Changes caused by heavy metals in micronutrient content and antioxidant system of forage grasses used for phytoremediation: an overview

Abstract

An increase in the content of heavy metals in the environment causes many socio-environmental problems, and phytoremediation is a tool to reduce the environmental impact caused by these elements, with prospects for the use of forage grasses. This group of plants features characteristics for the environment-decontamination process, but further studies are necessary about the damages caused by heavy metals on the uptake of cationic micronutrients and on the antioxidant system, which are essential processes for the growth of plants in contaminated sites. Exposure of forage grasses to heavy metals results in a lower content of Mn in the shoots of almost all plants, but the contents of Cu, Fe, and Zn vary according to heavy metal and forage grass. Activities of enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and guaiacol peroxidase (GPX) usually increase to reduce the oxidative stress induced by heavy metals, but when the content of any of these metals is high, enzymatic activity is decreased. Scale of toxicity of heavy metals to forage grasses can be described as: Pb ≈ Cr > Cd ≈ As > Zn ≈ Cu ≈ Ni > Mn.

A glimpse into the symplastic and apoplastic Cd uptake by Massai grass modulated by sulfur nutrition: Plants well-nourished with S as a strategy for phytoextraction

“…For this reason, several strategies to decrease the Cd concentration in the environment have been investigated, most notably phytoextraction (Sheoran et al, 2016). However, to this date, there are few known species of plants considered Cd hyperaccumulators, which fosters the study of other plants, as forage grasses (Zhao et al, 2002;Rabêlo and Borgo, 2016). These plants can offset the lower proportional accumulation of Cd with their higher biomass production, especially when grown with the adequate supply of sulfur (S) (Rabêlo and Borgo, 2016;Rabêlo et al, 2017a,b).…”

“…However, to this date, there are few known species of plants considered Cd hyperaccumulators, which fosters the study of other plants, as forage grasses (Zhao et al, 2002;Rabêlo and Borgo, 2016). These plants can offset the lower proportional accumulation of Cd with their higher biomass production, especially when grown with the adequate supply of sulfur (S) (Rabêlo and Borgo, 2016;Rabêlo et al, 2017a,b). Sulfur is a component of metabolites that act in the chelation and combat against the damage caused by Cd (eg), amino acids, reduced glutathione (GSH) and phytochelatins (PCs), and an adequate supply of this nutrient can increase the Cd extraction potential (Seth et al, 2012;Rabêlo et al, 2017a,b).…”

Alleviation of cadmium and lead stress by A‐mycorrhizal fungi and rock phosphate on maize (Zea mays L.) growth under calcareous soil conditions

“…The behavior of HMs in soil modifies the plant uptake of nutrients, particularly of essential micronutrients such as Cu 2+ , Fe 2+ , Mn 2+ , and Zn 2+ due to competition on the root sites for the absorption (Zhang et al., 2014). Similarly, Rabêlo and Borgo (2016) demonstrated that HMs caused reduction in plants’ micronutrient content. The negative effect of Cd (at its two rates) in all plants’ nutrient content is clearer than the negative effect of Pb.…”

Distribution and interactions of priority heavy metals with some antioxidant micronutrients in inhabitants of a lead-zinc mining community of ebonyi state, Nigeria

“…Particularly, a lead-zinc interaction has been observed at the absorptive as well as enzymatic sites [21]. high heavy metals concentrations [55].…”