Abstract:Plants make corresponding measures by modifying the physiological and biochemical processes in respond to heavy metal cadmium stress. Detoxification of reactive oxygen exposure caused by heavy metals serves as one of the important aspects. In this study, the expression of ZmOPR5 in roots and shoots under Cd treatment was analyzed in two inbred lines B73 (Cd tolerant) and Mo17 (Cd sensitive). Moreover, the relative dry matter yield, malondialdehyde (MDA) content, superoxide radical O2-, H2O2, Cd2+ content and Cd2+ transfer coefficient were analyzed. The results showed that ZmOPR5 was inducible in genotypes and tissues by Cd stress. The relative expression of ZmOPR5 was positively correlated with H2O2 content, MDA content, Cd2+ content and transfer coefficient. For examples, the correlation coefficients of ZmOPR5 and above-mentioned traits in roots of B73 were 0.778, 0.879, 0.893 and 0.822, respectively, suggesting that ZmOPR5 might be involved in the process of antioxidant stress induced by Cd stress. The remaining six traits showed phenotypic variations in materials and tissues, and the correlation coefficients of these traits were also different. In B73 roots, the relative expression of ZmOPR5, MDA content, Cd2+ transfer coefficient and Cd2+ content were abundant. We speculated that roots of B73 were able to absorb more Cd2+ thus resulting in the active oxygen burst, while the high expression of ZmOPR5 participated in the scavenging process of active oxygen free radicals. B73, with the higher Cd2+ transfer coefficient and could rapidly transfer excessive Cd2+ in the root system to stems and leaves, and might be stored in the vacuole of leaves in the form of chelates. These results raised an explanation of Cd accumulation and tolerance between maize genotypes, which provides a reference for further analysis of physiological mechanism of ZmOPR5 involved responses to Cd stress in maize.