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A planta Curcuma longa L. é rica em compostos bioativos. No entanto, há poucos estudos disponíveis que investigaram sua atividade alelopática. Neste trabalho, buscamos investigar preliminarmente os principais grupos químicos com atividade alelopática e bioherbicida presentes no extrato aquoso obtido dos rizomas de C. longa, bem como seu efeito na germinação e no crescimento inicial de plântulas de alface (Lactuca sativa L.) e trigo (Triticum aestivum L.). A análise fitoquímica foi realizada por técnicas de precipitação e colorimétricas. Para determinar o potencial alelopático do extrato, foram testadas sete concentrações (1 a 64 g L-1), além de dois grupos controle: água destilada (controle negativo) e glifosato (controle positivo). As sementes permaneceram em contato com as diferentes concentrações por 72 horas. Os parâmetros avaliados foram: porcentagem de germinação (PG), índice de velocidade de germinação (IVG), comprimento da raiz e da parte aérea das plântulas e concentração inibitória média (IC50). Foram identificados quatro compostos com potencial alelopático: alcaloides, esteroides, flavonoides e terpenos. Os resultados do ensaio biológico revelaram que o extrato aquoso exerceu impacto limitado sobre a PG, apresentando efeitos apenas na concentração mais elevada (64 g L-1), ocasionando redução de 20,70% desse parâmetro em ambas as espécies. Além disso, verificou-se que o índice de velocidade de germinação (IVG) foi significativamente influenciado por concentrações superiores a 4 g L-1 para ambas as espécies. O comprimento da raiz e da parte aérea das plântulas diminuiu com o aumento das doses. O comprimento da parte aérea foi o parâmetro mais sensível, sendo necessária a IC50 de 3,73 e 7,20 g L-1 para o trigo e a alface, respectivamente. Os resultados sugerem que o extrato dessa planta apresenta potencial para a produção de bioherbicidas de pós-emergência.

The plant Curcuma longa L. is rich in bioactive compounds. However, there are few available studies that have investigated its allelopathic activity. In this work, we sought to preliminarily investigate the main chemical groups with allelopathic and bioherbicide activity present in the aqueous extract obtained from the rhizomes of C. longa, as well as its effect on the germination and initial growth of lettuce (Lactuca sativa L.) and wheat (Triticum aestivum L.) seedlings. Phytochemical analysis was performed using precipitation and colorimetric techniques. To determine the allelopathic potential of the extract, seven concentrations (1 to 64 g L-1 ) were tested, in addition to two control groups: distilled water (negative control) and glyphosate (positive control). The seeds remained in contact with the different concentrations for 72 hours. The evaluated parameters were: germination percentage (GP), germination speed index (GSI), root and shoot length of the seedlings, and median inhibitory concentration (IC50). Four compounds with allelopathic potential were identified: alkaloids, steroids, flavonoids, and terpenes. The results of the biological assay revealed that the aqueous extract had a limited impact on GP, showing effects only at the highest concentration (64 g L-1 ), causing a reduction of 20.70% in this parameter in both species. Additionally, it was found that the germination speed index (GSI) was significantly influenced by concentrations higher than 4 g L-1 for both species. The length of the root and shoot of the seedlings decreased with increasing doses. Shoot length was the most sensitive parameter, with an IC50 of 3.73 and 7.20 g L-1 required for wheat and lettuce, respectively. The results suggest that the extract of this plant has potential for the production of postemergence bioherbicides. [ABSTRACT FROM AUTHOR]

RESUMO Para avaliar o potencial alelopático do sabiá (Mimosa caesalpiniaefolia Benth -Mimosoidae-Leg.), sementes de ipê-amarelo Tabebuia alba (Cham.) Sandw (Bignoniaceae) foram postas a germinar umedecidas com extratos aquosos de folhas verdes e secas em diferentes concentrações (1:8, 1:16 e 1:32). Os ensaios de germinação foram instalados com três repetições de 20 sementes de ipê-amarelo a 25ºC. Houve efeito da diluição e do tipo de folha empregado. Constatou-se inibição da germinação nas concentrações 1:16 e 1:32, para folha verde. O maior efeito inibitório foi obtido com a concentração 1:16. Verificou-se toxidez ou possível efeito alelopático das folhas verdes independente da dose.

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Pertencente à família Fabaceae a Leucena (Leucaena leucocephala (Lam.) de Wit) é uma espécie leguminosa originária da América Central. O trabalho teve como objetivo analisar a influência das distintas concentrações da infusão das folhas de aroeira (Schinus terebinthifolius) no potencial fisiológico de sementes de Leucena. O experimento foi realizado no laboratório de Fitotecnia do Campus de Engenharias e Ciências Agrárias da Universidade Federal de Alagoas em Rio Largo-AL. O delineamento experimental utilizado foi o inteiramente casualizado, com quatro repetições de 25 sementes por tratamento. As sementes de L. leucocephala foram submetidas às diferentes concentrações da infusão de folhas de aroeira, sendo: 0 (testemunha), 20, 40, 60, 80 e 100g de folhas de aroeira/ litro de água destilada. Em altas concentrações da infusão das folhas de aroeira, as variáveis primeiras contagem de germinação, germinação e índice de velocidade de germinação foram influenciadas negativamente. A infusão das folhas da aroeira possui efeito alelopático sobre o potencial fisiológico das sementes de L. leucocephala sobre altas concentrações.

Resumo A síntese e determinação estrutural de ésteres derivados do ácido cinâmico permitiu obter análogos dos ésteres naturais isolados de Lafoensia glyptocarpa Koehne e avaliar o potencial alelopático dos mesmos através de bioensaios de germinação de sementes de alface e tomate. As substâncias que promoveram maior inibição da germinação das sementes analisadas foram: 3,4-metilenodioxifenil acrilato de hexadecila; 3,4-metilenodioxifenil propionato de hexadecila; 3,4-metilenodioxi-6-nitrofenil propionato de hexadecila; e ferrulato de sitosterila. As estruturas foram determinadas através da análise de dados fornecidos por espectrometria de infravermelho, de massas e de RMN de 1H e 13C.

RESUMO Neste trabalho testou-se o efeito do extrato de capim colonião (Panicum maximum) sobre a germinação de sementes de alface, canafístula e angico. Os extratos foram elaborados na proporção de 200 g de parte aérea fresca e 100 g de parte aérea seca para cada litro de água destilada, resultando no extrato bruto (100%), sendo diluído para as concentrações de 20, 40, 60 e 80%. O extrato de capim colonião prejudicou a germinação de sementes de alface, porém, nas sementes de espécies nativas estudadas, o único efeito observado foi estimulatório. Dessa forma, o efeito exercido sobre as espécies nativas na Estrada do Colono do Parque Nacional do Iguaçu não deve ser alelopático, atribuindo-se a outros efeitos, como competição.

Resumo A jaqueira (Artocarpus heterophyllus) pertence à família Moraceae e tem sido considerada invasora no Brasil. Nas áreas dominadas por esta espécie pode ser observado um pequeno número de plântulas de outras espécies, o que leva a supor algum tipo de ação alelopática. Foi feito um bioensaio, visando detectar efeitos alelopáticos em polpa, folhas verdes e folhas secas de jaqueira (Artocarpus heterophyllus), utilizando sementes de alface, como espécie receptora. Em comparação com água destilada e extrato do solo, os extratos da planta tiveram forte efeito inibitório na germinação. Estes dados apontam para características relevantes e que devem ser consideradas para o controle de invasão desta espécie, em unidades de conservação.

RESUMO Neste trabalho, estudou-se a germinação de sementes de Lycopersicum esculentum submetidas a extratos Senna obtusifolia. Foram realizados ensaios para análise da germinabilidade e velocidade de germinação. Os dados obtidos foram submetidos à ANOVA e ao teste de Tukey a 5% de probabilidade. Os extratos foram submetidos à prospecção de constituintes químicos. Tanto a análise da germinabilidade como a da velocidade de germinação demonstraram efeitos negativos consideráveis, sendo que os extratos de folha foram os que mais evidenciaram resultados significativos. Na prospecção de constituintes químicos, foi caracterizada a presença de variados grupos de metabólitos secundários nos três tipos de extrato.

Sesbania virgata (Cav.) Pers é uma espécie arbustivo-arbórea nativa do Brasil com comportamento agressivo, que a torna espécie superdominante. Esse comportamento decorre de diversos fatores, como a produção de substâncias aleloquímicas (como a catequina), capazes de inibir o crescimento de espécies concorrentes, substâncias essas que variam de acordo com fatores ambientais. Sendo assim, no presente trabalho foram analisados os efeitos de diferentes solos e regimes hídricos na germinação e no desenvolvimento da espécie. Para tanto, sementes de matrizes produtoras e não produtoras de catequina foram semeadas em três tipos de solo (comercial, solo do local das matrizes produtoras e solo do local das matrizes não produtoras do aleloquímico) e submetidas a quatro sistemas de irrigação (100, 75, 50 e 25%). Os parâmetros avaliados foram o processo germinativo das sementes até a estagnação (ocorrido no quarto mês) e o desenvolvimento inicial pelo período de seis meses. No geral, a espécie germinou integralmente praticamente em todos os tipos de solo e condições de irrigação avaliados. Além disso, se desenvolveu bem em todos os tratamentos, inclusive nos solos menos férteis e sob estresse hídrico. Isso reforça a plasticidade da espécie e lhe confere uma vantagem adaptativa, mesmo em condições de estresse ambiental.

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Copyright of Revista Mexicana de Ciencias Agrícolas is the property of Instituto Nacional de Investigaciones Forestales, Agricolas y Pecuarias and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Understanding forest dynamics is fundamental to their ecological restoration. This is particularly important in forests rich in species of commercial value, such as those of the Juglans genus, which known allelopathic effect could have an impact on the diversity of locations where it exists. The objective of this study was to evaluate the floristic composition and tree diversity of a forest dominated by Juglans neotropica Diels, establishing a permanent plot of 100 x 100 m in the Chanchamayo valley. In the plot, all trees were evaluated with DBH = 10 cm. The permanent plot presented 300 individuals, which corresponded to 47 species in 20 families. The Fisher's Alpha diversity index value was 15.62, and the Shannon-Wiener index value 1.65. These values are notoriously low in comparison with similar sites located in tropical premontane forests referred to in the present work. Due to the allelopathic nature of J. neotropica Diels, it is possible that this condition is a determining factor for the high abundance of this species in the plot and the low tree diversity identified. Since J. neotropica Diels is categorized as endangered by IUCN, the area becomes an important location for its conservation and that of its gene pool. [ABSTRACT FROM AUTHOR]

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La agricultura es afectada por la aparición de malezas que reducen la producción de los cultivos, estas se controlan con químicos agrícolas que desequilibran el ambiente y la salud humana. Recientemente se ha reportado el empleo de extractos biológicos de plantas, donde se demuestra que poseen propiedades bioactivas fitotóxicas que alteran la estructura celular, por lo que surge la necesidad de extraer los compuestos bioactivos de estos, con el fin de producir y aplicar bioherbicidas potentes, que inhiban la propagación de malezas que perturban los sembradíos. El objetivo de esta revisión bibliográfica fue reportar los avances en el desarrollo de nuevos herbicidas biológicos, a partir de extractos vegetales fitotóxicos aplicados in vitro. La presente revisión describe los compuestos con capacidad fitotóxica en las plantas y su actividad biológica fitotóxica, como los polifenoles, taninos, alcaloides, quinonas, saponinas antagónicas y los glucósidos, por mencionar algunos, mediante los métodos experimentales más usados, que incluyen la extracción, la determinación y la cuantificación de los metabolitos. Además, se hace mención de las variables respuestas que se consideraron para evaluar el efecto de estas sustancias activas biológicas, donde se incluyen el porcentaje de inhibición de la germinación, el crecimiento y la longitud radical en plantas.

Tithonia diversifolia (Hemsl.) A. Gray has been recommended as a fertilizer species and its liquid extract as a biofertilizer in organic agroforestry systems. However, studies indicate that plant extracts have inhibitory effects on the germination and growth of several plant species, acting as allelopathic. In this sense, the work aims to evaluate, on a laboratory scale, the biological effect of concentrations of aqueous extract of T. diversifolia on the germination and initial development of seeds, using lettuce as an indicator species. Aqueous extracts were produced at concentrations of 5%, 10%, 15%, and 20%, using distilled water as a control. Lettuce seeds were arranged in Gerbox boxes, on filter paper, in the amount of 25 seeds per box, under a constant temperature of 20°C and natural light, for seven days. The percentage of final germination, mean germination time (MGT), germination speed index (GSI), and phytosanitary status of the seed on the seventh day were evaluated. The aqueous extracts of T. diversifolia in concentrations between 5% and 20% do not affect the final germination of the seeds, however, they reduce the germination speed; affect seedling size, and induce a higher percentage of abnormalities in germinated seeds. The results suggest that extracts of T. diversifolia have allelopathic potential for the germination of species. [ABSTRACT FROM AUTHOR]

The allelopathic effect of concentrations of extracts of the aerial section of Chloris gayana under the germination of soybean seeds and hairy beggartick is evaluated. Assay was conducted in a totally randomized design where seeds were placed on germitest paper with an aqueous extract of leaves of C. gayana in concentrations 0, 25, 50, 75 and 100% and maintained in a germination chamber at 25°C for a 12-h light photoperiod. Variables analyzed comprised first germination count, germination percentage, germination speed index, length and dry mass of root, aerial and total section. Data underwent analysis of variance by test F (p<0.05) and regression analysis for different concentrations of the extract. Results showed that aqueous extract of C. gayana may significantly affect the germination and initial growth of seedlings, with a reduction of up to 26% on soybean germination with 50% concentration, plus the lowest development of seedlings of both species as from 25% of extract. Results show that aqueous extracts of Chloris gayana leaves have an allelopathic effect on seed germination and growth of soybean seedlings at concentrations 50 and 100%, respectively. In the case of hairy beggartick, there was no significant effect of the extracts in seed germination, except for total length and total dry mass of the seedlings, at concentrations 50 and 75%, respectively. [ABSTRACT FROM AUTHOR]

Baccharis ulicina es una maleza ampliamente distribuida en los pastizales de la zona semiárida argentina. A fin de evaluar sus posibles efectos alelopáticos, se utilizaron extractos acuosos de B. ulicina (hoja, tallo, raíz y planta entera) a dos concentraciones (50 y 150 g tejido/L agua) sobre la germinación y crecimiento inicial de Avena sativa, Lolium perenne y Raphanus sativus. Para cada especie se regaron 100 semillas y se mantuvieron a 25°C y oscuridad. Se registraron la germinación de las semillas y la longitud de coleóptilo / hipocótile (C/H) y radícula (R). Con los datos obtenidos se determinó: porcentaje de germinación, coeficiente de velocidad de germinación, vigor de la germinación, inhibición de la germinación, inhibición de la longitud de la radícula y del coleóptilo / hipocótile e índice de vigor de radícula y de coleóptilo / hipocótile. Los extractos con alta concentración redujeron la germinación en promedio 65% mientras que inhibieron la longitud en 58,8% (C/H) y 93,3% (R) para A. sativa; 71,5% (C/H) y 87,9% (R) para L. perenne, y 93,8% (C/H) y 94,5% (R) para R. sativus. Se registró un evidente efecto fitotóxico de B. ulicina sobre las especies evaluadas, indicando que la alelopatía sería una estrategia ecológica de la especie.

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Agroforest systems make possible ecologically viable exploitation of forest and crop species. Pityrocarpa moniliformis is a forest species with high apiculture value and, consequently, an extra profit source for farmers, whilst corn is one of the main species as a food basis due to its carbohydrates and proteins. Research work is required on possible interactivities established between forest and crop species, such as allelopathy. A possible allelopathic influence of the dry leaves of Pityrocarpa moniliformis in decomposition may be identified on the establishment and development of corn seedlings, var. Ibra. The presence or absence of alkaloids, triterpenoids, steroids, saponins, coumarins, phenolic compounds, tannins, flavonoids, anthraquinones, anthocyanidins, chalcones, leucoanthocyanidins, catechins and flavonones, was identified through qualitative characteristics for the aqueous extract of the dry leaves of Pityrocarpa moniliformis by totally randomized and factorial design The establishment of seedlings through percentage, speed index and mean emergence time and early development, height of aerial part, length of root system, dry mass of aerial and root section and total were undertaken. Alkaloids, triterpenoids, saponins, phenolic compounds, tannins, flavonoids, anthraquinones, catechins and flavonones, potentially allelopathic compounds, were extant in the foliar extract. Corn as an integral part of an agri-forest system with P. moniliformis is not recommended. [ABSTRACT FROM AUTHOR]

Agriculture is affected by the appearance of weeds that reduce crop production. These are controlled with agricultural chemicals that unbalance the environment and human health. For this reason, the need arises to extract the bioactive compounds from these, to produce and apply powerful bioherbicides, which inhibit the spread of weeds that disturb the crops. Recently, the use of biological extracts of plants has been reported, where it is shown that they have phytotoxic bioactive properties that alter cell structure. The objective of this bibliographic review was to report the advances in the development of new biological herbicides, from phytotoxic plant extracts applied in vitro. This review describes the compounds with phytotoxic capacity in plants and their phytotoxic biological activity, such as polyphenols, tannins, alkaloids, quinones, saponins antagonists, and glycosides, to mention some, through the use of the most common experimental methods that include the extraction, determination, and quantification of the metabolites. In addition, the response variables that were considered to evaluate the effect of these biological active substances are mentioned, which include the percentage of inhibition of germination, growth, and root length in plants. [ABSTRACT FROM AUTHOR]

The aim of the present study was to investigate the potential allelopathic effects of isolated or intercropped aqueous forage extracts on the physiological performance of soybean [Glycine max (L.) Merr.] and corn (Zea mays L.) seeds, as well as their phytotoxicity to the weed species Bidens pilosa L. Aqueous extracts were prepared at a concentration of 5%, and the tests with soy and corn were conducted by wetting the germination papers with different treatments and performing procedures within the standards of the Brazilian Rules of Seed Analysis. Tests with the cover plant extracts on the seeds of B. pilosa used BOD-type repetitions. Fifty weed seeds were placed in a gerbox with filter paper moistened with the different treatments with five repetitions. Distilled water was used as the control in all tests. Extracts of Avena strigosa Schreb and Raphanus sativus L. (radish), cultivated individually and in combination, increased the seed germination percentage (%G) and the length of soybean seedlings. Similarly, extracts of Pennisetum glaucum (L.) R.Br and Crotalaria spectabilis Roth, in individual and combined cultivation, provided gains in corn %G. Furthermore, all tested extracts suppressed germination and decreased the speed of the germination index of the hairy beggarticks when compared to the control, with the radish extract showing the greater reduction effect on the %G of the weed plant B. pilosa. [ABSTRACT FROM AUTHOR]

Introduction: Allelopathy is a harmful effect indirectly or directly produced by one plant to another through the production of chemical substances that enter the environment. Allelopathy has a pertinent significance for systems of ecological, sustainable, and integrated management. These natural reactions have multiple effects, ranging from processes of inhibition and stimulation of growth in neighbor plants to inhibition of seed germination. Metabolomics is a discipline integral that studies all the metabolites in a particular tissue, organ, or organism in a specific developmental stage or under particular environmental conditions, and it allows for the assessment of the contribution of genetic and environmental factors to the modification of metabolism. With the growing number of "omics", new approaches can be used to understand metabolic changes that occur in plants, especially in proteomics and metabolomics, and thus those analyses could be profiled in coming years with the objective of knowing the allelopathome of a larger number of plant species and their interactions. Aim: To provide a recent update on the science of allelopathy in the context of physiology, practical application of metabolomics in allelopathic studies, allelochemicals analyzed by metabolomics in alfalfa, rice, canola, sorghum, rye, wheat and other crops and finally mentionated the biological activity of allelopathic secondary metabolites. Methods: A recent comprehensive literature search of allelopathy and metabolomics in journal databases was carried out. Results: The concept of allelopathy, allelopathic mechanisms, metabolomic studies in allelopathy, allelochemicals analysed by metabolomics in alfalfa, rice, canola, rye sorghum, wheat and other agro-industrially important crops, and the biological activity of allelopathic secondary metabolites are detailed. Conclusions: These studies suggest that a combination of secondary metabolites can be used to attack weeds. In situ and In vitro culture of secondary metabolites (allelochemical types) is recommended to be used as organics compounds in weed organic control in the future. [ABSTRACT FROM AUTHOR]

We tested the hypothesis that of the species studied in the Brazilian Semiarid, the ones most functionally similar to tree Azadirachta indica would be more affected by this exotic species during germination and early development. At first, we produced a crude extract of A. indica fresh leaves in six different dilutions. We placed 25 seeds of four native species (Cenostigma pyramidale, Libidibia ferrea, Mimosa caesalpiniifolia, and Amburana cearensis) to germinate in Petri dishes for each dilution, with four replicates for each species. We assessed: radicle length, emergence percentage, emergence speed index, and mean emergence time. We conducted an experiment in a greenhouse to assess how the exotic plant affected the development of individual plants of the studied species. We planted five seeds of each native species alone and five in interaction with the exotic species using ten 20-l buckets. The experiment lasted four months, and the functional attributes of the individuals were collected. Among the native species analyzed, according to the cluster analysis using the functional attributes of the species planted alone, M. caesalpiniifolia, C. pyramidale and L. ferrea were functionally more similar to the exotic species. In the germination experiment, the extract affected only root length, regardless of the functional similarity. We noticed that only M. caesalpiniifolia had its early development strongly inhibited when planted in interaction with the exotic species. Although the functional similarity between the exotic and the native species did not influence germination, it negatively affected the development. [ABSTRACT FROM AUTHOR]

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La investigación tuvo como objetivo evaluar el efecto alelopático de un extracto acuoso de Panicum maximum Jacq. sobre dos arvenses dicotiledóneas Amaranthus dubius Mart. y Euphorbia heterophylla L. en pre y post emergencia. Se desarrollaron cuatro ensayos, dos por especie de arvense desde febrero 2015 hasta agosto de 2016 en el Laboratorio Provincial de Sanidad Vegetal Cienfuegos. Para la obtención del extracto acuoso de rizomas de Panicum maximum se tomaron plantas en la fase de floración - fructificación con tres meses de edad. Se evaluaron cuatro tratamientos por ensayo con un extracto obtenido en una proporción 1:10 de rizomas agua (p/v) (tres concentraciones del extracto 30, 20 y 10% y un testigo). Los ensayos se dispusieron en un diseño completamente aleatorizado 4x5. Las unidades experimentales estuvieron constituidas por magentas donde se ubicaron semillas de las arvenses. A los 12 días se evaluó el porcentaje de germinación, la longitud de la radícula y del hipocótilo. Se realizaron los análisis de varianza, medias se compararon con la prueba de Tukey P≤0,05. Se usó el paquete SPSS para Windows versión 15. El extracto acuoso de Panicum maximum manifestó efecto alelopático negativo en pre emergencia sobre la germinación y se produjo una estimulación de la longitud del hipocótilo, mientras que en post emergencia disminuyó el porcentaje de germinación y la longitud contra Euphorbia heterophylla, mientras que contra Amaranthus dubius redujo la germinación tanto en pre como en post emergencia, y hubo reducción de la longitud de la radícula y del hipocótilo en pre emergencia.

No presente trabalho foi avaliada a composição química e atividade alelopática do óleo essencial (OE) de folhas de Blepharocalyx salicifolius (Kunth) O. Berg sobre a germinação e crescimento inicial de plântulas de Lactuca sativa L. (dicotiledônea) e de Sorghum bicolor (L.) Moench (monocotiledônea). O OE foi obtido por meio de hidrodestilação por 3 h. A análise da composição do OE foi feita por cromatografia gasosa acoplada a um espectrômetro de massas (CG-EM). A atividade alelopática do extrativo foi avaliada nas concentrações de 2,5; 5,0 e 7,5%. As sementes foram imersas nas soluções por 2 min e então foram distribuídas em placas de Petri. As placas foram mantidas em câmara incubadora BOD. No sétimo dia, foram avaliadas as variáveis germinação (%) e comprimento de raízes (cm), da parte aérea (cm) e total da plântula (cm). Os constituintes majoritários identificados no OE foram eucaliptol (49,6%), limoneno (13,6%) e β-cariofileno (12,2%). O OE afetou negativamente a porcentagem de germinação das sementes de L. sativa e os parâmetros sistema radicular e plântula total de S. bicolor. A atividade alelopática do OE foi negativa para as duas espécies avaliadas.

Introduction: Cyanobacterial blooms in tropical water bodies are increasingly common, because of eutrophication and rising temperatures. Consequently, many freshwater systems are affected, by reducing water quality, biodiversity, and ecosystem services. With the increased frequency of harmful algal blooms, the development of biological tools to improve water quality is an urgent issue. Objective: To evaluate the effects of a submerged macrophyte and a cladoceran on the microcystin-producing cyanobacteria Microcystis aeruginosa (NPLJ-4) and the chlorophyte Raphidocelis subcapitata (BMIUFRPE-02) in mixed cultures. Methods: Two parallel experiments were carried out for ten days to evaluate the effects of the submerged macrophyte Ceratophyllum demersum and the cladoceran Moina micrura on microalgal interactions. Microalgal strains were cultivated in the ASM1 culture medium, under controlled laboratory conditions. The first experiment presented four treatments: M (C. demersum), Z (M. micrura), MZ (C. demersum and M. micrura), and C (control). Meanwhile, the second experiment consisted of five treatments, in which the microalgae were cultivated together at different Microcystis:Raphidocelis ratios: 1:0, 3:1, 1:1, 1:3, and 0:1. Biomass and growth rates of the strains were evaluated every two days, which were statistically treated with three-way or two-way repeated-measures ANOVA. Results: In the first experiment, M. aeruginosa was significantly inhibited in M and MZ treatments from the second day, and Z from the fourth, while R. subcapitata showed no reduction in its biomass in any treatment. On the other hand, R. subcapitata was stimulated from the eighth and tenth days in M treatment and only on the eighth day in Z treatment. In the second experiment, M. aeruginosa was significantly inhibited when cultivated with R. subcapitata in low ratios (Microcystis:Raphidocelis ratio of 1:3) throughout the experiment, while the chlorophyte was stimulated in that treatment. Conclusions: The coexistence of a cyanobacterium with a green alga did not alter the main negative response of M. aeruginosa to the submerged macrophyte and zooplankton but stimulated the green alga. Accordingly, the introduction of submerged macrophytes and cladocerans already adapted to eutrophic conditions, both isolated and combined, proved to be a good method to control cyanobacterial blooms without negatively affecting other coexisting phytoplankton species. [ABSTRACT FROM AUTHOR]

The vegetable loofah (Luffa cylindrica) has multiple industrial aptitudes and its interaction with allelopathic substances of other species is important for the definition of management strategies and also in the search for control alternatives for invaders in organic crops. The objective of this research was to evaluate the effect of the crude aqueous extract of carqueja (Baccharis articulata) on the germination and growth of seedlings of vegetable loofah. The experimental design used was completely randomized, with four replications and the treatments were composed by the concentrations of carqueja extract (zero, 25, 50, 75 and 100 g L-1 ). Seed germination was tested by the paper roll method with 25 seeds properly spaced over each germination paper. The evaluations were performed at four and fourteen days after the test was installed. The percentage of abnormal seedlings, germination and vigor, length of shoot and roots, dry weight of cotyledons, hypocotyl and roots were evaluated. There was a negative allelopathic effect of the aqueous crude extract from the shoot dry of carqueja plants on germination and vigor and on the growth of seedlings of vegetable loofah. [ABSTRACT FROM AUTHOR]

O objetivo desse trabalho foi avaliar o efeito de diferentes culturas de cobertura do solo e de épocas de manejo das mesmas sobre a incidência de plantas daninhas e sobre a produtividade da cultura de milho. Foi conduzido um experimento em Canoinhas, SC, com seis alternativas de cobertura de inverno (nabo forrageiro, aveia-preta, centeio, azevém, aveia-preta + ervilhaca e consórcio entre as cinco espécies utilizadas no experimento), as quais foram roçadas em três épocas antes da semeadura do milho (1 dia, 10 e 25 dias). O manejo das coberturas próximo à semeadura do milho proporcionou elevada supressão de emergência e menor acúmulo de fitomassa seca da parte aérea pelas plantas daninhas. O azevém e o consórcio onde o azevém estava presente apresentaram maior capacidade de supressão de plantas daninhas.

Allelopathy is a natural phenomenon resulting from the release of substances capable of killing or inhibiting the growth of other plants. Several compounds of medicinal and aromatic plants have allelopathic properties, which may have a beneficial potential in agricultural management, as an alternative to the use in seed treatment, however, they may present some type of allelopathy inhibitory to the development of certain cultures of interest. Therefore, the objective of this work was to evaluate the allelopathic effect of basil oil on germination and on the development of lettuce and arugula seedlings. The experiment was carried out in the seed laboratory of the University Center of Várzea Grande, from September to December 2019. A completely randomized design was used with four treatments (basil oil concentrations - 0; 0.5 %; 1, 0% and 2.0% v v-1) and four repetitions, each repetition consisting of 25 seeds of each vegetable distributed in an acrylic gerbox box with blotting paper. The following characteristics were evaluated: germination at 4 and 7 days; root length and green mass of seedlings. Basil oil has allelopathic stimulatory potential for lettuce seeds in the evaluated concentrations. Basil oil did not affect seed germination, root length and green mass of arugula seedlings. Thus, it can be concluded that the allelopathic effect of basil oil depends on the species studied, and this effect can be positive, negative or neutral depending on the studied concentrations. [ABSTRACT FROM AUTHOR]

The objective of this work was to evaluate the effect of cover crops and fallow duration on the onion crop planted in direct sowing in trials carried out for three years. In the year 2013, two field trials were carried out in two sites. Two cover crops (oats and millet) and one uncovered control were evaluated at three planting dates. The studied variables were crop establishment and dry matter of the cover. In the field trials performed in 2014 and 2015 the effect of the length of the chemical fallow of oats on the establishment of onion was evaluated. The effect of the duration of the chemical fallow of oats was also evaluated in laboratory in 2015 in Petri dishes. In 2013, the greatest establishment was obtained in the treatments without cover in both sites. In 2014 the greater the duration was of the chemical fallow of the cover, the greater the onion establishment. In the field trial in 2015, no effects of fallow duration on crop establishment were observed, a result attributable to the intense rainfall recorded. In the laboratory, germination was higher in treatments with longer fallow periods. Based on the results, evidence was obtained of the negative effect of the cover crops in the establishment of the onion crop. These effects were inversely related to the duration of chemical fallow and may be attributable to allelopathic effects. [ABSTRACT FROM AUTHOR]

The interest in the exploration of compounds from the secondary metabolism is seen as a strategic alternative in agriculture, even for the control of invasive plants. The objective of this work was to measure the allelopathic activity of extracts CHCl3 and AcOEt from the leaves of O. puberula on the germination of lettuce. The ethanolic extract was obtained from the dried and milled leaves. The crude extract was solubilized in ethanol and acidified (hydroalcoholic fraction). The C6H14 fraction was obtained by liquid-liquid extraction of the hydroalcoholic fraction, the same procedure was used to extract the AcOEt fraction. The hydroalcoholic fraction was basified and extracted with CHCl3. The chemical profile of the obtained fractions was analyzed by Thin Layer Chromatography using specific revelators that confirmed the presence of alkaloids as majority compounds in AcOEt and CHCl3 fractions. The fractions were evaluated for allelopathic potential on lettuce cypselas at 0.8 g mL-1, 0.4 g mL-1 and 0.2 g mL-1. In germination tests the germination parameters analyzed were: germination percentage (% G) and germination speed index (IVG). The results indicated significant changes in the %G, IVG and root growth (CR) of the lettuce seeds and seedlings. The ethanolic extract of leaves of O. puberula showed allelopathic influence on the species L. sativa. Both the AcOEt and CHCl3 fractions reduced the germination rates evaluated, and the latter indicated a dose-response inhibition between the treatments applied. [ABSTRACT FROM AUTHOR]

A utilização indiscriminada de herbicidas na cultura do arroz tem provocado uma pressão de seleção de biótipos de arroz-vermelho resistentes aos herbicidas imidazolinonas. Diante disso, métodos alternativos de controle de plantas daninhas tornam-se uma alternativa para esta situação, tal como a busca de novos ingredientes ativos em compostos aleloquímicos de plantas. O trabalho foi realizado com objetivo de avaliar o potencial alelopático de diferentes concentrações do extrato aquoso de folhas de cultivares de arroz irrigado na germinação e no vigor de sementes de arroz-vermelho. O delineamento experimental adotado foi inteiramente casualizado, com quatro repetições, em esquema fatorial 4 x 5, onde: fator A - Extrato de folhas frescas das cultivares de arroz (BRS Querência, Irga 424, Roxinho e Cica 07) e fator B - Concentrações do extrato (0, 25, 50, 75 e 100%). Os extratos foram obtidos de folhas das plantas das cultivares em estádio reprodutivo R3 (saída da panícula). Estas foram trituradas em água destilada e posteriormente diluídas nas concentrações. Avaliaram-se a germinação, primeira contagem da germinação, índice de velocidade de germinação, comprimento da parte aérea e de raiz e massa seca da parte aérea e de raiz. De maneira geral, o efeito alelopático é maior nas cultivares desenvolvidas mais recentemente, sendo o extrato da cultivar IRGA 424, na concentração de 25%, o mais nocivo para o desempenho fisiológico de sementes de arroz-vermelho.

Dada la importancia cultural y económica para México del cultivo del maíz, y los efectos sobre la germinación y el desarrollo inicial provocado por malezas, fitopatógenos y condiciones ambientales adversas, el objetivo de esta investigación fue evaluar el efecto del osmoacondicionamiento de semillas de maíz sobre la germinación y el desarrollo inicial. Se realizaron dos ensayos; en el primero se estudiaron los resultados de tres extractos vegetales: Cinnamomum zeylanicum, Azadirachta indica y Zingiber officinale; bicarbonato de sodio y el biofertilizante magro. El primero con once tratamientos en un diseño completamente al azar, en el cual se cuantificó la velocidad de emergencia y el porcentaje de germinación. En el segundo ensayo se estudiaron nueve tratamientos, los cuales consistieron en las concentraciones que permitieron la germinación en el primer ensayo; como variables se cuantificaron altura, peso de materia fresca y seca total, y volumen de raíz. Se utilizaron semillas locales de Chiapas, la siembra se realizó en vivero, utilizando arena de río estéril como sustrato. Las semillas que fueron tratadas con bicarbonato de sodio y C. zeylanicum 10 % (V:V) presentaron mayor velocidad de emergencia; el tratamiento bicarbonato de sodio (30 g/L) favoreció la germinación y junto a los tratamientos C. zeylanicum al 10 % (V:V) A. indica al 20 % (V:V) y Z. officinale al 30 % (V:V) registraron los valores más altos de peso fresco de raíz, peso fresco y seco de biomasa aérea, además estimularon el crecimiento aéreo en un 56 % con respecto al tratamiento control (p

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The purpose of thisstudy was to carry out phytochemical prospecting of Norantea guianensis bark and to evaluate its allelopathic potential in seed germination and the initial growth of lettuce and tomato seedlings using aqueous and ethanolic extracts. We identified phenolic compounds and derivatives, flavonoids, and tannins, as well as coumarins, anthraquinones, alkaloids, and saponins. Negative interference was observed in germination and vigour tests, mainly in tomato seeds, with extracts negatively affecting seedling development. The species N. guianensis has the ability to interfere in the development of other plants, and for this reason, its use should be carefully evaluated. [ABSTRACT FROM AUTHOR]

In the present study we evaluated the chemical composition and allelopathic activity of the essential oil (EO) of Blepharocalyx salicifolius (Kunth) O. Berg leaves on the germination and initial growth of Lactuca sativa L. (dicotyledonous) and Sorghum bicolor (L.) Moench (monocotyledon). EO was obtained by hydrodistillation for 3 h. The EO composition analysis was performed by gas chromatography coupled to a mass spectrometry (GC-MS). The allelopathic activity of EO was evaluated at 2.5; 5.0 and 7.5%. The seeds were immersed in the solution for 2 min., distributed in Petri dishes, that were maintained in a BOD incubator. On the seventh day, the variables germination (%), root length (cm), shoot length (cm) and total seedling length (cm) were evaluated. The major constituents identified in the OE were eucalyptol (49.6%), limonene (13.6%) and β-caryophyllene (12.2%). The EO affected negatively the germination percentage of L. sativa seeds and the root system and total seedling length of S. bicolor. There was a negative allelopathic activity against the two evaluated species. [ABSTRACT FROM AUTHOR]

Soluble allelochemicals have generated great interest since they can be used for the biological control of pests, especially of weeds. However, few studies have evaluated the effectiveness of soluble compounds of exudates on germination in relation to exposure time. Here we evaluate the inhibitory effect of aqueous root, stem and leaf extracts of five South American species of Bothriochloa on the percentage of seed germination of four target species (lettuce, lovegrass, maize and wintergreen paspalum) over three exposure periods (48, 120 and 168 h). Aqueous extracts of the five Bothriochloa species inhibited germination; germination inhibition was strongly correlated with exposure time, with the longest treatment period (168 h) being the one of greatest inhibitory activity. Inhibitory activity differed among types of aqueous extracts. The suitable management of allelopathy might improve crop productivity and environmental protection through biologically friendly control of weeds. [ABSTRACT FROM AUTHOR]

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O trabalho teve como objetivo avaliar o potencial alelopático de resíduos da cana-de-açúcar utilizando bioensaios na germinação de sementes e crescimento de plantas daninhas e plantas bioindicadoras. As doses do bioextratode palha da cana-de-açúcar estimulou o comprimento da parte aérea das plantas daninhas (dente-de-leão epicão-preto) e inibiu o seu percentual de germinação. As doses de palha da cana-de-açúcar podem inibir ou estimular o desenvolvimento das espécies em estudo. As espécies foram inibidas quando pulverizado o pó da palha da cana-de-açúcar em todas as variáveis analisadas. Com os resultados deste estudo, verifica-se a necessidade da continuação deste trabalho, onde poderá ser isolado e identificado o composto fitoquímico de interesse do pó da palha e do bioextrato da palha de cana-de-açúcar, sendo utilizado como controle natural nas fases de germinação e/ou desenvolvimento de plântula ou planta de espécies daninhas (dente-de-leão e picãopreto).

Algumas plantas podem produzir compostos secundários com potencial benéfico no manejo agrícola, como alternativa à utilização no tratamento de sementes, porém, podem apresentar algum tipo de alelopatia inibitória ao desenvolvimento de determinadas culturas de interesse. Logo, o objetivo deste trabalho foi avaliar efeitos alelopáticos do extrato aquoso de manjericão (Ocimum basilicum L.) e babosa (Aloe vera L.) em concentrações na germinação e desenvolvimento inicial de sementes de rúcula (Eruca sativa L.). A concentração para o extrato aquoso foi de 20% (peso/volume) e a partir desta, foram obtidas as demais concentrações. Os tratamentos utilizados foram as concentrações de 25, 50, 75 e 100% dos extratos de babosa e manjericão extraídos pelo método a frio de turbólise, e testemunha com água autoclavada.Os efeitos dos extratos foram avaliados quanto as variáveis: índice de velocidade de germinação, porcentagem de germinação, comprimento de radícula e parte aérea. O experimento foi conduzido em delineamento inteiramente casualizado, com 6 repetições, sendo a unidade experimental composta por uma caixa gerbox com 50 sementes de rúcula. As doses de manjericão e babosa foram testadas em experimentos distintos. Os extratos de manjericão e de babosa apresentam substâncias que favorecem o desenvolvimento da parte aérea, influenciaram negativamente no desenvolvimento da radícula, porém, não apresentaram efeito alelopático na germinação final e velocidade de germinação de sementes de rúcula.

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Algumas plantas podem produzir compostos secundários com potencial benéfico no manejo agrícola, como alternativa à utilização no tratamento de sementes, porém, podem apresentar algum tipo de alelopatia inibitória ao desenvolvimento de determinadas culturas de interesse. Logo, o objetivo deste trabalho foi avaliar efeitos alelopáticos do extrato aquoso de manjericão (Ocimum basilicum L.) e babosa (Aloe vera L.) em concentrações na germinação e desenvolvimento inicial de sementes de rúcula (Eruca sativa L.). A concentração para o extrato aquoso foi de 20% (peso/volume) e a partir desta, foram obtidas as demais concentrações. Os tratamentos utilizados foram as concentrações de 25, 50, 75 e 100% dos extratos de babosa e manjericão extraídos pelo método a frio de turbólise, e testemunha com água autoclavada. Os efeitos dos extratos foram avaliados quanto as variáveis: índice de velocidade de germinação, porcentagem de germinação, comprimento de radícula e parte aérea. O experimento foi conduzido em delineamento inteiramente casualizado, com 6 repetições, sendo a unidade experimental composta por uma caixa gerbox com 50 sementes de rúcula. As doses de manjericão e babosa foram testadas em experimentos distintos. Os extratos de manjericão e de babosa apresentam substâncias que favorecem o desenvolvimento da parte aérea, influenciaram negativamente no desenvolvimento da radícula, porém, não apresentaram efeito alelopático na germinação final e velocidade de germinação de sementes de rúcula. [ABSTRACT FROM AUTHOR]

Allelopathy is a strategy of plants to defend and delimit their territory, greatly common in weeds. The snakeweed (Stachytarpheta cayennensis) is a type of weed widely found in cultivation areas and in urban areas in the Brazilian Amazon. Only few researches on allelopathy deal with anatomic changes that secondary metabolites cause on the affected plants. Current paper analyzes the allelopathic activity of five concentrations of the alcoholic extract (0; 0,5; 1; 2; 4%) of S. cayennensis at the level of anatomic changes in Cucumis sativus seedlings. Results evidence an increase in thickness of anatomic structures of the organs in aqueous and alcoholic extracts, revealing pronounced thickness as concentrations of the extract increase. The release of compounds that interfere in the development of C. sativus is an important datum to be employed in the development of alternative strategies instead of herbicides in other cultivations by an ecological management of weed. [ABSTRACT FROM AUTHOR]

Introduction: Use of allelochemicals as inexpensive, biodegradable and eco-friendly substitutes for the management of weeds in crops is a central topic nowadays. Objective: The current study represented the comprehensive screening of allelopathic activity of 73 weeds in Pakistan by the Sandwich method and dish pack method. To investigate the allelochemical compound in top most allelopathic weed. Methods: Allelopathic effects of selected weeds leaves leachate were determined through sandwich technique, while volatile allelopathic effects through dish pack techniques. Qualitative and quantitative phytochemical techniques were applied to investigate allelochemical potential of Melilotus indicus. The statistical analysis of the data described the allelopathic effect of 73 weed plants on lettuce seedling growth in terms of radicle and hypocotyl elongation. Results: Elongation percentage of radicle and hypocotyl ranged 0-74 % to 0-148 % and 0-75 % to 0-84 % respectively at 10 mg concentration of dry plant powder in sandwich method while it was 2-234 % and 7-150 % at in Dish Pack method. Among the plants screened for phytotoxic activity, M. indicus contained the strongest allelochemicals. Qualitative and quantitative analysis of M. indicus showed the presence of flavonoids and phenolic compound along with other allelochemical. Conclusions: Selected weeds may have strong allelochemical potential that can help in the development of bioactive compounds from plant species to be used as natural herbicides and pesticides for sustainable management of weeds and pest. [ABSTRACT FROM AUTHOR]

A família Piperaceae inclui cerca de 12 gêneros e mais de 1400 espécies de pimentas distribuídas em todas as regiões subtropicais e tropicais. Algumas espécies do gênero Piper podem apresentar efeito fungicida, inseticida ou mesmo alopático sobre as sementes de outras espécies. Diante disso, o presente trabalho teve como objetivo avaliar o efeito dos extratos alcóolicos de três diferentes espécies de pimentas na germinação e desenvolvimento inicial de sementes de alface. As sementes foram umedecidas com extratos alcoólicos das três espécies de pimentas: Piper callosum, Piper médium, Piper aduncum, em diferentes concentrações: 0, 20, 30, 40, 50, 60 e 70%. As avaliações foram diárias até o sétimo dia após a semeadura, e ao final foi determinada a porcentagem de germinação (G%), primeira contagem de germinação (PCG), índice de velocidade de germinação (IVG) e comprimento de plântula (CP). Os dados foram submetidos às analise de variância e de regressão. Para a primeira contagem de germinação e o índice de velocidade de germinação, o extrato da Piper medium se destacou em relação as outras duas pimentas, para o comprimento de plântulas, a Piper callosum e a Piper aduncum prejudicaram esta característica. Para o fator concentração houve a redução da germinação com o aumento das concentrações dos extratos. Para primeira contagem de germinação, observou-se que elevadas concentrações dos extratos alcóolicos prejudicaram o desenvolvimento inicial das plântulas. A utilização dos diferentes tipos de extratos nas diferentes concentrações sobre as sementes de alface foi prejudicial a germinação e desenvolvimento inicial das mesmas.