No ensino de Ciências, a Botânica é uma das áreas com maior dificuldade de assimilação de conteúdos. Destaca-se, dentre suas causas, o desinteresse dos alunos pelo tema, a falta de aulas práticas e de materiais didáticos facilitadores. Este estudo objetivou avaliar a realização de palestras e experimentos na aprendizagem de conceitos de Botânica por discentes do Ensino Fundamental. O presente estudo foi realizado no Município de São Gabriel, Rio Grande do Sul em três Escolas Municipais. As atividades realizadas foram construção de modelos didáticos, palestras e experimentos demonstrativos sobre Botânica em laboratório e a campo, totalizando a participação de 120 alunos em cada atividade realizada. Pode-se observar, neste estudo, que as atividades realizadas foram positivas para o processo de ensino-aprendizagem, com acréscimo no conhecimento; uma vez que, o conhecimento foi significativo tanto para o discente do Ensino Fundamental como para os acadêmicos da Universidade Federal do Pampa, especialmente, para sua formação profissional, especialmente os do Curso de Licenciatura em Ciências Biológicas.Palavras-chave: Recursos didáticos. Educação ambiental. Ensino-aprendizagem. Practical classes as a strategy for botanical teaching in middle schoolAbstractIn the teaching of science, Botany is one of the areas with the greatest difficulty in assimilating content. Among the causes, we highlight the students' lack of interest in the theme, the lack of practical classes and suitable materials. This study aimed to evaluate the performance of lectures and experiments on the learning of Botany concepts by elementary school students. The present study took place, in the city of São Gabriel in the state of Rio Grande do Sul, in three public schools. The classes were taught and performed at the laboratory and also in its own field , with the participation of 120 students in each activity. It could be observed in this study that the activities performed were positive for the teaching-learning process, with increased knowledge; since, the knowledge was significant for the students of the Elementary School as for the students of the Universidade Federal of Pampa, especially for their professional formation, especially those of the Degree in Biological Sciences.Keywords: Didactic materials. Environmental education. Teaching-learning.

Aims: The biological properties of essential oils represent possible therapeutic alternatives, with antimicrobial and antioxidant activities, and application in many areas of the industry. The objective was to determine the yield, chemical composition, antibacterial and antioxidant activities of the essential oils of Lavandula angustifolia, Pogostemon cablin, Rosmarinus officinalis, and Thymus vulgaris against Staphylococcus aureus, Salmonella enteritidis, Escherichia coli and Pseudomonas aeruginosa. Place and Duration of Study: The experiment was conducted at the microbiology laboratory of the Federal University of Technology - Paraná, Brazil, in the period between June 2016 to May 2017. Methodology: The essential oils were analyzed by gas chromatography coupled to mass spectrometry. The antibacterial activity was determined by microdilution in broth, showing minimum inhibitory concentration and minimum bactericidal concentration. The antioxidant activity was evaluated by scavenging of 2,2-diphenyl-1-picryl hydrazyl radical (DPPH). Results: The average yields of essential oils from L. angustifolia, P. cablin, R. officinalis,and  T. vulgaris were (%) 0.85; 2.0; 1.20, and 1.19, respectively. The major components of lavender essential oil were linalyl acetate (40.1%) and linalool (35.2%); for P. cablin - patchoulol (31.5%), seichelene (13.6%) and α-bulnesene (15.6%); for rosemary - camphor (32.5%), 1.8-cineole (13.6%) and α-pinene (9.8); for T. vulgaris - thymol (47%), o-scimene (21.6%), and carvacrol (11.4%). Thyme oil showed the best results for antibacterial activity, and low values (0.195 µL mL-1) of minimum inhibitory concentration were needed to inhibit S. aureus and S. enteritidis, and for L. angustifolia, P. cablin, and R. officinalis higher concentrations of essential oil were required. The essential oils of P. cablin and T. vulgaris had the strongest antioxidant properties (12.08 and 10.2 µmol trolox mL−1). Conclusion: The essential oils evaluated have an inhibitory effect on the microorganisms under study and also interesting antioxidant activity, which could be used by medicine to control bacterial infections, with potential application as natural food preservatives and as nutraceuticals.

An interesting aspect of the biology of Trifolium polymorphum, an endemic species of the natural pastures of Rio Grande do Sul State in Brazil, is that it is amphicarpic. Amphicarpy is a fascinating reproductive strategy in which aerial and subterranean seeds are produced by the same plant. We evaluated the number, size and weight of aerial and subterranean seeds of two populations (Bagé and Santana do Livramento) of T. polymorphum which have grown from the regrowth of storage roots and in the absence of herbivory. Aerial flowers produced more seeds than subterranean flowers, about 14 times in the Santana do Livramento population and nine times in the Bagé population. However subterranean seeds were heavier than aerial seeds. We suggest that in the natural pastures of Rio Grande do Sul, where intense grazing and trampling can periodically destroy the aerial part of the plants, the occasional formation of subterranean seeds in T. polymorphum provides an alternative safety system in terms of population persistence. Although amphicarpic, T. polymorphum invests early in asexual reproduction through the production of storage roots, which favors the persistence in unfavorable habitats for sexual reproduction, and thus plants may persist vegetatively year after year without the need of regeneration by seeds.

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