Tingqiang Li

Summary: In paddy fields near mining sites or transport corridors, elevated foliar cadmium (Cd) exposure is an emerging threat to rice ( Oryza sativa ) production. While rice recruits beneficial rhizosphere microbes against environmental stress, how this recruitment is coordinated under foliar Cd stress remains elusive. We assessed physiological responses to foliar Cd exposure in 26 rice cultivars and characterized rhizosphere bacterial communities and root exudates in six representative cultivars. Foliar Cd reduced leaf biomass by 6–29% and induced pronounced oxidative stress. In parallel, this foliar stress reshaped the rhizosphere microbiota, with consistent enrichment of Bacillus . This microbial shift was accompanied by increased root exudation of L‐valine and L‐leucine, which was associated with reactive oxygen species (ROS) signaling and increased root membrane permeability. Crucially, these amino acids promoted chemotaxis and root colonization by the representative Bacillus strains SRS50 and SRS107, selected from 11 candidates among 241 rhizosphere isolates, whereas colonization was reduced in ROS‐deficient mutants. Functionally, application of a ‘synbiotic’ (amino acid‐ Bacillus combination) reduced grain Cd concentrations by 40.5–43.3%, associated with Bacillus ‐induced leaf lignification. These findings highlight a plant–microbe feedback loop that contributes to rice adaptation to foliar Cd stress.

Combined lead (Pb) and cadmium (Cd) contamination of vegetable growing soils represents a globally underestimated dietary risk, as co-exposure generates synergistic phytotoxicity and elevates metal bioaccessibility beyond what single-metal models predict. This study evaluated foliar application of Moringa oleifera leaf extract and Zinc oxide nanoparticles (MZnO) as a contamination specific intervention to restore spinach physiology and reduce dietary metal risk under Pb (800 mg kg⁻¹), Cd (8 mg kg⁻¹), and combined Pb+Cd soil contamination. Foliar application was applied at two different doses: moringa zinc oxide low (MZnOL) (4% MLE + 100 mg L⁻¹ ZnO) and moringa zinc oxide high (MZnOH) (6% MLE + 200 mg L⁻¹ ZnO). Co-contamination caused synergistic phytotoxicity, reducing dry root weight by 75% and chlorophyll by 40%, while elevating H₂O₂ and malondialdehyde by 178% and 305% above the control, respectively, which exceeded the additive effects of either metal alone. Foliar MZnO dose-dependently restored antioxidant defense, elevating catalase and superoxide dismutase, while reducing electrolyte leakage from 64% under Pb+Cd to 35% under Pb+Cd+MZnOH. MZnO reduced Pb and Cd uptake in Spinach by up to 63% and 69%, respectively, and restored Fe, Zn, and other nutrients. MZnOH lowered HRI below 1 in all treatments for adults and children for both metals. A contamination-specific dosing framework was developed, with MZnOL sufficient for soils contaminated only with Pb and MZnOH for soils contaminated with Cd, and Pb+Cd to ensure food safety. These findings establish foliar MZnO as a practically deployable, dose-optimized food-safety intervention for heavy metal affected leafy vegetable production.

Intensified industrialization, urbanization, and agricultural activities have led to excessive heavy-metal accumulation in agricultural products, threatening food safety. Recent studies suggest that foliar exposure under atmospheric deposition is the dominant route for controlling metal accumulation in edible tissues. However, their specific mechanisms remain poorly understood. This Review synthesizes the foliar uptake and translocation of atmospheric heavy metals, focusing on the interactions among particle size, metal speciation, and leaf morphology. Key debates include the form of entry (ionic vs particulate), the mechanism of uptake (passive vs active), and the transporters involved. Emerging evidence shows that micrometer-sized particles enter leaves through stomata via passive diffusion, although intracellular transport may involve active mechanisms. In contrast, nanosized particles can penetrate both cuticular and stomatal pathways. Notably, leaves preferentially take up ionic heavy metals over particulate forms. The trichome pathway emerged as an additional route. However, whether it governs direct uptake or enhanced retention and if the chemical form taken up is ionic or particulate remains elusive. Specific transporters that mediate translocation to edible tissues have not yet been identified. This review represents a paradigm shift in crop safety, moving beyond the traditional root uptake perspective to foliar uptake of atmospheric matter.

Phytoremediation is an eco-friendly and in situ solution for remediating heavy metal-contaminated soils, yet practical application requires timely and accurate effectiveness evaluation. However, conventional chemical analysis of plant parts and soils is labor-intensive, time-consuming and limited for large-scale monitoring. This study proposed a rapid sensing framework integrating laser-induced breakdown spectroscopy (LIBS) with deep transfer learning and spectral indices to assess phytoremediation effectiveness of Sedum alfredii (a Cd/Zn co-hyperaccumulator). LIBS spectra were collected from plant tissues and diverse soil matrices. To overcome strong matrix effects, fine-tuned convolutional neural networks were developed for simultaneous multi-matrix quantification, achieving high-accuracy prediction for Cd and Zn (R²_test > 0.99). These predicted concentrations enabled calculating conventional phytoremediation indicators like bioconcentration factor (BCF), translocation factor (TF), plant effective number (PEN), and removal efficiency (RE), yielding recovery rates near 100% for TF and PEN. Additionally, novel spectral indices (SIs)—directly derived from characteristic wavelength combinations—were constructed to bypass intermediate quantification. SIs significantly improved the direct evaluation of Zn removal and translocation. Finally, a decision-level fusion strategy combining concentration predictions and SIs enhanced Cd removal assessment accuracy. This study validates LIBS combined with intelligent algorithms as a rapid sensor tool for monitoring phytoremediation performance, facilitating sustainable environmental management.

Aims Plants evolve with persistent core microbiomes that extend host functional repertoires, yet the assembly patterns and functions of these communities remain insufficiently understood, limiting their application in enhancing plant performance. Methods We investigated bacterial communities in the bulk soil, rhizosphere and root endosphere of various Cd-hyperaccumulators growing under controlled and field conditions, and identified core microbes linked to key plant traits using 16S rRNA gene sequencing and synthetic community (SynCom). Results Microbiome assembly along the soil-root continuum was predominantly shaped by plant species and compartment type rather than by soil type and pollution level, with host selection intensifying from the rhizosphere to the root endosphere. Stochastic processes dominated the assembly of endosphere generalists (59%), but less so for rhizosphere generalists (45%). We identified 24 rhizosphere and 9 root endophytic generalist species as core microbiomes, which were more strongly driven by host selection than non-core taxa. These core microbiomes were markedly enriched in their respective compartments, with over 60% consistently detected across controlled and field settings. Endophytic core microbes conferred greater biotic connectivity in co-occurrence networks and were stronger predictors of plant metal accumulation than soil-derived cores, whereas rhizosphere cores were more closely associated with plant biomass production and nitrogen and phosphorus acquisition. These compartment-specific contributions to plant phenotypic properties were further validated through SynComs with isolates of core microbes. Conclusions This study provides empirical insights into host selection and the compartment-specific functions of metal-hyperaccumulator core microbiota, laying the foundation for developing microbiome-based strategies for accelerating metal-contaminated soil restoration.