Comparative zinc tolerance and phytoremediation potential of four biofuel plant species

Soil pollution has become a serious environmental problem worldwide due to rapid industrialization and urbanization. Zinc (Zn) contamination has raised concerns about potential effects on plants and human health. This study was conducted to assess the capability of four biofuel plants: Abelmoschus esculentus, Avena sativa, Guizotia abyssinica, and Glycine max to remediate and restore Zn contaminated soil. Selected plants were grown in soil exposed to different Zn treatments (50, 100, 200, 300, 400, 600, 800 and 1000 mg Zn kg(-1)) for 12 weeks. Soil without spike taken as control. Zn induced toxicity significantly (p < 0.05) reduced seed germination and inhibited plant growth and leaf chlorophyll content. The investigated plants can tolerate a soil content of 800 mg Zn kg(-1) with the exception of A. sativa, which was most tolerant to high Zn concentrations (1000 mg Zn kg(-1)) for all growth criteria. Moreover, increasing Zn content in soil resulted in a significant (p < 0.05) increase in Zn accumulation in various tissues of the four biofuel plants. According to phytoremediation efficiency, the four biofuel plants studied were arranged as follows: A. sativa (5.05%) > A. esculentus (4.15%) > G. max (2.31%) > G. abyssinica (1.17%). This study concluded that all tested biofuel plants species, especially A. sativa exhibited high Zn concentrations in roots and shoots, high Zn uptake capability, high tolerance, and high biomass at 50-800 mg Zn kg(-1) treatments. Consequently, these biofuel plants are excellent candidates for phytoremediation in Zn contaminated soils. Novelty statement Heavy metal contamination of soil poses a serious threat to the environment. Physical and chemical remediation methods are commonly used to remediate metal contaminated sites. It is not commercially viable, except that it is harmful and causes soil degradation. Alternatively, biological remediation techniques are cheap and environmentally friendly. Different plant species have been found to differ in their ability to accumulate metals under contaminated soil. Therefore, the present study provides a unique opportunity to study the metal accumulation potential of four biofuel plants (Abelmoschus esculentus, Avena sativa, Guizotia abyssinica and Glycine max) under zinc metal spiked soils. These plants are able to grow rapidly by developing a strong root system, high biomass production, and high tolerance to metal toxicity that helps them survive in contaminated soil environments. The investigated biofuel plant can be used to decontaminate contaminated sites and serves as a source of commercially valuable products that extract metals from biomass through combustion.