Efeitos fisiológicos e bioquímicos causados pela deposição de ferro particulado em Clusia hilariana, uma espécie de restinga
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Data
2006-02-07
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Universidade Federal de Viçosa
Resumo
Clusia hilariana é uma espécie que apresenta o metabolismo ácido das crassuláceas (CAM), de grande distribuição nas restingas brasileiras, onde desempenha importante papel ecológico. Com o objetivo de avaliar os efeitos das diferentes formas de deposição do material sólido particulado de ferro (MSPFe), em aspectos bioquímicos e fisiológicos, nesta planta, foram implantados três experimentos. No experimento inicial, plantas jovens foram cultivadas em solução nutritiva de Hoagland em pH 5,5 e 4,0, com duas fontes de ferro, o citrato de ferro III (0 e 2,0 mM) e o complexo FeEDTA (0; 1,0 e 2,0 mM). No segundo experimento, as plantas foram expostas a 6 e 18 mg.cm-2.dia-1 de MSPFe aplicados sobre o solo. O último experimento, com aplicação de 2,14 mg. cm-2.dia-1 de MSPFe sobre a superfície foliar, foi realizado após a construção de uma câmara de deposição de MSPFe, que simula o que ocorre naturalmente nas áreas sujeitas à poluição por ferro. A fonte de ferro disponível na solução nutritiva foi determinante para a ocorrência do estresse, os parâmetros de trocas gasosas, nesse experimento, foram prejudicados apenas com a exposição das plantas ao FeEDTA. Foi verificado maior teor de ferro nos tecidos vegetais expostos às diferentes formas de deposição do MSPFe, em relação aos respectivos controles. A aplicação do MSPFe sobre as folhas de C. hilariana causou reduções significativas em vários parâmetros avaliados, como altura da planta, número de folhas, fotossíntese, condutância estomática, fluorescência da clorofila a, teor de pigmentos e acumulação de ácidos orgânicos, além de aumento na permeabilidade relativa de membrana e redução na atividade da enzima catalase. Entretanto, a peroxidação de lipídios de membrana não sofreu alterações. Com a deposição do MSPFe sobre o solo, os mesmos parâmetros permaneceram invariáveis. Houve incremento significativo na atividade da enzima superóxido dismutase em decorrência da deposição do MSPFe no solo, indicando controle efetivo das espécies reativas de oxigênio. A resposta fisiológica em C. hilariana, como conseqüência da
aplicação do MSPFe, depende da forma de deposição, como evidenciado pelos diversos danos causados quando o MSPFe foi aplicado sobre a superfície foliar, em relação à aplicação do mesmo material ao solo. Provavelmente, os danos causados pela aplicação do MSPFe sobre as folhas de C. hilariana, não se deve, primeiramente, à toxidez do ferro, mas sim devido aos efeitos físicos da deposição. A tolerância de C. hilariana, encontrada nesse experimento, à elevada concentração de ferro no solo e conseqüente acúmulo deste metal, fornece indícios para sua utilização em estudos com objetivos de fitoextração do ferro em ambientes contaminados.
Clusia hilariana, a CAM plant with crucial ecological role, has a broad distribution in brazilian restingas. With the aim to evaluate the physiological and biochemical effects of iron ore particulate matter (MSPFe), deposited in different fashions, on this species, three distinct experiments were carried out. Young plants were hydroponic cultivated in Hoagland solution at pH 5,5 and 4,0, using two source of iron, iron citrate III (0 and 2,0 mM) and FeEDTA complex (0, 1 and 2,0 mM). On the second experiment the plants were exposed to 6 and 18 mg.cm-2.day-1 of MSPFe, applied directly on the soil surface. On the final experiment, 2,14 mg.cm-2.day-1 of MSPFe was applied on the leaf surface by keeping the plant inside a MSPFe deposition chamber, in order to simulate the phenomenon that takes place in the field. The source of available iron in the hydroponic solution was critical for the stress onset. The gas exchange parameters were only affected on plants treated with FeEDTA. The iron content in plant tissues was greater in plants exposed to MSPFe deposition treatments than the control plants. The deposition of MSPFe on leaf surface caused significant decrease of a number of parameters such as plant height, leaf number, net photosynthesis, stomatal conductance, chlorophyll a fluorescence, pigments content and organic acid accumulation, yonder increment on the relative membrane permeability, reduction of activity of catalase enzyme, without similar effect on lipid peroxidation. These effects were less dramatic on the treatment with MSPFe deposited on the soil surface. The enzymatic activity of superoxide dismutase was enhanced in those plants treated with MSPFe applied on the soil surface, revealing an effective control of the reactive oxygen species. Thus, the set of physiological response of C. hilariana, as a consequence of MSPFe applications depends upon the target of the deposition, as supported by the significant results obtained when the MSPFe was applied directly on the leaves surface. The damages caused by the applications of MSPFe on the leaves of C. hilariana, were probably due to a physical effect rather than a toxic effect of the iron. The tolerance of C. hilariana to the high iron content in the soil, followed by iron accumulation in the plant, reveals the possibility of its use in iron phytoextraction of contaminated environments.
Clusia hilariana, a CAM plant with crucial ecological role, has a broad distribution in brazilian restingas. With the aim to evaluate the physiological and biochemical effects of iron ore particulate matter (MSPFe), deposited in different fashions, on this species, three distinct experiments were carried out. Young plants were hydroponic cultivated in Hoagland solution at pH 5,5 and 4,0, using two source of iron, iron citrate III (0 and 2,0 mM) and FeEDTA complex (0, 1 and 2,0 mM). On the second experiment the plants were exposed to 6 and 18 mg.cm-2.day-1 of MSPFe, applied directly on the soil surface. On the final experiment, 2,14 mg.cm-2.day-1 of MSPFe was applied on the leaf surface by keeping the plant inside a MSPFe deposition chamber, in order to simulate the phenomenon that takes place in the field. The source of available iron in the hydroponic solution was critical for the stress onset. The gas exchange parameters were only affected on plants treated with FeEDTA. The iron content in plant tissues was greater in plants exposed to MSPFe deposition treatments than the control plants. The deposition of MSPFe on leaf surface caused significant decrease of a number of parameters such as plant height, leaf number, net photosynthesis, stomatal conductance, chlorophyll a fluorescence, pigments content and organic acid accumulation, yonder increment on the relative membrane permeability, reduction of activity of catalase enzyme, without similar effect on lipid peroxidation. These effects were less dramatic on the treatment with MSPFe deposited on the soil surface. The enzymatic activity of superoxide dismutase was enhanced in those plants treated with MSPFe applied on the soil surface, revealing an effective control of the reactive oxygen species. Thus, the set of physiological response of C. hilariana, as a consequence of MSPFe applications depends upon the target of the deposition, as supported by the significant results obtained when the MSPFe was applied directly on the leaves surface. The damages caused by the applications of MSPFe on the leaves of C. hilariana, were probably due to a physical effect rather than a toxic effect of the iron. The tolerance of C. hilariana to the high iron content in the soil, followed by iron accumulation in the plant, reveals the possibility of its use in iron phytoextraction of contaminated environments.
Descrição
Palavras-chave
CAM, Poluição, Estresse oxidativo, CAM, Polution, Iron, Toxic effect
Citação
PEREIRA, Eduardo Gusmão. Physiological and biochemical effects of iron ore dust in Clusia hilariana, a plant of restinga. 2006. 66 f. Dissertação (Mestrado em Controle da maturação e senescência em órgãos perecíveis; Fisiologia molecular de plantas superiores) - Universidade Federal de Viçosa, Viçosa, 2006.