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The genus Amaranthus (Amaranthaceae) comprises plants considered to be weeds, but also consumed as food and in popular medicine. These plants are rich in biologically active compounds that can be exploited to produce bioherbicides. In this sense, the present work aimed to evaluate the allelopathic effect of the ethanolic leaf extract from five Amaranthus species (A. spinosum, A. viridis, A. deflexus, A. hybridus and A. retroflexus) by phytochemical screening, as well as its effects on germination, initial development and cell cycle of seedlings or meristematic cells of Lactuca sativa L. (lettuce). All five studied species presented organic acids, carotenoids and steroids in the obtained ethanolic extracts. Polysaccharides, proteins and amino acids, azulenes, depsides, coumarins and saponins were observed in extracts of at least one of the evaluated species. The tested extract concentrations (0.25–4.0 g/L) inhibited the germination and the germination speed index of the exposed L. sativa seeds in a dose-dependent manner. The highest tested concentration (4.0 g/L) caused more than 95% inhibition in all evaluated extracts. Consequently, a significant reduction in the development of treated seedlings was observed. In the microscopic analysis, mitodepressive effect was verified with extracts of A. spinosum and A. viridis, whereas those from A. deflexus, A. hybridus and A. retroflexus induced a significant increase in the frequency of mitotic cells with chromosomal alterations, most frequently c-metaphases and sticky chromosomes. Condensed nuclei were also observed as a consequence of cell exposure to the extracts, with a significant increase in the treatments with extracts from A. spinosum, A. deflexus and A. retroflexus.

Plants are rich in biologically active compounds. They can be explored for the production of bioherbicides. In this context, the present work aimed to evaluate the allelopathic effect of hydroalcoholic extracts from two Solanaceae species: Solanum muricatum Ait. and Solanum betaceum Cav. For this end, we conducted phytochemical screening and biological assays, determining the effects of the extracts on germination, early development, cell cycle, and DNA fragmentation in plantlets and meristematic cells of the plant model Lactuca sativa L. (lettuce). The percentage of seeds germinated under effect of S. muricatum extract did not differ from the control, but plantlet growth was reduced at the highest concentrations. For S. betaceum extract, dose dependence was observed for both germination and plantlet development, with the highest concentrations inhibiting germination. The growth curves revealed the concentrations of 2.06 and 1.93 g/L for S. muricatum and S. betaceum extracts, respectively, as those reducing 50% of root growth (RG). At these concentrations, both extracts presented mitodepressive effect, besides inducing significant increase in the frequency of condensed nuclei, associated to DNA fragmentation and cytoplasmic shrinkage. The frequency of chromosome alterations was not significant. We further discuss the mechanisms of action related to the chemical composition of the extracts, which presented organic acids, reducing sugars, proteins, amino acids, and tannins, besides catechins and flavonoids, only found in the extract of S. betaceum.

Essential oils from Mentha piperita, Cymbopogon citratus, Rosmarinus officinalis, Peumus boldus and Foeniculum vulgare were extracted by hydrodistillation, chemically characterized and quantified by GC/MS and GC/FID. The principal componentes in the essential oil of M. piperita (carvone and limonene), C. citratus (geranial, neral and myrcene), R. officinalis (1,8-cineole, camphor and α-pinene), P. boldus (α-terpinyl formate, p-cymene and 1,8-cineole) and F. vulgare (methyl chavicol, limonene and fenchone) were identified. The oils were tested for antioxidant activity employing the DPPH (2,2-diphenyl-1-picryl-hydrazyl) radical-capture method, the oxidation of the β-carotene/linoleic acid system, and the ABTS radical-capture method. The essential oils were not effective. The antioxidant activities of the oils were determined by the hydroxyl method, and the highest activity (62.80%) was observed with the essential oil from M. piperita. Activities of 1.54 and 1.82 μg μg-1, respectively, were observed for the essential oils from C. citratus and P. Boldus using the phosphomolybdenum method. No activity was observed with respect to reducing power. The essential oil from C. citratus was effective in inhibiting the growth of L. monocytogenes (15.63 mg·L-1), S. choleraesuis (15.63 mg·L-1) and E. coli (31.25 mg·L-1), and the essential oil from P. boldus inhibited the growth of S. aureus (62.5 mg·L-1). No essential oil inhibited the growth of P. aeruginosa. A low antioxidant activity and a promising antibacterial activity were observed for these essential oils.

A abobrinha, é mais uma hortaliça adotada para exploração em hidroponia. Outrossim, pouco se conhece acerca do seu comportamento em condições de saturação do sistema radicular que imponham hipoxia ou anoxia, fator reconhecido pelo elevado potencial estressor. Assim, avaliaram-se as respostas da cultivar Caserta ao alagamento da raiz em Telado com sombreamento de 50% em Teresina/PI, entre setembro e novembro de 2018. O delineamento experimental foi blocos casualizados com 3 repetições, com parcelas constituídas de um vaso com 02 plantas, e os tratamentos representados por tempos de inundação da raiz: 00; 24; 48 e 72 horas, aplicados na fase de pré-florescimento (6a folha), 14 dias após a emergência. A inundação mostrou ser um impactante fator de estresse, que em 24 horas provocou murcha da planta, afetou o peso da matéria fresca da raiz, da parte aérea e relação parte aérea/raiz; antecipou o fechamento das flores masculinas, comprometendo a antese das flores femininas, reduzindo o número de flores masculinas e femininas. Apesar da diferenciação ocasional de lenticelas a abobrinha suporta no máximo 24 horas de alagamento, de modo que exposição a maiores tempos conduzirá a danos irreparáveis.

Unconventional vegetables, in general, are plants that have been largely consumed by the population at some point and, because of changes in eating behavior, now present reduced economic and social expression and have lost ground to other vegetables. The objectives of this study were to perform phytochemical screening of the ethanol extracts of Rumex acetosa L., Tropaeolum majus L., Solanum muricatum, Stachys byzantina K. Koch and Solanum betaceum Cav. and evaluate their antioxidant potentials via the methods involving scavaging of the DPPH free radical and the ABTS radical, phosphomolybdenum and reducing power. In phytochemical screening, five species of unconventional vegetables tested positive for tannins; for sesquiterpene, lactones and other lactones. These tests were positive for Tropaeolum majus L. and Rumex acetosa L., Solanum betaceum Cav. and Solanum muricatum tested negative for steroids. Only Solanum betaceum Cav. gave positive tests for flavonoids. Among the five plant species studied, Stachys byzantina K. Koch presented the greatest antioxidant potential in all the methods evaluated.

The essential oils from Mentha viridis L. and Mentha pulegium L. were characterized by gas chromatography coupled to mass spectrometry (GC-MS). These oils were obtained by hydrodistillation and presented linalool (40.70%), carvone (13.52%) and α-terpinene (8.56%) as the principal constituents in the essential oil from Mentha viridis L. Pulegone (50.01%), menthol (31.90%) and menthone (16.56%) were the principal constituents in the essential oil from Mentha pulegium L. These essential oils (in concentrations ranging from 3.91 to 500 μL·mL-1) showed satisfactory activities against Escherichia coli, Listeria monocytogenes, Salmonella choleraesuis and Staphylococcus aureus. The antioxidant activities with 2-deoxyribose and phosphomolybdenum and the reducing power (in concentrations ranging from 0.78 to 1000 μL·mL-1) were determined. The antioxidant activity was observed for the two oils evaluated by the phosphomolybdenum and 2-deoxyribose methods, whereas the essential oil from M. viridis presented low antioxidant activity in the reducing power assay.

The objective of this study was to characterize and verify the in vitro antitumor activity of essential oils (EOs) extracted from the leaves and flowers of Callistemon viminalis. The EOs were extracted by hydrodistillation using a modified Clevenger apparatus. The identification and quantification of constituents were performed on a gas chromatograph coupled to a mass spectrometer and a gas chromatograph with a flame ionization detector. The antitumoral activity was evaluated by a colorimetric assay (MTS) using different cell lines derived from human tumors (breast, lung, glioblastoma, and melanoma). The major constituents of the EOs of leaves and flowers were similar, only quantitative differences being observed. The compounds 1,8-cineole, α-pinene and α-terpineol were found in concentrations of 50.4%, 25.8% and 8.7% in the EOs obtained from the leaves and 48.8%, 24.5% and 3.9% in the EOs obtained from the flowers, respectively. The cytotoxic activity of the EOs was observed only in melanoma cultures (HT144). Cultures treated for 48 h with EOs from leaves and flowers (200 μg·mL-1) reduced the viability by 40% and 25%, respectively. Thus, the antiproliferative activity of the EO from leaves was more pronounced than the EO from flowers in cells derived from melanoma.

O presente trabalho teve o objetivo geral de estudar as respostas produtivas de capins do gênero Cynodon em resposta a estratégias de corte. O experimento foi conduzido no campus da ESALQ em Piracicaba, SP. Foram avaliados três cultivares, Tifton 85 e Jiggs (estabelecidos vegetativamente) e Vaquero (propagado por sementes) submetidos a três intervalos de corte, 14, 28 e 42 dias. O delineamento experimental foi completamente casualizado com arranjo fatorial completo. Foram medidas a produção de forragem, composição morfológica da forragem produzida, o índice de área foliar (IAF), a interceptação luminosa (IL) e altura do dossel. Foi feito também um estudo de análise de crescimento. Os cultivares Jiggs (22,6 Mg MS ha-1) e Tifton 85 (21,8 Mg MS ha-1) apresentaram os maiores acúmulos de forragem total na média das frequências de 28 e 42 dias de rebrotação. Na frequência de 14 dias de rebrotação, não houve diferença para o acúmulo total de forragem entre os cultivares com média de 13,3 Mg MS ha-1. A proporção de folhas, em média, foi maior nas frequências de 14 (69,6%) e 28 (55,2%) dias de colheita no verão. No inverno a proporção de folhas foi de 57,6% e 59,8% para as frequências de 14 e 28 dias de corte, respectivamente. Tifton 85 e Vaquero apresentaram maior porcentagem de folhas no verão, com médias de 63,3% e 56,0%, respectivamente. No inverno o Tifton 85 apresentou maior porcentagem de folha, com média de 63%. As frequências de 14 e 28 dias resultaram em maiores porcentagens de folha. O Jiggs apresentou maior porcentagem de colmo (46,7%) no verão e no inverno (40,0%). A frequência de 42 dias de corte no verão resultou em maior porcentagem de colmo (51,2%) e maior IAF no pré-corte (4,8). No inverno, a porcentagem de colmo (43,9%) e o IAF pré-corte (3,9) também foram maiores sob a frequência de 42 dias de colheita. A altura pré-corte no verão foi maior na frequência de 42 dias com média de 32,7 cm e o cultivar Jiggs foi o que apresentou maior altura pré-corte com média de 26, 5 cm nessa estação. A frequência de 28 dias de colheita no verão resultou em IL de 93,4%. A frequência de 42 dias de colheita gerou maior taxa de crescimento de cultura, TCC (30,9 g MS m-2 dia-1) no verão. Maior taxa de crescimento relativo, TCR, ocorreu nas frequências de 28 (0,26 g g1dia1) e 42 dias (0,32 g g1dia1) também no verão. No inverno, maior TCR foi medida na frequência de 28 dias (0,21 g g-1 dia-1). Maiores razão de área foliar, RAF, e razão de peso foliar, RPF, ocorreram na frequência de 28 dias no verão. Jiggs e Tifton 85 são os cultivares mais recomendados para produção de forragem e a frequência de desfolhação a cada 28 dias é a que garante melhor produção quando o objetivo é produzir massa de forragem com uma proporção maior de folhas. The objectives in this study were to investigate the productive responses of Cynodon grasses to a range of defoliation strategies. The field trial was conducted at ESALQ-USP in Piracicaba, SP, Brazil. Three commercial Cynodon cultivars (Tifton 85 and Jiggs, vegetatively propagated; and Vaquero, a seeded type) were mechanically harvested every 14, 28, and 42 days under a completely randomized design in a complete factorial arrangement with four replicates. Responses measured included forage accumulation (yield), plant-part composition in the accumulated forage, leaf area index (LAI), sward light interception (LI), and sward height. A classical growth analysis study was also carried in the same field plots. Jiggs (22.6 Mg DM ha-1) and Tifton 85 (21.8 Mg DM ha-1) were the highest yielding materials under the 28- and 42-d schedules. Under the 14-d frequency, total forage accumulation did not differ among cultivars, averaging 13.3 Mg DM ha-1. On average, leaf percentage in the accumulated forage was higher in plots clipped every 14 (69.6%) and 28 (55.2%) days. In the cool-dry season, with irrigation, leaf percentage in the harvested forage was 57.6 and 59.8% in plots harvested every 14 and 28 days, respectively. Tifton 85 and Vaquero forage had more percent leaves in the warm-rainy season (63.3 and 56 %, respectively). In the cool season, Tifton 85 forage was leafier, at 63%. The 14- and the 28-d harvest schedules resulted in leafier forage. Jiggs forage had more % stem both in the warm (46.7) and in the cool (40) seasons. The 42-d harvest schedule resulted in highest stem percentage (51.2%) but also higher LAI (4.8) at harvest during the warm season. In the cool season, stem percentage (43.9%) and LAI at harvest (3.9) were also highest in plots clipped every 42 days. Sward height at harvest during the warm season was greater in plots clipped every 42 days, averaging 32.7 cm, with Jiggs being the tallest grass in the warm season, on average (26.5 cm). The 28-d schedule resulted in mean sward LI of 93.4 % on average. Crop growth rate (CGR) was highest (30.9 g DM m-2 d-1) under the 42-d frequency in the warm season. Higher warm-season relative growth rates (RGR) were registered under the 28- and the 42-d schedule (0.26 and 0.32 g g-1d-1, respectively). In the cool season, the highest RGR (021 g g-1 d-1) was measured under the 28-d schedule. The highest leaf area ratio (LAR) and leaf weight ratio (LWR) were measured in the 28-d treatment during the warm-season. Jiggs and Tifton 85 are recommended for their high yield potential under a 28-d harvest schedule, which ensures the production of leafy forage.