Bases fisiológicas da ação do arsênio em algumas espécies de cerrado

• Autor(a) principal: Costa, Alan Carlos
• Data de Publicação: 2007
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1009
• topic: Arsênio; Fitorremediação; Fotossíntese; Fluorescência; Nutrição; Espécies nativas; Arsenic; Phytoremediators; Photosynthesis; Fluorescence; Nutrition; Plant species; CNPQ::CIENCIAS BIOLOGICAS::BOTANICA::FISIOLOGIA VEGETAL

The aim in the present study was to evaluate the degree of resistance of some plant species to the As and characterize, by means of physiological parameters, mechanisms of resistance and sensitivity, and evaluate the potential of these species as phytoremediators of areas contaminated by As. The experiments were conducted under green house condition and in Hoagland & Arnon solution, half-strength, pH 5.5, repleneshed every five days. The treatments had consisted of the application of increasing doses of As as sodium arsenate (Na2HAsO4.7H2O). In the first stage eight independent experiments were conducted with seedlings of Psidium guineense Swartz, Schinus terebinthifolius Raddi, Mimosa caesalpinieafolia Benth, Eugenia jambolana Lam, Enterolobium contortisiliqum (Vell.) Morong., Acacia bahiensis Benth., Caesalpinia ferrea Mart. ex Tul. and Sesbania punicea (Cav.) Benth. After thirty days, the plants were harvested and the dry matter and the content of As in leaves, stems and roots were determined. Bioacumulation factors (BFA) and transference factor (TF) of As to the aerial part has been used to assist in the characterization of the plants response to the element. The results demonstrated that some species such as E. contortisiliqum, C. ferrea e M. caesalpinieafolia presented higher degree of sensitivity while S. terebinthifolius and P. guineense presented higher degree of resistance to As in nutritional solution. The species were not are characterized a phytoextractors, but species as S. terebinthifolius, P. guineense, S. punicea, and E. jambolana present potential for phytostabilization processes, recovery and restoration of areas contaminated by As. In the second stage of the studies, independent experiments were conducted with seedlings of M. caesalpinieafolia e P. guineense to characterize the sensitivity and resistance responses of them to As. For this purpose, the contents of, P, Ca, S, Mg and the content of nonprotein thiols groups (TNP) in the roots, stem and leaves of the species were evaluated. The gaseous exchanges, the chlorophyll fluorescence and the growth of the plants had been also evaluated. The content of P, Ca, Mg and S in leaves, stems and roots of the species was modified by As. M. caesalpinieafolia presented sudden increase in the concentrations of P in low concentrations of As in the solution.This behaivor led to the accumulation of As in quanteties greater than the species could metabolize, which resulted in severe injures under higher concentration of As in the solution. P. guineense showed greater content of Ca in roots, as well las increments in the contents of S and TNP that had contributed for the best performance of this species in presence of As. The photosynthetic and transpiratory rates, the stomatal conductance, the parameters of the chlorophyll fluorescence, in exception of the Fv/Fm, and the growth of the plants of M. caesalpinieafolia was drastically reduced in high concentrations of As in the solution. In P. guineense, however, it stimulated the photosynthetic rate and the growth of the plants. In both species the Fv/Fm ratio was maintained suggesting the absence of irreversible damages to photosystem II. The results demonstrated that the effect of As in plants is dependent of the species. The content of nutrients and TNP presents narrow relation with the sensitivity results and tolerance of the plants of M. caesalpinieafolia e P. guineense to the As in nutritional solution. As affects the gaseous exchanges of plants but it does not promote irreversible damages in the photosynthetic apparatus.