Hexavalent chromium [Cr(VI)] contamination has become an emergent concern in China. Previous field investigations have found that hybrid Napier grass is widely distributed in Cr(VI) contaminated areas. This study investigated the phytoremediation potential and biochemical response of hybrid Napier grass (Pennisetum americanus L. × Pennisetum purpureum Schumach) grown in soil contaminated with Cr(VI) (0, 20, 40, and 60 mg kg−1) with and without Ethylene diamine tetra acetic acid (EDTA) (4 mM) application. The results indicated that root length, shoot height, dry weight, leaf area, chlorophyll, and photosystem II (PSII) parameters viz.; apparent electron transport rate (ETR), effective quantum yield of PSII (ΦPSⅡ), maximal PSII photochemical efficiency (Fv/Fm), potential activity of PSII (Fv/Fo), photochemical quenching (qP), and non-photochemical quenching (qN) decreased with the increasing Cr(VI) concentration. EDTA application further aggravated reduction of dry biomass and photosystem II. The concentration and the accumulation of Cr in shoot and root, and both the bioaccumulation factor (BAF) and transfer factor (TF) increased with increasing Cr(VI) concentrations and further enhanced with EDTA application. Though the Cr(VI) and Ethylene diamine tetra acetic acid (EDTA) stress reduced tolerance, but, even at highest Cr(VI) concentration, plant could exhibited strong resistance, as evidenced by increase in superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities. Hybrid Napier grass, due to its BAF > 1 and a TF < 1, would be applicable for Cr phytostabilization. Moreover, limiting metal transport to aerial parts of plant would prevent animal’s ingestion, restrict soil mobility, and consequently reduce transmission across the food chain.

Heavy metal pollution by both uranium and arsenic has become a major environmental problem associated with uranium mining worldwide. At present, physical, chemical and biological technologies are available as the main remediation techniques. Among them, phytoremediation is relatively low cost, hinders more pollution and allows for fast recycling of the uranium as compared to other techniques. However, suitable phytoremediation depends critically on the better choice of plant species. In this study, field sampling of soils and plants surrounding a uranium mine was conducted, and atomic emission spectrometry of samples performed, in order to characterize the distribution of heavy metal pollution and to provide a scientific basis for the phytoremediation of uranium mining sites. Soil uranium concentrations were found to be highest in open-pit mine sites, followed by ore dressing investigation sites and also the river confluence sites. Uranium did not migrate from active mining areas and the highest uranium concentration measured 232.70 mg×kg-1. In contrast, arsenic regularly migrated downstream, with soil concentrations averaging 47.26 mg×kg-1 , two times the limit set by the Three Grade Standard of Soil Quality in China (GB 15618-1995). Rumex nepalensis accumulated high levels of uranium, with a bioconcentration factor of 3.60 and a transfer factor of 3.61. Polygonum viviparum was able to accumulate arsenic, with a root transfer factor of 3.69, and also uranium as indicated by a bioconcentration factor greater than one. Thus, our investigations improved the understanding of the potential role of Polygonum viviparum and Rumex nepalensis involved in phytoremediation of uranium or uranium-arsenic pollution.