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3 Acta Physiologiae Plantarum

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Arsenate and arsenite: the toxic effects on photosynthesis and growth of lettuce plants

100%

Gusman G. S. , Oliveira J. A. , Farnese F. S. , Cambraia J.

Acta Physiologiae Plantarum

2013

tom 35

nr 04

Arsenate (AsV) and arsenite (AsIII) contamination can promote several disturbances in plant metabolism, besides affecting directly human and animal health due to the insertion of this metalloid in the food chain. Therefore, the arsenic (As) uptake and accumulation, the changes in gas exchange and in chlorophyll a fluorescence parameters as well as the chloroplastic pigments content were measured. The As accumulation in leaves and roots increased with the increase of AsV and AsIII concentration, except at the highest AsIII concentration, probably because of AsIII extrusion mechanism. Although the highest As concentration has been found in roots, significant amount was transported to the leaves, especially when plants were exposed to AsIII. The As accumulation decreased the relative growth rate (RGR) of leaves and roots. However, at 6.6 lmol L-1 AsV, an increase in leaves RGR was observed, possibly related to the changes in phosphate (PV) nutrition caused by As. AsV and AsIII interfered negatively in the photosynthetic process, except at 6.6 lmol L-1 AsV. The observed reduction seemed to be associated to the interference in the photochemical and biochemical steps of photosynthesis; however, chlorophyll a fluorescence results indicate that the photosynthetic apparatus and chloroplastic pigments were not damaged. So, lettuce plants demonstrated to be able to accumulate As and also to protect the photosynthetic apparatus against the harmful effects of this metalloid, probably through the activation of tolerance mechanisms.

Impact of iron toxicity on oxidative metabolism in young Eugenia uniflora L. plants

75%

Jucoski G. d. O. , Cambraia J. , Ribeiro C. , de Oliveira J. A. , de Paula S. O. , Oliva M. A.

Acta Physiologiae Plantarum

2013

tom 35

nr 05

In excess, iron can induce the production and accumulation of reactive oxygen species (ROS), causing oxidative stress. The objective of this work was to evaluate the impact of toxic concentrations of iron (Fe) on the antioxidative metabolism of young Eugenia uniflora plants. Forty-five-day-old plants grown in Hoagland nutrient solution, pH 5.0, were treated with three Fe concentrations, in the form of FeEDTA, during three periods of time. At the end of the treatment, the plants were harvested and relative growth rate, iron content, lipid peroxidation and enzymes and metabolites of the antioxidative metabolism were determined. Iron-treated plants showed higher iron contents, reduced relative growth rates and iron toxicity symptoms in both leaves and roots. There was an increase in lipid peroxidation with increasing Fe, only in the leaves. The enzymatic activities of superoxide dismutase (SOD) and glutathione reductase (GR) increased with increasing Fe concentration and treatment exposure time. The activities of catalase (CAT), peroxidase (POX) and ascorbate peroxidase (APX) also increased with increasing Fe concentration but decreased with increasing treatment exposure time. Glutathione peroxidase activity (GPX) decreased with increasing Fe concentration and exposure time. The ascorbate (AA) and reduced glutathione (GSH) contents and the AA/DHA and GSH/GSSG ratios, in general, increased with increasing Fe concentration and treatment exposure time. The results indicate that under toxic levels of Fe, young E. uniflora plants suffer increased oxidative stress, which is ameliorated through changes in the activities of antioxidative enzymes and in the contents of the antioxidants AA and GSH.

Aluminum-induced citric acid secretion is not the sole mechanism of Al-resistance in maize

75%

Cardoso F. B. , Cambraia J. , de Oliveira J. A. , Ribeiro C. , de Souza L. T. , Braun H. , DaMatta F. M.

Acta Physiologiae Plantarum

2016

tom 38

nr 12