Hydrogen sulfide enhances cadmium tolerance in oilseed rape roots by augmenting glutathione-mediated antioxidant defense and ROS homeostasis

Hydrogen sulfide (H₂S) plays a crucial role in regulating plant development and stress responses. Here, the potential role of H₂S in enhancing cadmium (Cd) tolerance by modulating the antioxidant defense system and reactive oxygen species (ROS) homeostasis was investigated. The results shown that Cd (II) exposure significantly inhibited the growth and chlorophyll content of rapeseed seedlings. Optimal exogenous sodium hydrosulfide (NaHS; 50 μM) pretreatment markedly alleviated Cd-induced growth inhibition, chlorosis, and root morphology in contrast to increased Cd accumulation in the roots. The DW of the leaves and roots, and the total chlorophyll content increased by 23.8 %, 21.4 % and 114.8 %, respectively. Cd (II)-induced oxidative damage was significantly ameliorated by NaHS application through the reduction of hydrogen peroxide (H₂O₂) and superoxide (O₂^•-) accumulation, which were up to 47.3 % and 67.6 %, respectively. Moreover, exogenous NaHS elevated the glutathione (GSH) content and GSH/glutathione disulfide (GSSG) ratio in Cd-stressed roots from 21.9 - 33.3 % and 39.3-87.4 %, respectively. The activity of antioxidant enzymes, with the exception of ascorbate peroxidase, was further elevated by NaHS application. These results suggest that H₂S enhances Cd tolerance by augmenting GSH pools and activating antioxidant enzymes to control reactive oxygen species (ROS) homeostasis, thereby ameliorating Cd-induced oxidative stress in rapeseed seedling roots.