• Lead (Pb) at micromolar concentrations promotes plant growth and biomass accumulation in Arabidopsis and tobacco, as demonstrated by controlled plate experiments. • Lead (Pb) and cadmium (Cd) exhibit distinct effects on plant growth at the physiological, biochemical, and transcriptomic levels. • Pb enhances lateral root growth by upregulating auxin levels and activating the expression of AIR1 in Arabidopsis . Heavy metals are significant abiotic stresses that negatively affect plant growth and yield, thereby threatening food safety. However, in this study, we observed that low concentrations of Pb (lead) positively regulated plant growth in two model plants, Arabidopsis and tobacco, as demonstrated through controlled plate experiments. Pb treatment (e.g., 500 and 1000 μM) increased biomass accumulation, promoted chlorophyll biosynthesis, and enhanced the growth of both adventitious and lateral roots whereas cadmium (150 μM) exhibited significant toxicity to plant growth. Further biochemical analysis revealed that Pb treatment did not induce reactive oxygen species accumulation or activate antioxidant systems. To investigate the differing responses of Arabidopsis seedlings to Pb and Cd, a comparative transcriptome analysis was performed on the root and shoot of Arabidopsis seedlings. The transcriptomic analysis identified 400 and 589 differentially expressed genes (DEGs) in the Pb-treated leaves and roots, respectively, while Cd treatment resulted in 2,718 and 3,871 DEGs. Notably, KEGG analysis showed that the DEGs in response to Cd were strongly associated with stress defense and detoxification processes, whereas the gene expression patterns induced by Pb were more diverse, suggesting that Pb functions as a plant growth modulator rather than a toxicant. Moreover, Pb enhanced lateral and adventitious root growth by increasing endogenous indole-3-acetic acid content and activating its downstream signaling component, AIR1 , whose overexpression promotes lateral root growth. In conclusion, this study demonstrates the promotive effect of low Pb levels on plant growth and biomass accumulation, revealing distinct biological effects of Pb and Cd on plant roots and leaves through comparative transcriptome analysis. Model depicting the diverse effects of Pb and Cd on plant growth in Arabidopsis . Pb promotes Arabidopsis growth by regulating auxin-mediated lateral root development in seedlings, while Cd induces severe toxicity, as revealed by comprehensive transcriptomic, physiological, and biochemical analyses. Although Pb inhibit seed germination and early seedling establishment, it promotes plant growth once seedlings are established, demonstrating the contrasting effects of Pb at different developmental stages. In contrast, Cd consistently causes toxicity across all developmental stages. Numerous genes significantly upregulated by Cd treatment are closely associated with defense mechanisms, including cell wall growth, ROS scavenging systems, and detoxification. This model highlights the divergent effects of Pb and Cd on plant growth.
Liang et al. (2026) studied this question.