Efeitos do ferro em Setaria parviflora (Poir.) Kerguélen e Paspalum urvillei Steudel (Poaceae)

• Autor(a) principal: Araújo, Talita Oliveira de
• Data de Publicação: 2012
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/2543
• topic: Alterações anatômicas; Alterações fisiológicas; Excesso de ferro; Áreas impactadas; Anatomical changes; Physiological changes; Iron excess; Areas affected; CNPQ::CIENCIAS BIOLOGICAS::BOTANICA::MORFOLOGIA VEGETAL::ANATOMIA VEGETAL

In Ubu, coast of Espírito Santo, the restinga have been impacted by the presence of an iron pellet factory that prepares the ore for exporting. Considerable amount of iron ore powder and other wastes are deposited in water bodies used in pelletizing plants. It is common to find plant species, among them the grasses Setaria parviflora (Poir.) Kerguelen and Paspalum urvillei Steudel developing in this situation. This study aimed to evaluate the effects caused by iron in two grass species, characterizing possible anatomical changes and physiological responses. Seedlings of S. parviflora and P. urvillei were grown in Hoagland nutrient solution, at half ionic strength and 5.0 pH, with aeration constant. The plants were treated gradually with different concentrations of Fe3+ in the nutrient solution, in the form Fe-EDTA (0.009, 1, 2, 4 and 7 mM). After acclimatization, the plants remained exposed to treatments for 17 days for the analysis of iron accumulation, mineral composition and anatomical variables, and 20 days for analysis of physiological parameters. We evaluated growth, gas exchange, chlorophyll fluorescence, membrane permeability, pigments quantification, morphological, anatomical characterization (light microscopy, histochemical for iron and micromorphometric analysis), iron quantification and other nutrients in plant material and the nutrient solution. We also calculated the translocation factor (TF) and bioconcentration factor (BCF). The data were submitted to ANOVA and the means were compared by Tukey test at 5%. The greatest amount of Fe present on the board was found in concentration 7 mM Fe-EDTA concentration for both species. The concentration of nutrients Fe, Mn, Zn, P, K, Ca and Mg in the iron plate differs in regard to the treatment. The species accumulated more iron in roots than in shoots. The species showed similar behavior related to iron levels in the roots, but in the shoot, P. urvillei accumulated more iron in the 7 mM Fe-EDTA concentration than S. parviflora. Iron excess has significantly changed the content of Fe, Cu, K and Mg in the roots and Fe, Mn, Zn, N, P, K, Ca and Mg in the shoot. Among the growth parameters, the dry weight of shoot and root, leaves number and root volume increased significantly related to iron excess. Visual symptoms in the leaves appeared more discretely in S. parviflora than those observed in P. urvillei. In roots of these species it was observed, with increasing iron concentration, yellowish appearance of roots and mucilage. P. urvillei and S. parviflora had similar anatomical abnormalities. On the leaves, it was visualized changes in cell shape of epidermis, mesophyll and vascular bundle sheath, protoplast shrinkage and changes in cell shape of metaxylem. In roots, it was observed protoplast shrinkage, scar tissue formation and cortical cells collapse, changes in the cell shape of endoderm, protoxylem, metaxylem, phloem, and collapse of vascular cylinder cells. In relation to histochemical for iron, after 48 hours of exposure to the reactant, the leaves of S. parviflora exhibited stronger reaction (high blue staining intensity) than the leaves of P. urvillei. Significant reduction was observed among the Fe-EDTA treatments in the values of the abaxial epidermis and vascular bundle sheath on both species. There was a significant increase in the concentration of chlorophyll a and carotenoids in iron concentrations on the intermediate species. P. urvillei showed lower values for A, F0, Fv/Fm and increased electrolyte leakage at 7 mM Fe-EDTA concentration compared to S. parviflora. Furthermore, S. parviflora was more efficient in energy dissipation of the non-photochemical quenching (NPQ). We conclude that S. parviflora and P. urvillei species are indicated for use in areas affected by iron excess as phytoextractors. P. urvillei accumulated more iron in the shoot showing more intense visual and anatomic damage when compared to S. parviflora. However, analyzing the physiological damage, S. parviflora proved to be more sensitive than P. urvillei when subjected to stress caused by iron excess.