Efficacy of synthesized copper oxide nanoparticles to mitigate chromium toxicity in Pisum sativum L. through improving photosynthetic efficiency and antioxidant capacity.

Chromium (Cr) stress poses a severe threat to plant growth and productivity, necessitating effective mitigation strategies. In this study Pisum sativum L. plants were subjected to Cr stress (200 µM K2Cr2O7) and treated with CuSO4 and CuONPs foliar spray (100 mg L-1 for both) to evaluate their effects on growth, physiological, and biochemical attributes. Cr stress severely inhibited plant growth, reducing shoot length, fresh weight, and dry weight by 16%, 20%, and 20%, respectively, while increasing root length by 23%. Photosynthetic pigments, gas exchange attributes, and water use efficiency (WUE) were also significantly impaired under Cr stress. CuONPs surpassed the effects of CuSO4 and increased shoot length, shoot fresh weight, and shoot dry weight by 27%, 27%, and 24%, respectively, in Cr-stressed plants. Additionally, CuONPs enhanced photosynthetic efficiency, reduced oxidative stress markers (malondialdehyde and hydrogen peroxide), and improved antioxidant enzyme activities (SOD, POD, APX, and CAT). Principal component analysis revealed that CuONPs-treated plants under Cr stress were closely aligned with control plants, demonstrating their effectiveness in mitigating Cr-induced damage. These results demonstrate that CuONPs hold significant potential as a foliar treatment to enhance Cr stress tolerance in P. sativum, offering a sustainable approach to improving crop resilience in heavy metal-contaminated environments.