Biological responses of duckweed (Lemna minor L.) exposed to the inorganic arsenic species As(III) and As(V): effects of concentration and duration of exposure

Abstract

The accumulation of arsenic (As) and physiological responses of Lemna minor L. under different concentration (0, 1, 4, 16 and 64 microM) and duration (1, 2, 4 and 6 days) of two species As, NaAsO(2) and Na(2)HAsO(4).7H(2)O, were studied in hydroponics. The accumulation of both As species depended on As concentration and exposure duration. The highest accumulation of As was found as 17408 and 8674 microg g(-1), for plants exposed to 64 microM of As(III) and As(V), respectively, after 6 days. Two-way ANOVA analyses indicated that, for plants exposed to arsenite (As(III)), exposure duration had a greater effect than concentration on As accumulation. Conversely, exposure concentration had a greater effect on As accumulation in plants exposed to arsenate (As(V)). Arsenic exposure levels, approaching 16 microM for As(III) and 64 microM for As(V), did not significantly affect EC values. Beyond these exposure concentrations, EC values increased in a manner that depended on duration. Significant effect of As(III) on lipid peroxidation was observed at 1 microM application whereas, this effect started to be significant after an exposure to 16 microM As(V). For both As(III) and As(V), photosynthetic pigment levels slightly increased for the first day with respect to the control, followed by a gradual decline at higher concentrations and durations. An increase in protein content and enzyme activity was observed at moderate exposure conditions, followed by a decrease. Significant positive correlations were determined between accumulated As and ion leakage and lipid peroxidation. Negative correlations were found between accumulated As and total chlorophyll and protein content. Our results suggested that exposure duration and concentration had a strong synergetic effect on antioxidant enzyme activity. The findings of the present study may be useful when this plant is used as a phytoremediator in arsenic-polluted water.

Selenium and auxin mitigates arsenic stress in rice (Oryza sativa L.) by combining the role of stress indicators, modulators and genotoxicity assay

“…In case of proline, which acts as radical scavenger and cellular redox potential buffer, co-application of Se and auxin has more prominent effects than their individual applications. Our findings are in concordance with the observations reported previously under single or mixed metal conditions [15,30,32], which showed improvement or modulation in the levels of cysteine, proline and stress protective role of auxin under metal stress. Increase in the level of these stress modulators may be one of the strategies to enhance As stress tolerance in the selected rice variety under the influence of Se or auxin.…”

Arsenic Toxicity: The Effects on Plant Metabolism

“…H 2 O 2 produced in a plant cell either directly or enzymatically through enzymes such as SOD can be neutralized by catalase, an enzyme that is often induced by As exposure (Mylona et al, 1998; Cao et al, 2004; Srivastava et al, 2005; Geng et al, 2006; Duman et al, 2010). In addition to catalase, plants have a two-component system for regulating the balance of H 2 O 2 , and therefore of ROS, within cells.…”

Evaluation of effects of exposure conditions on the biological responses of Gammarus pulex exposed to cadmium

“…Prior to the experiment, glass containers were disinfected by immersing them in 1 % (v/v) NaCl for 3-5 min and then rinsed with distilled water three times (Duman et al 2010). The organisms were quickly transported to the laboratory in plastic vessels, where they were kept at 12°C in a container filled with spring water.…”