Physiological, biochemical and histochemical evaluations of Ipomoea pes-caprae cultivated at different concentrations of iron / Avaliações fisiológicas, bioquímicas e histoquímica de Ipomoea pes-caprae cultivada em diferentes concentrações de ferro

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

The aim of this study was to evaluate the effects of excess iron over Ipomoea pescaprae, a native species common to Restinga. Saplings presenting three pairs of leaves were grown under 2, 3, 4 and 5 mM Fe-EDTA concentrations in Hoagland solution at half strength. After seven days, it was evaluated the accumulation of iron in plant tissues, alterations in the content of chlorophyll a, chlorophyll b, carotenoids, in fluorescence of chlorophyll a and gas exchanges parameters and the development of oxidative stress. After 48 hours there were visual symptoms on leaves. The iron was absorbed and accumulated in roots and leaves, reaching phytotoxic values under the lowest iron concentration. The accumulation sites of iron were identified hystochemicaly in roots and leaves tissues. Significant alterations were observed for fluorescence parameters, for enzymatic activity of peroxidase, superoxide dismutase and ascorbato peroxidase and malondialdehyde concentration, indicating the development of oxidative stress. There were also significant reductions of 67.3% in the content of chlorophyll a, 64.0% in chlorophyll b and 48.9% in carotenoids. The alterations observed in chlorophyll content, as well as in fluorescence of chlorophyll a parameters, were obtained at concentrations above of 2 mM Fe-EDTA. On the other hand, gas exchanges parameters were affected under all iron concentrations. The assimilation of CO2 decreased 87%, the stomatal conductance 63% and the ratio Ci/Ca decreased 22%. The 50% reduction of photosynthesis was reached at lower concentration, in comparison to stomatal conductance, chlorophyll content and electron transport rate, which presented reductions at higher concentrations. It can be concluded that Ipomoea pes-caprae showed to be sensitive to iron in concentrations above 2 mM and that the parameters evaluated in this studies may be potential tools as biomarkers of environmental hazards.

ASSUNTO(S)

iron toxicity ipomoea pes-caprae toxidez ipomoea pes-caprae botanica ferro

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