Arsenic accumulation and speciation in the submerged macrophyte Ceratophyllum demersum L.

Abstract

Introduction Ceratophyllum demersum L. is a widespread submerged macrophyte in aquatic environments.Methods Simulation experiments were conducted in the laboratory to investigate arsenic (As) accumulation, speciation, and efflux of C. demersum exposed to arsenate and arsenite solutions. Results Plant shoots showed a significant accumulation of As with a maximum of 862 and 963 μg As g −1 dry weight after 4 days of exposure to 10 μM arsenate and arsenite, respectively. Regardless of whether arsenate or arsenite was supplied to the plants, arsenite was the predominant species in plant shoots. Furthermore, a dramatically higher influx rate of arsenate compared with arsenite was observed in C. demersum exposed to As solutions without the addition of phosphate (P). Arsenate uptake was considerably inhibited by P in this study, suggesting that arsenate is taken up by C. demersum via the phosphate transporters. However, arsenite uptake was unaffected by P and markedly reduced in the presence of glycerol and antimonite (Sb), indicating arsenite shares the aquaporin transport pathway. In addition, C. demersum rapidly reduces arsenate to arsenite in the shoot of the plant and extrudes most of them (>60 %) to the external solutions. The efflux of arsenite was much higher than that of arsenate; the former is supposed to be both active and passive processes, and the latter through passive leakage. Conclusion C. demersum is a strong As accumulator and an interesting model plant to study As uptake and metabolism due to the lack of a root-to-shoot translocation barrier.

A different sequence of events than previously reported leads to arsenic-induced damage in Ceratophyllum demersum L.

“…27,35 Therefore, in the following we only use the label ''As'' for this mixture of redox states. Since all figures (except Fig.…”

“…Although it is not a crop species, it is still a flowering plant (belonging to the dicotyledons) and has been accepted as a good model for laboratory studies of shoot toxicity in higher plants. 27 Mechanisms of metal toxicity found in Ceratophyllum are similar to other plants and like other non-accumulator plants including crops it detoxifies arsenic by phytochelatins. 12,28 It has been shown to be effective for removing the metal from low-concentration wastewater and has also been used successfully in tests of biological life support systems on space flights.…”

Speciation and Distribution of Arsenic in the Nonhyperaccumulator Macrophyte Ceratophyllum demersum

“…Although As was provided as As(V), it is known that in solution it becomes a mixture of As(V) and As(III) due to efflux from plants (Xu et al, 2007;Xue et al, 2012). Therefore, in the following, we only use the label "As" for this mixture of redox states.…”

“…Since C. demersum has no roots, it takes up all nutrients directly via the leaves, allowing for studies of shoot effects without interference from root uptake and root toxicity. While it is not a crop species, it is still a flowering plant (belonging to the dicotyledons) and has been accepted as a good model for laboratory studies of shoot toxicity in higher plants (Xue et al, 2012). Mechanisms of metal toxicity found in C. demersum are similar to other plants (Küpper et al, 1996), and like other nonaccumulator plants including crops, it detoxifies As by PCs (Mishra et al, 2008).…”

Arsenic efflux from Microcystis aeruginosa under different phosphate regimes

“…Similar findings have been reported for P. vittata, C. demersum, Chlorella sp., and M. arcuatum [19,35,36]. After being transported into cells, arsenate can act as an alternative substrate of inorganic phosphate for various enzymatic reactions [37], but arsenoanalogues would be unstable due to degradation by hydrolysis [38].…”