EN
Several lines of evidence suggest that nitric oxide (NO) and hydrogen peroxide (H₂O₂) are important signal molecules involved in plant development and other physiological processes. Marigold (Tagetes erecta L. ‘Marvel’) was used to understand the role and relationship of NO and H₂O₂ in adventitious root development of plants. The results showed that the effects of H₂O₂ or NO on adventitious root organogenesis of explants were dose dependent, with maximal biological responses at 200 µM H₂O₂ or 50 µM NO donor sodium nitroprusside (SNP). The results also indicated the importance of both putative NO synthase (NOS)-like and nitrate reductase (NR) enzymes, which might be responsible for the production of NO in explants during rooting. Additionally, guanosine 3', 5' -cyclic monophosphate (cGMP) was involved in NO-induced root formation of marigold, but it was not involved in H₂O₂- mediated rooting process. The root number and length of explants treated with NO and H₂O₂ simultaneously were significantly higher than those of explants treated with H₂O₂ or NO alone. Moreover, NO treatments enhanced endogenous H₂O₂ levels in hypocotyls. Together, these results indicate that NO and H₂O₂ play crucial roles in the adventitious root development of marigold explants both synergistically and independently.