Essential Oil of Deverra tortuosa Aerial Parts: Detailed Chemical Profile, Allelopathic, Antimicrobial, and Antioxidant Activities.

Essential oils (EOs) are a promising group of natural products of the aromatic plants due to their various biological effects such as allelopathic, antioxidant, antimicrobial activities. The present study aimed to construct the detailed chemical profile of the EO derived from Deverra tortuosa aerial parts along with assessing its allelopathic, antimicrobial, and antioxidant potentialities. The EO was extracted by hydrodistillation and analyzed via gas chromatography-mass spectrometry (GC/MS). The allelopathic activity of the EO was assessed against the germination and seedling growth of the weed Chenopodium murale. Also, the EO was tested against five microbes. The antioxidant activity was determined using the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). The GC/MS analysis of EO revealed the presence of 86 compounds with a preponderance of oxygenated sesquiterpenes and monoterpene hydrocarbons. Widdrol, ß-phellandrene, piperitol, cubedol, α-terpinene, (E)-10-heptadecen-8-ynoic acid methyl ester, citronellyl tiglate, and m-cymene were the major compounds. A comparative profile was established between the EOs constituents of our study with the documented EOs of D. tortuosa and the other Deverra species around the world via agglomerative hierarchical clustering (AHC) and principal components analysis (PCA). The EO showed a substantial allelopathic activity against C. murale, as well as it showed considerable antimicrobial and antioxidant activities. Thereby, the EO of D. tortuosa could be considered as a promising environmental-friendly bioherbicide against weeds. Also, it could be integrated into food preservation due to its potent antimicrobial and antioxidant activities. However, further study is recommended for more characterization of the major compounds and evaluation of their activities, either singular or synergistic, and assess their efficiency and biosafety.

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.

Characterization and Quantitation of Triterpenoid Saponins in Raw and Sprouted Chenopodium berlandieri spp. (Huauzontle) Grains Subjected to Germination with or without Selenium Stress Conditions.

Pseudocereal Chenopodium berlandieri spp. (huauzontle) was evaluated to determine saponin composition. Saponins were evaluated in raw and germinated grains subjected to chemical stress induced by sodium selenite. Analysis by liquid chromatography coupled with ELSD detector revealed the presence of 12 saponins, identified according to compounds previously assayed in Chenopodium quinoa. Saponins found at the highest concentrations in raw grains were derived from oleanolic and phytolaccagenic acids. Total saponin concentration significantly decreased in germinated compared to raw grains due to the significant loss of 90.1% and 95.7% of the phytolaccagenic acid without and with chemical selenium stress, respectively. The most abundant saponin in germinated sprouts decreased during normal germination. Interestingly, the concentration of this particular saponin significantly increased during the Se-induced stress germination. Chemical stress with selenium salts proved to change the saponin composition in geminated Chenopodium berlandieri spp. grains, therefore affecting their potential use as ingredient in the food industry.

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.

Surfactant-induced deposit structures in relation to the biological efficacy of glyphosate on easy- and difficult-to-wet weed species.

BACKGROUND: Typical active ingredient (AI) residue patterns are formed during droplet drying on plant surfaces owing to the interaction of spray solution characteristics and leaf micromorphology. Currently, comparatively little is known about the influence of AI deposit patterns within a spray droplet residue area on the penetration and biological efficacy of glyphosate. A scanning electron microscope with energy dispersive X-ray microanalysis has been used to characterise residue patterns and to quantify the area ultimately covered by glyphosate within the droplet spread area. RESULTS: The easy-to-wet weed species Stellaria media L. and Viola arvensis L., as well as the difficult-to-wet Chenopodium album L. and Setaria viridis L., differing in their surface micromorphology, have been used. Rapeseed oil ethoxylates (RSO 5 or RSO 60) were added to glyphosate solutions to provide different droplet spread areas. Addition of RSO 5 enhanced droplet spread area more than RSO 60, and both caused distinct glyphosate residue patterns. The biological efficacy of treatment solutions showed no significant correlation with the area ultimately covered by glyphosate. CONCLUSION: The results have implications on herbicide uptake models. This study shows that droplet spread area does not correspond to the area ultimately covered by glyphosate, and that the latter does not affect glyphosate phytotoxicity.

Extracellular alkaline phosphatase is a sensitive marker for cellular stimulation and exocytosis in heterotroph cell cultures of Chenopodium rubrum.

We investigated the response of extracellular phosphatase to heat shock in heterotrophic Chenopodium rubrum L. cell cultures. Surprisingly, in contrast to the generally used acid phosphatase, an extracellular alkaline phosphatase showed the most sensitive response. This phosphatase was characterized as a marker for cellular stimulation by its high correlations with induced changes of extracellular pH: 10microM nigericin (correlation coefficient r=0.91), 100microM salicylic acid (r=0.84), heat shock 5min 37 degrees C (r=0.79), and heat shock after pre-treatment with 5microM fusicoccin (r=0.92) or 0.5% ethanol (r=0.90). Cellular stimulation was estimated with concentrations of acids and bases, yielding similar levels of pH change (0.5 pH) in cell-free supernatant: salicylic acid (200microM), benzoic acid (600microM), HCl (140microM), NaOH (100microM), and KOH (100microM). The Golgi apparatus inhibitor Brefeldin A (200microM) reduced the heat-shock-induced phosphatase (-33%). The pH optimum of heat-shock-induced phosphatase was 3; however, there the proportion of constitutive phosphatase was higher than at pH 8-9.5, indicating different pH dependence of constitutive and induced activity. Thus, heat-shock-induced phosphatase was characterized by alkaline activity with inhibitors (10microM molybdate: -52%, 2.5mM phosphate: -64%, 10microM ZnCl(2): -82%), substrates (2.5mM, tyrosine phosphate: 255pkat g(-1), p-nitrophenyl phosphate: 92pkat g(-1), serine phosphate: 0, threonine phosphate: 0), Hill coefficient (nH=1.4) indicating two binding sites, and the extent of heat-shock stimulation (p-nitrophenyl phosphate: +190%, tyrosine phosphate: +180%). SDS-PAGE showed a correlation of alkaline phosphatase with the heat-shock-induced release of highly N-glycosylated 53kDa protein, detected by peroxidase-labeled concanavalin A affinoblotting after endoglycosidase H treatment. The 53kDa protein showed no in-gel phosphatase activity after SDS-PAGE and regeneration treatment, in contrast to a putative dimer (105kDa).

Impact of Bt maize pollen (MON810) on lepidopteran larvae living on accompanying weeds.

Environmental risks of Bt maize, particularly pollen drift from Bt maize, were assessed for nontarget lepidopteran larvae in maize field margins. In our experimental approach, we carried out 3-year field trials on 6 ha total. Three treatments were used in a randomized block design with eight replications resulting in 24 plots: (i) near-isogenic control variety without insecticide (control), (ii) near-isogenic control variety with chemical insecticide (Baytroid) and (iii) Bt maize expressing the recombinant toxin. We established a weed strip (20 x 1 m) in every plot consisting of a Chenopodium album (goosefoot)/Sinapis alba (mustard) mixture. In these strips we measured diversity and abundance of lepidopteran larvae during maize bloom and pollen shed. C. album hosted five species but all in very low densities; therefore data were not suitable for statistical analysis. S. alba hosted nine species in total. Most abundant were Plutella xylostella and Pieris rapae. For these species no differences were detected between the Bt treatment and the control, but the chemical insecticide treatment reduced larval abundance significantly. Conclusions regarding experimental methodology and results are discussed in regard to environmental risk assessment and monitoring of genetically modified organisms.

Study on the weed-crop competition for nutrients in maize.

Considering the effect of crop-weed competition the rate of weed growing, the competitiveness of the occurring weed species and the duration of competition are determining factors. Experiments were carried out on fields in order to collect data on the effect of early weed competition on maize, including the competition for nutrients and the possible rate of nutrient removal by weeds. From 7 sampling areas of the 9.2 ha field weeds and maize samples were collected 1 month after the sowing of maize. We determined the total numbers and the species numbers of weeds by plots. The removed plant species and maize were weighed then dried until the weight balance was reached. The samples were tested for N, P, K and Ca. Comparison was done with the weight and nutrient element content of maize plants taken from the treated, weed-free area. At the same time comparative analyses were made with the mass and nutrient contents of maize plants. There were 12 occurring weed species in this experiment. Based on the rate of weed cover the following species were dominant: Datum stramonium L., Cannabis sativa L., Amaranthus chlorostachis Willd., Chenopodium album L., Chenopodium hybridum L. Our experiments revealed that in the areas being likely to produce high weed populations and showing a considerable high nutrient removal by weeds, the competition between weed plants and maize occurs at an earlier stage of the vegetation period of maize than on fields with moderate weed populations. Weeds have utilised significant amount of nutrients which has been many fold of maize in case of unit area.

Weed control in rose-scented geranium (Pelargonium spp).

Abstract: Field investigations were carried out during 1999 and 2000 to identify effective chemical/ cultural methods of weed control in rose-scented geranium (Pelargonium spp). The treatments comprised pre-emergence applications of oxyfluorfen (0.15, 0.20 and 0.25 kg AI ha(-1)) and pendimethalin (0.50, 0.75 and 1.00kg AI ha(-1)), successive hand weeding, hoeing and mulching using spent of lemon grass (at 5 tonnes ha(-1)) 45 days after planting (DAP), three hand-weedings 30, 60 and 90 DAP, weed-free (frequent manual weeding) and weedy control. Broad-leaf weeds were more predominant than grass and sedge weeds, accounting for 85.8% weed density and 93.0% weed dry weight in 1999 and 77.2% weed density and 93.9% weed dry weight in 2000. Unrestricted weed growth significantly reduced geranium oil yield, by 61.6% and 70.6% in 1999 and 2000, respectively. Pre-emergence application of pendimethalin (0.75-1.00 kgAI ha(-1)) or oxyfluorfen (0.25 kg AI ha(-1)), successive hand-weeding, hoeing and mulching and three hand-weedings were highly effective in reducing weed density and dry weight and gave oil yield comparable to the weed-free check. Application of oxyfluorfen (0.15 or 0.20 kg AI ha(-1)) and pendimethalin (0.50 kg AI ha(-1)) were less effective in controlling the weed species in geranium. None of the herbicides impaired the quality of rose-scented geranium oil measured in terms of citronellol and geraniol content.

Activity of mesotrione on resistant weeds in maize.

Mesotrione is a new callistemone herbicide that inhibits the HPPD enzyme (p-hydroxyphenylpyruvate dioxygenase) and introduces a new naturally selective tool into weed-management programmes for use in maize. Mesotrione provides control of the major broad-leaved weeds, and it can be used in integrated weed-management programmes depending on the grower's preferred weed-control strategy. At post-emergence rates of 150 g AI ha-1 or less, mesotrione provides naturally selective control of key species that may show triazine resistance (TR), e.g. Chenopodium album L, Amaranthus species, Solanum nigrum L, as well as species of weed that show resistance to acetolactase synthase (ALS) inhibitors e.g. Xanthium strumarium L, Amaranthus spp and Sonchus spp. The data presented show that resistant and susceptible biotypes of these species with resistance to triazine herbicides, such as atrazine, simazine, terbutylazine and metribuzin, or ALS-inhibitor herbicides, such as imazethepyr, remain susceptible to mesotrione. These results confirm that there is no cross-resistance in biotypes with target site resistance to triazine or ALS-inhibiting herbicides. It is important that herbicide choice and rotation becomes an integral part of planning weed management, so as to minimise the risks of crop losses from weed competition, build-up of weed seed in the soil and the further development of weed resistance across a range of herbicide modes of action.

Decoupling of light intensity effects on the growth and development of C3 and C4 weed species through sucrose supplementation.

Light availability has a profound effect on plant growth and development. One of the ways to study the effects of light intensity on plant growth and development without the confounding problem of photosynthate availability is sucrose injection/supplementation. A greenhouse experiment was conducted to evaluate the effects of light levels (0% and 75% shade) and sucrose injection (distilled water or 150 g sucrose l(-1)) on three weed species: redroot pigweed (Amaranthus retroflexus L., C4), lambsquarters (Chenopodium album L., C3) and velvetleaf (Abutilon theophrasti Medic., C3). The average total sucrose uptake was 7.6 and 5.9 g per plant for 0% and 75% shading, respectively, representing 47% of the average total weed dry weight. Plants injected with sucrose had greater dry weights and shoot-to-root ratios under both light levels. In spite of sucrose supplementation the reduction in dry matter due to shading was greater for roots and reproductive structures than vegetative shoot tissues, indicating light level regulation of morphological changes resulting in changed C allocation that are independent of photosynthate availability. Dry weights of plants injected with sucrose under 75% shading were not different from distilled water-injected unshaded plants. However, both sucrose-injected and control plants, regardless of their photosynthetic pathways, underwent similar changes in allocation of dry matter and morphology due to shading, suggesting that these effects are strictly due to light intensity and not related to photosynthate availability.

Herbicidal action of 2-hydroxy-3-alkyl-1,4-naphthoquinones.

The main mode of herbicidal activity of 2-hydroxy-3-alkyl-1,4-naphthoquinones is shown to be inhibition of photosystem II (PSII). The herbicidal and in vitro activities have been measured and correlated with their (Log)octanol/water partition coefficients (Log Ko/w). The length of the 3-n-alkyl substituent for optimal activity differed between herbicidal and in vitro activity. The maximum in vitro activity was given by the nonyl to dodecyl homologues (Log Ko/w between 6.54 and 8.12), whereas herbicidal activity peaked with the n-hexyl compound (Log Ko/w = 4.95). The effect of chain branching was also investigated using isomeric pentyl analogues substituted at position 3. All exhibited similar levels of in vitro activities but herbicidal activities differed, albeit moderately, with the exception of one analogue that was much less phytotoxic. Other modes of action were also investigated using two representative compounds. They did not show any activity on photosystem I or mitochondrial complex I, or generate toxic oxygen radicals by redox cycling reactions. Only moderate activity was found against mitochondrial complex III from plants, in contrast to much higher corresponding activity using an insect enzyme.