Role of Aquatic Macrophytes in Biogeochemical Cycling of Heavy Metals, Relevance to Soil-Sediment Continuum Detoxification and Ecosystem Health. In: Sherameti I, Varma A, editors. Detoxification of Heavy Metals. Berlin: Springer Berlin Heidelberg; 2011. pp. 345-68. [DOI: 10.1007/978-3-642-21408-0_18]

Kinetics of nickel bioaccumulation and its relevance to selected cellular processes in leaves of Elodea canadensis during short-term exposure

Elodea canadensis is an aquatic macrophyte used widely as a bioindicator for the monitoring of water quality and in the phytoremediation of metal-contaminated waters. This study considers the kinetics of nickel bioaccumulation and changes in accompanying metabolic and stress-related physiological parameters. These include photosynthetic activity, pigment content, the accumulation of thiol-containing compounds, thiobarbituric acid-reactive substance (TBARS) products, and the activity of selected antioxidant enzymes (catalase, glutathione reductase, superoxide dismutase). Elodea leaves accumulated nickel according to pseudo-second-order kinetics, and the protective responses followed a time sequence which was related to the apparent rates of nickel accumulation. The applicability of second-order kinetics to the Ni uptake by Elodea leaves during the first 8 h of exposure to the metal suggested that the passive binding of metal ions (chemisorption) was a rate-limiting step at the initial phase of Ni accumulation. This phase was accompanied by an increase in photosynthetic activity together with elevated photosynthetic pigments and protein synthesis, the enhanced activity of antioxidant enzymes, and increased thiol concentration. In contrast, there was a decrease in metabolic activity upon the accumulation of TBARS, and the decline in enzyme activity was observed in the saturation phase of Ni accumulation (8-24 h). These results show that a correlation exists between the protective response and the apparent kinetic rate of Ni uptake. Thus, the time of exposure to the toxicant is a crucial factor in the activation of specific mechanisms of Ni detoxification and stress alleviation.

Potential for chromium (VI) bioremediation by the aquatic carnivorous plant Utricularia gibba L. (Lentibulariaceae)

The aquatic carnivorous plant Utricularia gibba has one of the smallest known genomes among flowering plants, and therefore, it is an excellent model organism for physiological and developmental studies. The main aim of our work was to check whether the ubiquitous U. gibba might be useful for the phytoremediation of the highly toxic and mobile hexavalent chromium in waters. Plants were incubated for 1 week in a 50 μM (2.6 mg dm(-3)) Cr(VI) solution in laboratory conditions. Our results revealed that the plant exhibits a very high accumulation capacity for Cr. The accumulation level was higher than 780 mg kg(-1) and a bioconcentration factor >300. On the other hand, the plants showed a low tolerance to the elevated Cr concentration, which was expressed in a significant decrease of the photosystem II activity. However, the most pronounced negative influence of chromate was found on the morphology and activity of the traps. Due to its high accumulation capacity, we suggest that U. gibba may be efficient in the removal of chromate over a short time scale. It can also provide a new molecular resource for studying the mechanisms of Cr(VI) detoxification.

Chromium distribution in shoots of macrophyte Callitriche cophocarpa Sendtn

The aim of the study was the analysis of Cr distribution in shoots of the macrophyte Callitriche cophocarpa by means of two X-ray-based techniques: micro X-ray fluorescence (μXRF) and electron probe X-ray microanalysis (EPXMA). Plants were treated with 100 μM (5.2 mg l(-1)) chromium solutions for 7 days. Cr was introduced independently at two speciations as Cr(III) and Cr(VI), known for their diverse physicochemical properties and different influence on living organisms. A comparative analysis of Cr(III)-treated plants by EPXMA and μXRF demonstrated high deposition of Cr in epidermal glands/hairs localized on leaves and stems of the plant shoots. Cr in Cr(III)-treated plants was recorded solely in glands/hairs, and the element was not present in any other structures. On the other hand, Cr in Cr(VI)-treated group of plants was rather found in vascular bundles. Moreover, the concentration of Cr in Cr(VI)-treated plants was significantly lower than in plants incubated in Cr(III) solution. The results obtained in this work suggest differences in chromium uptake, transport and accumulation dependent on the oxidative state of the element.

Phytoremediation of water polluted by thallium, cadmium, zinc, and lead with the use of macrophyte Callitriche cophocarpa

The objective of the present work was to study the phytoremediation capacity of Callitriche cophocarpa concerning water contaminated with thallium (Tl), cadmium (Cd), zinc (Zn), and lead (Pb) derived from the natural environment. We found that after a 10-day incubation period, shoots of C. cophocarpa effectively biofiltrated the water so that it met (for Cd, Zn, and Pb) appropriate quality standards. The order of accumulation of the investigated elements by shoots (mg kg(-1) dry weight) were as follows: Zn (1120) < Tl (251) < Cd (71) < Pb (35). The order of bioconcentration factors were as follows: Cd (1177) < Tl (1043) < Zn (718) < Pb (597). According to Microtox bioassay, C. cophocarpa significantly eradicated polluted water toxicity. During the experiment, the physiological status of plants was monitored by taking measurements of photosystem II activity (maximum efficiency of PSII, photochemical fluorescence quenching, nonphotochemical fluorescence quenching, and quantum efficiency of PSII), photosynthetic pigment contents, and shoot morphology. Plants exposed to metallic pollution did not exhibit significant changes in their physiological status compared with the control. This work is potentially applicable to the future use of C. cophocarpa in the phytoremediation of polluted, natural watercourses.

Ceratophyllum demersum L. and Potamogeton alpinus Balb. from Iset' river, Ural region, Russia differ in adaptive strategies to heavy metals exposure--a comparative study

We examined the uptake of five heavy metals (Cu, Fe, Ni, Zn, and Mn) in Ceratophyllum demersum L. (hornwort) and Potamogeton alpinus Balb. (pondweed) from Iset' river, Ural region, Russia. This study was conducted in a territory that is highly urbanized where the surface waters are contaminated by a wide spectrum of pollutants. The environmental situation in this territory drastically deteriorated due to anthropogenic activity. The water quality in most of the water bodies in the Ural region is rather poor. In a comparative study of C. demersum and P. alpinus, differential accumulation pattern was noted for heavy metals (HMs). Higher amounts of HMs accumulated in C. demersum compared to P. alpinus. Also it was shown that in leaves of C. demersum there were high amount of total phosphorus, nitrogen, organics acids and ash; high activity of guaiacol peroxidase; high content of nonenzymatic antioxidants viz., flavonoids, ascorbate, glutathione and proline; high amount of thiols (soluble and membrane bound) compared to P. alpinus.