Abstract
Multi-walled carbon nanotubes (MWCNTs) can modulate plant growth and development, but the signaling mechanisms underlying their effects on organogenesis remain unclear. Here, we found that MWCNTs promote adventitious root (AR) formation and that RBOH-dependent hydrogen peroxide (H₂O₂) production plays a key role in this process in cucumber (Cucumis sativus L.) and Arabidopsis thaliana. MWCNTs treatment promoted AR formation in cucumber hypocotyls. Concomitantly, endogenous H₂O₂ levels increased rapidly, along with enhanced CsRBOHD expression and NADPH oxidase activity, suggesting activation of an RBOH-dependent H₂O₂ response. Consistent with this, scavenging H₂O₂ or inhibiting NADPH oxidase markedly reduced MWCNTs-induced rooting, whereas exogenous H₂O₂ partially restored AR formation under NADPH oxidase inhibition. Genetic evidence further supported this relationship, as Atrbohd and Atrbohf mutants showed reduced responses to MWCNTs but remained responsive to exogenous H₂O₂, suggesting that RBOH-mediated H₂O₂ generation is a critical step in MWCNTs-induced adventitious rooting. In parallel, MWCNTs and H₂O₂ treatments enhanced the expression of genes associated with adventitious root development. Together, these findings support a model in which MWCNTs promote adventitious rooting through RBOH-dependent H₂O₂ signaling, providing new insight into nanomaterial-mediated regulation of plant development.