Establishment of an Aseptic Culture System and Analysis of the Effective Growth Conditions for Eleocharis acicularis Ramets for Use in Phytoremediation

Abstract

Eleocharis acicularis, an aquatic macrophyte of the Cyperaceae family, has been shown to accumulate multiple heavy metals and has great potential for use in the phytoremediation of contaminated soil and water. To investigate the mechanism of accumulation of heavy metals in E. acicularis while excluding biotic and abiotic environmental effects and to acquire homogenous and sufficient populations of E. acicularis, we established an aseptic culture system and analyzed the applicability of this species for phytoremediation. Young ramet bases and stolon tips of E. acicularis grown in the field were sterilized, cultured, and established in an aseptic culture system, and the effective growth conditions of isolated ramets were determined. Isolated ramets grew remarkably well in a medium of pH 4.8 to 5.7 with 0.25 mg/L kinetin as a plant hormone. Furthermore, capacity for the accumulation of heavy metals was examined using E. acicularis subcultured with or without Si. Aseptically cultured E. acicularis showed a sufficient capacity for Cs and Zn accumulation and exceeded the criteria for hyperaccumulator plants in accumulating Pb, Cd, and In regardless of the addition or not of Si during its subculture. The aseptic culture of E. acicularis enhances its capacity for the accumulation of heavy metals and its applicability for phytoremediation.

Biogenic Synthesis of Self-Incorporated Indium Graphitic Composites from Electronic Waste Using Eleocharis acicularis

“…Table 2 compares the results obtained in this study with those of similar previous studies reported by Ha et al 15 and Sato et al 31 Ha et al 15 used initial indium feeds of 0.1, 0.2, and 0.4 mg/L and reported a maximum uptake of 0.83 mg/g dry weight (roots and shoots) by E. acicularis. A similar study was conducted by Sato et al 31 with an increased feed concentration (38 mg/L), which demonstrated a significantly higher accumulation reaching 17.8 mg/g with a BCF of 468. In our study, indium accumulation in dry biomass was astonishingly high, although the calculated BCF values were approximately half of those reported by Sato et al 31 Thus, fresh and pyrolyzed plant biomass samples were subjected to extensive EDS analyses, as discussed further in the text.…”

“…A similar study was conducted by Sato et al 31 with an increased feed concentration (38 mg/L), which demonstrated a significantly higher accumulation reaching 17.8 mg/g with a BCF of 468. In our study, indium accumulation in dry biomass was astonishingly high, although the calculated BCF values were approximately half of those reported by Sato et al 31 Thus, fresh and pyrolyzed plant biomass samples were subjected to extensive EDS analyses, as discussed further in the text. Notably, we used the highest indium feed concentrations reported to date, which were orders of magnitude higher than those reported in the literature.…”

Effect of Dissolved Silicon on the Removal of Heavy Metals from Aqueous Solution by Aquatic Macrophyte Eleocharis acicularis

“…There has likely been a central debate regarding the role of Si for mediating metal stress [9,33]. Many studies stated the role of Si in diminishing plants' metal absorption [25,27,34], while some others reported a co-absorption of Si and metals into plants [24,32]. In our study, it was obvious that Si favored the absorption of heavy metals (except In and Tl) into E. acicularis (Table 1).…”

“…longiseta Svenson is an emergent herbaceous perennial with a worldwide distribution [19]. This species has been reported to accumulate multiple metals from mine drainage, water, and sediment, and shows a great potential for phytoremediation [12,[20][21][22][23][24][25][26]. However, currently, there is no available information regarding the simultaneous accumulation of rare metals (i.e., gallium (Ga) and thallium (Tl)) in E. acicularis.…”

“…However, currently, there is no available information regarding the simultaneous accumulation of rare metals (i.e., gallium (Ga) and thallium (Tl)) in E. acicularis. Despite the fact that an application of materials containing easy-soluble Si together with E. acicularis showed great effects on increasing the accumulation of chromate (Cr), zinc (Zn), arsenic (As), and cadmium (Cd) [24,27], there have also been contrasting observations in which evidence on the relation between the concentration of dissolved Si in the solution and the removal of heavy metals by E. acicularis was not confirmed [25]. This suggests that more works on the accumulation of heavy metals in E. acicularis under the presence of different levels of Si are necessary.…”