Avaliação da embebição e do desenvolvimento inicial das estruturas embrionárias de sementes de milho submetidas a diferentes potenciais hídricos

Substrates with water potentials between O and -12atm, were used to evaluate the behavior of corn seeds during the germination process. Water deficiency treatments were compared with the control (adequate available water) using seeds with and without fungicide treatment. The analysis and the interpretation of the results permitted to conclude that the absorption of water, the emergency and the initial development of the embryonic structures are interdependent and vary with the water deficit. For these cases the reduction of water potential promotes difficulties in the evolution of the processes. The presence of fungicide treatment may not influence quantitatively the processes occurring in the beginning of the germination.Empregando substratos com potenciais hídricos variáveis entre 0 e -12atm, o presente trabalho objetivou avaliar o comportamento das sementes de milho postas a germinar. As situações de deficiência hídrica foram diretamente comparadas à testemunha (plena disponibilidade de água), usando sementes com e sem tratamento fungicida. A análise e a interpretação dos resultados permitiram concluir que a absorção de água, a emergência e o desenvolvimento inicial das estruturas embrionárias são interdependentes e reagem no mesmo sentido ao déficit hídrico; para esses casos, a redução do potencial hídrico promove dificuldades na evolução dos processos. Paralelamente, a presença de tratamento fungicida pode não influenciar, quantitativamente, os fenômenos envolvidos no início da germinação

A possible mode of action of static fusimotor axons as revealed by system identification techniques

Fusimotor axons are classified by their effects on the discharge of the primary muscle spindle ending during a ramp stretch of the parent muscle. In this paper techniques of system identification and parameter estimation are used to provide an alternative approach to the development of models relating the characteristics of the discharge of the muscle spindle primary sensory ending to the stretch applied to the muscle. Results suggest that system identification methods provide useful quantitative estimates of muscle spindle parameters that could lead to the development of methods for indirect measurement of the mechanical properties of intrafusal fibres

Assessment, disability, student engagement and responses to intervention

Assessment is central to the provision of meaningful and productive learning experiences for all students. The majority of students in today’s classroom benefit from core instruction; however, for a small percentage of students with a disability, learning requires more intensive instruction. It is this cohort of learners that we consider in this chapter. While the needs of these learners are diverse, they have in common some teaching and learning challenges that have direct implications for assessment practices. We consider three major challenges: (1) the various learning priorities for students in need of intensive instruction, and how to maximise the connection between current and targeted skills and knowledge; (2) how to measure change through skill or knowledge acquisition when the rate and magnitude of change may be achieved in small increments; and (3) how to determine whether change that does occur is attributable to our teaching, and what to do when teaching is not effective in achieving change. In the absence of this information, there is a serious risk that instruction will be less than effective, will lack social validity and that learners will fail to make progress and achieve positive learning outcomes. Within the context of a cycle typical of intensive instruction, we examine how assessment can play a key role in enhancing and facilitating teaching and learning in the classroom by addressing these three major challenges. We also review the practical challenges that teachers in regular classrooms face in utilising systematic assessment and programming strategies to meet the needs of all the students in their classrooms