The effects of cadmium on the AsA-GSH cycle and antioxidant compounds in different cultivars of perennial ryegrass

Cadmium (Cd) is a common heavy metal contaminant in agricultural soils; its high bioaccumulation potential and toxicity mean it enters the human body via the food chain, posing a health risk. Perennial ryegrass (Lolium perenne L.) is renowned for its high tolerance to heavy metal toxicity and is frequently used in phytoremediation. This study examined growth morphology, activities of ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), glutathione peroxidase (GPX), and glutathione reductase (GR), as well as non-enzymatic antioxidant contents in two perennial ryegrass cultivars: WNS (Venus, low Cd accumulation) and YY (Excellent, high Cd accumulation), under Cd treatments of 0, 3, 6, and 12 mg/kg Cd2+. Under Cd stress, WNS exhibited significantly higher plant height, leaf length, tiller number, GPX activity, and glutathione (GSH) content compared with YY. At 12 mg/kg Cd, GR activity in WNS was also significantly higher than in YY (P < 0.05). In contrast, at each Cd level, YY showed significantly higher leaf Cd accumulation, APX and DHAR activities, and ascorbic acid (AsA) content than WNS (P < 0.05), accompanied by elevated oxidised glutathione (GSSG) content. The comprehensive response index of YY under 3, 6, and 12 mg/kg Cd was 2.77, 2.91, and 2.94 times that of WNS, respectively. These findings suggest that WNS mitigates Cd toxicity and sustains growth homeostasis by maintaining higher GPX and GR activities and higher GSH content within the GSH-GSSG cycle. This study provides a theoretical basis for elucidating the differential Cd tolerance mechanisms among ryegrass cultivars with contrasting Cd accumulation capacities and offers insights to refine phytoremediation strategies in Cd-contaminated soils.