Arbuscular mycorrhizal Fungi and germanium: a dual approach to enhancing oat growth and mitigating oxidative damage due to bismuth contamination.

This study investigated the adverse effects of Bismuth (Bi) on oat () growth and its impact on detoxification mechanisms, oxidative stress markers, antioxidant capacity, and osmoregulation. Additionally, it examined the potential of germanium (Ge) and arbuscular mycorrhizal fungi (AMF), individually or in combination, to mitigate these effects. Bi exposure significantly reduced fresh weight and dry weight by ‎65% and 68.9% of control ‎, respectively. However, the combined application (AMF + Ge + Bi) increased fresh and dry weights by 92.8% and 123.9%, respectively, and improved photosynthesis by 67%, mitigating Bi-induced reductions. Bi exposure significantly increased oxidative stress markers, including H₂O₂ and MDA, while treatments with Ge and AMF mitigated these effects. Antioxidant metabolites (e.g., polyphenols, ASC and GSH) and enzymes activities (e.g., SOD, APX and CAT) increased, particularly under the combined Ge + Bi treatment, which enhanced the plant defense system, with total antioxidant capacity showing the highest rise (129.2%) compared to untreated plants. Detoxification responses such as increased phytochelatins and glutathione-related compounds were observed under Bi stress, while Ge and AMF improved detoxification efficiency by reducing metallothionein levels. At the same time, the accumulation of proline and soluble sugars supported osmotic adjustment. Overall, the synergistic action of Ge and AMF alleviated Bi-induced stress by enhancing growth, boosting photosynthesis, reducing oxidative damage, and strengthening detoxification capacity, highlighting their potential for improving crop resilience.