Hydrogen peroxide foliar spray alleviates chromium toxicity through modulation of antioxidant defence mechanism, photosynthetic machinery and ions regulation in Brassica oleracea L.

Abstract The economy of Pakistan largely depends on agriculture. Agriculture lands are facing the challenges of heavy metals contamination. Soil is an important source of nutrients which is continuously polluted with heavy metal due to anthropogenic activities. In this study the effect of hydrogen peroxide in mitigating chromium contamination in cabbage (Brassica oleracea var. capitate) was evaluated. Brassica oleracea var. capitata is a crop that is vulnerable to Cr toxicity. In order to reduce Cr contamination in B. oleracea, this study explored use of hydrogen peroxide (H₂O₂) as a signalling molecule. Plants were subjected to 100 and 200 µM of Cr stress, and they were either treated with H₂O₂ (10 mM) or in combination with Cr. Our studies suggested that H₂O₂ greatly enhanced morphological characters, such as plant growth and development in Cr-stressed environment. Antioxidant activity elevated in response to Cr stress and the use of H₂O₂ enhanced it further. Biochemical factors, such as enzyme activity, elevated under Cr stress but maintained in response to H₂O₂ foliar application. Chromium stress reduced physiological parameters like photosynthesis and water use efficiency, but H₂O₂ treatment upgraded them. With the application of H₂O₂, inorganic ionic strength and gas exchange parameters showed a significant improvement. According to our research, H₂O₂ is efficient for reducing Cr stress in B. oleracea as it boosted physiological, antioxidant, and morphological characteristics. This suggests a possible method for promoting crop tolerance to heavy metal stress.