Evaluation of phytotoxicity and genotoxicity of uranyl nitrate in Allium assay system.

Uranyl nitrate inhibited root growth of Allium cepa at > or = 25 microM concentration. Fluorimetric analysis of metal uptake indicated the entry and accumulation of uranium into the root cell. Uranyl nitrate was neither clastogenic nor aneugenic as it failed to induce micronuclei significantly, but between 25 and 100 microM concentration, it increased significantly the frequency of sister chromatid exchange over that of control, implying its genotoxicity that possibly interfered with DNA replication and/or repair process.