Tactical games approach: teaching collective sports invasion games

Os jogos desportivos coletivos de invasão (JDC-I) assumem uma grande expressão no curriculum da Educação Física no contexto escolar. A forma como os JDC-I têm sido tradicionalmente ensinados na escola é problemática, uma vez que se privilegia o ensino dos skills em detrimento da consciência tática, crítica para uma melhor performance em jogo. Partindo do pressuposto que os estudantes transferem aprendizagens do conhecimento de um jogo para outro jogo, dentro da mesma categoria, provavelmente, seja mais sensato e rentável ensinar os JDC-I partindo de objetivos táticos similares (problemas táticos). Neste sentido, os princípios de jogo operacionais do ataque e da defesa, emergem como conteúdos de ensino transversais ao ensino dos jogos nas aulas de Educação Física. Entendemos que o ensino dos JDC-I de uma forma integrada, recorrendo a uma abordagem tática ao jogo, é uma forma de rentabilizar o processo de ensino aprendizagem ao longo do ano letivo escolar. A investigação, embora escassa, tem demostrado que este tipo de abordagem torna as aulas mais motivantes, mais dinâmicas e potenciadoras da criatividade do aluno.The invasion games (JDC-I) have been assumed a great expression in the curriculum of Physical Education in the school context. The way as JDC-I has traditionally been taught in school is problematic, since it emphasizes the teaching of skills rather than tactical awareness, critical to a better performance in game. Based on the assumption that students transfer knowledge from one game to another in the same game category, it is probably more sensible and profitable to teach the JDC-I from similar tactical goals (tactical problems). In this sense, the operational principles of attack and defense are assumed as an important teaching content. The JDC-I teaching in an integrated perspective, using a tactical approach to the game, is a way of making the learning process profitable throughout the school year. The research, although scarce, has shown that this type of approach makes the classes more motivating, more dynamic and enhancing the creativity of the student.info:eu-repo/semantics/publishedVersio

Teaching invasion games: an intervention study in students from basic school

Objetivos: (1) apresentar um estudo quasi-experimental para aferir a eficácia de uma abordagem tática ao ensino dos jogos desportivas coletivos de invasão (JDC-I), e (2) apresentar os resultados da fiabilidade da equipa de avaliação num estudo piloto. Neste estudo, serão incluídas 4 turmas do 3º Ciclo, divididas em dois grupos: experimental (GE) e controlo (GC). O GE será submetido a uma abordagem tática ao ensino do jogo nos JDC-I. No GC manter-se-á a prática usual do ensino dos jogos. A intervenção decorrerá durante 18 a 20 horas. O tempo de empenhamento motor será avaliado através da observação direta. Avaliação da performance em jogo será realizada através do Game performance Assessment Instrument. A preparação da equipa de observadores incluiu um estudo piloto em 8 alunos, filmados em situação de jogo de basquetebol. Cada aluno foi observado durante 10 min. por todos os observadores no mesmo frame de tempo. Os coeficientes de correlação intra-classe entre os observadores e o valor critério variaram entre .997 e .448. O presente estudo procura acrescentar informação sobre a eficácia de uma abordagem tática ao ensino dos JDC-I. Os resultados do estudo piloto permitiram fazer adaptações à observadores no estudo principal.Aims: (1) to present a quasi-experimental study to assess the effectiveness of a tactical approach to the teaching of Invasive Collective Sports Games (JDC-I), and (2) to present the results of the reliability of the assessment team in a pilot study. In this study, 4 groups of the 3rd Cycle will be included, divided into two groups: experimental (GE) and control (CG). The GE will be submitted to a tactical approach to teaching the game in the JDC-I. The GC will maintain the usual practice of teaching games. The intervention will take place for 18 to 20 hours. The time-on-task will be assess through direct observation. Game performance assess will be performed through the Game performance Assessment Instrument (GPAI). The preparation of the research team included a pilot study with 8 students, filmed in a basketball game situation. Each student was observed through 10 min by all researchers in the same frame time. The intra-class correlation coefficients between the observers and the criterion value ranged from .997 to .448. The present study search for to add information on the effectiveness of a tactical approach to JDC-I teaching. The results of the pilot study made it possible to make adaptations to the researcher tasks in the main study.info:eu-repo/semantics/publishedVersio

Efficient preparation of Arabidopsis pollen tubes for ultrastructural analysis using chemical and cryo-fixation

The pollen tube (PT) serves as a model system for investigating plant cell growth and morphogenesis. Ultrastructural studies are indispensable to complement data from physiological and genetic analyses, yet an effective method is lacking for PTs of the model plant Arabidopsis thaliana. Methods: Here, we present reliable approaches for ultrastructural studies of Arabidopsis PTs, as well as an efficient technique for immunogold detection of cell wall epitopes. Using different fixation and embedding strategies, we show the amount of PT ultrastructural details that can be obtained by the different methods. Results: Dozens of cross-sections can be obtained simultaneously by the approach, which facilitates and shortens the time for evaluation. In addition to in vitro-grown PTs, our study follows the route of PTs from germination, growth along the pistil, to the penetration of the dense stylar tissue, which requires considerable mechanical forces. To this end, PTs have different strategies from growing between cells but also between the protoplast and the cell wall and even within each other, where they share a partly common cell wall. The separation of PT cell walls in an outer and an inner layer reported for many plant species is less clear in Arabidopsis PTs, where these cell wall substructures are connected by a distinct transition zone. Conclusions: The major advancement of this method is the effective production of a large number of longitudinal and cross-sections that permits obtaining a detailed and representative picture of pollen tube structures in an unprecedented way. This is particularly important when comparing PTs of wild type and mutants to identify even subtle alterations in cytoarchitecture. Arabidopsis is an excellent plant for genetic manipulation, yet the PTs, several-times smaller compared to tobacco or lily, represent a technical challenge. This study reveals a method to overcome this problem and make Arabidopsis PTs more amenable to a combination of genetic and ultrastructural analyses

An Osmotic Model of the Growing Pollen Tube

Pollen tube growth is central to the sexual reproduction of plants and is a longstanding model for cellular tip growth. For rapid tip growth, cell wall deposition and hardening must balance the rate of osmotic water uptake, and this involves the control of turgor pressure. Pressure contributes directly to both the driving force for water entry and tip expansion causing thinning of wall material. Understanding tip growth requires an analysis of the coordination of these processes and their regulation. Here we develop a quantitative physiological model which includes water entry by osmosis, the incorporation of cell wall material and the spreading of that material as a film at the tip. Parameters of the model have been determined from the literature and from measurements, by light, confocal and electron microscopy, together with results from experiments made on dye entry and plasmolysis in Lilium longiflorum. The model yields values of variables such as osmotic and turgor pressure, growth rates and wall thickness. The model and its predictive capacity were tested by comparing programmed simulations with experimental observations following perturbations of the growth medium. The model explains the role of turgor pressure and its observed constancy during oscillations; the stability of wall thickness under different conditions, without which the cell would burst; and some surprising properties such as the need for restricting osmotic permeability to a constant area near the tip, which was experimentally confirmed. To achieve both constancy of pressure and wall thickness under the range of conditions observed in steady-state growth the model reveals the need for a sensor that detects the driving potential for water entry and controls the deposition rate of wall material at the tip

Signal processing and transduction in plant cells: the end of the beginning?

Plants have a very different lifestyle to animals, and one might expect that unique molecules and processes would underpin plant-cell signal transduction. But, with a few notable exceptions, the list is remarkably familiar and could have been constructed from animal studies. Wherein, then, does lifestyle specificity emerge