Meloidogyne enterolobii-induced Changes in Guava Root Exudates Are Associated With Root Rotting Caused by Neocosmospora falciformis

Despite the worldwide importance of disease complexes involving root-feeding nematodes and soilborne fungi, there have been few in-depth studies on how these organisms interact at the molecular level. Previous studies of guava decline have shown that root exudates from Meloidogyne enterolobii-parasitized guava plants (NP plants), but not from nematode-free plants (NF plants), enable the fungus Neocosmospora falciformis to rot guava roots, leading to plant death. To further characterize this interaction, NP and NF root exudates were lyophilized; extracted with distinct solvents; quantified regarding amino acids, soluble carbohydrates, sucrose, phenols, and alkaloids; and submitted to a bioassay to determine their ability to enable N. falciformis to rot the guava seedlings’ roots. NP root exudates were richer than NF root exudates in amino acids, carbohydrates, and sucrose. Only the fractions NP-03 and NP-04 enabled fungal root rotting. NP-03 was then sequentially fractionated through chromatographic silica columns. At each step, the main fractions were reassessed in bioassay. The final fraction that enabled fungal root rotting was submitted to analysis using high performance liquid chromatography, nuclear magnetic resonance, mass spectrometry, energy-dispersive X-ray fluorescence, and computational calculations, leading to the identification of 1,5-dinitrobiuret as the predominant substance. In conclusion, parasitism by M. enterolobii causes an enrichment of guava root exudates that likely favors microorganisms capable of producing 1,5-dinitrobiuret in the rhizosphere. The accumulation of biuret, a known phytotoxic substance, possibly hampers root physiology and the innate immunity of guava to N. falciformis

Arthur Ramos e Anísio Teixeira na década de 1930

O artigo busca mostrar o movimento Escola Nova e autores ligados a ele. Foca-se a atuação de Arthur Ramos, médico que trabalhou ao lado de Anísio Teixeira, eminente pensador escolanovista, quando este foi diretor da instrução pública no Distrito Federal, nos anos 30. Ramos, que tinha fortes ligações com a Psicanálise, dirigiu o Instituto de Higiene Mental, órgão da administração municipal na gestão de Teixeira, onde foi instalada uma Seção de Ortofrenia e Higiene Mental. Ramos atuou empregando Freud, Jung e Adler tendo que adequar as teorias psicológicas que dispunha em meios aplicáveis à educação brasileira. Dados indicam que a inserção da psicanálise na educação foi favorecida pelas idéias deweyanas de Anísio Teixeira. Esse estudo é oriundo de pesquisa bibliográfica focada nas obras de Arthur Ramos: "Educação e Psicanálise" e "A criança problema"