Eugenol-inhibited root growth in Avena fatua involves ROS-mediated oxidative damage

Comparative study of two indoor microbial volatile pollutants, 2-Methyl-1-butanol and 3-Methyl-1-butanol, on growth and antioxidant system of rice (Oryza sativa) seedlings

2-Methyl-1-butanol (2MB) and 3-Methyl-1-butanol (3MB) are microbial volatile organic compounds (VOCs) and found in indoor air. Here, we applied rice as a bioindicator to investigate the effects of these indoor microbial volatile pollutants. A remarkable decrease in germination percentage, shoot and root elongation, as well as lateral root numbers were observed in 3MB. Furthermore, ROS production increased by 2MB and 3MB, suggesting that pentanol isomers could induce cytotoxicity in rice seedlings. The enhancement of peroxidase (POD) and catalase (CAT) activity provided evidence that pentanol isomers activated the enzymatic antioxidant scavenging systems, with a more significant effect observed in 3MB. Furthermore, 3MB induced higher activity levels of glutathione (GSH), oxidized glutathione (GSSG), and the GSH/GSSG ratio in rice compared to the levels induced by 2MB. Additionally, qRT-PCR analysis showed more up-regulation in the expression of glutaredoxins (GRXs), peroxiredoxins (PRXs), thioredoxins (TRXs), and glutathione S-transferases (GSTUs) genes in 3MB. Taking the impacts of pentanol isomers together, the present study suggests that 3MB exhibits more cytotoxic than 2MB, as such has critical effects on germination and the early seedling stage of rice. Our results provide molecular insights into how isomeric indoor microbial volatile pollutants affect plant growth through airborne signals.

Characterization key genes of Arabidopsis seedlings in response to β-caryophyllene, eugenol using combined transcriptome and WGCN analysis

Weeds present a significant challenge to high crop yield and quality. In our study, we investigated the phytotoxic activity of β-caryophyllene (BCP) and eugenol, which are natural allelopathic chemical compounds, on Arabidopsis seedlings. We found that these compounds inhibited the growth of Arabidopsis thaliana plants. When either BCP or eugenol was applied, it led to decrease in the content of cell wall components such as lignin, cellulose, hemicellulose, and pectin; and increase in the levels of endogenous hormones like ETH, ABA, SA, and JA in the seedlings. Through transcriptome profiling, we identified 7181 differentially expressed genes (DEGs) in the roots and shoots that were induced by BCP or eugenol. The genes involved in the synthesis of lignin, cellulose, hemicellulose, and pectin were down-regulated, whereas genes related to synthesis and signal transduction of ABA, ETH, SA, and JA were up-regulated. However, genes related to IAA synthesis and signal transduction were found to be down-regulated. Furthermore, we characterized 24 hub genes using Weighted Correlation Network Analysis (WGCNA). Among them, the identified 16 genes in response to BCP was primarily associated with hypoxia stress, while 8 genes induced by eugenol were linked to inhibition of cell division. Our results suggested that BCP and eugenol had ability to target multiple genes to inhibit growth and development of Arabidopsis plants. Therefore, they can serve as excellent candidates for natural biological herbicides.

Catalase associated with antagonistic changes of abscisic acid and gibberellin response, biosynthesis and catabolism is involved in eugenol-inhibited seed germination in rice

KEY MESSAGE

The inhibitory effect of eugenol on rice germination is mediated by a two-step modulatory process: Eugenol first regulates the antagonism of GA and ABA, followed by activation of catalase activity. The natural monoterpene eugenol has been reported to inhibit preharvest sprouting in rice. However, the inhibitory mechanism remains obscure. In this study, simultaneous monitoring of GA and ABA responses by the in vivo GA and ABA-responsive dual-luciferase reporter system showed that eugenol strongly inhibited the GA response after 6 h of imbibition, whereas eugenol significantly enhanced the ABA response after 12 h of imbibition. Gene expression analysis revealed that eugenol significantly induced the ABA biosynthetic genes OsNCED2, OsNCED3, and OsNCED5, but notably suppressed the ABA catabolic genes OsABA8ox1 and OsABA8ox2. Conversely, eugenol inhibited the GA biosynthetic genes OsGA3ox2 and OsGA20ox4 but significantly induced the GA catabolic genes OsGA2ox1 and OsGA2ox3 during imbibition. OsABI4, the key signaling regulator of ABA and GA antagonism, was notably induced before 12 h and suppressed after 24 h by eugenol. Moreover, eugenol markedly reduced the accumulation of H2O2 in seeds after 36 h of imbibition. Further analysis showed that eugenol strongly induced catalase activity, protein accumulation, and the expression of three catalase genes. Most importantly, mitigation of eugenol-inhibited seed germination was found in the catc mutant. These findings indicate that catalase associated with antagonistic changes of ABA and GA is involved in the sequential regulation of eugenol-inhibited seed germination in rice.

Citronella essential oil-based nanoemulsion as a post-emergence natural herbicide

A natural herbicide nanoemulsion was fabricated from citronella (Cymbopogon nardus L.) essential oil (CEO) and a nonionic surfactant Tween 60 mixed with Span 60 at hydrophilic-lipophilic balance 14 using a microfluidization method. The main constituents of CEO were citronellol (35.244%), geraniol (21.906%), and citronellal (13.632%). CEO nanoemulsion droplet size and polydispersity index (PI) were evaluated by dynamic light scattering (DLS). The smallest droplet size (33.2 nm, PI 0.135) was obtained from a microfluidizer at 20,000 psi, 7 cycles. Nanoemulsion droplet in transmission electron microscopy correlated with DLS confirmed CEO to successfully produce nanoemulsion. The herbicidal activity of the nanoemulsion as a foliar spray was evaluated against Echinochloa cruss-galli and Amaranthus tricolor as representative narrow- and broadleaf weed plants, both of which presented visual toxicity symptoms. The modes of action of the nanoemulsion were then determined in terms of membrane integrity (relative electrolyte leakage; REL), malondialdehyde (MDA), and photosynthetic pigment contents. The results showed increase in REL and MDA which indicated the destruction of the treated plants; additionally, chlorophylls and carotenoid contents were decreased. Consequently, CEO nanoemulsion may have the possibility to act as a natural herbicide resource, and natural herbicides from citronella nanoemulsions could be good alternatives for use in sustainable agriculture.

Chavibetol: major and potent phytotoxin in betel (Piper betle L.) leaf essential oil

BACKGROUND

Many essential oils and their constituent volatile organic compounds are known to be phytotoxic and potential bioherbicides. This study aims to investigate the phytotoxicity of propenylbenzene-rich essential oils and identify active molecule(s) therein.

RESULTS

Five commercially available propenylbenzene-rich oils were screened, of which betel (Piper betle L.) oil was identified as a potent natural phytotoxin. It dose-dependently inhibited wheatgrass (Triticum aestivum) seed germination and growth in water and agar medium with half maximal inhibitory concentration (IC50 ) in the range 23.2-122.7 μg mL-1 . Phytotoxicity-guided fractionation and purification revealed chavibetol as the major and most potent phytotoxic constituent of betel oil, followed by chavibetol acetate. A structure-activity relationship study involving 12 propenylbenzenes indicated the structural and positional importance of aromatic substitutions for the activity. Furthermore, the phytotoxic efficacy of chavibetol was established against wheatgrass germination and growth in water (IC50 15.8-53.4 μg mL-1 ), agar (IC50 34.4-53.6 μg mL-1 ) and aerial (IC50 1.7-4.5 mg L-1 ) media with a more pronounced effect on the radicle. Also, in open phytojars, chavibetol efficiently inhibited the growth of 3-7-day-old bermudagrass (Cynodon dactylon) seedlings when sprayed directly (IC50 2.3-3.4 mg jar-1 ) or supplemented in agar (IC50 116.6-139.1 μg mL-1 ). The growth of pre-germinated green amaranth (Amaranthus viridis) was inhibited more effectively in both application modes (1.2-1.4 mg jar-1 and IC50 26.8-31.4 μg mL-1 respectively).

CONCLUSION

The study concluded betel oil as a potent phytotoxic herbal extract and its major constituent chavibetol as a promising volatile phytotoxin for the future management of weeds in their early phase of emergence. © 2023 Society of Chemical Industry.

Polymeric nanoparticles for enhanced delivery and improved bioactivity of essential oils

Essential oils are volatile constituents that give aromatic plants their characteristic odour. The application of these plant actives in food, agriculture, pharmaceutics, and cosmetics has been widely studied. Aromatherapy, a complementary therapy involving the use of essential oils to treat several diseases ranging from microbial infections to metabolic dysfunctions, has been utilised for centuries. Anticancer, antimicrobial, and anti-inflammatory activities are well-established among other pharmacological properties of these aromatic oils. The oils, which are composed mainly of terpene-based compounds, have also been explored as nutraceuticals, alternative green preservatives, and functional additives in foods. However, due to their physicochemical properties, viz high volatility and low aqueous solubility, essential oil delivery to target receptors were challenging when administered as chemotherapeutics. Hence, formulating essential oils with suitable excipients to enhance their delivery and bioavailability, invariably improving their bioactivity and therapeutic efficacy becomes expedient. Nanotechnology presents a unique strategy to develop a particulate delivery system for the controlled, sustained, and extended release of essential oils. In this review, we examine and summarize the trends and developments in the formulation of essential oils using polymeric nanoparticles.

Effects of Piper betle L. Extract and Allelochemical Eugenol on Rice and Associated Weeds Germination and Seedling Growth

Natural herbicide is considered as a sustainable approach for weed management in agriculture. Here, allelopathic activities of Piper betle L. extract (BE) and known allelochemical eugenol (EU) were studied against rice and associated weeds in terms of germination and seedling growth. Five plant species including a rice crop (Oryza sativa L.); a dicot weed, false daisy (Eclipta prostrata (L.) L.); and three monocot weeds, barnyard grass (Echinochloa crus-galli (L.) P. Beauv.), swollen fingergrass (Chloris barbata Sw.), and weedy rice (Oryza sativa f. spontanea Roshev.) were studied. The paper-based results demonstrated that BE and EU had inhibitory effects on seed germination and seedling growth. The IC₅₀ values of BE and EU for seed germination were ranked from swollen fingergrass, to false daisy, barnyard grass, rice, and weedy rice, respectively. The ratio of root to shoot length of the seedlings indicated that the roots were more affected by the treatments than the shoots. In addition, the gel-based results showed the reduction of the rice seedling root system, especially on lateral root length and the numbers upon the treatments. Taken together, BE had an allelopathic activity similar to that of EU. Interestingly, the major paddy weed, barnyard grass, was more sensitive to BE than rice, underlining BE as a natural herbicide in rice agriculture.

Elucidating the Neuroprotective Effect of Tecoma stans Leaf Extract in STZ-Induced Diabetic Neuropathy

Background

Diabetes is considered one of the most encyclopedic metabolic disorders owing to an alarming rise in the number of patients, which is increasing at an exponential rate. With the current therapeutics, which only aims to provide symptomatic and momentary relief, the scientists are shifting gears to explore alternative therapies which not only can target diabetes but can also help in limiting the progression of diabetic complications including diabetic neuropathy (DN).

Methods

Tecoma stans leaf methanolic extract was prepared using the Soxhlet method. A streptozotocin (STZ; 45 mg/kg)-induced diabetic animal model was used and treatment with oral dosing of T. stans leaf extract at the different doses of 200 mg/kg, 300 mg/kg, and highest dose, i.e., 400 mg/kg, was initiated on day 3 after STZ administration. The pharmacological response for general and biochemical (angiogenic, inflammatory, and oxidative) parameters and behavioral parameters were compared using Gabapentin as a standard drug with the results from the test drug.

Results

Parameters associated with the pathogenesis of diabetic neuropathy were evaluated. For general parameters, different doses of T. stans extract (TSE) on blood sugar showed significant effects as compared to the diabetic group. Also, the results from biochemical analysis and behavioral parameters showed significant positive effects in line with general parameters. The combination therapy of TSE at 400 mg/kg with a standard drug produced nonsignificant effects in comparison with the normal group.

Conclusion

The leaves of T. stans possess antidiabetic effects along with promising effects in the management of DN by producing significant effects by exhibiting antioxidative, antiangiogenic, and anti-inflammatory properties, which are prognostic markers for DN, and thus, T. stans can be considered as an emerging therapeutic option for DN.

Formulation process, physical stability and herbicidal activities of Cymbopogon nardus essential oil-based nanoemulsion

Essential oil-based bioherbicides are a promising avenue for the development of eco-friendly pesticides. This study formulated nanoemulsions containing citronella (Cymbopogon nardus) essential oil (CEO) as an herbicidal product using a high-pressure homogenization method with hydrophilic-lipophilic balance (HLB) values ranging 9–14.9 for the surfactant mixture (Tween 60 and Span 60). The CEO was high in monoterpene compounds (36.333% geraniol, 17.881% trans-citral, 15.276% cis-citral, 8.991% citronellal, and 4.991% β-citronellol). The nanoemulsion at HLB 14 was selected as optimal due to having the smallest particle size (79 nm, PI 0.286), confirmed by transmission electron microscopy. After 28 days of storage, particle size in the selected formulation changed to 58 and 140 nm under 4 °C and 25 °C, respectively. Germination and seedling growth assays with Echinochloa crus-galli showed that the nanoemulsion exerted a significant dose-dependent inhibitory effect at all tested HLBs (9–14.9) and concentrations (100–800 µL/L). The inhibitory effect was greatest at HLB 14. Treatment of E. cruss-galli seed with the HLB 14 nanoemulsion significantly reduced seed imbibition and α-amylase activity. Our findings support that CEO nanoemulsions have a phytotoxic effect and hence herbicidal properties for controlling E. cruss-galli. Accordingly, this nanoemulsion may have potential as a bioherbicide resource.

The regulatory role of γ-aminobutyric acid in chickpea plants depends on drought tolerance and water scarcity level

γ-Aminobutyric acid (GABA) is a non-protein amino acid with multifunctional roles in dynamic plant responses. To determine the effects of exogenous GABA application (0, 25 and 50 µM) on drought response, two chickpea cultivars with contrasting tolerance to water deficit were examined. Plants were exposed to four irrigation levels (irrigation to 100, 60, 40 and 20% field capacity). Water deficit decreased growth, chlorophyll content, and photosynthetic efficiency. It increased electrolyte leakage and lipid peroxidation owing to both higher ROS accumulation and lower antioxidant enzyme activity. These negative effects of water deficit and the alleviating role of GABA application were more prominent in the sensitive, as compared to the tolerant cultivar. Water deficit also increased proline and GABA contents more in the tolerant cultivar, whereas their content was more enhanced by GABA application in the sensitive one. This may confer an additional level of regulation that results in better alleviation of drought damage in tolerant chickpea cultivars. In conclusion, the stimulatory effect of GABA on growth and physiological modulation depends on both the water stress severity and the cultivar sensitivity to it, implying a probable unknown GABA-related mechanism established by tolerant chickpea cultivars; a lost or not gained mechanism in susceptible ones.

Status and Prospects of Botanical Biopesticides in Europe and Mediterranean Countries

Concerning human and environmental health, safe alternatives to synthetic pesticides are urgently needed. Many of the currently used synthetic pesticides are not authorized for application in organic agriculture. In addition, the developed resistances of various pests against classical pesticides necessitate the urgent demand for efficient and safe products with novel modes of action. Botanical pesticides are assumed to be effective against various crop pests, and they are easily biodegradable and available in high quantities and at a reasonable cost. Many of them may act by diverse yet unexplored mechanisms of action. It is therefore surprising that only few plant species have been developed for commercial usage as biopesticides. This article reviews the status of botanical pesticides, especially in Europe and Mediterranean countries, deepening their active principles and mechanisms of action. Moreover, some constraints and challenges in the development of novel biopesticides are highlighted.

Bioactivity and molecular properties of Phenoxyacetic Acids Derived from Eugenol and Guaiacol compared to the herbicide 2,4-D

Herbicides are agrochemicals applied in the control of weeds. With the frequent and repetitive use of these substances, serious problems have been reported. Compounds of natural origin and their derivatives are attractive options to obtain new compounds with herbicidal properties. By aiming to develop compounds with potentiated herbicidal activity, phenoxyacetic acids were synthesized from eugenol and guaiacol. The synthesized compounds were characterized and the herbicidal potential of phenoxyacetic acids and precursors was evaluated through bioassays regarding the germination and initial development of Lactuca sativa and Sorghum bicolor seedlings, with the induction of DNA damage. The induction of changes in the mitotic cycle of meristematic cells of roots of L. sativa was also analyzed. At the concentration of 3 mmol L-1, phenols and their respective phenoxyacetic acids presented phytotoxic and cytotoxic activities in L. sativa and S. bicolor. Eugenol and guaiacol also presented genotoxic action in L. sativa. The toxic effect of eugenoxyacetic acid was more pronounced in L. sativa than in S. bicolor, similar to the commercial 2,4-D herbicide. Molecular properties of the phenols and their derivatives phenoxyacetic acids were compared with the ones obtained for the herbicide 2,4-D, where it was found a correlation between their molecular properties and bioactivity.

Influence of eugenol on algal growth, cell physiology of cyanobacteria Microcystis aeruginosa and its interaction with signaling molecules

Essential oils (EOs) are naturally occurring substances that have shown great prospect in the field of antimicrobial, antioxidant and pest control by nontoxic mechanisms. In this regard, EOs are considered the promising and eco-friendly approach for controlling harmful algae. In this study, the anti-cyanobacterial activity of EOs eugenol against Microcystis aeruginosa are evaluated from the perspective of photosynthetic efficiency, the behavior of extracellular organic matter (EOM), endogenous plant hormone synthesis, and nitric oxide signaling pathway. Results showed that the photosynthetic activity of M. aeruginosa decreased significantly after eugenol treatments. Eugenol treatment resulted in cells rupture and the release of EOM. Levels of endogenous plant hormones salicylic acid (SA) and jasmonic acid (JA) were enhanced separately by 2.32 and 2.01 times after 4 d of exposure to eugenol. And the inhibition of SA and JA biosynthesis further promotes the inhibitory effects of eugenol on algae. Additionally, the signaling molecule nitric oxide (NO) increased significantly by 3.78-fold. Furthermore, the influence of NO on microalgae exposed to eugenol was also determined, suggesting that the inhibitory effect of eugenol stress might be associated with NO generation in M. aeruginosa. These findings will be helpful for the understanding of the fate and potential of eugenol in harmful algae control.

Natural herbicide activity of Satureja hortensis L. essential oil nanoemulsion on the seed germination and morphophysiological features of two important weed species

The aim of the present study was to obtain an oil/water (O/W) nanoemulsion (NE) containing garden savory (Satureja hortensis) essential oil (EO) and evaluating its herbicidal activity against Amaranthus retroflexus and Chenopodium album. Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) were employed to determine the chemical composition of the EO. Carvacrol (55.6%) and γ-terpinene (31.9%) were the major EO components. Low energy method was applied, allowing achievement of EO nanodroplets. The NE also presented low polydispersity, and the mean droplet was below 130nm even after storage for 30d. Laboratory tests showed that the NE at different concentrations (100, 200, 400, 800, and 1000μL.L^-1) significantly (P≤0.05) reduced the germination indices and the seedling's growth in dose-response. The inhibitory effect was the greatest at 800μL.L^-1 NE. Overall, root length was more inhibited as compared to shoot length. Post-emergence application of NE at different concentrations (1000, 2000, 3000, 4000 and 5000μL.L^-1 of EO) on 2-4 true leaves' stage of the weeds caused significant (P≤0.05) decrease in the growth factors in dose-dependent manner. Complete lethality was observed by 4000μL.L^-1 NE sprayed on the weeds. Spraying of NE significantly (P≤0.05) reduced chlorophyll content in the tested weeds. Increasing in relative electrolyte leakage (REL) 1 and 5d after treatment represented significant cell membrane disruption and increased cell membrane permeability. Transmission electron microscope (TEM) pictures confirmed NE droplet size and demonstrated membrane destruction. The study approved that the NE of S. hortensis EO has herbicidal properties as it has high phytotoxic effect, and interferes with the germination, growth and physiological processes of the weeds. The production of NE from S. hortensis EO is a low energy method that offers a promising practical natural herbicide for weed control in organic agricultural systems.

Fungal endophyte-derived Fritillaria unibracteata var. wabuensis: diversity, antioxidant capacities in vitro and relations to phenolic, flavonoid or saponin compounds

Diverse fungal endophytes are rich fungal resources for the production of an enormous quantity of natural products. In the present study, 53 fungal endophytes were isolated from the bulbs of Fritillaria unibracteata var. wabuensis (FUW). Of these, 49 strains were identified and grouped into 17 different taxa, and priority was conferred to the Fusarium genus. All fungal fermented filtrates displayed antioxidant activities. The DPPH activity, total antioxidant capacities (ABTS), reduction power (FRAP), total phenolic content (TPC), total flavonoid content (TFC) and total saponin content (TSC) were evaluated using petroleum ether, ethyl acetate, n-butyl alcohol and ethanol fractions extracted from five representative fungal cultures. The last three fractions showed more potent antioxidant activity than the first fraction. Significant positive correlations were found between the compositions (TPC, TFC and TSC) and antioxidant capacities (DPPH, ABTS and FRAP). In addition, multifarious natural antioxidant components were identified from the fungal extracts, including gallic acid, rutin, phlorizin, 2,4-di-tert-butylphenol and 2,6-di-tert-butyl hydroquinone; these were determined preliminarily by TLC-bioautography, HPLC and GC-MS analysis. This study showed abundant fungal resources in FUW. Phenolics, flavonoids and saponins are crucial bioactive constituents in these abundant fungal endophytes and can be viewed as new potential antioxidant resources.

The Essential Oil of Monarda didyma L. (Lamiaceae) Exerts Phytotoxic Activity in Vitro against Various Weed Seed

The chemical composition of the essential oil of the flowering aerial parts of Monarda didyma L. cultivated in central Italy was analyzed by Gas Chromatography/Mass Spectrometry (GC/MS). The major compounds of the oil were thymol (59.3%), p-cymene (10.3%), terpinolene (9.2%), δ-3-carene (4.4%), myrcene (3.7%), and camphene (3.4%). The essential oil was tested in vitro for its anti-germination activity against Papaver rhoeas L., Taraxacum officinale F. H. Wigg., Avena fatua L., Raphanus sativus L. and Lepidium sativum L. seeds, demonstrating good inhibitory activity in a dose-dependent way. The exposure of the employed weed seeds to M. didyma essential oil and thymol solution (59.3%) increased the level of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), markers of oxidative stress, in emerging 5-day-old rootlets.

Biological responses of wheat (Triticum aestivum) plants to the herbicide simetryne in soils

The rotation of rice and wheat is widely used and highly endorsed, and simetryne (s-triazine herbicide) is one of the principal herbicides widely used in this rotation for weed and grass control. However, little is known regarding the mechanism of the ecological and physiological effects of simetryne on wheat crops. In this study, we performed a comprehensive investigation of crop response to simetryne to elucidate the accumulation and phytotoxicity of the herbicide in wheat crops. Wheat plants exposed to 0.8 to 8.0mgkg(-1) simetryne for 7 d exhibited suppressed growth and decreased chlorophyll content. With simetryne concentration in the soil varied from 0.8mgkg(-1) to 8.0mgkg(-1), simetryne was progressively accumulated by the wheat plants. The accumulation of simetryne in the wheat plants not only induced the over production of ROS and injured the membrane lipids but also stimulated the production of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR) and glutathione S-transferase (GST). A test of enzymatic activity and gene expression illustrated that the wheat plants were wise enough to motivate the antioxidant enzymes through both molecular and physiological mechanisms to alleviate the simetryne-induced stress. This study offers an illuminating insight into the effective adaptive response of the wheat plants to the simetryne stress.

Mistletoe (Viscum album) infestation in the Scots pine stimulates drought-dependent oxidative damage in summer

This study sought to contribute to the understanding of the detrimental effect of the mistletoe (Viscum albumL.), a hemiparasitic plant, on the mortality of the Scots pine (Pinus sylvestrisL.). Fieldwork was conducted in the town of Kelkit (Gumushane province, Turkey) from April to October in 2013. Pine needles of similar ages were removed from the branches of mistletoe-infested and noninfested Scots pine plants, then transported to the laboratory and used as research materials. The effects of the mistletoe on the Scots pine during infestation were evaluated by determining the levels of water, electrolyte leakage (EL), malondialdehyde (MDA, being a product of lipid peroxidation) and reactive oxygen species (ROS) such as superoxide anion (O2 (-•)), hydrogen peroxide (H2O2) and hydroxyl radical ((•)OH). In addition, the activities of antioxidative enzymes such as superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX) were measured in the same samples. The highest level of drought stress was found in summer (especially in August) as a result of the lowest water content in the soil and the highest average temperature occurring in these months. The drought stress induced by mistletoe infestation caused a regular decrease in water content, while it increased the levels of EL, MDA and ROS (H2O2, O2 (-•)and(•)OH). The infestation also stimulated the activities of CAT and POX, with the exception of SOD. On the other hand, in August, when the drought conditions were the harshest, the levels of EL and MDA, which are two of the most important indicator parameters for oxidative stress, as well as the levels of H2O2and(•)OH, which are two of the ROS leading to oxidative stress, reached the highest values in both infested and noninfested needles, whereas the O2 (-•)level decreased. For the same period and needles, CAT activity increased, while SOD activity decreased. Peroxidase activity, however, did not exhibit a significant change. Our findings indicate that the increased mortality of the Scots pine may result from the mistletoe-induced very severe drought stress, and that the increase in the capacity of antioxidative enzyme system does not protect the plant against oxidative stress in dry summer seasons.

Analysis of effects of a new environmental pollutant, bisphenol A, on antioxidant systems in soybean roots at different growth stages

Bisphenol A (BPA) is an important industrial raw material. Because of its widespread use and increasing release into environment, BPA has become a new environmental pollutant. Previous studies about BPA's effects in plants focus on a certain growth stage. However, the plant's response to pollutants varies at different growth stages. Therefore, in this work, BPA's effects in soybean roots at different growth stages were investigated by determining the reactive oxygen species levels, membrane lipid fatty acid composition, membrane lipid peroxidation, and antioxidant systems. The results showed that low-dose BPA exposure slightly caused membrane lipid peroxidation but didn't activate antioxidant systems at the seedling stage, and this exposure did not affect above process at other growth stages; high-dose BPA increased reactive oxygen species levels and then caused membrane lipid peroxidation at all growth stages although it activated antioxidant systems, and these effects were weaker with prolonging the growth stages. The recovery degree after withdrawal of BPA exposure was negatively related to BPA dose, but was positively related to growth stage. Taken together, the effects of BPA on antioxidant systems in soybean roots were associated with BPA exposure dose and soybean growth stage.

Essential Oil Composition and Antigermination Activity of Artemisia Dracunculus (Tarragon)

The chemical composition of an Italian oil of tarragon ( Artemisia dracunculus L.) was analyzed by GC/EIMS. The major compound of the oil was estragole (73.3%), followed by limonene (5.4%), ( E)-β-ocimene (5.3%), β-pinene (3.4%) and ( Z)-β-ocimene (3.0%). The essential oil was tested “ in vitro” for its antigermination activity against Raphanus sativus L., Lepidium sativum L, Papaver rhoeas L. and Avena fatua L. seeds and demonstrating a good inhibitory activity in a dose-dependent way.