While carbon dots (CDs) are promising green nanomaterials for sustainable agriculture, how they regulate cotton growth via physiological and metabolic reprogramming remains poorly understood. This study evaluated foliar CD application (0–200 mg·L−1) to uncover dose–response patterns and metabolic drivers. CDs exerted a concentration-dependent impact, with 100 mg·L−1 yielding optimal results. This application markedly boosted shoot and root biomass (fresh weight: 103.43% and 44.28%; dry weight: 56.03% and 40.39%) and enhanced specific leaf area by 52.51% over the control. CDs improved photosynthetic efficiency (elevated Pn, Gs, and E values, alongside increased chlorophyll a and carotenoids) and strengthened antioxidant defenses (enhanced leaf POD/SOD and root POD/CAT activities). Despite mild MDA increases indicating oxidative stress, accumulated proline and soluble sugars in roots suggested adaptive osmotic adjustment. These findings suggest that CDs maintain physiological homeostasis by modulating antioxidant defense and osmotic adjustment. Untargeted metabolomics identified 2440 metabolites. Phenylpropanoid biosynthesis and flavonoid biosynthesis were the most prominently enriched pathways based on KEGG enrichment results. K-means and correlation analyses revealed key metabolites linked to cotton biomass. Overall, CDs facilitate cotton development through synergistic physiological and metabolic reprogramming, underscoring their potential as innovative agricultural growth regulators.
Microplastics (MPs) and antibiotics represent escalating emerging contaminants in global agricultural soils, posing substantial threats to crop health and ecosystem functionality worldwide. However, a comprehensive understanding of their joint toxicity and the underlying rhizosphere mechanisms under co-contamination remains elusive, leaving a critical knowledge gap. This study conducted a pot experiment using the globally cultivated peanut (Arachis hypogaea) exposed to polystyrene (PS) or polylactic acid (PLA) MPs (0.25 and 2% w/w) and oxytetracycline (OTC, 10 mg·kg⁻¹), integrating metagenomic sequencing and untargeted metabolomics to elucidate root-zone microecological responses. High-concentration co-exposures significantly suppressed peanut shoot biomass, and OTC was identified as the primary contributor to reduced leaf catalase activity (CAT) (p < 0.01). Metagenomic profiling revealed that co-exposure significantly reshaped the rhizosphere microbiota (R2 = 0.939, p = 0.001), enriching Pseudomonadota while inhibiting Actinobacteriota. Untargeted metabolomics detected 3789 metabolites, revealing that co-exposure significantly regulated the accumulation of defensive flavonoids (taxifolin and daidzin) and stress-responsive steroids (ponasterone A). Particularly, the combined exposure of PLA MPs and OTC induced the most severe metabolic disruption in the rhizosphere, generating 374 differential metabolites compared to the PLA-alone treatment. Procrustes analysis confirmed a tight coupling between microbial communities and metabolomes (M2 = 0.619, p = 0.004). Network analysis further identified key regulatory nodes (Nocardioides and taxifolin) that bridge the associations between the rhizosphere microenvironment and plant growth traits. This study demonstrates that microbial shifts and metabolic adjustments are essential in mediating plant responses to multi-pollutant stress, providing crucial theoretical and mechanistic insights for global agricultural environmental risk assessment under co-contamination scenarios.
Xiaotong Li, Yudong Chen, Jinlong Wang et al.· Ecotoxicology and Environmen...· 0 citations
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