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The changed phenolic acids (PAs) allelochemicals exuded by the roots induced by interspecific interactions is related to intercropping alleviates soil-borne disease. However, the presence of PAs in roots and root exudations and their rhizodeposition under intercropping are still unclear. Hydroponic and soil experiments of wheat, faba bean, and wheat intercropped with faba bean were conducted, and the major compositions and contents of PAs in roots, root exudations, and rhizospheric soil were determined. The results showed that ρ-hydroxybenzoic, vanillic, and syringic acids were the major components of PAs in roots, root exudations, and rhizospheric soil in a wheat and faba bean intercropping system. The compositions and percentages of PAs in roots of faba bean were altered when faba bean intercropped with wheat. The total exudation rate of PAs in root exudations was decreased by 30%–60% under the wheat and faba bean intercropping (W//F) system as compared to mono-cropped faba bean (MF). ρ-hydroxybenzoic acid was identified in the root exudation of both MF and mono-cropped wheat (MW), but not detected in the intercropping on 60 days after transplanting. Vanillic acid was only detected in the root exudation of MF on 30 days after transplanting. The rhizodepostion of vanillic and cumaric acid were decreased at both branching and pod setting stages in W//F as compared to MF. In conclusion, interspecific interaction changed the compositions and contents of PAs in faba bean roots and root exudations. W//F constrained vanillic acid exuded by roots and decreased vanillic and coumaric acid rhizodeposition by faba bean, which provides insight into root-soil interactions in the intercropping systems.

Lonchocarpus cultratus (Vell.) A.M.G. Azevedo & H.C. Lima (Fabaceae) is a native tree species and from which flavonoids, triterpenes, alkaloid were isolated. In addition, potent antiproliferative activity of hexane fraction and chalcone, obtained from this plant, has been described in different cell lines of human tumors. However, no studies were found on the allelopathic and/or bioherbicidal action, using aerial parts of L. cultratus. Thus, the aim of the present work was to evaluate the allelopathic activity of methanol extract, fractions and compounds from aerial parts of L. cultratus. Dried aerial parts were extracted by exhausting extraction with methanol at room temperature, and the solvent was evaporated under reduced pressure providing the crude extract. The crude extract was partitioned in a liquid-liquid extraction and to obtain hexanic (HF), chloroform (CF), ethyl acetate (EAF), and hydromethanolic (HMF) fractions. The compounds were extracted from fractions through chromatographic methods. Crude extract and its fractions inhibited Lactuca sativa germination mean time (GMT) and germination speed index (GSI), but not the germination percentage (GP) of Lactuca sativa. Crude extract and hexane fraction inhibited the hypocotyl growth of L. sativa seedlings and the other fractions inhibited the primary root of seedlings. Hexane, chloroform, and ethyl acetate fractions inhibited primary root growth of Euphorbia heterophylla. Chalcone 2’,4’-dihydroxy-5’-prenylchalcone, flavanone 8-prenylpinocembrin and alkaloid 4-hydroxy-N-methylproline were tested on lettuce early growth. Thirty-three metabolites were identified by UHPLC-MS/MS analysis, with flavonoid derivatives being the most abundant constituents.

One new eudesmane sesquiterpene 1 and one new chromolaevane sesquiterpene 2, along with 19 known compounds, have been isolated from the invasive plant Solidago canadensis. Their structures were established by spectroscopic means, including 1D/2D-NMR and HR-ESIMS analyses. Compounds 10 and 12, in combination with fluconazole, showed significant activity in an in vitro synergistic antifungal assay against Candida albicans, with FIC values of

Sicklepod is an important weed in Brazil pastures, but control measures are not yet effective. Thus, allelopathy can be an alternative, due to its ecological importance and for being able to provide new structures sources for agrochemicals production. This research aimed to verify the allelopathic potential of sesame (Sesamum indicum L.) on germination and seedling development of sicklepod (Senna occidentalis L.) and brachiaria (Brachiaria brizantha). The treatments were root and leaf extract of sesame, and control (distilled water). Germination percentage, speed of germination, hypocotyl and radicle length were evaluated. Speed of germination, germination percentage and radicle length had no interference from the aqueous extracts. However, in brachiaria these traits had lower values than sicklepod. Hypocotyl length was not influenced by the extracts, however, the leaf extract showed lower growth of this feature. Allelopathy did not affect germination and speed of germination in both species, but interfered in brachiaria development.

In aquatic ecosystems, allelopathic activity depends on the production and secretion of allelopathic compounds and their effective dispersal in the environment. In addition, macroalgae have been found to produce active metabolites that affect other organisms that compete with them for nutrients. However, the allelopathic activity of Baltic red and brown macroalgae on filamentous cyanobacteria is still insufficiently understood. Therefore, the main objective of this study was to demonstrate and compare the allelopathic effects of macroalgae Fucus vesiculosus L. and Coccotylus brodiei (Turner) Kütz. on the growth and photosynthetic activity of two Baltic cyanobacteria Aphanizomenon sp. and Nostoc sp. It was found a stimulating effect of different concentrations (5, 25, and 50 µL mL–1) of the aqueous extract obtained from C. brodiei on the number of cells of Nostoc sp. which constituted 108%, 140%, and 147%, respectively, relative to the control treatment. On the other hand, extracts obtained from F. vesiculosus had no statistically significant effect on the number of cells of the cyanobacteria Aphanizomenon sp. and Nostoc sp. Moreover, the C. brodiei extracts had no significant impact on the growth of Aphanizomenon sp. Furthermore, Baltic macroalgae F. vesiculosus and C. brodiei was able to exert allelopathic effects on photosynthesis performance of Nostoc sp. and Aphanizomenon sp. and compounds produced by them had inhibitory, stimulatory, or no significant effect on the maximum PSII quantum efficiency (Fv/Fm) and the effective quantum yield of PSII photochemistry (ΦPSII). The results obtained in this work constitute an important contribution to the knowledge on the allelopathic activity of Baltic red and brown algae on certain bloom-forming species of filamentous cyanobacteria.

Prymnesium parvum is a toxin-producing harmful alga that has caused ecological and economic damage worldwide. Effective methods to control blooms of this species in the field, however, are unavailable. This study examined five natural compounds present in the invasive plant Arundo donax and one synthetic derivative (5,6-dichlorogramine) for their effect on P. parvum growth. All compounds except one inhibited growth in the following order of potency: ellipticine > > 5,6-dichlorogramine > 1 H-indole = 2,4,6-trimethyl-benzonitrile > gramine. Ellipticine was by far the most potent inhibitor, with full algicidal activity at concentrations as low as 0.04 mg L−1 and 3- and 9-day IC50 values of 0.012 and 0.007 mg L−1, respectively. A reduction in chlorophyll content and swimming activity and an increase in length and volume (swelling) were documented in algal cells exposed to 0.01–0.02 mg ellipticine L−1. These results show that ellipticine is among the most potent natural algicides identified to date. The sixth compound tested, oleamide, unexpectedly stimulated algal growth above control levels. Overall, these observations confirm the existence of highly potent anti-P. parvum allelochemicals in giant reed and demonstrate potential for using products derived from this plant in the development of natural, environmentally friendly methods to control harmful algal blooms.

Tectona grandis L.f. (Teak) is a highly cultivated forest species in Brazil. When industrially processed, it generates a large amount of sawdust, a waste that has limited reuse and accumulates in the industrial yards. The aim of this study was to evaluate the effect of fresh teakwood sawdust on the development of Urochloa brizantha (Hochst. ex A.Rich.) R.D.Webster cv. Xaraés in a nursery. The treatments consisted of concentrations of 0, 5, 10, 20, 33 and 50% of sawdust, arranged in four randomized blocks in split-plots. At 45, 75 and 120 days, plant heigh (h), average tillers diameter (d), number of live (nll) and dead leaves per plant, fresh and dry mass of shoots and roots, and Dickson's quality index (dqi) were measured. There was a decrease in h growth, d, nll, fresh and dry mass of shoots and roots and in the dqi of the cv. Xaraés as it increased to concentration of wood sawdust in the substrate. This negative effect can be attributed to the high C/N ratio of sawdust (196/1), which influences the decomposition of organic matter. In addition, the possible Teak allelopathic effects, which are the subject of other studies, should be considered. Unlike the other variables, number of live leaves was not influenced by the treatment with 5% sawdust. Teakwood sawdust has negative effects on the U. brizantha cv. Xaraés development.

Asparagus is a popular vegetable rich in healthy functional components. However, the process of its production leaves ferns from aboveground parts and roots from underground parts as unusable parts, and this is an issue to be resolved. In our previous studies, large amounts of rutin were noted in the cladophylls and storage roots (brown and epidermis), and the protodioscin content was high in buds, in the soil-covered section of spears, and in rhizomes. This study was conducted to examine the distribution of growth-inhibitory activity and mineral contents in different parts of asparagus. Correlations, including representative functional components (rutin and protodioscin), were examined. The results suggest there are differences in growth-inhibitory activity of different parts of asparagus. The growth-inhibitory activity was strong in the buds, rhizome, and absorptive and storage roots, and weak in the cladophylls and lateral branches. The percent N content of the aboveground part of asparagus was high compared with that in the aboveground part of other crops. Although the percent K content was similar to the mean of the aboveground part of other crops, it was higher than that in general green manure, suggesting the residual stems and leaves of the aboveground part of asparagus are effective green manure. In the aboveground part of asparagus, the rutin content and percent N and K content were higher, whereas growth-inhibitory activity tended to be low, suggesting that when no disease developed in the aboveground part, it can be used as an organic substance.

Overaccumulation of allelochemicals in soil from trees has a negative effect on the growth of Panax notoginseng and cause root rot. Many plant secreted phenols are water-soluble substances that can be depleted by leaching. However, comprehensive understanding of the effect of leaching of phenols in Chinese fir soil on P. notoginseng root rot disease is still lacking. Soil with high level of phenols was leached with five intensities and their effect on the root rot of P. notoginseng was assessed. Then, the relationship of root rot with changes in soil chemical properties and phenol content as well as rhizospheric microorganisms was analyzed. With increasing leaching intensity, the levels of phenols in soils and the incidence of root rot decreased significantly. Decreased phenol content could alleviate root rot by modifying the soil microbial community. Network analysis showed that root rot incidence was positively correlated with the p-hydroxybenzoic acid-enriched pathogenic fungus Ilyonectria but negatively correlated with p-hydroxybenzoic acid (HA)-, ferulic acid (FA)- or vanillic acid (VA)-suppressed bacteria, including Sphingomonas, Lysobacter, Massilia and Burkholderia. Culture experiments confirmed that individual HA, FA and VA as well as a mixture of the five phenols with increasing concentrations could stimulate the growth and sporulation of I. destructans but suppress the growth and biofilm formation of bacteria (Burkholderia and Lysobacter). Moreover, Burkholderia isolates showed antagonistic activity against the growth of I. destructans. Leaching could relieve the stimulation of pathogenic fungi by phenols and reduce the pressure on phenolic-suppressed bacteria, thereby reducing the incidence of root rot disease.

Soil sterilization integrated with agronomic measures is an effective method to reduce soilborne replant diseases. However, the effect of vermicompost or biochar application after soil sterilization on soilborne diseases is poorly understood. A pot experiment was conducted in American ginseng to investigate the effects of vermicompost (VF), biochar (BF), and a combination of vermicompost and biochar (VBF) applied after soil sterilization on the incidence of Fusarium root rot using natural recovery (F) as control. After one growing season, the disease index of root rot, the phenolic acids, and the microbial communities of American ginseng rhizosphere soil were analyzed. The disease index of VF, BF, and VBF decreased by 33.32%, 19.03%, and 80.96%, respectively, compared with F. The highest bacterial richness and diversity were observed in the rhizosphere soil of VBF. Besides, VF and VBF significantly increased the relative abundance of beneficial bacteria (Pseudomonas, Lysobacter, and Chryseolinea) in the rhizosphere soil. Higher concentrations of vanillin, one of the phenolic acids in the roots exudates, were recorded in the rhizosphere soils of BF and VBF. The vanillin concentration showed a significant negative correlation with the disease index. To conclude, vermicompost improved the beneficial bacteria of the rhizosphere soil, while biochar regulated the allelopathic effect of the phenolic acids. The study proposes a combined application of biochar and vermicompost to the rhizosphere soil to control Fusarium root rot of replanted American ginseng effectively. KEY POINTS: Vermicompost improves the relative abundance of rhizosphere beneficial bacteria. Biochar inhibits the degradation of phenolic acids by adsorption. The combination of vermicompost and biochar enhances the disease control effect.

Various kinds of agricultural products are needed to support organic farms to produce superior quality products, one of it was natural herbicides. Some plants have the potential to become natural herbicides by producing chemical compounds, namely allelopathy which can inhibit the growth of surrounding plants and Murraya keonigii is one of it. This study aims to see the potential of M. keonigii to become a natural herbicide. Grass seeds were given M keonigii’s extract at a dose of 0 gr / l (control / M0), 50 gr / lt (M1), 60 gr / lt (M2), and 70 gr / lt (M3). The results showed that the aromatic or allelopathic compounds in M ​​keonigii affected the germination. Germination was slower at doses of 60 gr / l (M2) and 70 gr / lt (M3) compared to controls (M0) and 50 gr / lt (M1). Radicle length did not increase rapidly in M2 and M3 treatment. Germination power of grass seeds in control and M0 had a value of 100% or all germinated, while M1 and M2 had 67% germination. The higher the dose of M keonigii extract, the slower the process of grass seed germination.

Plants can respond to competition with a myriad of physiological or morphological changes. Competition has also been shown to affect the foraging decisions of plants belowground. However, a completely unexplored idea is that competition might also affect plants' foraging for specific elements required to inhibit the growth of their competitors. In this study, we examined the effect of simulated competition on root foraging and accumulation of heavy metals in the metal hyperaccumulating perennial plant Arabidopsis halleri, whose metal accumulation has been shown to provide allelopathic ability. A. halleri plants originating from both metalliferous and non-metalliferous soils were grown in a "split-root" setup with one root in a high-metal pot and the other in a low-metal one. The plants were then assigned to either simulated light competition or no-competition (control) treatments, using vertical green or clear plastic filters, respectively. While simulated light competition did not induce greater root allocation into the high-metal pots, it did result in enhanced metal accumulation by A. halleri, particularly in the less metal-tolerant plants, originating from non-metalliferous soils. Interestingly, this accumulation response was particularly enhanced for zinc rather than cadmium. These results provide support to the idea that the accumulation of metals by hyperaccumulating plants can be facultative and change according to their demand following competition.

From the first half of the XX century, the maritime Antarctic was a region with high regional warming rates. At the beginning of the XXI century, regional warming strongly slowed down, but during the next twenty years the near-surface temperatures and mean annual precipitation at the Antarctic Peninsula will most probably increase. Higher temperatures and precipitation make the conditions in the maritime Antarctic more favourable for plants, including invasive species. Moreover, the increasing number of Antarctic tourists unintentionally transport thousands of seeds to the Antarctic on their clothes and equipment. In such circumstances, it is important to evaluate possible defensive mechanisms of native plant species, including their allelopathic potential. The objective of this study was to evaluate the allelopathic potential and cytostatic activity of Sanionia georgicouncinata. This species is widespread in the maritime Antarctic and is one of the most abundant moss species on the Argentine Islands (Wilhelm Archipelago). Seeds of cucumber Cucumis sativus, radish Raphanus raphanistrum subsp. sativus, wheat Triticum vulgare, and amaranth Amaranthus paniculatus were used as bioassay species. Fresh green biomass of S. georgicouncinata was used to prepare aqueous extracts with 1 : 10, 1 : 50, and 1 : 100 plant to water ratios. The average root length of wheat sprouts and cucumber sprouts in distilled water did not differ significantly from those in plant extracts. The root length of radish sprouts in 1 : 50 plant extract was significantly shorter than in distilled water. Meanwhile, in 1 : 50 and 1 : 100 water extracts, roots of amaranth plants were significantly longer than in water. The number of lateral roots of cucumber sprouts in water and studied aqueous extracts varied from 1 to 6 with medians from 3 to 4. The medians of control (distilled water) and sample groups (aqueous extracts) did not differ significantly, but only 38.1 ± 6.1% of cucumber sprouts developed lateral roots in the 1 : 10 aqueous extract of S. georgicouncinata, and even less – 28.3 ± 7.5% in the 1 : 50 aqueous extract. The results of this study show that the allelopathic potential of S. georgicouncinata is low. However, a significant cytostatic activity of the studied extracts shows that this species may still affect other plants and animals. Further research is needed to evaluate the impact of the studied extracts on root growth and germination of the invasive plants, particularly Poa annua.

Cover crops included in a crop rotation can help increase nitrogen (N) availability to subsequent crops, raise soil organic matter, and suppress emergence and growth of various weed species. However, weed suppression by cover crops has mostly been investigated shortly after cover crop termination and not over a longer period spanning into the next cropping season. The effects of sunn hemp (Crotalaria juncea) and sorghum-sudangrass (Sorghum ×drummondi) planted the previous year on N availability before transplanting of late summer cabbage (Brassica oleracea), weed germination and growth, and cabbage yield was examined in field studies conducted in 2018 and 2019 at Pittstown, NJ. Results established that there was little evidence for a functional difference in soil N availability for fall cabbage production because of previous cover crop type. Heavy rainfall events both years may have caused major losses of available N that might otherwise be expected to come from N mineralization of residues of legume cover crop like sunn hemp. During the cover crop season, smooth pigweed (Amaranthus hybridus) and common lambsquarters (Chenopodium album) dry biomass was 77% and 82% lower, respectively, in sorghum-sudangrass compared with sunn hemp plots. The subsequent season following sorghum-sudangrass cover crop, dry biomass of broadleaf weeds was lower by 74% and 56% in June and July, respectively, compared with preceding sunn hemp. Smooth pigweed, common lambsquarters, and hairy galinsoga (Galinsoga quadriradiata) were the weed species most consistently affected by preceding sorghum-sudangrass cover crop with biomass decreased by up to 80%, 78%, and 64%, respectively. Thus, it appears that sorghum-sudangrass can provide suppression of some broadleaf species over a relatively long period and is indicative of sorghum-sudangrass allelopathic activity. On the contrary, density and biomass of grassy weeds as well as commercial yield of transplanted cabbage were unaffected by the preceding cover crop. These results suggest that sorghum-sudangrass cover crop could be integrated to transplanted cole crop rotation for providing weed suppression benefits without altering crop yield in New Jersey organic vegetable cropping systems.

Background The root rot of fragrant solomonseal (Polygonatum odoratum) has occurred frequently in the traditional P. odoratum cultivating areas in recent years, causing a heavy loss in yield and quality. The phenolic acids in soil, which are the exudates from the P. odoratum root, act as allelochemicals that contribute to the consecutive monoculture problem (CMP) of the medicinal plant. The aim of this study was to get a better understanding of P. odoratum CMP. Results The phenolic acid contents, the nutrient chemical contents, and the enzyme activities related to the soil nutrient metabolism in the first cropping (FC) soil and continuous cropping (CC) soil were determined, and the differentially expressed genes (DEGs) related to the regulation of the phenolic acids in roots were analyzed. The results showed that five low-molecule-weight phenolic acids were detected both in the CC soil and FC soil, but the phenolic acid contents in the CC soil were significantly higher than those in the FC soil except vanillic acid. The contents of the available nitrogen, available phosphorus, and available potassium in the CC soil were significantly decreased, and the activities of urease and sucrase in the CC soil were significantly decreased. The genomic analysis showed that the phenolic acid anabolism in P. odoratum in the CC soil was promoted. These results indicated that the phenolic acids were accumulated in the CC soil, the nutrient condition in the CC soil deteriorated, and the nitrogen metabolism and sugar catabolism of the CC soil were lowered. Meantime, the anabolism of phenolic acids was increased in the CC plant. Conclusions The CC system promoted the phenolic acid anabolism in P. odoratum and made phenolic acids accumulate in the soil.

New products, including natural extracts, have been evaluated for the control of phytopathogens. This study aimed to evaluate the antibacterial potential of ethanolic extracts from mushrooms, followed by an evaluation of allelopathic effects. Characterization of phenolic acids in Russula xerampelina (Schaeff.) Fr., Crab Brittlegill. and Suillus granulatus (L.) Roussel, Weeping Bolete extracts were evaluated by high-performance liquid chromatography, followed by assessment of their antibacterial potential, alone and combined, against Pseudomonas aeruginosa. The allelopathic effects of Lactuca sativa (lettuce) and Solanum lycopersicum (tomato) were measured in terms of germination and length parameters. The results demonstrated an additive profile of the combined extracts against P. aeruginosa. Both extracts caused a decrease in the percent germination of L. sativa and S. lycopersicum seeds at higher concentrations. Seeds were positively influenced when analyzing the allelopathic index. These results indicate the potential of these extracts for control of genus Pseudomonas phytopathogens, mainly because they do not cause phytotoxicity in terms of the evaluated parameters.

Allelochemicals are secondary metabolites which are not edible and can be used as growth regulators and bio-herbicides. The goal of current study was to assess allelopathic ability of Lantana camara (Sage-plant) flowers against weeds viz. Avena fatua (Wild oat), Euphorbia helioscopia (Sun-spurge), Chenopodium album (Goosefoot), Phalaris minor (Canary-grass), and Rumex dentatus (Knotweed). Bioassay analysis of three methanolic fractions of the Combiflash from L. camara was performed at 50%, 75% and 100% concentration using germination percentage parameters, inhibition of plumule and radicle size. The fraction II of Combiflash strongly suppressed all weeds with negligible effect on T. aestivum. Gas chromatography-mass spectroscopy was conducted for the fraction, and isolated compounds were used to perform bioassays. From fraction II GC-MS detected four methyl esters of allelopathic fatty acid viz. Methyl oleate, methyl palmitate, methyl stearate and methyl linoleate. The evaluation of physiological effects of the bioassay revealed substantial suppression of chlorophyll, antioxidant enzymes (superoxide, dismutase peroxidase) and protein material in all weeds by methyl palmitate. Bioassay activity and study of physiological parameters revealed that the effective bio-herbicidal compound in Lantana camara flowers is methyl palmitate. This is the first time that methyl palmitate (a fatty acid methyl ester) has been related to herbicidal activity in L. camara flowers. It is proposed that field studies based on hormesis research and the mechanism of action of this compound be carried out.

This study was carried out to determine the chemical composition of essential oils of the spearmint and the peppermint dry leaves and their allelopathic effects on seed germination and seedling gro...

Tabebuia serratifolia known as ipe-amarelo is a symbol species of the Brazilian Cerrado. The objective of this work was to evaluate the phytochemistry, physicochemical and bioactive compounds of the floral hydroethanolic extract of Tabebuia serratifolia. The flowers were collected and the extract produced by fresh maceration and ultrasound. The following tests were carried out, organoleptic characteristics for color and odor, yield (%), dry mass (%), moisture content (%), pH, total solids (%), refractive index (nD), density (g mL-1 20 °C), scan between 330 to 800 nm, antioxidant activity in reducing DPPH (IC50), photoprotection, total phenolic compounds (mg AGE 100 g-1) and hemolytic activity (%). The following results were found, hydroethanolic extract, light and dark yellow, homogeneous and crystalline for in natura and assisted by ultrasound. Yield 9.65% and 10.16%, pH 7.23 and 6.87, total solids 1.94% and 2.0%, refractive index 1.3057 nD and 1.3094 nD, density of 0.8554 g mL-1 and 1.1529 g mL-1, SPF UVA, antioxidant activity with IC50 of 17.51 µg mL-1 ​​and 14.36 µg mL-1, total phenolic compounds of 266.13 mg AGE 100 g-1 and 268.41 mg AGE 100 g-1 and hemolytic activity between 53.78% to 32.45%, and from 64.85 to 36.42%, respectively for extract in natura and ultrasound, and dry mass = 82.64% and moisture content = 17.36% for both floral extracts. Both floral extracts especially for those assisted by ultrasound, showed rich results, being the floral organ a potential candidate as a new source for the development of drugs, allelopathic agricultural, biological, food and biotechnology products.

Volatilization, one of the most important mechanisms of the allelopathic effects of an exotic noxious weed Mikania micrantha, has not been adequately investigated to date. In this study, laboratory bioassays showed that the effects of volatiles from the leaves and flowers of M. micrantha on seed germination and seedling growth were negative for all four tested plants (Lactuca sativa, Chrysanthemum coronarium, Bidens pilosa, Abutilon theophrasti). Moreover, the inhibitory effect of the leaf volatiles was generally greater than that of the flower volatiles. To assess the reason for the above differences and further explore which compounds played the most crucial roles, the volatiles from the two tissues were absorbed by solid phase microextraction (SPME) and identified by gas chromatography and mass spectrometry (GC–MS). Then, 19 and 10 terpenes were determined respectively. α-Terpineol, β-ocimene, β-myrcene, α-pinene and caryophyllene had the maximum differences in content and concentration, which were selected for further bioassays with B. pilosa. The results indicated that morphological indices and SOD activity decreased with increasing concentrations of chemicals, whereas the contents of chlorophyll, soluble protein and MDA represented adverse changes. In addition, significant responses were observed in the treatments with α-terpineol at 1.0 μL·L−1 and lower concentrations, while similar trends were observed in the treatments with β-ocimene, β-myrcene, α-pinene and caryophyllene at 10 μL·L−1 and higher concentrations. It was concluded that terpenoids released through volatilization have an important role in the allelopathic effect of M. micrantha, and the oxygenated monoterpene α-terpineol played a crucial role in these effects.

We intensively studied faba bean (Vicia faba L.) and wheat (Triticum aestivum L.) intercropping and found that this type of intercropping can effectively control the occurrence of faba bean wilt under field conditions. We conducted hydroponic experiments to explore the role of plant extracts in the process of soil-borne diseases and the mechanism of disease control of faba bean and wheat intercropping. In this experiment, three concentration gradients of faba bean and wheat stem, leaf, and root extracts were added to study the effects of faba bean and wheat extracts on faba bean growth, the physiological resistance of roots, and the growth of Fusarium oxysporum f. sp. fabae (FOF). Faba bean extracts significantly inhibited the growth of faba bean seedlings and the activity of root defense enzymes and significantly stimulated the growth of FOF at high concentrations. Compared with the treatment with faba bean extracts, wheat extracts significantly enhanced the growth of faba bean seedlings, increased the activity of defense enzymes, and inhibited the growth of FOF. Based on these results, we believe that wheat extracts can effectively alleviate the autotoxicity of faba beans and also control the occurrence of faba bean wilt in the field. This provides a theoretical basis for practical intercropping to reduce the damage caused by faba bean wilt.

Recent carbon dioxide (CO2) concentrations promoted higher parthenin concentrations in an invasive Parthenium hysterophorus biotype. Mean concentrations of parthenin, an allelopathic and defensive sesquiterpene lactone, were 49% higher at recent (~400 ppm) than at mid-twentieth-century (~300 ppm) CO2 concentrations, but did not vary in a non-invasive biotype, suggesting that recent increases in atmospheric CO2 may have already altered the chemistry of this destructive weed, potentially contributing to its invasive success. Not only is climate change having an impact on invasive plants through changes in ecosystem, atmospheric carbon may be changing the plants themselves. This analysis finds higher concentrations of parthenin at higher levels of CO2, making an invasive weed more toxic.

Allelopathy is considered as a physiological phenomenon with ecological implications that have stimulatory or inhibitory effects on organisms. The aim of the present study was focused on the effect of Ulva lactuca aqueous extract on growth and some physiological and metabolic aspects as well as gene expression of both Dunaliella salina and Chlorella salina. Linoleic acid ethyl ester; Propanoic acid, 3-(methylthio); Ethanol, 2-(9-octadecenyloxy)-, (Z); Oleic Acid; and 9-Octadecynoic acid, methyl ester were active phytochemical compounds detected from the gas chromatography-mass spectrometry (GC–MS) analysis for the donor species aqueous extract. Data revealed that U. lactuca contains appreciable amounts of Mg, K, Ca, Na and Fe. Results showed a dramatic effect of U. lactuca extracts on growth of both D. salina and C. salina, which significantly increased at low extract concentrations and vice versa. The activity of total antioxidants achieved a gradual increase by increasing the extract concentration. Furthermore, the two recipient algae attained the highest value of protein polymorphism under 10% extract concentration. Sequences of soluble inorganic pyrophosphatases (sPPases) gene showed that, allelochemicals of U. lactuca extract reflected the highest genetic variation in C. salina and D. salina while causing a significant variation in different biochemical parameters.

This study aims to determine the allelopathic activities of six plants that belong to Asteraceae family such as China wedelia (Wedelia chinensis), sunflower (Helianthus annuus), cosmos (Cosmos bipinnatus), marigolds (Tagetes erecta), Mexico sunflower (Tithonia diversifolia), and zinnia (Zinnia elegans) by applying their methanolic extracts on barnyardgrass (Echinochloa crus-galli L.) and mustard green (Brassica juncea) with different concentrations (0.03, 0.1, 0.3, 1 g/ml). Results conducted from the study showed that the aqueous solutions extracted from the above-mentioned plants inhibited shoot and root length of barnyardgrass, mustard green at different intensity ranges in which cosmos aqueous extract gave the strongest impact, says, 23.01 and 97.54% of shoot length inhibition; 56.45 and 93.52% of root length inhibition at 0.3 and 1.0 g/ml respectively for mustard green. In case of barnyradgrass, the same results were also reported, says, 8.5 and 88.15% of shoot length inhibition; 36.35 and 99.99% of root length inhibition at 0.3 and 1.0 g/ml respectively. Total phenolic contents of the fresh plants of cosmos, China wedelia, sunflower, Mexico sunflower, marigolds and zinia were 4.51, 3.96, 1.05, 1.45, 3.61, and 0.99 mg/g, respectively; their total flavonoid contents were 1.58, 0.76, 0.29, 0.39, 0.65, and 0.45 mg/g, respectively. It is obvious that cosmos aqueous extract can be effectively and safely used for biological control of barnyardgrass.

Induced water hyacinth with purple roots (PRWH) exerts a significant inhibitory effect on the growth of blue-green algae. Interestingly, its chemical constituents differ from those of wild-type water hyacinth and have not yet been reported. This study aimed to explore the chemical constituents of PRWH and its bioactive components serving as allelopathic agents against blue-green algae. Phytochemical investigation of the bioactive ethyl acetate fraction of a crude methanol extract from PRWH led to the isolation of 56 compounds, including 11 new phenylphenalene derivatives. The structures of these compounds were elucidated by comprehensive analyses through NMR, HRMS, and X-ray techniques. Bioactivity evaluation against Microcystis aeruginosa indicated that compounds 7, 12, 15, 37, 39, 45, and 47 potently inhibited blue-green algae growth.

With the increasing eutrophication of the aquatic environments, cyanobacteria blooms caused certain damage to the animals and plants in the aquatic environments. In this experiment, two species were selected from six species of submerged macrophytes, the experimental conditions were changed to achieve the best inhibitory effect on Microcystis aeruginosa, and oxidative damage analysis was carried out. The experiment results demonstrated that the inhibition rate of Vallisneria natans and Ceratophyllum demersum was nearly 100% at the concentration of 3 g/L after 15 days of anaerobic soaking extract. In addition, the longer the soaking time of the two submerged macrophytes, the weaker the photosynthesis effect, and the lower the chlorophyll fluorescence parameters, the more obvious the inhibition effect on M. aeruginosa. Lipid peroxidation injury of M. aeruginosa could be reflected by malondialdehyde (MDA) concentration. The MDA concentration in the experimental group was significantly higher than the control group. Results showed that V. natans and C. demersum could induce oxidative damage in M. aeruginosa. It was also observed that the secondary metabolites produced by V. natans were mainly fatty acids (e.g., the oxidative acid was 6.92 w/%, and the successful acid was 9.85 w/%) which inhibited M. aeruginosa in gas chromatography-mass spectrometry (GC-MS). The main secondary metabolites in C. demersum were hydroxyl acids (e.g., the 4-hydroxy-3-methoxyphenylacetic acid was 24.33 w/%), which could inhibit the algae through allelopathy. This study provided reference for submerged macrophytes to inhibit M. aeruginosa under different conditions.

Weeds are one of the most damaging crop pests with estimated annual global damage of around U$ 40 billion. About four million tonnes of pesticide are applied to crops worldwide each year. Currently, there is a growing demand for the use of natural products in agriculture in order to ensure the health of plants and environment. This trend has stimulated research on biodefensives from plant origin. Here, the phytotoxicity of organic extracts and fractions from Piper divaricatum leaves was evaluated on inhibition of emergence and initial growth in lettuce (Lactuca sativa) seedlings. Bioassays were carried out in chamber growth and the detection of compounds classes was performed by Thin Layer Chromatography. Hexane extract completely inhibited emergence and seedling growth at 7.5 and 10.0 mg/mL. Ethanol/methanol extract was highly toxic to seedlings in all concentrations, displaying 100% of inhibition on emergence. Aqueous and alcoholic extracts were submitted to partition and fractions assayed at 2.5 mg/mL. Chloroform fraction of aqueous extract displayed a higher inhibition rate on emergence (100%), however, the fractions obtained from Ethanol/Methanol extract displayed a range of inhibition rate from 33 to 71%, which drastically affected the root and seedling growth. Phytochemical screening using thin layer chromatography combined with chemical revelators was applied. Alkaloids and coumarins were found in chloroform fraction of aqueous extract, both reported as potent inhibitors of emergence, causing changes in cell division, tissue damage, and interfering in cellular transport. Other compounds such as fatty acids and anthracene derivatives were also found in Methanol/Ethanol extract fractions and are reporting for the first time as potential allelochemicals in P. divaricatum.

Green tides have been increasing in frequency and severity in coastal areas in recent years, and thus, the adverse effects of green tides on the environment have attracted much research attention. Allelopathy is one of the most significant effects of green tide algae on the surrounding organisms. In this study, a series of experiments were developed to fully investigate the allelopathic effects of the green tide alga Ulva linza on two common coastal phytoplankton species and to isolate and identify the chemical compositions of the allelochemicals. Our results indicated that the fresh tissue, dry powder, and aqueous extracts all inhibited the population growth of the two experimental phytoplankton species, indicating the occurrence of allelopathy; further analysis of the allelochemicals identified multiple kinds of fatty acids as allelopathic compounds, in which the most abundant ones were hexadecanoic acid; 9Z, 12Z, 15Z-octadecatetrienoic acid; and 9E-octadecenoic acid. Our findings enrich the database for research on allelopathy between marine green tide algae and phytoplankton. Both algae and phytoplankton could increase their own competitive abilities during bloom formation, thereby changing the phytoplankton community structure.

Euphorbia hypericifolia, a non-native herbaceous weedy plant was found to often form disproportionately dense, virtually monospecific stands in the Mount Bambouto Caldera, Cameroon. This observation is within the purview of allelopathy and is attributed to the release of botanicals by non native plants that harm naïve native flora, creating significant problems for agriculture and the environment. We investigated if the invasiveness of E. hypericifolia could be explained by its allelopathic potential at varying concentrations on five indicator plants. The results showed that the leaf, root and stem aqueous extracts of the plant exhibited significant inhibitory effects on the germination, radicle and plumule lengths of Biden pilosa, Amaranthus spinosus, Lactuca sativa, Zea mays and Lycopersicon esculentum at 100 % by 75.0, 69.4, 95.6, 28.0 and 97.2 %, respectively. The leaf extract was the most potent, while the stem extract was the least. The extract of E. hypericifolia was stimulatory (Lower concentrations) and inhibitory to the germination and growth of the test plants and its effect was concentration-dependent with the roots of target plants being more sensitive to the extracts than the plumule. L. esculentum was the most susceptible species to E. hypericifolia extracts while Z. mays was more tolerant than any of the tested plants. Results of total chlorophyll pigment accretion showed declining levels of chlorophyll detected in the leaves of tomato transplants cultivated in the augmented soils with rising dosage of the leaf residue of E. hypericifolia. B. pilosa planted on E. hypericifolia infested soil (EIS) showed very poor emergence recording only 7.5 % after 6 weeks as compared to 83.0 % in non E. hypericifolia infested soil (NIS). Qualitative phytochemical screening indicates E. hypericifolia is rich in secondary metabolites including alkaloids, glycosides, flavonoids, phenolics, tanins, Steriods and saponins. Acetone was the best extractant amongst the solvents used. This study has proven the allelopathic potential of E. hypericifolia and revealed some allelochemicals that may be exploited for the development of bioherbicides and plant growth promotion from natural products.

This research aims to exploit total polyphenol, flavonoid contents, antioxidant and allelopathic activities of leaf extracts, and essential oil compositions from leaves of Acronychia pedunculata (L.) Miq. The results indicated that the leaf extract from ethanol 100% (E100) possessed a lower total polyphenol and flavonoid content than the extract from ethanol 70% (E70). In contrast, the antioxidant activity from E100 extract with IC50=612.9±12.9 μg/ml was stronger than that of E70 extract with IC50=1225.5±6.9 μg/ml. Regarding allelopathic activity, while the extracts from E100 and E70 inhibited root growth of radish, both extracts promoted root growth of lettuce. Especially, E100 extract with 3 mg/ml inhibited root growth of radish up to 48.1%. Moreover, using water solvents, the extracts reduced root growth of both the radish and lettuce. By GC-MS analyses, 33 compounds were identified from A. pedunculata essential oil. The major constituents were caryophyllene (47.09%), humulene (17.28%), α-copaene (4.98%), isoledene (3.59%), and (-)-α-panasinsen (3.51%), other compounds were accounted for lower 3%.

The damage to crops and food commodities by pests and diseases remains a major public health concern. Globally, investigations were carried out to develop harmless natural products from essential oils (EOs) and advances were made to meet users’ acceptance as an alternative to chemical fungicides and insecticides. Recently, many EOs have shown potential results against a wide range of plant pathogens and insect pests, and are thus, attractive substitutes to synthetic chemicals. Remarkably, EOs based commercial pesticides remain lesser in number and this opens several prospects for their claim for use in present agriculture. The present paper provides a summary of the current status and prospects in evaluating the efficiency of the use of EO of Dysphania ambrosioides (L.) Mosyakin & Clemants syn. Chenopodium ambrosioides L. (Mexican tea) belonging to the family Amaranthaceae, in crop protection strategies against plant pathogens and insect pests, considering the opportunities and problems linked with the prospects of sustainable environment-friendly agriculture in the future. In addition, the chemical composition of D. ambrosioides EO from different geographical regions along with the pharmacological application, probable modes of action, and indication for or against the use of this EO as an alternative to chemicals, in several applications have been discussed. The EO of D. ambrosioides possessed potential pharmacological activities, such as antitumor, antiprotozoal, allelopathic, antiviral, immunoregulatory, anti-inflammatory, and antioxidant activities. Most of the chemically characterized EO of D. ambrosioides contained ascaridole, α-terpinene, p-cymene, and caryophyllene oxide as major components, and have shown efficient antibacterial, antifungal, and insecticidal activities against pests and pathogens of economically important crops. Thus, the EO of D. ambrosioides and its major constituents can be utilized as potential botanical pesticides for crop protection after large-scale evaluation.

Impact of macrophyte Lemna trisulca on the growth rate and synthesis of cylindrospermopsin (CYN) by cyanobacterium Raphidiopsis raciborskii was determined. The presence of L. trisulca inhibited the biomass accumulation of the cyanobacterium by 25% compared to the control during co-cultivation. The simultaneous cultivation of these organisms slightly affected the inhibition of macrophyte growth rate by 5.5% compared to the control. However, no morphological changes of L. trisulca after incubation with cyanobacteria were observed. It was also shown that the long-term (35 days) co-cultivation of R. raciborskii and L. trisulca led to a decrease in CYN concentration in media and cyanobacterial cells by 32 and 38%, respectively, compared to the values obtained for independent cultivation of cyanobacterium. Excessive absorption of phosphate ions by L. trisulca from the medium compared to nitrate ions led to a significant increase in the nitrate:phosphate ratio in the media, which inhibits the development of cyanobacterium. The obtained results indicate that L. trisulca in the natural environment may affect the physiology of cyanobacteria. The presented study is the first assessment of the allelopathic interaction of macrophyte and R. raciborskii.