Effects of Zinc Toxicity on Chlorophyll Fluorescence and Translocation Factor of Potentilla chinensis

Zinc (Zn) is essential for plant metabolism but becomes toxic at high concentrations. In this study, we investigated the effects of Zn concentrations (40, 80, 160, 240, 320, 400 mg L−1) on plant growth, root morphology, chlorophyll fluorescence, and Zn accumulation in Potentilla chinensis grown in soil for 21 days. The results showed that total root length, root surface area, root volume, qP, qL, ETR, and SPAD values responded at ≤240 mg L−1, whereas plant height was affected at 400 mg L−1, indicating that SPAD, some fluorescence, and root traits responded before major biomass effects became statistically significant. At 400 mg L−1, shoot and root Zn concentrations reached 1353.75 and 187.16 mg kg−1 DW, respectively, and the translocation factor was 7.24. Fm, Fv, Fv/Fm, and ΦPSII remained stable, whereas F0 decreased and NPQ increased, indicating that PSII function was largely maintained, with partial reaction center damage offset by enhanced protective thermal dissipation. Shoot Zn concentrations exceeded root Zn concentrations across all treatments, indicating efficient root-to-shoot Zn translocation. These findings show that P. chinensis exhibits Zn accumulation and efficient root-to-shoot translocation under the tested conditions and warrants further investigation as a candidate species for Zn phytoextraction.