Rhizofiltration of lead using an aromatic medicinal plant Plectranthus amboinicus cultured in a hydroponic nutrient film technique (NFT) system

Abstract

Heavy metal contamination of water bodies and groundwater is a major concern of the modern world. Rhizofiltration--the use of plant root system to remove/extract pollutants from wastewater--has proven advantages over conventional methods of treatment. However, commercialization of this in situ remediation technology requires a better understanding of plant-metal interactions especially on the ability of different plant species to accumulate metals at different parts of the plant system which is critical for the successful remediation of contaminated medium. Many aquatic and terrestrial plants have been reported to accumulate heavy metals when grown hydroponically. Therefore, a batch experiment with different concentrations of lead and a nutrient film technique (NFT) experiment with recycling of wastewater were employed in this study in order to investigate the rhizofiltration of lead-containing wastewater using Plectranthus amboinicus, an aromatic medicinal plant. Results show that P. amboinicus is tolerant to a wide range of lead concentrations and nutrient deficiency. The plant accumulates considerable amount of lead, particularly in the roots, and translocation to the stem and leaf was limited, indicating that the use of leaves/above-ground parts of the plant for medicinal purposes is not hindered by its ability to remove lead from the soil or water. The study also suggests that the plant can be considered for the clean-up of lead-contaminated wastewater in combination with safe biomass disposal alternatives.

Effects of Pb and Zn toxicity on chlorophyll fluorescence and biomass production of Koelreuteria paniculata and Zelkova schneideriana young plants

“…In the present study, Pb was mainly accumulated in roots of both plants ( Table 2), implying that this metal was limited to the apoplastic space of the cortex and its loading into the vascular cylinder was effectively stopped by the endodermal Casparian strips of the root. Thus, Pb was often found to be accumulated in or beyond the endodermis (Jones et al 1973, Ignatius et al 2014. Our results were in agreement with previous studies (Michalak and Wierzbicka 1998, Antosiewicz et al 2003, Sharma and Dubey 2005.…”

Hydroponics with wastewater: a review of trends and opportunities

“…Ignatius et al . (2014) used Mexican mint in hydroponic systems type NFT to evaluate the rhizofiltration of Pb at different concentrations. The study demonstrated that the plants have the capacity to accumulate Pb in the roots, without translocating it to stems or leaves.…”

Plant traits related to the heavy metal removal capacities of wetland plants

“…Plants with large fibrous root systems removed markedly more metals than did plants with coarser roots (Table 2). Larger root systems have greater surface areas, which absorb and adsorb more metals (Li et al 2015); this is especially important for Pb, which readily binds to organic matter such as roots (Ignatius et al 2014). The lack of restricting tissue, such as exodermis, in young fine roots enables high absorption to the apoplast.…”