Mitigation effect of dimethyl thiourea on tall fescue (Festuca arundinacea) roots under cadmium stress

Under hydroponic conditions, root growth; hydrogen peroxide (H₂O₂), indole-3-acetic acid (IAA), and zeatin riboside (ZR) content; and related gene expression were assessed in two tolerant tall fescue (Festuca arundinacea) varieties, ‘Commander’ (Cd-tolerant) and ‘Crossfire Ⅲ’ (Cd-sensitive), under different conditions (CK, 50 μmol·L^–1 Cd, 50 μmol·L^–1 Cd + 1 mmol·L^–1 dimethyl thiourea DMTU). Our results showed that the growth of primary roots of both varieties was inhibited, and the number of lateral roots significantly increased under Cd stress (P < 0.05). IAA and ZR contents decreased significantly (P < 0.05), and cell mortality rate in the root tip elongation area increased. H₂O₂ content displayed an upward trend with increasing Cd stress time. Among the varieties, ‘Crossfire Ⅲ’ showed significant changes. After DMTU treatment, H₂O₂ content and the cell mortality rate in the elongation zone of the root tip decreased, and IAA content increased significantly (P < 0.05). The inhibition of the growth of primary roots was alleviated, and it was more prominent in ‘Crossfire Ⅲ’. The trend of AUX1 gene expression was opposite to that of IAA content, and the trend of ipt gene was consistent to that of ZR content. This showed that DMTU can reduce the accumulation of H₂O₂ caused by Cd stress in plants, reducing the level of cell death, regulating the balance of H₂O₂ and hormones, and thus alleviating root growth inhibition induced by Cd stress. In addition, the mitigation effect of DMTU on the tolerant tall fescue varieties differed under Cd stress, and the mitigation effect on ‘Crossfire Ⅲ’ is greater than on ‘Commander.’