Co-Occurrence of Essential and Non-Essential Heavy Metal(loid)s in Plants: Physiological, Biochemical, and Molecular Perspectives for Soil Bioremediation
Naila Shah1,2, Muhammad Awais3, Haiyan Li1,*
1 Medical School, Kunming University of Science and Technology, Kunming, China
2 Department of Botany, Govt. Girls’ Degree College Lundkhwar, Higher Education Department, Mardan, KP, Pakistan
3 School of Life Sciences, Yunnan University, Kunming, China
* Corresponding Author: Haiyan Li. Email: 
(This article belongs to the Special Issue: Abiotic and Biotic Stress Tolerance in Crop)
Phyton-International Journal of Experimental Botany https://doi.org/10.32604/phyton.2026.087781
Received 23 June 2026; Accepted 03 September 2026; Published online 14 September 2026
Abstract
The co-occurrence of essential and non-essential heavy metal(loid)s in agricultural soils intensifies land degradation by disrupting soil biochemical cycling, plant productivity, and ecosystem resilience. Essential metal(loid)s Zinc (Zn
2+), Copper (Cu
2+), Manganese (Mn
2+) and Iron (Fe
2+) are required as micronutrients but become phytotoxic above threshold concentrations, while non-essential metal(loid)s such as Cadmium (Cd
2+), Lead (Pb
2+), Mercury (Hg
2+), and Arsenic (As
3+/As
5+) have no biological function and are toxic even at trace levels. Their coexistence amplifies stress through shared transporter-mediated uptake, ionic competition, nutrient imbalance, and excessive production of reactive oxygen species. This review synthesizes current knowledge on the comparative uptake, toxicity, and detoxification mechanisms of essential versus non-essential metal(loid)s, with emphasis on co-contamination scenarios. Unresolved contradictions in the literature are identified, including concentration-dependent and species-specific interactions that determine whether metal mixtures act synergistically or antagonistically. Significant knowledge gaps remain in understanding which transporters dominate under multi-metal exposure and how plant-microbe-metal networks influence land restoration outcomes. The link between metal co-occurrence and quantitative indicators of land degradation is further advanced, covering soil enzyme suppression, microbial biomass decline, and disrupted carbon-nitrogen-phosphorus cycling. While phytoremediation and microbial-assisted strategies show promise, integration with soil physicochemical management is needed for sustainable restoration. The review concludes by proposing a systems-level framework that integrates multi-omics, CRISPR-based gene editing, and predictive modeling to develop metal-tolerant crops and remediate degraded lands under increasing environmental pressures.
Keywords
Heavy metal co-occurrence; plant responses; metal interactions; oxidative stress; bioremediation; soil microbiome; nutrient uptake; land sustainability
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