Acetylsalicylic Acid at Trace Concentrations Induces Cellular Toxicity and Phytotoxicity in the Roots of Cultivated Plants

Acetylsalicylic acid (ASA) is frequently detected in wastewater and sewage sludge, which may represent potential pathways of entry into agricultural environments. However, its effects on cultivated plants at trace concentrations remain unexplored. This study evaluated the effects of ASA (1–1000 ng·L−1) on germination and root growth of Daucus carota, Solanum lycopersicum, and Cucumis sativus, as well as cytotoxic and genotoxic effects in the root meristems of Allium cepa bulbs and biochemical responses associated with redox homeostasis in the roots of all four species. No significant adverse effects were observed at the lowest concentrations tested; however, exposure to 100 and 1000 ng·L−1 reduced root growth in all species, with a relative growth index below 0.8. In A. cepa, these concentrations induced mitodepressive effects, with mitotic indices below 70% relative to controls, and increased the frequency of chromosomal abnormalities, with total CAI values of 9.6% and 11.9%, respectively. At 100 ng·L−1, C-metaphases and chromosomal disorganization during prophase were observed, characterizing an aneugenic effect, whereas at 1000 ng·L−1, these abnormalities were accompanied by metaphases with sticky chromosomes, indicating a clastogenic effect. ASA also altered redox homeostasis in the roots of all four species, as indicated by concentration-dependent modulation of antioxidant enzymes, increased lipid peroxidation, and the absence of a compensatory non-enzymatic antioxidant response. These findings indicate that trace concentrations of ASA can impair early plant development and induce cytotoxic, genotoxic, and biochemical alterations in the roots of the species studied under the experimental conditions used. These findings emphasize the importance of assessing ASA effects under soil-based and field-relevant conditions to better understand its environmental implications.