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    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
    (2010) Duman, Fatih; Ozturk, Fatma; Aydin, Zeki
    The accumulation of arsenic (As) and physiological responses of Lemna minor L. under different concentration (0, 1, 4, 16 and 64 ?M) and duration (1, 2, 4 and 6 days) of two species As, NaAsO2 and Na2HAsO 4•7H2O, 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 ?g g-1, for plants exposed to 64 ?M 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 ?M for As(III) and 64 ?M 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 ?M application whereas, this effect started to be significant after an exposure to 16 ?M 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. © 2010 Springer Science+Business Media, LLC.
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    Effects of Exogenous Glycinebetaine and Trehalose on Cadmium Accumulation and Biological Responses of an Aquatic Plant (Lemna gibba L.)
    (Springer International Publishing Ag, 2011) Duman, Fatih; Aksoy, Ahmet; Aydin, Zeki; Temizgul, Ridvan
    This study aimed to investigate and compare the effects of exogenous glycinebetaine (GB) and trehalose (TR) on the biological responses of duckweed (Lemna gibba L.) against cadmium (Cd) accumulation. Duckweed samples were exposed to 0.5, 1, and 3 mM of Cd for 6 days in the presence and absence of GB (0.5, 1, 2, and 5 mM) or TR (0.5, 1, 2, and 5 mM). The accumulation of Cd, GB, and TR were investigated, and their influence on the rates of lipid peroxidation, photosynthetic activity, proline content and enzymatic antioxidant performance was examined. Two-way ANOVA showed that exposure to Cd and/or GB or TR caused an increase in Cd accumulation concentration dependently. TR had significant effects on Cd accumulation. The application of 0.5 mM TR increased Cd accumulation, whereas 5 mM decreased Cd accumulation. However, Cd accumulation was not significantly affected by the presence of GB. Cd concentration alone or in combination with GB or TR had a significant effect on lipid peroxidation, photosynthetic activity, proline content, and antioxidant enzyme activities. In addition, statistically significant GB-Cd and TR-Cd interactions were observed. We conclude that both GB and TR play protective roles against Cd stress in aquatic plants. The use of a low level of TR (i.e., 0.5 mM) may be more useful than GB in phytoremediation studies.