Rice seedling nursery systems regulate the uptake and translocation of seed‐coated imidacloprid

BACKGROUND: Rice nursery systems vary markedly in hydrological and agronomic conditions, yet how these practices influence the uptake efficiency of seed-coated pesticides remains poorly understood. This study aimed to elucidate the uptake and translocation dynamics of the model insecticide imidacloprid in rice seedlings under different nursery systems and identify the underlying mechanisms. RESULTS: Under tray and dryland nursery, biological concentration factors (BCF) for imidacloprid in shoots reached 0.0278 and 0.0167 at 7 days, respectively, with 7.13- and 4.28-fold increases compared to conventional paddy nursery. Pathway-specific experiments demonstrated that root-mediated uptake contributed substantially more to shoot accumulation than seed-mediated uptake, exceeding it by 1.68- to 5.61-fold. Quantitative analysis showed that the concentration-time (CT) index for seed-surface imidacloprid was 5.73- and 5.14-fold higher under tray and dryland nursery than under paddy nursery at 7 days. Soil column experiments further demonstrated that imidacloprid was retained within the root zone under nonflooded conditions, whereas rapid vertical leaching occurred under paddy nursery. CONCLUSION: Tray and dryland nursery systems enhance imidacloprid uptake by prolonging its retention on the seed surface and concentrating it within the rhizosphere, thereby maximizing both seed- and root-mediated systemic delivery. These findings provide a mechanistic basis for optimizing nursery management to improve seed-coating efficacy and early-stage pest protection in rice.