, Ac5, Ac6, Ac10, Ac11, and Ac12), 5 accessions were moderately susceptible (Ac1, Ac2, Ac4, Ac8, and Ac13), and the remaining 12 accessions were susceptible to salinity stress and discarded from further study. The selected 13 purslane accessions could assist in the identification of superior genes for salt tolerance in purslane for improving its productivity and sustainable agricultural production.

Exploring the phytoremediation capacity of Portulaca oleracea naphthalene aromatic hydrocarbon contaminants: a physiological and biochemical study.

This study is aimed to explore the potential of purslane (Portulaca oleracea L.) as a phytoremediation candidate for the removal of naphthalene in a hydroponic system; moreover, the impacts of naphthalene on the physiological and biochemical characteristics of the plant were investigated. Four different naphthalene concentrations (0, 15, 30, and 60 ppm) were selected for the experiments, with an additional control treatment without plants containing 60 ppm naphthalene. Each treatment, utilizing a total of 20 hydroponic containers, consisted of 4 replicates. The results indicated that naphthalene led to a reduction in root and shoot growth. The root weight decreased from 17 mg in the control group to 6 mg in the 60 ppm naphthalene treatment, while the shoot weight decreased from 107.5 mg in the control group to 65.7 mg in the 60 ppm naphthalene treatment. Besides, the different naphthalene concentrations had an impact on the photosynthetic pigments. Compared to the control treatment, under severe stress conditions, chlorophyll a decreased by 51.85%, chlorophyll b decreased by 48.14%, and carotenoids decreased by 54.59%; however, anthocyanin, compared to the control treatment, increased by 30.1% under severe stress conditions. The presence of naphthalene also resulted in increased levels of malondialdehyde, hydrogen peroxide, and proline in both roots and shoots at various naphthalene concentrations. In roots, malondialdehyde increased by 40.74%, H2O2 increased by 3%, and proline increased by 75.6%, while malondialdehyde increased by 43.16%, H2O2 increased by 5.34%, and proline increased by 59.48% in shoots under severe stress conditions and compared to the control treatment. Root and shoot protein levels decreased by 64.49% and 32.26%, respectively. Furthermore, the antioxidant enzymes of glutathione S-transferase, superoxide dismutase, catalase, and ascorbate peroxidase showed increased activities in both roots and shoots under severe naphthalene stress conditions. Purslane demonstrated the ability to remove approximately 80% of naphthalene from the medium. In conclusion, this plant has an effective participation in naphthalene uptake and mitigates the adverse effects of naphthalene by enhancing antioxidant enzyme and proline activities.

Allelopathic Effect of Calotropis procera, Hyoscyamus muticus and Pulicaria undulata Extracts on Seed Germination of Portulaca oleracea and Chenopodium murale.

BACKGROUND AND OBJECTIVE: The use of herbicides leads to severe damage, especially to the environment. The aim of this investigation was operated to study the allelopathic effect of Calotropis procera, Hyoscyamus muticus and Pulicaria undulata aqueous extracts on the seed germination of Portulaca oleracea and Chenopodium murale. MATERIALS AND METHODS: The aerial parts of the plants (Calotropis procera, Hyoscyamus muticus and Pulicaria undulata) washed well in distilled water and were dried in room temperature then ground to fine powder. Aqueous extract was prepared using distilled water. RESULTS: In this study, different concentrations of plant extracts (1, 3 and 5%) were used to illustrate which of these concentrations have the potential to inhibit seed growth of Portulaca oleracea and Chenopodium murale. Concentration of 5% for all plant extracts used to inhibited the growth of all seeds of Chenopodium murale while, concentration of 5% for Pulicaria undulata extract only inhibited the growth of all seeds of Portulaca oleracea. CONCLUSION: This work dealt with the use of allelopathy strategy in preventing the growth of some weeds to be one of the safest alternative ways of using herbicides. The results showed the effective effect of plant extracts for both Calotropis procera, Hyoscyamus muticus and Pulicaria undulata on the seed germination of Portulaca oleracea and Chenopodium murale.

Interaction of Salinity and CaCO3 Affects the Physiology and Fatty Acid Metabolism in Portulaca oleracea.

As a result of the extreme conditions that usually occur in Mediterranean climates, the objective of this work is to study the combined and/or separate effects of saline and alkaline stresses in Portulaca oleracea. The study was carried out to determine the nutritional food potential in relation to plant physiological parameters. The results show that alkaline media in which CaCO3 was present did not affect growth but exposure to 100 mM NaCl decreased it greatly. Fatty acid content increased under all stress conditions but to a higher extent with salinity; however, the protein content was increased only by alkaline media. The beneficial effect of each stress on P. oleracea is discussed in light of the physiological response, pointing out the suitability of this plant for human nutrition.

Mixture toxicity assisting the design of eco-friendlier plant protection products: a case-study using a commercial herbicide combining nicosulfuron and terbuthylazine.

The development of environmentally friendly plant protection products (PPPs), including pesticides, is a challenge nowadays. A commercial herbicide combining terbuthylazine and nicosulfuron as active substances (a.s.) was selected as a model PPP. The suitability of manipulating the ratio between a.s. towards alternative formulations with reduced impacts in a non-target indicator (Lemna minor) was assessed. The efficacy of such eco-friendlier a.s. ratios was then assessed using a target weed, Portulaca oleracea. Single and mixture toxicity testing with L. minor revealed an antagonistic joint action of the a.s., suggesting an environmentally protective effect of the combination compared to single dosing of a.s. The efficacy testing against the target weed of single and combined treatments of the a.s. showed that (i) the a.s. behave antagonistically throughout the whole P. oleracea response surface; (ii) there were no environmentally safe a.s. combinations ensuring target-efficacy; (iii) terbuthylazine alone was effective in controlling P. oleracea with no environmental hazardous potential, dosed at concentrations 10-fold lower than those involved in commercially recommended application doses. Overall, this case-study suggests that modelling tools widely used in the field of environmental risk assessment of PPPs may also have application in PPP design stages for a more efficient meeting of efficacy and environmental friendliness requirements.

Deciphering the growth, organic acid exudations, and ionic homeostasis of Amaranthus viridis L. and Portulaca oleracea L. under lead chloride stress.

Lead (Pb) stress adversely affects in planta nutrient homeostasis and metabolism when present at elevated concentration in the surrounding media. The present study was aimed at investigation of organic acid exudations, elemental contents, growth, and lipid peroxidation in two wild plants (Amaranthus viridis L. and Portulaca oleracea L.), exhibiting differential root to shoot Pb translocation, under Pb stress. Plants were placed in soil spiked with lead chloride (PbCl2) concentrations of 0, 15, 30, 45, or 60 mg Pb/kg soil, in rhizoboxes supplied with nylon nets around the roots. The plant mucilage taken from root surfaces, mirroring the rhizospheric solution, was analyzed for various organic acids. Lead stress resulted in a release of basified root exudates from both plants. Exudates of P. oleracea roots showed a higher pH. In both plants, the pH rising effect was diminished at the highest Pb treatment level. The exudation of citric acid, glutamic acid (in both plants), and fumaric acid (in P. oleracea only) was significantly increased with applied Pb levels. In both plant species, root and shoot Pb contents increased while nutrients (Ca, Mg, and K) decreased with increasing Pb treatment levels, predominantly in A. viridis. At 60 mg Pb/kg soil, shoot Na content of A. viridis was significantly higher as compared to untreated control. Higher Pb treatment levels decreased plant fresh and dry masses as well as the quantity of photosynthetic pigments due to enhanced levels of plant H2O2 and thiobarbituric acid reactive substances in both species. Photosynthetic, growth, and oxidative stress parameters were grouped into three distinct dendrogram sections depending on their similarities under Pb stress. A positive correlation was identified between Pb contents of studied plants and secretion of different organic acids. It is concluded that Pb stress significantly impaired the growth of A. viridis and P. oleracea as a result of nutritional ion imbalance, and the response was cultivar-specific and dependent on exogenous applied Pb levels. Differential lipid oxidation, uptake of nutrients (Ca, Mg, and K) and exudation of citric acid, fumaric acid, and glutamic acid could serve as suitable physiological indicators for adaptations of P. oleracea to Pb enriched environment. The findings may help in devising strategies for Pb stabilization to soil colloids.

Herbicide effects on cuticle ultrastructure in Eleusine indica and Portulaca oleracea.

Eleusine indica and Portulaca oleracea are two common weeds in peanut crops in southern Córdoba. Two chemicals are frequently used to control them, quizalofop for grasses and lactofen for dicots. The objective is to study the effects of quizalofop and lactofen on cuticle ultrastructure in E. indica and P. oleracea, respectively. In the lab, quizalofop was applied on E. indica and lactofen on P. oleracea. Three plant categories were analyzed in each species: 3, 1-2, and no tiller in E. indica, and 8, 6, and 2 nomophylls in P. oleracea. Leaf samples from both species were collected at 7 and 16 days post-application and were treated for scanning electron microscopy. E. indica cuticle treated with lethal dose shows areas where epicuticular waxes disappear, specially in the youngest individuals. These areas are located predominantly on periclinal walls of typical epidermic cells and subsidiary cells. On the other hand, P. oleracea shows cuticle discontinuities that may be caused by lactofen entry. They are smaller and less frequent in plants having 8 or more nomophylls. The remaining waxes act as a herbicide accumulation compartment and, therefore, would partially prevent the active ingredient entry to epidermic cells.

Alternative Strategies in Response to Saline Stress in Two Varieties of Portulaca oleracea (Purslane).

Purslane (Portulaca oleracea) is a globally-distributed plant with a long history of use in folk medicine and cooking. We have developed purslane as a model system for exploring plant responses to stress. We exposed two varieties of purslane to saline stress with the objective of identifying differences between the varieties in the plasticity of morphological and physiological traits. The varieties responded to saline stress with significantly different changes in the measured traits, which included inter alia biomass, flower counts, proline concentrations and betalain pigment concentrations. The alternative responses of the two varieties consisted of complex, simultaneous changes in multiple traits. In particular, we observed that while both varieties increased production of betalain pigments and proline under saline stress, one variety invested more in betalain pigments while the other invested more in proline. Proline and betalain pigments undoubtedly play multiple roles in plant tissues, but in this case their role as antioxidants deployed to ameliorate saline stress appears to be important. Taken holistically, our results suggest that the two varieties employ different strategies in allocating resources to cope with saline stress. This conclusion establishes purslane as a suitable model system for the study of saline stress and the molecular basis for differential responses.

Isolation of phytotoxic compounds from tree-of-heaven (Ailanthus altissima swingle).

The aqueous root extract of Ailanthus altissima showed allelopathic activity against radish (Raphanus sativus L. cv. "Saxa"), garden cress (Lepidium sativum L.), and purslane (Portulaca oleracea L.) seeds. A bioassay-oriented purification of active extracts, chromatographic fractions, and compounds demonstrated dose-dependent activity on germination and radicle growth of test seeds; radish seed was the most sensitive to allelochemicals. Active compounds have been isolated: ailanthone, ailanthinone, chaparrine, and ailanthinol B (quassinoid derivatives); the alkaloid 1-methoxycanthin-6-one is not active. The compound with greatest inhibitory activity is ailanthone. The data obtained suggest a possible use of tree-of-heaven root extracts or of its active constituents as natural herbicides.

Stimulation of betacyanin synthesis through exogenous methyl jasmonate and other elicitors in suspension-cultured cells of Portulaca.

Betacyanin production in suspension-cultured cells of Portulaca was significantly enhanced by both abiotic and biotic elicitors. Betacyanin levels increased 1.3 and 1.5-fold over the controls in the presence of two abiotic elicitors (20 mumol/L CuSO4 and 100 mumol/L FeEDTA) and increased 1.8 and 1.6-fold in the presence of two biotic elicitors (0.5 mg/L beta-glucan and 0.5 mg/L chitosan). Maximum betacyanin synthesis with the two most effective elicitors was obtained when cultures were treated on day 1 and day 0 by beta-glucan and FeEDTA, respectively. A concentration-dependent response was exhibited by cultures treated with exogenous methyl jasmonate (MJ). MJ alone at 0.1 mumol/L caused a 2.6-fold increase in betacyanin synthesis when administered to the suspension culture on day 3. However, no additive effect on betacyanin accumulation was observed in treatments, which combined MJ and beta-glucan or FeEDTA. Treatment with ibuprofen (IB), an inhibitor of jasmonate biosynthesis, reduced the level of betacyanin in cells cultured in standard medium at all concentrations tested (25, 50, 100 mumol/L). The effect of IB on betacyanin synthesis in the cells treated with MJ or beta-glucan, however, differed with the IB concentration applied. The two higher concentrations (50 and 100 mumol/L) of IB significantly reduced the betacyanin content while the lower concentration (25 mumol/L) did not show an adverse effect on the betacyanin enhancement triggered by MJ or beta-glucan. Our findings suggest that, in suspension-cultured cells of Portulaca, an MJ-mediated signal transduction pathway prominently exists in betacyanin synthesis. This pathway seems to act antagonistically towards beta-glucan-mediated signaling. As far as we know this is the first report on the elevation of betacyanin level by jasmonate or other elicitors in cell suspension cultures.

Use of adjuvant-enhanced formulations to increase bipyridylium-herbicide effectiveness.

Paraquat and diquat are two popular, non-selective; bipyridylium herbicides commonly used in citrus orchards and horticultural row crops as the main chemical weed control method. However, since diquat lacks of an effective spectrum against grass weeds, and paraquat mammal toxicity raises strong environmental concerns, both an increase in diquat toxicity against grasses and a reduction in paraquat rates may be desired. Using grass-weed Lolium rigidum and broad leave weed Portulaca oleracea as experimental systems, the effects of six commercial adjuvants (poly-1-p-menthene, mixture of methyl oleate and palmitate, alkylglycol ester, dodecylbenzene ammonium sulphonate, and two paraffinic oils) on paraquat and diquat effectiveness have been studied under laboratory controlled conditions. Dose-response assays showed that adjuvants failed in increasing paraquat efficacy in both broad and grass weeds, yet antagonistic effects being observed in some mixtures such as paraquat + polymentene. However, all adjuvants tested did succeed in increasing significantly diquat effectiveness in P. oleracea and (most important) L. rigidum grass weed. Formulated-diquat ED50 rates were reduced down to 15% (diquat + DBSA) and 30% (diquat + fatty acid ester, diquat + polimentene) of those obtained on non-formulated-diquat trials for P. oleracea and L. rigidum, respectively. Results showed that formulated diquat proved to be a valid alternative to paraquat, and could be used as a more environmentally friendly substitute with comparable effectiveness and herbicide rate.

Chemical composition, antimicrobial, insecticidal, phytotoxic and antioxidant activities of Mediterranean Pinus brutia and Pinus pinea resin essential oils.

Essential oils of the resins of Pinus brutia and Pinus pinea were evaluated for their biological potential. Essential oils were characterized using GC-MS and GC/FID. in vitro antimicrobial, phytotoxic, antioxidant, and insecticidal activities were carried out using the direct contact and the fumigant assays, respectively. The chemical profile of the essential oils of the resins of P. pinea and P. brutia included mainly α-pinene (21.39% and 25.40%), ß-pinene (9.68% and 9.69%), and caryophyllene (9.12% and 4.81%). The essential oils of P. pinea and P. brutia exerted notable antimicrobial activities on Micrococcus luteus and Bacillus subtilis, insecticidal activities on Ephestia kuehniella eggs, phytotoxic activities on Lactuca sativa, Lepidium sativum, and Portulaca oleracea, as well as antioxidant potential. Indications of the biological activities of the essential oils suggest their use in the formulation of ecofriendly and biocompatible pharmaceuticals.

Evaluation of Atriplex halimus, Medicago lupulina and Portulaca oleracea for phytoremediation of Ni, Pb, and Zn.

Suitable plant species are able to accumulate heavy metals and to produce biomass useful for non-food purposes. In this study, three endemic Mediterranean plant species, Atriplex halimus, Portulaca oleracea and Medicago lupulina were grown hydroponically to assess their potential use in phytoremediation and biomass production. The experiment was carried out in a growth chamber using half strength Hoagland's solutions separately spiked with 5 concentrations of Pb and Zn (5, 10, 25, 50, and 100 mg L(-1)), and 3 concentrations of Ni (1, 2 and 5 mg L(-1)). Shoot and root biomass were determined and analyzed for their metals contents. A. halimus and M. lupulina gave high shoot biomass with relatively low metal translocation to the above ground parts. Metals uptake was a function of both metals and plant species. It is worth noting that M. lupulina was the only tested plant able to grow in treatment Pb50 and to accumulate significant amount of metal in roots. Plant metal uptake efficiency ranked as follows: A. halimus > M. lupulina > P. oleracea. Due to its high biomass production and the relatively high roots metal contents, A. halimus and M. lupulina could be successfully used in phytoremediation, and in phytostabilization, in particular.

Chemical composition and herbicidal activity of the essential oil from a Cistus ladanifer L. population from Spain.

The essential oil composition of Cistus ladanifer grown in central Spain was analysed by gas chromatography and gas chromatography/mass spectrometry, revealing it to be rich in oxygenated compounds, with trans-pinocarveol (20.00%), bornyl acetate (7.03%) and terpinen-4-ol (6.37%) as the main monoterpene compounds. Viridiflorol (13.59%) and ledol (4.36%) were the main constituents of the oxygenated sesquiterpene fraction. Large amounts of α-pinene (4.70%) were found in the hydrocarbonated fractions. To study its possible use as a natural herbicide, the oil was tested in vitro against Amaranthus hybridus, Portulaca oleracea, Chenopodium album, Conyza canadensis and Parietaria judaica, completely inhibiting A. hybridus germination, and nearly blocking C. canadensis and P. judaica germination at all concentrations assayed. In P. oleracea, the oil showed less effect, inhibiting its germination at the higher doses studied. It did not control C. album germination. Regarding seedling length, the oil had strong phytotoxic activity, being effective at all concentrations tested.

Testing the homogenizing effect of low copper sulfate concentrations on the size distribution of Portulaca oleracea seedlings in vitro.

Traditionally, toxicological bioassays rely upon the differences in mean-based statistical tests between the exposed and unexposed plants, and exceptional plant individuals are treated as statistical outliers. Recently, low toxicant concentrations have been observed to affect gene regulation in exposed plant stands and to change the frequency of the largest individuals even if mean plant size remains unchanged. In this paper, we present the results that the latter phenomenon is not restricted to a single toxicant and plant species. Our data analysis consists of two statistical methods that may be of general interest. We utilized the one-tailed Moses extreme reactions test by comparing exposed groups to control plants with and without the trimming of a certain amount of potential outliers from both treatments compared. We also propose that Mann-Whitney U or other tests at ordinal scale can be utilized to analyze if the largest plant individuals in exposed and control treatments come from a single 'survivor' population. We conclude that the results supported the hypothesis that very low toxicant concentrations may have ecological effects on fast-growing plant species. Finally, we discuss the limitations of the statistical methods currently in use.