Acorus calamus L. Essential Oil Induces Oxidative Stress and DNA Replication Disruptions in Root Meristem Cells of Two Fabaceae and Two Brassicaceae Species

Environmental concerns regarding synthetic herbicides have sparked interest in plant-derived bioactive compounds as eco-friendly alternatives. This study investigated the cellular targets of sweet flag essential oil (<i>Acorus calamus</i> L., SEO at IC₅₀ concentration) in root meristem cells of Fabaceae (<i>Vicia faba</i>, <i>Lupinus luteus</i>) and Brassicaceae (<i>Brassica napus</i>, <i>Arabidopsis thaliana</i>), focusing on reactive oxygen species (ROS) accumulation (DAB, NBT staining), DNA replication dynamics (EdU labeling), and genome integrity (γ-H2AX immunocytochemistry, TUNEL assay, and DNA electrophoresis). SEO induced oxidative stress (200-250% of control depending on the species) and replication stress, causing DNA double-strand breaks in 50% of proliferating cells, confirmed by γ-H2AX/TUNEL. Consequently, cells were prolonged in the G₁ phase, replication activity dropped to 70% of control in Fabaceae and 80% in Brassicaceae, and EdU incorporation intensity decreased to 80% and 70% of control, respectively. An increased proportion of cells replicating heterochromatin indicated slowed S-phase progression. Despite genotoxic effects, SEO did not trigger endoreplication, apoptotic DNA fragmentation, or extensive cell death. All species exhibited a uniform stress response, although sensitivity varied, which previously enabled the establishment of selective SEO doses between Fabaceae and Brassicaceae. These findings suggest that SEO exerts phytotoxicity by disrupting S-phase progression, supporting its potential as a selective bioherbicide.