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

Alterações no conteúdo de reservas em sementes de Melanoxylon brauna durante o processo de envelhecimento natural e acelerado

The decay of seeds is irreversible and at best can only be delayed by applying techniques that reduce the velocity of the metabolic reactions involved. There is little information on the biochemistry of tropical forest tree seeds related to their storability. It was investigated the influence of the composition of lipids and soluble sugars of two storage compartments, the cotyledons and the embryonic axis, of Melanoxylon brauna Schot. (Leguminosae- Caesalpinioideae), a hardwood known as black brauna, seeds stored at 20 °C for 0, 3, 6, 9 and 12 months (natural ageing) and for 0, 24, 48, 72 and 96 hours at 40 °C (accelerated ageing). The levels of fatty acids and monosaccharides varied differentially in each of the embryo storage compartments. Changes in oligosaccharide levels were similar for both types of ageing, diminishing in both compartments. Ageing can be attributed to the significant decrease of oligosaccharides and the increase of glucose in both types of ageing and both embryo compartments

Estudo enzimático da deterioração de sementes de melanoxylon brauna submetidas ao envelhecimento natural e acelerado

There is no specific knowledge of forest tree seeds regarding the metabolic processes involved during storage which makes the establishment of techniques for their suitable conservation difficult. The object of the present research was to study the role of oxidative stress enzymes and fat metabolism during storage and artificial ageing. Seeds of Melanoxylon brauna - Leguminosae- Caesalpinodeae (brauna) were naturally aged during storage for 0, 3, 6, 9 and 12 months in a cold chamber, and artificially aged (accelerated ageing) during 0, 24, 48, 72 and 96 hours, in order to evaluate the changes in the activity of the enzymes superoxide dismutase and catalase and also the oil content. Germination tests were made and the enzymatic activity and quantification of fat content were measured in the embryonary axis and cotyledons. The natural and accelerated ageing affected the behavior of the seeds in a similar manner causing a reduction in vigour. Although the artificial and natural ageing of the seeds affected the germination in a similar way, the accelerated ageing at 45 °C for 72 hours adequately simulated the enzymatic behavior as demonstrated by the seeds stored for 12 months in the cold chamber. There was a similar gradual reduction in the fat reserves in both ageing systems but without any correlation between natural storage and accelerated ageing

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

Mobilização de reservas durante a germinação das sementes e crescimento das plântulas de Caesalpinia peltophoroides Benth. (Leguminosae-Caesalpinoideae)

Este trabalho teve como objetivo estudar a mobilização de reservas de sementes de Caesalpinia peltophoroides Benth. durante a germinação e crescimento inicial das plântulas. As variações nas reservas de carbiodratos, lipídios e proteínas foram analisadas desde o período pré-germinativo (0 a 5 dias após a semeadura – DAS) até a total senescência e abscisão dos cotilédones, aos 35 DAS, por meio de testes bioquímicos nos cotilédones das sementes. Os resultados indicaram que os lipídios constituem o principal composto de reserva nos cotilédones, contribuindo com cerca de 50% de massa seca. Carboidratos solúveis representaram 32%, as proteínas solúveis 7,7% e o amido 6,8% de massa seca dos cotilédones. Os lipídios sofreram marcante decréscimo entre 5 e 10 dias após a semeadura, período em que se observou elevada taxa de crescimento das plântulas. Carboidratos e proteínas solúveis exibiram tendência gradativa de queda, enquanto no amido, isso quase não foi detectado. A redução do peso de massa seca dos cotilédones foi bem correlacionada com o aumento da biomassa da plântula.This work aimed at studying the mobilization seed reserves during germination and initial growth of seedlings of Caesalpinia peltophoroides Benth. The variations in carbohydrate, lipid and protein reserves were analyzed from the pre-sprouting period (0 to 5 days after sowing -DAS) to the total senescence and abscission of seeds. The results showed that lipids constitute the main reserve compound in the cotyledon, contributing with almost 50 % of its dry mass weight. Soluble carbohydrates represent 32 %, the soluble proteins 7.7 % and starch 6.8 % of the dry mass weight of cotyledons. Lipids showed a marked decrease between 5 and 10 days after sowing, period of a high seedling growth rate. Carbohydrates and soluble proteins showed a gradual tendency to decrease, while starch was almost non-detectable. The reduction in cotyledon dry mass of weight was well correlated with the increase in the seedling biomass

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

Histochemical, biochemical and physiological studies of Caesalpinia peltophoroides Benth. during germination and early growth of the seedlings

Este trabalho teve como objetivo estudar a composição química do cotilédone de sementes de Caesalpinia peltophoroides Benth. (Leguminosae - Caesalpinoideae) e a mobilização de reservas durante a germinação e crescimento inicial das plântulas. As análises foram feitas a cada cinco dias, desde a semeadura até a completa abscisão dos cotilédones, aos 35 dias. Foram realizados testes histoquímicos, em cotilédones de sementes frescas, fixadas em FAA50 e incluídas em glicol-metacrilato. Os testes utilizados foram: PAS para carboidratos neutros, vermelho de rutênio para pectinas, azul de astra/ fucsina básica para paredes celulósicas e compostos fenólicos, Lugol para amido, azul de alciano para mucopolissacarídeos ácidos, azul de bromofenol e xylidine Ponceau para proteínas, sudan III, black B e escarlate para lipídios totais, sulfato azul do Nilo para lipídios ácidos e neutros, ácido rubeânico para ácidos graxos, tetróxido de ósmio para lipídios insaturados, cloreto férrico para compostos fenólicos totais, vanilina clorídrica para taninos, reagente de Wagner, de Dittmar e de Draggendorf para alcalóides, reagente de Nadi, tricloreto de antimônio, ácido sulfúrico e 2,4-dinitrofenilhidrazina para terpenóides e, para cristais, ácido clorídrico e nítrico. O azul de toluidina foi utilizado para metacromasia e contracoloração com Lugol, e a luz polarizada para evidenciar substâncias anisotrópicas. Testes bioquímicos foram utilizados para determinação quantitativa de lipídios totais, proteínas solúveis, carboidratos solúveis, e amido, com 5 repetições de 20 cotilédones cada. As sementes contêm lipídios (50%) como principal reserva nos cotilédones, seguido de carboidratos solúveis (32%), proteínas solúveis (7,7%) e amido (6,8%). Drusas de oxalato de cálcio estão presentes apenas na face adaxial dos cotilédones, enquanto compostos fenólicos, alcalóides e terpenóides estão ausentes no mesofilo cotiledonar. Grandes cavidades secretoras, distribuídas por todo o cotilédone, são ricas em compostos fenólicos. Resultados bioquímicos e histoquímicos concordaram que tanto lipídios quanto proteínas foram consumidos gradativamente até os 25 dias após a semeadura (DAS). Os grãos de amido, presentes em pequena quantidade e distribuídos uniformemente em todo cotilédone apresentaram leve aumento aos 10 DAS, seguindo-se de contínuo consumo e desaparecendo 30 DAS. Nesse caso, a quantificação bioquímica não detectou o aumento sutil visualizado in situ pela histoquímica. Cristais de oxalato de cálcio não foram consumidos, mas mudaram seu padrão de distribuição nas células durante o período estudado.The aim of this work was to study the chemical composition of the cotyledon from seeds of Caesalpinia peltophoroides Benth. (Leguminosae Caesalpinoideae) and the mobilization of the reserves during germination and initial growth of the seedlings. The analyses were done every five days, from the sowing to the complete fall of the cotyledons, at the day 35. Histochemical tests were carried out in cotyledons from fresh seeds, fixed in FAA50 and included in glycol-metacrilate. The tests used were: PAS for neutral carbohydrates, red of ruthenium for pectins, astra blue/ basic fucsin to the cellulosic walls and phenolic compounds, Lugol for starch, alcian blue for acid mucus polysaccharides, blue of bromophenol and xylidine Ponceau for the proteins, Sudan III, black B and scarlet for the total lipids, blue sulphate from Nile for the acid and neutral lipids, rubeanic acid for the fatty acid, ferric chloride for the total phenolic compounds, hydrochloric vanillin for the tannins, Wagner , Dittmar and Draggendorf reagents for the alkaloids, Nadi reagent, antimony thichloride , sulphuric acid and 2,4-dinitrofenilhidrazine for the terpenoids, and for the crystals, chloride and nitric acid. The toluidine blue was used for metacromasie and counter-coloration with Lugol, and polarized light to evince the anisotropic substances. Biochemical tests were used for the quantitative determination of the total lipids, soluble proteins, soluble carbohydrates, and starch with 5 repetitions of 20 cotyledons each. The seeds have lipids (50%) was the main storage in the cotyledons, followed by soluble carbohydrates (32%), soluble proteins (7.7%) and starch (6.8%). Druses of calcium oxalate are present only in the adaxial face of the cotyledons, while phenolic compounds, alkaloids and terpenoids are absent in the cotyledonal mesophyll. Big secretor cavities, spread all over the cotyledon, are rich in phenolic compounds. Biochemical and histochemical results have agreed that that both lipids and proteins were gradually consumed until 25 days after sowing (DAS). The starch grains, present in a small quantity and evenly distributed for all over the cotyledon showed a slight increase on the 10 DAS, followed by a continue consumption and disappearing on 30 DAS. In this case, the biochemistry quantification didn t detect the subtle increase visualized in situ through the histochemistry. Crystals of calcium oxalate weren t consumed, but they changed their standard of distribution in the cells during the studied period.Coordenação de Aperfeiçoamento de Pessoal de Nível Superio