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Wheat (Triticum aestivum L.) is an important cereal crop in Pakistan which is suffering from major grain production loss because of weed infestations. Control of weeds by herbicides is a primary weed management tool in wheat crop which can be detrimental to the environment and grain produce. Development of an efficient and eco-friendly alternate to the herbicidal weed control, testing the effectiveness of cultural weed control (crop row orientation, selected wheat genotypes and hand weeding) and plants water extracts was undertaken for weed control in wheat. An experiment was run under field conditions in winter season in 2016–2017 and in 2017–2018 in Khyber Pakhtunkhwa Province, Pakistan. The repeated experiment was each time undertaken using a randomized complete block design with a double split plot arrangements at the New Developmental Farm, University of Agriculture, Peshawar, Pakistan. The crop row orientations used were assigned to the main plots. The wheat genotypes used were assigned to the sub-plots. The allelopathic water extracts and hand weeding were assigned to the sub-sub plots. The averaged mean values for row orientations of both the years revealed lowest weed density (95.7 weeds m−2), highest grains per spike (47.3), 1000 grains weight (44.7 g) in north to south row orientation. The averaged mean values of weed density (101.6 weeds m−2), grains per spike (48.2), 1000 grains weight (45.9 g), crude protein content (12.793%), crude fat content (1.533%) and ash content (1.586%) were greater for the wheat genotype Pirsabaq-2013 and Atta-Habib-2010. Water extract of S. halepense, P. hysterophorus, H. annuus and hand weeding showed significantly lower weed density (84.0 to 93.3), grains per spike (50.9 to 48.3), 1000 grains weight (48.3 to 46.2 g), grains protein content (12.280 to 12.209%), grains crude fat content (1.471 to 1.464%) and grains ash content (1.523 to 1.515%). Interaction effect of different tested weed control treatments i.e. N-S × Pirsabaq-2013 and Atta-Habib-2010 × water extract of S. halepense, P. hysterophorus and H. annuus were found to show further reduction in weed density and enhance grains per spike and grains nutrition contributing parameters. Our results show that sowing wheat genotypes Pirsabaq-2013 and Atta-Habib-2010 in north-to-south row orientation, and application of water extract of S. halepense, P. hysterophorus, H. annuus can give an effective weed management and increased quality grain yield of wheat.

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.

Invasive plant species pose a serious threat to agricultural yield, although how the threat varies with the distance of crops from invasive plants remains unclear. Therefore, utilizing this viewpoint, objectives were formulated to quantify differences in the native vegetation and performance of crops growing near A. adenophora–invaded (treatment plots) and uninvaded ridges (control plots) in the terraced agricultural fields of Kumaun Central Himalaya. Morphological and yield parameters of two crops, viz. rice (Oryza sativa L.) and soybean (Glycine max L.), were assessed systematically by laying parallel transects from the ridge of the field up to 5 m towards the centre of the field in three equal distance intervals of 1 m in the order: 0–1 m, 2–3 m, and 4–5 m. Crofton weed showed 95–100% crown cover throughout invaded ridges/risers of terraced fields, with stem densities of 134–208 ind. m−2 and an average basal area of 0.15 cm2. The total mean density of herbs (other than A. adenophora) in invaded ridges/risers decreased by 38–85% compared to uninvaded ridges, but species richness increased by 31–37%. Soil nutrient availability was high across invaded ridges/risers as well as crop fields. The average irradiance level near uninvaded ridges was 19.6 ± 1.80%, and near invaded ridges, it was 1.8 ± 0.31%. Compared to straw, root, and grain yields obtained at the farthest distance, the yield of rice near uninvaded ridges was reduced by 27%, 19%, and 33%, while near invaded ridges, it was reduced by 37%, 39%, and 43%, respectively; the yield of soybean near uninvaded ridges declined by 62%, 66%, and 42%, while near invaded ridges, it decreased by 59%, 69%, and 47%, respectively. Compared to the values obtained at the farthest distance, the harvest index (HI) of rice near ridges was reduced by 7% and 13%, while the HI of soybean increased by 15 and 10% across uninvaded and invaded field ridges, respectively. The findings indicated that the Crofton weed could suppress field crops and could form a single dominant population in the invaded area, causing a serious threat to the plant community, its diversity, and the yield of the native agroecosystem in the foreseeable future if timely management actions would not be taken.

Weed management is essential for sustainable crop production in all cropping systems. The use of herbicides is causing the problems of herbicide resistant weeds and environmental pollution. Plant-released phytotoxins have ability to promote or inhibit the germination and seedling growth of surrounding crops and weeds. Therefore, it is imperative to identify plant species having the herbicidal potential to use as more safe and sustainable weed management approach. The present study was planned in 2018 to investigate the germination and seedling growth of Daucus carota and Medicago polymorpha influenced by the root extract of Polygonum bistorta and fruit extract of Terminalia chebula. Different concentrations of aqueous extract (0, 2.5, 5, 10, 20, 40 and 80%) significantly reduced the germination and seedling growth of target species. Results of these experiments revealed that thefruit extract of T. chebula was more phytotoxic as compared to root extract of P. bistorta regarding seedling growth of weed. However, fruit extract of T. chebula having 80% concentration fully inhibit the germination of D. carota and M. polymorpha. One the bases of these finding it was concluded that the fruit extract of T. chebula and root extract of P. bistorta have comparatively more active substances with ability to suppress germination and growth of plants which could be exploited as prospective source of bio-herbicides. O manejo de ervas daninhas é essencial para a produção agrícola sustentável em todos os sistemas de cultivo. O uso de herbicidas está causando problemas de ervas daninhas resistentes a herbicidas e poluição ambiental. As fitotoxinas liberadas pelas plantas têm a capacidade de promover ou inibir a germinação e o crescimento das mudas de culturas e ervas daninhas circundantes. Portanto, é imperativo identificar espécies de plantas com potencial herbicida para uso como abordagem de manejo de ervas daninhas mais segura e sustentável. O presente estudo teve como objetivo investigar a germinação e o crescimento de plântulas de Daucus carrota e Medicago polymorphaas influenciados pelo extrato de raiz de Polygonum bistorta e extrato de fruto de Terminalia chebula. Diferentes concentrações de extrato aquoso (0, 2, 5, 5, 10, 20, 40 e 80%) reduziram significativamente a germinação e o crescimento de plântulas das espécies-alvo. Os resultados desses experimentos revelaram que o extrato do fruto de T. chebula foi mais fitotóxico do que o extrato da raiz de P. bistorta em relação ao crescimento de mudas de plantas daninhas. No entanto, o extrato de frutos de T. chebula com concentração de 80% inibe totalmente a germinação de D. carrota e M. polymorpha. Uma das bases deste achado concluiu-se que o extrato do fruto de T. chebula e o extrato da raiz de P. bistorta possuem comparativamente mais substâncias ativas com capacidade de suprimir a germinação e o crescimento das plantas, o que poderia ser explorado como fonte potencial de bio-herbicidas.

This study was conducted to evaluates the allelopathic potential of Peganum harmala L. (Zygophyllaceae) on the growth of Cynodon dactylon L. (Poaceae). Seeds, stems, and a mixture of (seeds and stems) aqueous extracts of P. harmala plants were applied as a foliar application to three weeks old seedlings of Cynodon dactylon weeds. The result indicated that the application of aqueous extracts of different plant parts of P. harmala caused a significant reduction in growth traits of Cynodon dactylon including plant height, number of branches, number of leaves, and plant weight. Moreover, the result revealed that the Inhibitory effect of P. harmala aqueous extract on Cynodon dactylon L was more pronounced in plant height and number of leave plant-1 traits. In addition, the results illustrated that among the different P. harmala plant parts used in this study, seeds extract was the most toxic and caused the greatest negative effect on growth traits of Cynodon dactylon. According to the results, the degree of toxicity of different P. harmala plant parts can be arranged in the following order: seeds > mixture > stems. The results of this study concluded that the use of Peganum harmala L plant has the potential to be developed further as a bio-herbicide system to control weed such as Cynodon dactylon L.

Selecting wheat varieties with allelopathic potential or high competitiveness against weeds is a sustainable solution for organic farming to eliminate the use of synthetic herbicides. Wheat is one of the most economically important crops. This study focuses on screening the allelopathic or competitive potential of four wheat cultivars, Maurizio, NS 40S, Adesso and Element, on two weeds of interest due to acquired herbicide resistance, Portulaca oleracea and Lolium rigidum, through germination and growth bioassays and the identification and quantification of benzoxazinoids (BXZs) and polyphenols (phenolic acids and flavonoids).

Eight different compounds inspired by benzoxazinones were synthesized in one simple step with easy purification. These compounds have a sulfur atom instead of the oxygen atom present in benzoxazinones. Furthermore, a new derivative obtained by a Rutkauskas–Beresnevicius reaction was synthesized. These compounds were evaluated in vitro to assess their phytotoxicity in plant cells by the elongation of wheat coleoptiles. The novel compounds showed higher inhibition than benzoxazinones and the positive control, especially at higher concentrations (1000 and 300 μM). Benzoxazinones have been described as histidine deacetylase inhibitors and we therefore evaluated the effect of 1.4-benzothiazinones and 1.4-benzoxathianones against HDA6, one of the most important enzymes of the family, in silico by molecular docking and molecular dynamics. In vitro studies against Echinochloa crus-galli, Lolium rigidum and Portulaca oleracea weeds gave interesting results against the growth of the roots for both monocots and dicots. Specifically, the inhibition was more pronounced against dicots, as in the case of common purslane, whose inhibition at a concentration of 1000 μM was similar to that of the classical herbicide employed as a positive control. Higher inhibition was obtained when an aliphatic group was present in the C2 position of 1.4-benzothiazinones.

Screening suitable allelopathic crops and crop genotypes that are competitive with weeds can be a sustainable weed control strategy to reduce the massive use of herbicides. In this study, three accessions of common buckwheat Fagopyrum esculentum Moench. (Gema, Kora, and Eva) and one of Tartary buckwheat Fagopyrum tataricum Gaertn. (PI481671) were screened against the germination and growth of the herbicide-resistant weeds Lolium rigidum Gaud. and Portulaca oleracea L. The chemical profile of the four buckwheat accessions was characterised in their shoots, roots, and root exudates in order to know more about their ability to sustainably manage weeds and the relation of this ability with the polyphenol accumulation and exudation from buckwheat plants. Our results show that different buckwheat genotypes may have different capacities to produce and exude several types of specialized metabolites, which lead to a wide range of allelopathic and defence functions in the agroecosystem to sustainably manage the growing weeds in their vicinity. The ability of the different buckwheat accessions to suppress weeds was accession-dependent without differences between species, as the common (Eva, Gema, and Kora) and Tartary (PI481671) accessions did not show any species-dependent pattern in their ability to control the germination and growth of the target weeds. Finally, Gema appeared to be the most promising accession to be evaluated in organic farming due to its capacity to sustainably control target weeds while stimulating the root growth of buckwheat plants.

Notorious invasive Bohemian knotweed Reynoutria × bohemica Chrtek et Chrtková is a hybrid of two species, Reynoutria japonica Houtt. and Reynoutria sachalinensis (F. S. Petrop.) Nakai in T. Mori which spontaneously developed in Europe, outside the natural distribution of its parental species. Its success could potentially lie in its allelopathic activity, which was confirmed in a number of experiments conducted with the leaf and root exudates, testing their effect on the germination and growth of various test plants. Here, we tested its allelopathic potential using different concentrations of leaf exudates on two test plants, Triticum aestivum L. and Sinapis alba L., in Petri dishes and pots with soil and by growing test plants in the soil sampled in knotweed stands on the edges of stands and outside of stands. Tests in Petri dishes and pots with soil to which leaf exudates were added have shown a decrease in germination and growth in comparison to the control, hence confirming the allelopathic effect. However, this was not confirmed in a test with in situ soil samples, where no statistically significant differences were observed, neither in the growth of test plants nor in the chemical characteristics (pH, soil organic matter, humus content) of the soil. Therefore, the persistence of Bohemian knotweed at already invaded sites could be attributed to its efficient use of resources (light and nutrients) through which it outcompetes native plants.

In Southeastern Nigeria, weeds such as Chromolaena odorata, Ageratum conyzoides, Eleusine indica, Tridax procumbens and Euphorbia hirta thrive. The decaying remnants of these weeds left on or in the soil have been found to contain a variety of chemical compounds. The effect of aqueous leaf extracts of these weeds on Zea mays seed germination and growth was investigated. Results of this study showed that plant species and their concentrations had a significant effect (p Euphorbia hirta (26.16%) > Ageratum conyzoides (23.45%) > Eleusine indica (22.42%) and Chronolaena odorata (18.73%). Eleucine indica had more inhibitory effect on shoot length (42.83%), seedling length (41.70%) and seedling vigour index (51.79%) of Zea mays. This was compared to aqueous leaf extract of Chromolaena odorata, Ageratum conyzoides, Tridax procumbens and Euphorbia hirta. The results suggest that potential allelopathic substances produced by studied weed species may hinder germination and growth of Zea mays.

Lantana camara L., introduced as an ornamental plant in India a century ago, has invaded over 40% forest lands today. It is also actively spreading through Indian states in agricultural farms and interfering with the productivity of several food crops. The detrimental effect of L. camara has been recognised on various plants, however, to the best of our knowledge, published studies have not explored its effect on an important cash crop of India i.e., Arachis hypogea. Hence, in the present study, the allelopathic effect of aqueous extracts of L. camara on germination and chlorophyll, protein profile of peanut seeds was determined. It was observed that 1% L. camara aqueous extracts has negligible effect on seed germination, and chlorophyll a and protein content of germinated A. hypogea seeds, but significantly affected total chlorophyll and chlorophyll b concentration. At higher concentrations (1% and 3%), the allelopathic effect of L. camara aqueous extracts was clearly evident on all three growth parameters of peanuts evaluated in this study. In conclusion, our study reports that L. camara may prove to be a much bigger challenge in management of peanut productivity as compared to other invasive weeds, if proper preventive measures are not recognized immediately.

Barley (Hordeum vulgare) is one of the most widely cultivated crops for feedstock and beer production, whereas lupins (Lupinus spp.) are grown as fodder and their seeds are a source of protein. Both species produce the allelopathic alkaloids gramine and hordenine. These plant-specialized metabolites may be of economic interest for crop protection, depending on their tissue distribution. However, in high concentrations they pose a health risk to humans and animals that feed on them. This study was carried out to develop and validate a new method for monitoring these alkaloids and their related metabolites using fluorescence detection. Separation was performed on an HSS T3 column using slightly acidified water-acetonitrile eluents. Calibration plots expressed linearity over the range 0.09–100 pmol/µL for gramine. The accuracy and precision ranged from 97.8 to 123.4%

Evaluation of the allelopathy relationship between different crops is a sensible strategy fallowing the correct use of positive effects and to avoid the disadvantageous effects among plants. This study aimed to detect the allelopathic effect of aqueous extracts of sunflower (Helianthus annuus L.), grown in a boreal climatic zone, on the growth, subsequent development, and physiological traits of pea (Pisum sativum L.). Three factors have been studied: donor plant fertilization (unfertilized and fertilized), aqueous extracts from donor plant organs (leaves and stems (L+S), heads (H) and roots (R)); four concentrations of extracts (0%, 25%, 50% and 75%). The aqueous extracts from fertilized sunflower donor plant at 25% and 50% concentration acted as potential biostimulants that stimulated pea seed germination (SG), whereas L+S and R extracts at 75% concentration from unfertilized donor plant inhibited SG, at 4 days after sowing. The aqueous extracts demonstrated a stimulating effect on above-ground and root dry mass, compared to the control. The concentration of extracts demonstrated a significant inhibitory effect on SPAD. R extract revealed the strongest allelopathic effect on physiological traits of pea. L+S and H extracts at 25% concentration had stimulating effects, while 50% and 75% concentrations showed inhibiting effects on the photosynthetic rate. The water use efficiency, stomatal conductance, and stomatal limitation were inhibited, whereas, the transpiration rate, photosynthetic water use efficiency and intercellular CO2 concentration were stimulated, with an increasing of extract concentrations, comparatively to the control.

Background: Roadside grass cuttings are currently considered a waste product due to their association with road sweepings as contaminated waste, therefore, their potential as a biofertilizer is understudied. Aim: This study aimed to determine whether grass liquid fraction (GLF) collected from a roadside verge in Maldegem, Belgium, and pressed using a screw press was suitable as a biofertilizer. Methods: The characterization of the heavy metal content of the GLF was conducted using an ICP-OES. From May to September 2019, a pot experiment was set up using a randomized block design to compare tomato plant growth, yield, and nutrition for GLF-treated plants to two commercial fertilizers and tap water as a control. Results: The heavy metal content of the GLF was below the maximum permissible concentrations (MPCs) for organic fertilizers as set out by the European Comission fertilizer regulation 1069/2009 and 1107/2009 (European Comission, 2019). However, despite having a fairly well-balanced nutrient content (0.1% N, 0.04% P2O5, and 0.2% K2O), GLF had a negative effect on the growth, root weight, and yield of the tomato plants, killing six out of ten plants. GLF also promoted mold growth in the soil of some plants. Since the GLF was uncontaminated, heavy metal toxicity did not cause the negative effect. Conclusions: Previous research showed that liquid fractions from some plants negatively affect the growth of others due to allelopathic chemicals; this, together with the stimulation of fungal growth, could have caused the negative effects observed. Future experiments will investigate the herbicidal property of GLF and possible treatments to potentially recover the nutrients contained within the GLF for application as a biofertilizer.

To understand the insect resistance mechanism of the larch, Larix olgensis, in a mixed forest, larch (Larix olgensis) seedlings and ashtree (Fraxinus mandshurica) seedlings were planted with mixed banding forests in the proportion of 1:1 (BMF1:1), 3:3 (BMF3:3) and 5:5 (BMF5:5), in pots and in the field. One year later, the content of secondary metabolites in the needles of each larch treatment were tested with an ultraviolet spectrophotometer. The results showed that the allelopathic effect of F. mandshuricas (ashtree) on L. olgensis (larch) could increase the content of secondary metabolites in larch needles. It was found that the flavonoid content in the needles of BMF5:5 was higher than that in the needles of BMF1:1 and BMF3:3 (p < 0.05). The tannin content in the needles of FBMF3:3 and FBMF5:5 was significantly higher than that of FBMF1:1, whereas the tannin content in the needles of PBMF3:3 reached 1.27 mg/g, which was the highest (p < 0.05). The lignin content in the needles of FBMF3:3 reached 2.27 mg/g, which was significantly more increased than that in the control group in a dose-dependent manner, while that in the needles of PBMF3:3 and PBMF5:5 was higher than that in the needles of PBMF1:1 (p < 0.05). The tannin and lignin content in the needles of FBMF was higher than that of PBMF. However, there was no difference in the content of flavonoids in the needles of FBMF and PBMF. These results suggest that banding mixed larches and ashtrees can significantly increase the content of secondary metabolites (phenolic compounds) in the needles of L. olgensis and improve its chemical defense, and the allelopathic effect of ashtrees on larches is related to the mixed proportion. Thus, the effect of mixed banding forests in the proportion of 3:3 and 5:5 is better.

Improving the efficacy of bioherbicides to overcome weed resistance phenomena is one of the main challenges within agriculture. Organic encapsulation is attracting attention as an alternative and eco-friendly tool, mainly in organic farming. In this research, for the first time, across three different wheat field trials, we tested the weed-suppressive ability (WSA) and crop response of a nanoparticle formulation of DiS-NH2 (2,2′-disulfanediyldianiline) applied as post-emergence foliar herbicide, both at standard (T1, 0.75 g m−2) and double dosages (T2, 1.5 g m−2), compared to no weeding (NC) and chemical weed control (PC). Averaged over locations, T2 showed the highest WSA (51.3%), followed by T1 (40.9%) and PC (33.5%). T2 induced also a wheat grain yield and a plant height comparable to PC (3185 kg ha−1 and 67.7 cm vs. 3153 kg ha−1 and 67.7 cm, respectively). Moreover, compared to NC, T2 increased the number of spikes m−2 (+19%) and the number of kernel spikes−1 (+26%). Similar results were observed for T1, which caused also a significant reduction in non-vitreous kernels (‒40%). These promising results suggest that the nanoencapsulated DiS-NH2 could be a good candidate as a post-emergence bioherbicide in wheat crop production.

Allelopathy, i.e. plant-plant inhibition via the release of secondary metabolites into the environment, has potential for the management of weeds by circumventing herbicide resistance. However, mechanisms underpinning allelopathy are notoriously difficult to elucidate, hindering real-world application either in the form of commercial bioherbicides or allelopathic crops. Such limited application is exemplified by evidence of limited knowledge of the potential benefits of allelopathy among end-users. Here, we examine potential applications of this phenomenon, paying attention to novel approaches and influential factors requiring greater consideration, with the intention of improving the reputation and uptake of allelopathy. Avenues to facilitate more effective allelochemical discovery are also considered, with a view to stimulating the identification of new compounds and allelopathic species. Synthesis and Applications: We conclude that tackling increasing weed pressure on agricultural productivity would benefit from greater integration of the phenomenon of allelopathy, which in turn would be greatly served by a multi-disciplinary and exhaustive approach, not just through more effective isolation of the interactions involved, but through greater consideration of factors which may influence them in the field, facilitating optimisation of their benefits for weed management.

Domoic acid (DA) is a natural occurring marine biotoxin. Oxidative stress generation due to DA exposure was reported in animals, but little is known on the phytoplankton community. The aim of this work was to verify whether exposure to DA in the marine diatom Phaeodactylum tricornutum favors reactive oxygen species (ROS) generation in the intracellular environment modifying its antioxidant capacity. Active species production, non-enzymatic antioxidant content, and antioxidant enzyme activities over the three growth phases of P. tricornutum exposed to 64 µM DA were evaluated. Results obtained in exponential growing cells showed a time-depending seven-fold increase in the 2′,7′ dichlorofluorescein diacetate dye oxidation rate. Superoxide dismutase and catalase activities showed a two-fold increase, and glutathione related enzymes activities were also significantly increased in treated diatoms as compared to controls. However, glutathione and ascorbate contents significantly decreased after incubation of the cells with DA. Similar effects were observed in latent and stationary phases of cell development. These results showed that DA could cause a severe oxidant-dependent impact on a non-toxic algae.

Invasive species employ competitive strategies such as releasing allelopathic chemicals into the environment that negatively impact native species. Decomposing Amur honeysuckle (Lonicera maackii) leaves leach various allelopathic phenolics into the soil, decreasing the vigor of several native species. Notable differences in the net negative impacts of L. maackii metabolites on target species were argued to depend on soil properties, the microbiome, the proximity to the allelochemical source, the allelochemical concentration, or environmental conditions. This study is the first to address the role of target species’ metabolic properties in determining their net sensitivity to allelopathic inhibition by L. maackii. Gibberellic acid (GA3) is a critical regulator of seed germination and early development. We hypothesized that GA3 levels might affect the target sensitivity to allelopathic inhibitors and evaluated differences in the response of a standard (control, Rbr), a GA3-overproducing (ein), and a GA3-deficient (ros) Brassica rapa variety to L. maackii allelochemicals. Our results demonstrate that high GA3 concentrations substantially alleviate the inhibitory effects of L. maackii allelochemicals. A better understanding of the importance of target species’ metabolic properties in their responses to allelochemicals will contribute to developing novel invasive species control and biodiversity conservation protocols and may contribute to applications in agriculture.

Allelopathy is a frequent interaction between species in Mediterranean ecosystems and it is also one of the proposed strategies to explain the colonisation of invasive species. To confirm the importance of allelopathic potential as a mechanism of invasion of non-native species in Mediterranean ecosystems, it would be advisable to compare the allelopathic effects of non-native plants with native plants on the same target species and thus avoid overestimating the role of phytotoxicity in the invasion process. The main objective of this work was to compare the allelopathic activity of native species typical of Mediterranean ecosystems, classified as allelopathic, with the allelopathic activity of non-native species that may have an invasive character in these ecosystems. To this end, we selected three native species (Cistus ladanifer, Pistacia lentiscus, and Pistacia terebithus) and three non-native species (Acacia dealbata, Acer negundo, and Salix babylonica), and we analysed their effect on the species Lactuca sativa and the native species Lavandula stoechas and Echium plantagineum. The tests on L. sativa showed that all species have allelopathic activity. The tests on L. stoechas and E. plantagineum revealed that P. terebinthus exerted the greatest effect, being the only species that maintained an inhibitory effect at extract concentrations of 50% and 25% in all the analysed parameters, except in germination and cotyledon emergence for E. plantagineum. There were no significant differences in the effect on germination between non-native and native species, although significant differences were found in the effect on root size in the three analysed concentrations, with the native species producing greater inhibition. In conclusion, these species exert a negative effect on the selected native target species, but the negative effect of the native species is greater than that of the non-native species. These results indicate that it is important to compare the allelopathic effects of invasive and native species to correctly estimate the phytotoxic effect of invasive species on their invasiveness

Natural products have been postulated as an alternative to the use of synthetic herbicides in pest control. The latter compounds have caused numerous problems and these include the appearance of resistance to such herbicides. Aminophenoxazinones are natural products that have shown multiple biological activities, such as pharmacological or phytotoxic effects. In the case of phytotoxicity, the mode of action of aminophenoxazinones has not been widely exploited in agriculture and resistant weeds have not been reported to date. This fact makes aminophenoxazinones promising candidates in the development of herbicides. In the study reported here, seven aminophenoxazinone derivatives have been synthesized and their phytotoxicity has been evaluated on wheat coleoptiles and two important agricultural weeds (Lolium rigidum and Portulaca oleracea). Several derivatives have shown phytotoxic activity, which is similar to the positive control pendimethalin, and even higher in some cases at the highest concentrations tested. The most affected parameter in weeds was root length and the most susceptible weed was P. oleracea. Compound 2, in which nitrogen atoms are present in the heterocycles, was the most active and this was followed by compound 1. Modifications at C-8 led to a reduced activity, with the exception of the nitro compound on the root length of P. oleracea. However, the phytotoxicity also increased on introducing an iodo-substituent at C-4. The results highlight aminophenoxazinones as promising candidates in the development of natural herbicides.

The presence of monodominant vegetative formations almost exclusively composed of Acuri palm trees (Attalea phalerata) stands out in some regions of the Pantanal Sul-Mato-Grossense. These formations are generally associated with anthropic, edaphic and/or hydrological factors. However, little is known about the effect of allelopathy on the formation and maintenance of these areas. Herein, we investigated the chemical composition of A. phalerata aqueous leaf extract and the potential allelopathic effects on germination and growth of target L. sativa, L. esculentum and S. obtusifolia species. Thus, extracts at concentrations of 0, 2.5, 5, 10, 15, and 20% were used for germination and growth bioassays with a completely randomised design in a germination chamber and greenhouse. The results showed that the A. phalerata extracts negatively affected the germination speed index and mean germination time of the target species and positively affected seedling length under controlled conditions and were also stimulated in the greenhouse. Thus, the formation of Acurizals can be related to the presence of secondary metabolites in the leaves, in addition to other environmental factors. Resumo No Pantanal Sul-Mato-Grossense se destaca, em determinadas regiões, a presença de formações vegetacionais monodominantes, compostas quase que exclusivamente por uma espécie de palmeira, o Acuri (Attalea phalerata). Normalmente estas formações estão associadas a fatores antrópicos, edáficos e/ou hidrológicos. Porém pouco se sabe sobre o efeito da alelopatia na formação e manutenção destas áreas. Desta maneira, objetivou-se estudar a composição química dos extratos aquosos das folhas de A. phalerata e seus possíveis efeitos alelopáticos na germinação e crescimento das espécies-alvo, alface, tomate e fedegoso. Para os bioensaios de germinação e crescimento, foram utilizados extratos nas concentrações de 0, 2,5, 5, 10, 15 e 20%, com delineamento inteiramente casualizado, em câmara de germinação e casa de vegetação. Os resultados demostraram que em condições controladas (câmara de germinação), os extratos de A. phalerata afetaram negativamente o índice de velocidade de germinação e o tempo médio de geminação das espécies-alvo e positivamente, o comprimento das plântulas, que também foram estimuladas em casa de vegetação, indicando a presença de fitormônios. Desta maneira, a formação de Acurizais pode estar relacionada à presença de metabolitos secundários nas folhas, além de outros fatores ambientais.

The chemical investigation of Eugenia pyriformis, popularly known as uvaia, led to the isolation of three compounds, the triterpene β-amiryn (1) and the porphyrin derivatives pheophytin a (2) and b (3). Their structures were assigned based on spectroscopic NMR analysis, as well as by comparison with literature data. Most of the compounds found in the essential oil from leaves are terpenes derivatives, such as ο-cymene; 1,8-cineol; linalol, terpinen-4-ol; 2-carene. Flavonoids, steroids and/or terpenoids, lactones, saponins, tannins and fixed acids were detected in both the leaf and stem crude extracts and fractions generated from the Brazilian E. pyriformis plant. According to the results of the DPPH assay, the ethyl acetate fraction of the leaf extract showed higher antioxidant activity than the other samples tested. In the phosphomolybdenum complex assay, the crude ethanol extract of the leaf and stem, and the ethyl acetate fraction of the leaf, showed a higher antioxidant capacity than rutin. It was observed that the chloroform and ethyl acetate fractions of the leaf, and the hexane, ethyl acetate and hydroalcoholic fractions of the stem were toxic to Artemia salina brine shrimp with LD50 < 1.0 µg/mL. The hexane fraction of the stem was also allelopathic in inhibiting the radicle growth of Lactuca sativa seeds. These results adding contributions to chemical and biological studies of this medicinal species.

This study determined the influence of cattle manure compost, chemical fertilizers, and mulch on the growth of weeds, sugar content, and growth of sweet sorghum (Sorghum bicolor (L.) Moench). The inhibitory potential of root exudates from two sweet sorghum cultivars (A; K1151 and B; K3351) was also evaluated. Chemical fertilizers increased the plant height, stem weight, biomass production, and sugar content of sweet sorghum. The total phenolic contents in the root exudates were 22.93 mg gallic acid equivalent per g dry weight (GAE/g DW) for cultivar A and 15.66 mg GAE/g DW for cultivar B. The total flavonoid contents in the root exudates were 14.77 mg rutin equivalent per g dry weight (RE/g DW) for cultivar A and 12.44 mg RE/g DW for cultivar B. The leaf extracts contained a higher amount of total phenolics and flavonoids than that of the stem and root. The inhibitory level of the root exudates from cultivar A on the seed germination and shoot growth of lettuce was greater than for cultivar B. Six phenolic acids, including protocatechuic, p-hydroxybenzoic, syringic, sinapic, p-coumaric, and benzoic acids, were detected from root exudates, root, stem, and leaf of both cultivars. The amount of p-coumaric acid in root exudates was greater than the other plant parts; however, protocatechuic acid was only found in the root exudates. p-Coumaric and protocatechuic acids may play an important role in the allelopathy of sweet sorghum to help reduce the dependence on synthetic herbicides in agricultural practice. This study indicates that cultivation methods and fertilization are important to increase both agronomic and economic values of sweet sorghum in agricultural production.

In this article, we propose to explore the chemical interaction between Pseudosphinx tetrio L. and Allamanda cathartica L. using different analytical methods, including an innovative electrochemical approach (called electrochemical ecology) and multivariate analysis, and we investigate the potential antimicrobial effects (antibacterial and antifungal activities) of this interaction in order to gain a better understanding of their specific interaction. The analytical study presents a similar chemical profile between the leaves of healthy and herbivorous A. cathartica and the excretions of the caterpillars. The similar analytical profile of the leaves of A. cathartica and the excretions of P. tetrio, and the difference with the caterpillar bodies, suggests a selective excretion of compounds by the caterpillar. The measured antimicrobial activities support the physicochemical tests. The natural products found selectively in the excretions (rather than in the body) could explain the ability of P. tetrio to feed on this toxic Apocynaceae species.

The consumption of fresh vegetables has been consistently associated with numerous health benefits. However, several factors (such as allelochemicals) influence yield, quality, and metabolites, which inevitably affect the fruit quality and health benefits. The present study was conducted to investigate the yield, quality, metabolic responses, and potential toxicity of Cucumis sativus grown in juglone-containing soils. For the treatments, pure juglone (100 µM, 1 mM) and walnut leaf extracts (100 µM) in soil concentrations found in walnut orchards were used. A total of 36 phenolic compounds were identified and quantified in fruits, leaves, and roots using a mass spectrometer coupled with high-performance liquid chromatography. We concluded that juglone at a concentration of 100 µM or walnut leaf extract at the same juglone concentration does not affect the yield of C. sativus, while juglone at a concentration of 1 mM strongly affects it. In the case of juglone, juglone itself was found only in the roots of C. sativus, but not in the leaves or fruits, so C. sativus fruits are considered safe for cultivation in juglone-containing soils. However, this could prove problematic if the plants grown are tubers or root vegetables. The data suggest that juglone itself inhibits secondary metabolism in the plant, making it more susceptible to stress and pathogen attacks.

ROS (Reactive Oxygen Species) production is a usual plant reaction to environmental stresses such as allelopathy. Plants possess antioxidant enzymes to scavenge cells and resist against the ROS. This study was conducted to evaluate changes in antioxidant enzymes (CAT, GPX, APX) in radish seedlings in response to allelopathic effect of safflower root and shoot residues grown under normal irrigation and drought stress. Safflower allelopathic effect led to an increase in antioxidant enzymes activities. GPX activity increased more than CAT and APX. Radish seedlings exposed to safflower residue grown under drought stress showed more antioxidant enzymes activities. Root residues enhanced the activities of antioxidant enzymes greater than shoot. Seedlings exposed to root residues grown under drought stress had the highest level of antioxidant enzymes activities.

The aim of the paper was to evaluate the influence of water stress i.e., different net irrigation water on the allelopathic potential of petunia (Petunia hybrida L.). Water extracts were prepared from aboveground biomass of petunias grown at different net irrigation water (51.5 mm, 91.5 mm and 132.5 mm) in three concentrations (1%, 2.5% and 5%). The experiment was performed under controlled laboratory conditions in Petri dishes and the allelopathic potential of petunia water extracts was assessed by measuring seed germination, root and shoot length, and fresh weight of radish seedlings. The results of the experiment showed a statistically significant allelopathic effect of petunia water extracts on all the measured parameters. The allelopathic potential largely depended on the extract concentration. Petunia extracts of higher concentrations showed a greater negative effect and reduced germination, shoot and root length, and fresh weight of seedlings up to 79.9%, 93.4%, 83.1% and 69.5%, respectively. Positive effect was determined on shoot length and fresh weight of radish seedlings with 1% concentration extracts. As a rule, water stress i.e., net irrigation water did not have a significant effect on the allelopathic potential of petunia. The exception was recorded with the highest extract concentration on the shoot length of seedlings where extracts from petunias grown at 51.5 mm had greater inhibitory effect compared to extracts from petunias grown at 91.5 and 132.5 mm.

Medicinal and aromatic plants with allelopathic effect are a potential source of natural herbicides. The experiment was conducted in order to assess herbicidal potential of meadow sage (Salvia pratensis L.) on germination and growth of weed species velvetleaf (Abutilon theophrasti Med.) and common corn-cockle (Agrostemma githago L.). Water extracts from S. pratensis dry biomass in different concentrations were evaluated under controlled laboratory conditions in Petri dish bioassay. Herbicidal effect of S. pratensis extracts depended on the extract concentration and weed species. In general, higher concentrations of water extract showed greater negative effect on germination and growth parameters of weed seedlings. A. githago had greater sensitivity to S. pratensis extracts with reductions in germination and seedlings growth up to 100% in treatments with 7.5% and 10% extract concentrations. A. theophrasti germination was not affected by water extracts, however, substantial reductions of root and shoot length as well as fresh weight of seedlings were recorded. S. pratensis proved as promising plant species for further studies., Ljekovite i aromatične biljke s alelopatskim djelovanjem potencijalni su izvor prirodnih herbicida. Pokus je proveden kako bi se utvrdio herbicidni potencijal livadne kadulje (Salvia pratensis L.) na klijanje i rast korovnih vrsta Teofrastov mračnjak (Abutilon theophrasti Med.) i poljski kukolj (Agrostemma githago L.). Vodeni ekstrakti od suhe biomase S. pratensis u različitim koncentracijama procijenjeni su u kontroliranim laboratorijskim uvjetima u pokusu u Petrijevim zdjelicama. Herbicidni utjecaj ekstrakata S. pratensis ovisio je o koncentraciji ekstrakta i vrsti korova. Općenito, više koncentracije vodenog ekstrakta pokazale su veći negativan učinak na klijavost i parametre rasta klijanaca korova. Vrsta A. githago pokazala je veću osjetljivost na ekstrakte S. pratensis sa smanjenjem klijavosti i rasta klijanaca do 100 % u tretmanima s koncentracijama ekstrakta od 7,5 % i 10 %. Vodeni ekstrakti nisu imali utjecaja na klijavost A. theophrasti, ali je zabilježeno značajno smanjenje duljine korijena i izdanaka kao i svježe mase klijanaca. S. pratensis pokazala se kao perspektivna biljna vrsta za daljnja istraživanja.

Proso millet (Panicum miliaceum) is an important source of energy and protein for people and as well animals. At present, there are practically no data available on the allelopathic effect of proso millet. The aim of the work was to evaluate the alle-lopathic effects of common millet on selected crops and to suggest the possibility of using the acquired knowledge. Laboratory experiments included evaluation of the effect of extracts from plant parts of millet and millet seeds on seed germina-tion and growth of selected plant species, as well as evaluation of autotoxicity of millet extracts, evaluation of the effect of different densities of millet seeds on allelopathic activity and stability of millet allelochemicals. The most effective extract inhibiting the growth of selected plants was the extract from young millet plants. However, millet allelochemicals do not seem to be suitable for weed control due to their low stability.

Weed control tries to suppress competitors for a crop and often relies on differential intoxication, making use of differences in uptake, development, or metabolism. We explored the possibility of using natural signals to shift competition in favour of the crop. Using the competitive horsemint (Mentha longifolia) as a paradigm, we showed that essential oils from certain mint species suppress the seedling development of different target species in a specific and efficient manner. The specificity concerned both the donor and the receptor. We demonstrated further that the effect of horsemint oil was specific for actin filaments, and not for microtubules. Since the elimination of actin will impair auxin transport, which is essential for root regeneration in vegetatively propagating weeds, we tested the efficacy of horsemint essential oil in combination with a slow-release carrier against field bindweed (Convolvulus arvensis), a pertinent weed in organic cereal production. We observed that the development of this weed can be specifically blocked, especially if the carrier is worked into the soil. We propose that allelopathic interactions, often relying on manipulative chemical signalling, harbour significant potential for organic weed control.

In this study, the allelopathic potential of aqueous extracts of Codiaeum variegatum L. Rumph. Ex A. Juss. (40%, 20%, 10%, 5%, 2.5%, and 1.25%) on germination, early growth, and physiological activity of the selected plant recipient Lolium perenne L. was investigated. The obtained results confirmed the existence of allelopathic potential, which differed in its possibilities of adverse effects on the morphological and physiological characteristics of the recipient plant. The monitoring of the germination characteristics of the recipient plant showed that the tested extracts exhibited a concentration-dependent effect, i.e., stronger concentrations had a stronger inhibitory effect. A weaker negative effect on the growth of the selected species was observed, and it was shown that the root length of the seedling was usually under the stronger inhibitory effect of higher concentrations of extracts, in contrast to the length of the shoot, where all the applied extracts had a significant stimulatory effects. Moreover, allelochemicals of C. variegatum were shown to interfere with the synthesis of phenolic compounds and antioxidant capacity of L. perenne seedlings, the values of which decreased with increasing concentration of test extracts.

The excessive growth of phytoplankton and the development of water bloom leading to the damage to aquatic ecosystems are becoming a more and more frequent problem. There are many methods to control the water bloom from which mainly those that use interactions of living organisms have been developing lately, with the utilisation of aquatic plant allelopathy being one of them. Allelopathy is a type of relationship between two organisms when one of them influences the other by secreting allelopathically active compounds in the environment. However, the effect of these secondary metabolites depends on many biotic and abiotic factors, which also has consequences for their potential use to control the water bloom. Although the results of many studies suggest that allelopathy can affect the community of phytoplankton, its role in aquatic ecosystems is still unclear. This thesis summarizes the knowledge about the occurrence of allelopathy among aquatic organisms, the modes of action of allelochemicals and the impacts of the key factors influencing the allelopathic effect. At the same time, it evaluates the prospects of using the allelopathy of aquatic plants to control water bloom and reviews experimental approaches to studying allelopathic interactions.

The chemical content of essential oils (EO) obtained from the leaves of four Pinaceae (Abies alba, Picea abies, Pinus cembra and Pinus mugo) was investigated by SPME-GC-MS technique. The vapor phase was characterized by the monoterpenes with values higher than 95.0%. Among them, α-pinene (24.7–48.5%), limonene (17.2–33.1%) and β-myrcene (9.2–27.8%) were the most abundant. The monoterpenic fraction prevailed over the sesquiterpenic one (≥74.7%) in the EO liquid phase. Limonene was the major compound in A. alba (30.4%), P. abies (20.3%) and P. mugo (78.5%), while α-pinene in P. cembra (36.2%). Regarding the phytotoxic properties, EOs were studied at different doses (2–100 μL) and concentrations (2–20/100 μL/mL). All EOs were found to be significantly active (p-value ˂ 0.05) against the two recipient species in a dose-dependent way. In pre-emergence tests, germination of Lolium multiflorum and Sinapis alba was reduced by up to 62–66% and 65–82%, respectively, as well as their growth by up to 60–74% and 65–67%, due to the effects of compounds in both the vapor and liquid phases. In post-emergence conditions, at the highest concentration, the phytotoxicity of EOs caused heavy symptoms and, in the case of S. alba, A. alba EO completely destroyed (100%) the treated seedlings.

Murray-Darling Freshwater Research CentreMDFRC item.1. The hypothesis is tested that large daphnids are able to suppress their own and other species' feeding and reproduction by means of excreting an inhibitory chemical (or chemicals).2. In laboratory experiments with an Australian species, Daphnia carinata, water preconditioned with 3–67 daphnids 1-−1 for 30 h had the effect of reducing feeding rates of D. carinata and D. lumholtzi provided with Selenastrum capricornutum.3. For the two Daphnia species, there were highly significant negative correlations between feeding rate and the preconditioning density of D. carinata.4. Water preconditioned with 20–30 daphnids 1-−1 for 1–2 weeks reduced the grazing rates of Daphnia, Moina, and Diaphanosoma 2–3-fold.5. Moina kept in such water for 2 days stopped feeding. Conditioned water kept for 3 days without animals still inhibited grazing by Moina. Hearing to 100°C removed the inhibitory effect.6. Given excess food, and in non-renewed water, a gradient of D. carinata densities developed a strong negative correlation between clutch size and daphnid density after a 6-day time lag. This result may help explain the direct density-dependent regulation of cladoceran reproduction observed earlier in a subtropical lake.

Notorious invasive Bohemian knotweed Reynoutria × bohemica Chrtek et Chrtková is a hybrid of two species, Reynoutria japonica Houtt. and Reynoutria sachalinensis (F. S. Petrop.) Nakai in T. Mori which spontaneously developed in Europe, outside the natural distribution of its parental species. Its success could potentially lie in its allelopathic activity, which was confirmed in a number of experiments conducted with the leaf and root exudates, testing their effect on the germination and growth of various test plants. Here, we tested its allelopathic potential using different concentrations of leaf exudates on two test plants, Triticum aestivum L. and Sinapis alba L., in Petri dishes and pots with soil and by growing test plants in the soil sampled in knotweed stands on the edges of stands and outside of stands. Tests in Petri dishes and pots with soil to which leaf exudates were added have shown a decrease in germination and growth in comparison to the control, hence confirming the allelopathic effect. However, this was not confirmed in a test with in situ soil samples, where no statistically significant differences were observed, neither in the growth of test plants nor in the chemical characteristics (pH, soil organic matter, humus content) of the soil. Therefore, the persistence of Bohemian knotweed at already invaded sites could be attributed to its efficient use of resources (light and nutrients) through which it outcompetes native plants.

В статье представлены результаты изучения аллелопатической активности растений на разных стадиях онтогенеза. Показаны закономерноcти изменения аллелопатической активности выбранных растений в онтогенезе., The article results of studying the allelopathic activity of plants at different stages of ontogenesis are presented. The regularities of changes in the allelopathic activity of selected plants in ontogenesis are shown., ВЕСТНИК МОСКОВСКОГО ГОРОДСКОГО ПЕДАГОГИЧЕСКОГО УНИВЕРСИТЕТА. СЕРИЯ: ЕСТЕСТВЕННЫЕ НАУКИ, Выпуск 3 (47) 2023

The congeneric approach assesses the relative role of exotic invasive plants compared to native plants on associated species. However, most studies on seed germination have been conducted in Petri dishes that do not reflect natural soil conditions. Here, we compared the effects of different litter extracts of the exotics Prosopis juliflora (Sw.) DC. and Prosopis pallida (Willd.) Kunth, as well as native Prosopis cineraria (L.) Druce, on seed germination and seedling dry weight of two weedy plants (Amaranthus graecizans L. and Sisymbrium irio L.) and the native Senecio flavus (Decne.) Sch.Bip. in both Petri dishes and potted soil experiments. The results indicate that non-treated seeds (control) of the three species attained more than 95% germination in the Petri dishes (in vitro). The increase in the litter concentrations of both invasive Prosopis species inhibited the native Senecio flavus germination and significantly reduced germination and seedling weight of the weedy A. graecizans and Sisymbrium irio. Nevertheless, the native P. cineraria extracts had significant depressive effects on seed germination and seedling growth of the native Senecio flavus but limited effects on the weedy A. graecizans and Sisymbrium irio. The results support a greater impact of exotic than native congener on native plants. To better assess allelopathic effects, it is recommended to not rely on germination in Petri dishes.

The cucurbitaceae family comprises of economically important vegetable crops grown for food and medicine. Most cucurbit crops produce cucurbitacins in leaves, flowers, fruit, seed and roots which possess various pharmacological and pharmaceutical values. Cucurbitacins are toxic to pests and diseases, and allelopathic to noxious weeds thus providing opportunities for improving tolerance to biotic stresses. Further, cucurbitacins are responsive to environmental stimuli and can therefore enhance tolerance to abiotic stress. The objective of this review was to highlight the breeding value of cucurbitacins to develop cucurbitacins-enriched genotypes for food and medicine, and for management of biotic and abiotic stresses. The following themes were discussed: a comparative analysis of cucurbitacin concentrations in edible and non-edible plant parts; genetic control and associated quantitative trait loci and molecular markers associated with cucurbitacins; pharmacological and pharmaceutical values of cucurbitacins, and potential applications for management of biotic and abiotic stresses. Results of the present study will guide genetic improvement of cucurbitacins for use as food and medicine, and in the development of genotypes tolerant to biotic and abiotic stresses.

A pot experiment was conducted at Alzaiem Alazhari University during 2020/2021 to study the effect ofAmaranthus viridispowder incorporated into the soil on germination and growth of garden rocket (Eruca sativa). The experiment was arranged in completely randomized design (CRD) with four replicates. Five concentrations (0, 0.5, 1.0, 1.5 and 2.0% w/w) on basis ofAmaranthus viridispowder incorporated in the soil. Results indicated thatAmaranthus viridispowder decreased germination, shoot length, leaf area, shoot and root fresh and dry weight as well as chlorophyll content and some chemical elements (P, Ca, Mg, Fe).

A pot experiment was conducted at Faculty of Education, Alzaiem Alazhari University, Sudan, during 2019/2020 to evaluate the effect ofAmaranthus viridispowder on the emergence and growth of Swiss chard (Beta vulgarisvar. cicla). The experiment was set as a completely randomized design (CRD) with four replicates. In the treatments the powder ofAmaranthus viridiswas incorporated into the soil at rate of (0, 0.5, 1.0. 1.5 and 2.0% w/w) representing T1(control), T2, T3, T4and T5respectively. Results indicated thatAmaranthus viridispowder decrease germination, plant height, number of leaves, leaf area, shoot and root fresh and dry weight, chlorophyll content (a, b) and some chemical elements (P, Ca, Mg, Fe) of Swiss chard (Beta vulgarisvar. cicla).

Allelopathy is a plant-plant interaction in which one plant releases biologically active compounds that have negative effects on the fitness of the target plant. The most pronounced effects are inhibition of seed germination and growth of neighboring plants. The roots of these plants are in contact with the allelochemicals released into the soil, as the primary target of the allelopathic action. To date, the best documented allelopathic activities relate to some weeds and invasive alien plants that show rapid spread and successful growth. A better understanding of the mechanisms of allelopathy will help to improve crop production and to manage and prevent plant invasions. At the cellular level, allelochemicals induce a burst of reactive oxygen species in the target plants, which leads to oxidative stress, and can promote programmed cell death. Lipid peroxidation and cell membrane changes, protein modifications, and increased protease activities are the early signs of cell damage. When enzymatic and nonenzymatic antioxidants cannot scavenge reactive oxidants, this can result in hydrolytic or necrotic degradation of the protoplast. Cell organelles then lose their integrity and function. In roots, the structure and activity of the apical meristem are changed, which affects root growth and water absorption. Such allelopathically active compounds might thus be applied to control and manage weeds and invasive plants in a more sustainable way, to reduce chemical pollution.

The aim of this study was to test the allelopathic effects of the plant extracts isolated from immature walnut fruits on the germination and early seedling growth of two weed species (Amaranthus retroflexus and Chenopodium album), and its phytotoxic effects on the germination and early seed growth of maize, Zea mays. Additionally, the goals was to also conduct an analysis of the plant extracts and determine its antioxidant properties. Antioxidant activity of the plant extracts were determined via its ability to neutralize DPPH (2,2-diphenyl-1-picrylhydrazyl) radicals and by testing their potential for iron reduction using the FRAP method. The inhibition of the measured parameters (total germination and seedling length) decreased proportionally, with the reduction of concentrations of plant extracts isolated from immature walnut fruits. Also, the seedling length parameter has shown greater sensitivity when compared with the parameters of total seed germination in both weed species. Even though the results of both biotests with seeds show a high inhibitory effect on the germination and early growth of the tested weed species, they also point to phytotoxicity in early growth of Z. mays seeds. Future research will be focused on the HPLC analysis of the plant extracts isolated from immature walnut fruits and their allelopathic effects on the early growth of plants of the tested species.

Florações de cianoabactérias são consideradas um dos maiores desafios na preservação de fontes hídricas, especialmente quando estão presentes espécies como Microcystis aeruginosa. A descoberta de alternativas de remediação faz-se necessária, e uma delas é o uso de macrófitas aquáticas, como as espécies do gênero Myriophyllum, que apresentam atividades alelopáticas para o controle fitoplanctônico. Diante disso, este trabalho teve como objetivos avaliar a inibição do crescimento de células de M. aeruginosa em uma coexposição com Myriophyllum aquaticum e avaliar a remoção de microcistina-LR. Os experimentos foram conduzidos com cultivos de M. aeruginosa (1x106células mL-1) em coexposição com M. aquaticum por sete dias. Os efeitos inibitórios foram investigados por contagem celular. Os efeitos nos pigmentos fotossintéticos foram mensurados, além da quantificação de microcistina-LR no último dia experimental. Para avaliar possíveis efeitos de competição por nutrientes e espaço, realizou-se a quantificação da concentração de ortofosfato total e utilizou-se um tratamento com planta de plástico. Os experimentos com M. aquaticum apresentaram inibição total do crescimento de M. aeruginosa e redução significativa na concentração dos pigmentos fotossintéticos (> 98%). Além disso, foi constatada redução na concentração de microcistina-LR (79%) nos testes com macrófitas quando comparadas ao grupo controle. Não foi observada competição por espaço e nutrientes, o que demonstra que os efeitos sobre M. aeruginosa foram causados pela presença da macrófita aquática. Dessa forma, estes resultados podem demonstrar que M. aquaticum gerou a inibição no crescimento de cianobactérias por efeitos alelopáticos, além de remover a microcistina-LR das águas. Harmful algal blooms are one of the greatest challenges when preserving water sources, especially when involving cyanobacteria such as Microcystis aeruginosa. Finding remediation possibilities is needed, and one of them has been the use of macrophytes such as the species Myriophyllum, which have presented allelopathic mechanisms of phytoplankton control. Thus, this work aimed to evaluate the inhibition of M. aeruginosa cell growth in a co-exposure with Myriophyllum aquaticum and the influence on microcystin-LR concentration. The experiments were carried out using a culture of M. aeruginosa (1x106 cells mL-1) in a co-exposure with M. aquaticum for seven days. The inhibitory effects were investigated by counting the cells; the effects on photosynthetic pigments were measured and microcystin-LR was quantified in the culture medium on the last experimental day. To evaluate the possible effects of competition for nutrients and space, the concentration of total orthophosphate was quantified and treatment with plastic plants was used. The experiments with Myriophyllum aquaticum achieved the total inhibition of M. aeruginosa growth and a significant reduction of the photosynthetic pigments (> 98%). Additionally, we observed a reduction of microcystin-LR concentration (79%) in the tests with macrophytes when compared to the control. Competition for space and nutrients was not observed, demonstrating that the effects on M. aeruginosa were caused by aquatic macrophyte presence. These results may indicate that M. aquaticum causes inhibitory effects on cyanobacteria growth by allelopathic effects and removes microcystin-LR.

Premise of research. The gametophytes of ferns are nutritionally independent of the sporophytes and are potentially hermaphroditic. The sexual expression of fern gametophytes is based on environmen...

A comprehensive understanding of mechanisms of allelopathy and resource availability is critical for protecting rare and endangered species, biodiversity, and ecosystems. We treated 20 major plant species with three concentrations of an aqueous extract of Dacrydium pierrei Hickel litter and different irrigation and nutrients to compare the relative importance of allelopathy and resource availability on roots, stem growth, and seed germination, using bioassays. The results showed that the height, ground diameter, and aboveground biomass of individuals increased more quickly in the early stage, and the rate of increase tended to slow down in the later stages. The allelopathy was species specific (inhibitory, neutral, or promotive), and the survival rate and growth rate of saplings changed significantly along a resource treatment gradient (P < 0.05), indicating that the native species diversity was reduced by lower or higher resource availability in natural forests. The effect of allelopathy on trees was relatively weak during the treatments, and that of resource availability was relatively strong. Resource availability is relatively more important than allelopathy in mediating the reduction in plant biodiversity. Therefore, water and nutrient availability and the species and number of allelochemicals released by plants have substantial influences on the survival and growth of plant species in a natural Dacrydium forest.

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

Cilj istraživanja bio je utvrditi alelopatski potencijal lucerne (Medicago sativa L.) na klijavost sjemena i rast klijanaca rotkvice (Raphanus sativus L.), radiča (Cichorium intybus L. var. foliosum) i rajčice (Lycopersicon esculentum Mill.). Vodeni ekstrakti pripremljeni od suhe nadzemne mase lucerne u tri koncentracije (1 %, 2,5 % i 5 %) testirani su u laboratorijskim uvjetima. Alelopatski potencijal lucerne ovisio je o test vrsti, koncentraciji vodenog ekstrakta te mjerenom parametru. Najslabije djelovanje zabilježeno je na klijavost te rast klijanaca rajčice. Povećanjem koncentracije vodenog ekstrakta povećavao se i negativni alelopatski potencijal. Najmanji utjecaj vodenih ekstrakata zabilježen je na suhu masu klijanaca test vrsta., The aim of the study was to determine the allelopathic potential of alfalfa (Medicago sativa L.) on seed germination and seedling growth of radish (Raphanus sativus L.), radicchio (Cichorium intybus L. var. foliosum) and tomato (Lycopersicon esculentum Mill.). Water extracts prepared from dry alfalfa biomass in three concentrations (1%, 2.5% and 5%) were tested under laboratory conditions. The allelopathic potential of alfalfa depended on the test species, the water extract concentration, and the measured parameter. The weakest effect was recorded on germination and growth of tomato seedlings. As the concentration of the water extract increased, the negative allelopathic potential also increased. Dry weight of seedlings of test species was the least affected.