Past reports indicate that some nanoparticles (NPs) affect seed germination; however, the biotransformation of metal NPs is still not well understood. This study investigated the toxicity on seed germination/root elongation and the uptake of ZnO NPs and Zn²⁺ in alfalfa (Medicago sativa), cucumber (Cucumis sativus), and tomato (Solanum lycopersicum) seedlings. Seeds were treated with ZnO NPs at 0–1600 mg L^–1 as well as 0–250 mg L^–1 Zn²⁺ for comparison purposes. Results showed that at 1600 mg L^–1 ZnO NPs, germination in cucumber increased by 10 %, and alfalfa and tomato germination were reduced by 40 and 20 %, respectively. At 250 mg Zn²⁺ L^–1, only tomato germination was reduced with respect to controls. The highest Zn content was of 4700 and 3500 mg kg^–1 dry weight (DW), for alfalfa seedlings germinated in 1600 mg L^–1 ZnO NPs and 250 mg L^–1 Zn²⁺, respectively. Bulk X-ray absorption spectroscopy (XAS) results indicated that ZnO NPs were probably biotransformed by plants. The edge energy positions of NP-treated samples were at the same position as Zn(NO₃)₂, which indicated that Zn in all plant species was as Zn(II).