Phenotypic plasticity and water flux rates of Citrus root orders under salinity

Knowledge about the root system structure and the uptake efficiency of root orders is critical to understand the adaptive plasticity of plants towards salt stress. Thus, this study describes the phenological and physiological plasticity of Citrus volkameriana rootstocks under severe NaCl stress on the level of root orders. Phenotypic root traits known to influence uptake processes, for example frequency of root orders, specific root area, cortical thickness, and xylem traits, did not change homogeneously throughout the root system, but changes after 6 months under 90 mM NaCl stress were root order specific. Chloride accumulation significantly increased with decreasing root order, and the Cl− concentration in lower root orders exceeded those in leaves. Water flux densities of first-order roots decreased to <20% under salinity and did not recover after stress release. The water flux densities of higher root orders changed marginally under salinity and increased 2- to 6-fold in second and third root orders after short-term stress release. Changes in root order frequency, morphology, and anatomy indicate rapid and major modification of C. volkameriana root systems under salt stress. Reduced water uptake under salinity was related to changes of water flux densities among root orders and to reduced root surface areas. The importance of root orders for water uptake changed under salinity from root tips towards higher root orders. The root order-specific changes reflect differences in vulnerability (indicated by the salt accumulation) and ontogenetic status, and point to functional differences among root orders under high salinity

Considerações sobre o processo de alfabetização : uma perspectiva sócio-interaccionista

Orientador: Carlos Alberto FaracoCoorientadora: Maria Dativa de Salles GonçalvesDissertação (mestrado) - Universidade Federal do Parana, Setor de Educação, Curso de Pós-Graduação em EducaçãoInclui referências: p. 108-111Resumo: Este trabalho estuda o processo de alfabetização de crianças a partir das inter-relações de três áreas do conhecimento (psicologia, pedagogia e linguística) e a forma pela qual estas inter-relações se apresentam em diferentes práticas deste processo na Rede Municipal de Ensino de Curitiba. Essa abordagem decorre da compreensão de que os pressupostos teóricos de linguagem e educação, na alfabetização, se justificam e se expressam nas atividades de ensino que o professor realiza, interagindo com seus alunos, na sala de aula. As concepções de linguagem e de educação utilizadas se apoiam, teoricamente nos trabalhos do linguista Valentin N. Voloshinov e do pedagogo Paulo Freire. Os subsídios da área da psicologia, especificamente sobre a aquisição do conhecimento, tem como referencial os trabalhos de L. S. Vygotsky.Abstract: This paper is a study on the teaching of reading and writing in the public school system in Curitiba. The process of teaching children to read and write is studied here in the light of the interrelationship of psychology, pedagogy and linguistics. The author also focuses her attention on the ways these interrelationships appear in different phases of the process. Such an approach derives from the fact that the assumptions regarding language end education - in the process of teaching reading and writing - are justified and expressed by the activities carried out by the teacher as he or she interacts with his or her pupils. The concepts of language and education used in this paper are based on the works of linguist Valentin N. Voloshinov and pedagogue Paulo Freire. Subsidies in the field of psychology - and specifically those regarding children's learning - were collected in the works of L. S. Vygotsky