Modelos didáticos como estratégia investigativa e colaborativa para o ensino de Botânica

A desmotivação dos alunos é frequentemente tida pelos professores de Biologia como causa do insucesso escolar. Para superar tal dificuldade, um projeto de pesquisa foi realizado, liderado pelos estudantes de uma escola pública de ensino médio no município de Vitória-ES. Em atividade investigativa acerca das principais dificuldades na aprendizagem de biologia, os conceitos de Botânica mostraram-se prioritários. Modelos didáticos para aulas de botânica foram elaborados pelos alunos de forma coletiva e colaborativa, e utilizados em aulas mais tarde, com o objetivo de tornar as aulas mais interessantes. Uma avaliação dos modelos foi realizada pelos professores de biologia e pelos alunos. A utilização dos modelos didáticos e a liderança dos alunos autores do projeto, mostram-se importantes estratégias motivadora, tendo tornado as aulas mais participativas, as relações mais horizontais entre alunos e professores e, assim, facilitou a aprendizagem de conceitos relacionados à botânica entre muitas outras habilidades

Piper nigrum allelopathy on the germination and initial growth of Lactuca sativa and Panicum maximum

The increased demand for food promotes greater use of agricultural inputs and pesticides used in pest control. Many of these products have negative environmental and public health impacts. Thus, there is a need for alternative products, with allelopathic capacity that reduce such impacts. The objective of this work was to verify the allelopathic potential of Piper nigrum L. extracts on the germination and initial growth of Panicum maximum Jacq. and Lactuca sativa seeds. The experimental design used was completely randomized, using two plant organs (leaf and seed), three extractors (hexane, ethyl acetate and methanol) and five concentrations (0 mg/L, 200 mg/L, 400 mg/L, 600 mg/L and 800 mg/L). It was verified the influence of these extracts on germination speed index (IVG), germination percentage (G), mean germination time (TMG), allelopathy index (IA), shoot growth (CPA) and in the root growth (CR) of seeds and seedlings. The leaf and seed extracts, at all concentrations and extractors tested, did not show phytotoxicity or had a very small inhibitory effect on germination and initial growth of Lactuca sativa. For Panicum maximum, ethyl acetate and methanol seed extracts, at the highest concentrations tested, had the most significant negative effects on the weed. Thus, it was possible to infer that extracts from Piper nigrum seeds have potential use in the control of the weed Panicum maximum.The increased demand for food promotes greater use of agricultural inputs and pesticides used in pest control. Many of these products have negative environmental and public health impacts. Thus, there is a need for alternative products, with allelopathic capacity that reduce such impacts. The objective of this work was to verify the allelopathic potential of Piper nigrum L. extracts on the germination and initial growth of Panicum maximum Jacq. and Lactuca sativa seeds. The experimental design used was completely randomized, using two plant organs (leaf and seed), three extractors (hexane, ethyl acetate and methanol) and five concentrations (0 mg/L, 200 mg/L, 400 mg/L, 600 mg/L and 800 mg/L). It was verified the influence of these extracts on germination speed index (IVG), germination percentage (G), mean germination time (TMG), allelopathy index (IA), shoot growth (CPA) and in the root growth (CR) of seeds and seedlings. The leaf and seed extracts, at all concentrations and extractors tested, did not show phytotoxicity or had a very small inhibitory effect on germination and initial growth of Lactuca sativa. For Panicum maximum, ethyl acetate and methanol seed extracts, at the highest concentrations tested, had the most significant negative effects on the weed. Thus, it was possible to infer that extracts from Piper nigrum seeds have potential use in the control of the weed Panicum maximum

A nanoemulsion of Rosmarinus officinalis L. essential oil with allelopathic effect against Lactuca sativa L. seeds / Uma nanoemulsão a partir do óleo essencial de Rosmarinus officinalis L com efeito alelopático em sementes de Lactuca sativa L

Plant's essential oils have a wide range of allelopathic effects with potential uses as bioherbicides. In addition, the application of oils through nanoemulsions represents a promising alternative for agriculture, as it offers better performance and lowers toxic waste generation. Therefore, this study aimed to evaluate the chemical constitution of Rosmarinus officinalis (rosemary) essential oil, as well as its effects on germination, initial growth, Catalase (CAT), Peroxidase (POX), and Superoxide-Dismutase (SOD) enzymes activity of Lactuca sativa seeds. Nanoemulsions were produced at 5% concentration and then diluted with distilled water to 5.0, 7.0, and 10.0 mg/mL. We compared data obtained using variance (ANOVA) analysis, followed by Tukey's test at 5% probability. Rosemary oil showed a wide variety of terpenoid compounds, mainly the 1,8-cineol monoterpene, which accounted for 46% of the sample. The oil showed a dose-dependent negative allelopathic influence on all variables analyzed, causing a drop in germination percentage (%G), germination speed index (GVI), mean germination time (MTG), and leaf and root length. There was no change in CAT and SOD activity. The POX activity showed a reduction starting at the concentration of 7.0 mg/mL. The results showed allelopathic effects of rosemary oil, with potential use as a natural bioherbicide

Dormancy Breaking in Senna Pendula (Willd.) H. S. Irwin & Barneby

ABSTRACT Senna pendula seeds dormancy is caused by impermeability of the seed coat to water. In order to determine the best methodology to overcome dormancy and to perform a morphological characterization, two batches of seeds were submitted to the following treatments: a) mechanical scarification of the seed coat; b) immersion in hot water at 70 °C for 5, 10, 15 and 20 minutes; c) immersion in hot water at 90 °C for 5, 10, 15 and 20 minutes; d) sulfuric acid concentrate for 5, 10, 15 and 20 minutes; e) no treatment. The experiment was conducted in laboratory using a completely randomized design, with four replications of 25 seeds each, with daily verification for 7 days. The results showed that the use of water does not overcome the dormancy, however mechanical and chemical scarifications were the most effective treatments, with germination percentage of up to 94%