Bioherbicidal activity of terpenes and phenylpropenes against Echinochloa crus-galli

Abstract

This study was undertaken to evaluate the herbicidal activity of twelve natural compounds belonging to monoterpenes, phenylpropenes, and sesquiterpenes against Echinochloa crus-galli under laboratory and glasshouse conditions. Experiments were conducted to determine the impact of different concentrations (0.5, 1, 2, 4 and 8?mM) of these compounds on the seed germination and root and shoot growth of barnyard grass. trans-Cinnamaldehyde, eugenol, and thymol caused the highest impact on barnyard grass reducing its seed germination and shoot growth. p-Cymene (EC₅₀ = 0.22?mM) and trans-cinnamaldehyde (EC₅₀ = 0.34?mM) were the most potent compounds in limiting the root growth of the E. crus-galli. In a post-emergent experiment, thymol, trans-cinnamaldehyde, eugenol, farnesol, and nerolidol significantly reduced the shoot growth, fresh and dry weight of two-leaf stage barnyard grass after 2 days of the foliar treatment with the concentrations of 0.5, 1.0 and 2.0%. These compounds induced severe visible injury symptoms where trans-cinnamaldehyde, eugenol, farnesol and nerolidol showed a complete weed control at 1.0 and 2.0%. These compounds were successfully formulated as emulsifiable concentrates and showed higher herbicidal activities against barnyard grass. Altogether, our data showed that trans-cinnamaldehyde, eugenol, thymol, farnesol, and nerolidol can be developed as novel bioherbicides for managing E. crus-galli.     

Herbicide effects on typha latifolia (Linneaus) germination and root and shoot development

Aqueous 7-d germination and growth experiments were performed to compare responses of T. latifolia to exposures of atrazine (2-chloro-4-ethylamino-6-isopropylamine-s-atrazine) and paraquat dichloride (1,1′-dimethyl-4,4′-bipyridinium dichloride). T. latifolia seed germination was < 50 % in concentrations ≥ 1.0 mg/L of paraquat dichloride. No observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) for paraquat and root growth were 0.001 and 0.01 mg/L, respectively, while NOEC and LOEC for paraquat and shoot growth were 0.01 and 0.1 mg/L, respectively following 7-d exposures. Greater than 72 % of seeds germinated in each concentration up to 30 mg/L atrazine. After 7-d exposure, NOEC and LOEC for atrazine and root growth were 0.1 and 1.0 mg/L, while atrazine and shoot growth NOEC and LOEC values were 15 and 30 mg/L, respectively. This research provides data concerning relative sensitivity of T. latifolia seedlings to the herbicides atrazine and paraquat, as well as the potential use of T. latifolia as a representative plant test species.     

Bioremediation of crude oil polluted soil by the white rot fungus, <Emphasis Type="Italic">Pleurotus tuberregium</Emphasis> (Fr.) Sing.

Bioremediation has become an attractive alternative to physicochemical methods of remediation of polluted sites. White rot fungi (WRF) are increasingly being investigated and used in bioremediation, because of their ability to degrade an extremely diverse range of very persistent or toxic environmental pollutants. The white rot fungus, Pleurotus tuberregium, was examined for its ability to ameliorate crude oil polluted soil. This was inferred from the ability of the polluted soil to support seed germination and seedling growth in Vigna unguiculata, at 0, 7 and 14 days post treatment. Results obtained from the present study showed that bioremediation of soil contaminated with crude oil was possible, especially when the fungus had been allowed to establish and fully colonize the substrate mixed with the soil. There were significant improvements in % germination, plant height and root elongation values of test plants, when seeds were planted 14 days post soil treatment. At 1 to 5% crude oil pollution, % germination values were comparable with the values in control plants in the 14 days treatment, and significantly higher than values obtained in the day 0 treatment. Also, at the highest level of crude oil pollution (15%), there was about 25% improvement in % germination value over the 0 day treatment. This trend of improvement in values was also observed for plant height, root elongation and biomass accumulation as well as decreased total hydrocarbon content.     

Potential effects of Thiram on medicago ‐ R. meliloti symbiotic association†

Abstract

The effects of Thiram and 2 commercial Thiram formulations on the growth and respiration of rhizobia were tested to compare the extent of bacteriostasis under controlled conditions. Although bacteriostasis was measurable at all concentrations tested, liquid cultures grew to maximum optical density in Thiram suspensions containing less than 10 μg/ml. Percentage germination, root elongation, and subsequent nodulation by R. meliloti of 2 cultivars of alfalfa, were determined in thiram suspensions to determine potential physiological effects of the fungicide on the host plant. Conditions were identified which produced enhancement or inhibition of germination, root elongation and development of nodular nitrogenase activity. At concentrations of the fungicide recommended for seed application, only minor, temporary bacteriostasis was observed as a possible negative effect while germination rates of fungi‐contaminated seed were markedly increased.     

Morphological,physiological and biochemical responses of two Australian biotypes of Parthenium hysterophorus to different soil moisture regimes

Parthenium weed is a problematic invasive species in several countries around the world. Although it is considered to be a highly invasive species within Australia, not all biotypes of parthenium weed exhibit the same ability in regard to aggressive colonization and distribution. Differences among biotypes, particularly in regard to environmental ranges as a possible basis for this variation, have not always been elucidated. To determine whether drought tolerance could be a factor in biotype demographics, we quantified the biological responses of two Australian parthenium weed biotypes known to differ in invasive ability Clermont (“high”) and Toogoolawah (“low”) to 100, 75 and 50% of soil water holding capacity (WHC). The Clermont biotype had greater vegetative growth, seed production and chlorophyll content than Toogoolawah, across all moisture levels. Net photosynthesis, stomatal conductance, internal CO₂ concentration, seed production per plant, 1000 seed weight and subsequent germination percentage were also higher for Clermont than for Toogoolawah and were maximum at 75% WHC. Clermont plants also had higher total soluble sugar, phenolics and free proline content than Toogoolawah, and a significant increase in the levels of all of these biochemicals was observed at 50% WHC. In conclusion, Clermont grew and reproduced better than Toogoolawah across all moisture regimes consistent of enhanced invasive ability of this biotype. Overall, the ability of parthenium weed to maintain good growth, physiology and seed production under moisture stress may enable it to colonize a wide range of Australian environments.

     

Effects of composting on phytotoxicity of spent pig-manure sawdust litter

The phytotoxicity of spent pig-manure sawdust litter (spent litter) was evaluated during further composting. Aqueous extracts of the spent litter were prepared by shaking the sample with water (1:10 w/v), and the toxicity of these extracts was determined on relative seed germination, relative root elongation and germination index (GI, a factor of relative seed germination and relative root elongation). The sensitivity of six plant species, namely Brassica parachinensis (Chinese cabbage), Brassica albogalera (Chinese kale), Allium sativum (onion), Cucumis sativus (cucumber), Amaranthus espinosus (Chinese spinach), and Lycopersicon esculentum (tomato) were compared. The effect of different moisture levels during composting on the phytotoxicity of the spent litter was also examined. Phytotoxicity of the spent litter was only evident during the earlier stage of composting (first 14 days) and, that seed germination and root elongation reached 100% (same as the control) towards the end of the composting. The concentrations of the major inhibitors, water-extractable Cu and Zn, and NH4(+)-N of the spent litter, declined during composting, indicating that these inhibitors were gradually eliminated as composting proceeded. Multiple regression analysis showed that the NH4(+)-N content of the spent litter was the most important chemical factor affecting phytotoxicity of the plant species selected for this study. Relative root elongation and GI were more sensitive indicators of phytotoxicity than seed germination. In the present study, the GI's of all plant species were >80% at day 60, indicating that the spent litter had reached its maturation by day 60. The responses of different plant species to the water-extracts of the spent litter were different. Among the six species, Chinese cabbage and Chinese spinach were the most sensitive species, and tomato and cucumber were the least sensitive species to indicate phytotoxicity of the spent litter. Moisture adjustment during the composting process did not affect the results of the phytotoxicity test.     

Bio-herbicidal effects of five essential oils on germination and early seedling growth of velvetleaf (Abutilon theophrasti Medik.)

The evaluation of the inhibition effect exerted by the essential oils of basil (Ocimum basilicum), sage (Salvia officinalis), thyme (Thymus vulgaris), lemon balm (Melissa officinalis) and goldenrod (Solidago virgaurea) on seeds germination and early seedling growth of velvetleaf (Abutilon theophrasti Medik.) weed was examined in a laboratory bioassay. The essential oils were obtained by hydrodistillation and characterized chemically by gas chromatography coupled with both mass spectrometry and flame ionization detector. The working solutions of essential oil emulsified with Tween 20 and dissolved in distilled water were prepared at three concentration levels (0.01%, 0.1% and 1%, vol/vol). The results obtained showed that increase of essential oil concentration leads to decrease of seed germination, shoot and radical length of velvetleaf. The obtained data revealed a highly significant effect (P?<?0.05) between control and 1% and 0.1% oil concentrations in all treatments. The essential oils of basil, thyme and lemon balm exhibited more powerful bio-herbicidal effect compared to sage and goldenrod essential oils on the germination and early seedling growth of velvetleaf weed.     

Effect of cadmium on germination, amylases and rate of respiration of germinating pea seeds

Growth of embryonic axis of germinating pea seeds (Pisum sativum cv. Bonneville) was significantly inhibited by as low as 0.25 mM cadmium and the elongation of the radicle was affected more severely than that of the plumule. Total amylolytic activity, as well as activities of alpha- and beta-amylases, diminished progressively with increasing concentrations of the metal in the media. The deleterious effect on alpha-amylase persisted throughout, whereas beta-amylase activity recovered with time. The rate of respiration of seeds, measured by oxygen uptake, was markedly impeded by cadmium and the phase of rapid and linear development of respiratory activity (after 3 days of imbibition) was almost completely, suppressed in the presence of higher concentrations (1 mM) of the metal. The observed impact of cadmium on starch mobilization and on respiratory activity are discussed in relation to its adverse effects on seed germination.     

Effects of distillery waste on the performance of Cicer arietinum L

The impact of distillery effluent in various concentrations (1, 2.5, 5, 10, 25, 50, 75 and 100%) on the seed germination, Speed of Germination Index, growth behaviour, leaf area, biomass, net primary productivity, pigment content, reproductive capacity, seed output, seed weight, seed density and the seed protein content of Cicer arietinum L. plants was investigated. The percentage and speed of germination of seeds were increasingly retarded with increase in effluent concentration and at 100% concentration there was no germination. The seedlings exhibited maximum shoot length at 5% concentration and maximum root length at 2.5% concentration. The values of root and shoot lengths, leaf area, biomass, net primary productivity, pigment content, reproductive capacity, seed output, seed weight, seed density and seed protein content in pot plants exhibited a gradual increase from the control up to 5% concentration and decreases at higher concentrations. The very high BOD load and the presence of excessive concentrations of soluble salts could be responsible for the toxicity of the effluent. The effluent at up to 5% concentration was, however, beneficial for the overall growth parameters studied and can thus be used as a liquid fertilizer.     

Bioremediation of HCH-contaminated soil: elimination of inhibitory effects of the insecticide on radish and green gram seed germination

The effects of technical grade hexachlorocyclohexane (tech-HCH) on the germination of different seeds were tested. Two types of seeds, radish and green gram showed marked reduction in germination percentage and seeding vigour index. The abnormalities and reduction in germination increased with increasing concentration of tech-HCH. At 100 microg HCH level the germination of radish and green gram seeds was inhibited almost completely on moist filter paper and soil. Protease and amylase activities were reduced in seeds grown in soil spiked with tech-HCH. Bioremediation of HCH-spiked soils with a HCH-degrading microbial consortium helped in eliminating the toxic effects of tech-HCH towards seed germination. The degradation of 25 microg tech-HCH g(-1) soil was complete by 120 h. The seed germination and the activities of the assayed enzymes, amylase and protease, were same as before or better in bioremediated soils.     

Uptake and toxicity of Cr(III) in celery seedlings

The present study shows that in celery Cr(III) induces deleterious effects on seedling development and morphology, and a number of metabolic responses related to stress. Exogenous CrCl3 from 0.01 to 1 mM increasingly inhibited seed germination and hypocotyl elongation, or completely blocked it (10 mM), while the root apparatus was dramatically damaged even at the lowest dose. Seedlings took up exogenous Cr(III) in a dose-dependent manner, roots being the site of major metal accumulation; translocation towards the hypocotyl and cotyledonary leaves was also detected. Either total or chlorophyll a content was significantly reduced by chromium as low as 0.01 mM. A large accumulation of free and, to a lesser extent, conjugated polyamines occurred in all segments of treated plants. A dose-dependent relationship linking actual amounts of Cr(III) recovered in the entire seedling or organ and the respective polyamine titre was evidenced. Free putrescine, in particular, was the polyamine exhibiting the highest rate of increase, and cotyledonary leaves the organ where the major response occurred. A marked increase in ubiquitin-protein conjugates after Cr(III) treatment was also observed, particularly in roots. Thus, the study suggests for the first time a possible relationship between ubiquitination and Cr(III)-stress. The putative function of polyamines as a stress response, and the recruitment of the ubiquitin pathway to remove damaged or aberrant proteins which might have been produced in metal-treated seedlings are discussed.     

Phytotoxicity of nanoparticles: inhibition of seed germination and root growth

Plants need to be included to develop a comprehensive toxicity profile for nanoparticles. Effects of five types of nanoparticles (multi-walled carbon nanotube, aluminum, alumina, zinc, and zinc oxide) on seed germination and root growth of six higher plant species (radish, rape, ryegrass, lettuce, corn, and cucumber) were investigated. Seed germination was not affected except for the inhibition of nanoscale zinc (nano-Zn) on ryegrass and zinc oxide (nano-ZnO) on corn at 2000 mg/L. Inhibition on root growth varied greatly among nanoparticles and plants. Suspensions of 2000 mg/L nano-Zn or nano-ZnO practically terminated root elongation of the tested plant species. Fifty percent inhibitory concentrations (IC50) of nano-Zn and nano-ZnO were estimated to be near 50mg/L for radish, and about 20mg/L for rape and ryegrass. The inhibition occurred during the seed incubation process rather than seed soaking stage. These results are significant in terms of use and disposal of engineered nanoparticles.     

Interactions between glyphosate and autochthonous soil fungi surviving in aqueous solution of glyphosate

The survival of autochthonous fungi in soil treated with 1mM aqueous solution of glyphosate was investigated. Significant differences in the total number of fungi in the studied objects were observed, and additionally significant qualitative changes were encountered. The dominating group of fungi belonged to genus Fusarium: Fusarium solani H30, Fusarium solani H50 and Fusarium oxysporum H80. Interactions between the isolated strains of fungi and varying concentrations of glyphosate were determined. The studied strains possessed high tolerance against the applied doses of glyphosate (0.5-2.0 mM). In the presence of glyphosate (as a sole source of phosphorus) applied in concentrations of 1.0-1.5 mM the increase in dry mass of the tested fungi was highly significant. In the presence of glyphosate the phenotypic changes of studied strains were observed as was shown as the presence of colorants being indicators of such changes. Thus, their color and intensity depended on the age, pH and species present in the culture. The degradation of glyphosate by studied fungi was determined by means of TLC. Two types of compounds were formed. One of them (Rf=0.21-0.35) contained free amino group but was not either glycine nor AMPA. Survival of Fusarium in soil environment is potentially dangerous.     

Phytotoxicity data safeguard the performance of the recipient plants in leachate irrigation

Leachates from an operating and a closed landfill were examined for their phytotoxicity by seed germination/root elongation tests using seeds of Brassica chinensis and Lolium perenne. Their EC50s ranged from 3% to 46% v/v, which varied remarkably with the operating status of the landfills. Seedlings of twelve tree species were grown in pots, which were irrigated with landfill leachate at the EC50 levels, with tap water as control. No tree mortality or growth inhibition was observed after 90 days of leachate application. Chlorophyll fluorescence measurement also showed that plants receiving leachate did not suffer from a decline in photosynthetic efficiency. Litsea glutinosa and Hibiscus tiliaceus had remarkable growth, and other non-N-fixers were not inferior to the N-fixing Acacia auriculiformis. Leachate irrigation improved soil N content, though P deficiency is still a problem. The seed bioassay provided a conservative estimate of the phytotoxicity of landfill leachate. Plants irrigated can be protected from growth inhibition when the leachate irrigation plan is designed with reference to phytotoxicity data.     

Effects of DDT on the growth of crop plants

The effects of DDT on the germination and growth of plants were studied using many crop species. Of the species tested, oil-rich seeds of plants, such as peanut (Arachis hypogaea) and mustard (Brassica juncea), were more prone to DDT induced inhibition of germination and subsequent plant growth than cereals, pulses and fibre crops, like rice (Oryza sativa), barley (Hordeum vulgare), mung bean Vigna radiata), pigeon pea (Cajanus cajan) and cotton (Gossypium hirsutum). Studies with (14)C labelled DDT showed that insecticide uptake by seeds was directly proportional to seed size. However, there was no direct relationship between DDT uptake by the seeds and its subsequent translocation to the growing regions or the degree of growth inhibition. Data suggest that oil content of the seeds per se has a bearing on the susceptibility or tolerance of a plant to DDT. It is suggested that lipids of the plant cell solubilize and disperse DDT in the cytoplasm, which, in turn, affects normal metabolism within the cell.     

Microwave irradiation and citric acid assisted seed germination and phytoextraction of nickel (Ni) by <Emphasis Type="Italic">Brassica napus</Emphasis> L.: morpho-physiological and biochemical alterations under Ni stress

The complex bio-geochemistry of soil allows pollutant to persist for a longer period of time which further decreased the fertility and natural composition of land. Nickel, an inorganic pollutant, coming from a wide range of industrial and manufacturing units possesses serious threat to soil degradation and crop productivity around the world. The present study was carried to evaluate the combined role of microwave irradiation (MR) and citric acid (CA) on the phytoextraction potential of Brassica napus L. under Ni stress. An initial seed germination test was conducted to select effective time scale of MR exposure. Highest seed germination was observed at exposure of 2.45 GHz frequency for 30 s. Healthy seeds of B. napus L. genotype Faisal Canola (RBN-03060) treated with MR at 2.45 GHz for 30 s were sown in plastic pots filled with 5 kg of soil. Nickel and CA applied exogenously in solution form with different combinations to both MR-treated and untreated B. napus plants. The MR-treated plants showed higher growth, biomass, photosynthetic pigments (Chl a, b, total, and carotenoids) and activities of antioxidant enzymes (SOD, POD, APX, CAT) as compared to untreated plants who showed higher reactive oxygen species (MDA, H₂O₂) and electrolyte leakage. Increasing Ni concentration significantly decreased the physiological and biochemical attributes of B. napus both in MR-treated and untreated plants. The addition of CA alleviated Ni-induced toxic effects in both MR-treated and untreated plants by improving antioxidant defense system. The degree of Ni stress mitigation was higher in MR-treated plants. The Ni concentration was higher in root, stem, and leaves of MR-treated plants under CA application as compared to untreated plants. The present study concluded that seeds treated with MR before sowing showed higher accumulation and concentration of Ni from soil, and this phenomenon boosted with the application of CA.     

Phytotoxicity of composted herbal pharmaceutical industry wastes

This work demonstrates the phytotoxicity screening of composted herbal pharmaceutical industry waste (HPIW) using seed bioassay method. The composted industrial waste should be tested at lab scale prior to recommendation for land application. HPIW was mixed with soil to produce four treatments: T(1) (1:1), T(2) (1:2), T(3) (1:3), and T(4) (1:0) for toxicity screening using Pisum sativum seeds. After 72?h relative seed germination (RSG), relative root growth (RRG) and germination index (GI) were recorded. Seedlings were observed for further plant growth and tissue biochemistry (chlorophyll, soluble sugar, starch, carotenoid, and protein) estimation. RSG, RRG, and GI values were better in T(1) and T(2) than others. GI was in the ranges of 36.62?% (T(4)) to 170.38?% (T(2)). The seedling growth and biochemical parameters were better in seedling obtained from potting media containing low proportion of HPIW (i.e., T(1) and T(2)). Results clearly suggested that composted HPIW may be utilized effectively for crop production after dilution under sustainable farming system program.     

Photoinduced toxicity of fluoranthene on germination and early development of plant seedling

The influence of light on phytotoxicity of increased concentration (2, 5, 10 mg/l) of intact fluoranthene (FLT) and photomodified fluoranthene (phFLT) diluted in experimental solutions was investigated. The germination rate of lettuce (Lactuca sativa L.), onion (Allium cepa L.) and tomato (Lycopersicum esculentum L.) seeds and some parameters of seedlings primary growth of these plant species were used as laboratory indicators of phytotoxicity. Among them a length of root and shoot, their dry weight and a content of photosynthetic pigments in shoot were measured. The results demonstrated that the higher concentration (5 and 10 mg/l) of FLT and especially of phFLT significantly inhibited the germination rate of seeds and the length of root and shoot seedlings of all plant species. Decreased production of biomass expressed by dry weight of root and shoot was found in lettuce seedlings under the inhibitory effect of FLT and phFLT. An increased concentration of FLT and phFLT did not exhibit an unambiguous effect on the content of photosynthetic pigments in shoot of experimental plants. Only the highest concentration (10 mg/l) of FLT significantly increased content of chlorophylls a and b in lettuce, onion and tomato plants and content of carotenoids in lettuce and onion. Light intensified a significant inhibitory effect of phFLT in the most testified parameters of germination and seedling growth.     

Effect of Zn toxicity on root morphology,ultrastructure, and the ability to accumulate Zn in Moso bamboo (Phyllostachys pubescens)

The effects of zinc (Zn) on seed germination and growth of Moso bamboo (Phyllostachys pubescens) were investigated. Under zinc stress, the seed germination rate did not show significant difference from that of the control. Hydroponics experiments indicated that Moso bamboo had a strong ability to accumulate Zn in the shoot and it reached its maximum value in the shoot at 100 μM Zn. The root Zn concentration ranged from 2,329.29 to 8,642.51 mg kg^?1, with the root Zn concentration at 10 μM Zn being 58.23 times that of the control. The root morphology parameters slightly increased at the lower Zn treatments, while growth restriction was evident at higher Zn treatments. Root ultrastructural studies revealed that the cell structure, root tips, and organelles were significantly changed under Zn stress as compared to those of the control. Some abnormalities were evident in the cell walls, vacuoles, mitochondria, plasmalemma, tonoplast, and xylem parenchyma of root cells. While Moso bamboo seems a suitable candidate for phytoremediation, its metal remediation ability should be further explored in future investigations.     

Effect of vermicast generated from an allelopathic weed lantana (Lantana camara) on seed germination,plant growth,and yield of cluster bean (Cyamopsis tetragonoloba)

In perhaps the first-ever study of its kind, the effect of vermicompost, derived solely from an allelopathic weed, on the germination, growth, and yield of a botanical species, has been carried out. In test plots, the soil was treated with the vermicompost of lantana (Lantana camara) at the rates of 5, 7.5, and 10 t ha^?1, and cluster bean (Cyamopsis tetragonoloba) was grown on it. The performance of these systems was compared with the systems in which the soil was fortified with inorganic fertilizers (IFs) in concentrations equivalent to those present in the respective vermicompost (VC) treatments. Additionally, a set of control was studied in which the soil was used without fortification by either VC or IF. It was seen that up to 51.5 % greater germination success occurred in the VC treatments compared to controls. VC also supported better plant growth in terms of stem diameter, shoot length, shoot mass, number of leaves, and leaf pigments. The positive impact extended up to fruit yield. In addition, vermicast application enhanced root nodule formation, reduced disease incidence, and allowed for a smaller number of stunted plants. The results indicate that allelopathic ingredients of lantana seem to have been totally eliminated during the course of its vermicomposting and that lantana vermicompost has the potential to support germination, growth, and fruit yield better than equivalent quantities of IFs.