Stress Responses and Accumulation Characteristics of Duckweed (Landoltia punctata) to Lead Oxide Nanoparticles

• • PbO NPs at 10–20 mg·L−1 promoted duckweed growth, but ≥30 mg·L−1 inhibited fresh weight and growth rate; root length decreased significantly at ≥20 mg·L−1, indicating a hormetic threshold around 20 mg·L−1. • • Chlorophyll b content dropped by 14.09%, 10.79%, and 18.48% at 20, 30, and 40 mg·L−1 PbO NPs, respectively, while carotenoids increased, signaling photosynthetic pigment disruption and oxidative stress. • • Lead accumulation reached 1265.65 mg·kg−1 at 30 mg·L−1 and 2030.01 mg·L−1 at 40 mg·L−1, with bioconcentration factors >1 and lead removal rates >68.94%, confirming hyperaccumulator status. • • Subcellular fractionation revealed lead predominantly in the cell wall (followed by soluble and organelle fractions), suggesting a detoxification mechanism that sequesters Pb in cell walls, critical for phytoremediation stability.