Heavy metal (HM)-induced stress can lead to the enrichment of HMs in plants thereby threatening people’s lives and health via the food chain. For this reason, there is an urgent need for some reliable and practical techniques to detect and analyze the absorption, distribution, accumulation, chemical form, and transport of HMs in plants for reducing or regulating HM content. Not only does it help to explore the mechanism of plant HM response, but it also holds significant importance for cultivating plants with low levels of HMs. Even though this field has garnered significant attention recently, only minority researchers have systematically summarized the different methods of analysis. This paper outlines the detection and analysis techniques applied in recent years for determining HM concentration in plants, such as inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS), atomic fluorescence spectrometry (AFS), X-ray absorption spectroscopy (XAS), X-ray fluorescence spectrometry (XRF), laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), non-invasive micro-test technology (NMT) and omics and molecular biology approaches. They can detect the chemical forms, spatial distribution, uptake and transport of HMs in plants. For this paper, the principles behind these techniques are clarified, their advantages and disadvantages are highlighted, their applications are explored, and guidance for selecting the appropriate methods to study HMs in plants is provided for later research. It is also expected to promote the innovation and development of HM-detection technologies and offer ideas for future research concerning HM accumulation in plants.

Although Platycodon grandiflorum (Jacq.) A.DC. is a renowned medicine food homology plant, reports of excessive cadmium (Cd) levels are common, which affects its safety for clinical use and food consumption. To enable its Cd levels to be regulated or reduced, it is necessary to first elucidate the mechanism of Cd uptake and accumulation in the plant, in addition to its detoxification mechanisms. This present study used inductively couple plasma-mass-spectrometry to analyze the subcellular distribution and chemical forms of Cd in different tissues of P. grandiflorum. The experimental results showed that Cd was mainly accumulated in the roots [predominantly in the cell wall (50.96%–61.42%)], and it was found primarily in hypomobile and hypotoxic forms. The proportion of Cd in the soluble fraction increased after Cd exposure, and the proportion of insoluble phosphate Cd and oxalate Cd increased in roots and leaves, with a higher increase in oxalate Cd. Therefore, it is likely that root retention mechanisms, cell wall deposition, vacuole sequestration, and the formation of low mobility and low toxicity forms are tolerance strategies for Cd detoxification used by P. grandiflorum. The results of this study provide a theoretical grounding for the study of Cd accumulation and detoxification mechanisms in P. grandiflorum, and they can be used as a reference for developing Cd limits and standards for other medicine food homology plants.

Mirabilis himalaica is a Tibetan medicinal plant whose tuberous root is its principal medicinal organ. To characterise molecular and metabolic differences associated with root enlargement, we integrated untargeted metabolomic and transcriptomic analyses of enlarged and non-enlarged roots. We identified 1465 metabolites, including 336 differentially accumulated metabolites, and 4058 differentially expressed genes. Flavonoids and phenolic acids were predominantly less abundant in enlarged roots, whereas several alkaloids showed higher relative abundance. Three gibberellin-related metabolites were lower in enlarged roots, while 1-Aminocyclopropanecarboxylic acid (ACC), L-tryptophan, tryptamine, and several cytokinin-related metabolites showed higher relative signals. Tryptophan metabolism was a shared enriched pathway in the integrated analysis. L-Tryptophan was positively correlated with Anthranilate synthase beta subunit 2 (ASB2) and negatively correlated with Tryptophan synthase alpha chain (TSA) and Probable indole-3-pyruvate monooxygenase (YUC) across the six samples; these exploratory correlations do not establish regulatory relationships. The observed patterns are consistent with coordinated changes in hormone-related metabolites, secondary metabolism, and gene expression during root enlargement. Because Indole-3-acetic acid (IAA) and lignin were not directly quantified, the study does not infer their concentrations or deposition. These findings provide a multi-omics resource for investigating tuberous-root development and for guiding future functional and targeted validation studies in this endangered medicinal species.