Excessive copper induces toxicity in Mentha arvensis L. by disturbing growth, photosynthetic machinery, oxidative metabolism and essential oil constituents

Abstract

Copper (Cu) is an essential micronutrient and plays numerous morphological, physiological, and biochemical functions in plant growth and development, however, the yield of crops is now threatened by the excessive accumulation of Cu in soil. In this study, the growth, photosynthetic traits, antioxidant activity, and oxidative biomarkers, as well as yield parameters including essential oil (EO) percentage and constituents of Mentha arvensis L., were investigated under different concentrations of Cu. The Cu treatment was given in the form of CuSO4 to the soil with various concentrations, viz. 10, 20, 40, 60, and 80 mg kg−1, and one set was kept as the control. Data reveal that the plants treated with higher Cu concentrations over 20 mg kg−1 showed toxicity symptoms i.e., stunted growth, inhibited photosynthetic pigments, accelerated antioxidant activity, evoked reactive oxygen species production, and decreased essential oil production. Notably, Cu applied at 20 mg kg−1 of soil significantly improved all the metrics examined, including the constituents of EO, especially menthol and menthyl acetate levels. Thus, the current study demonstrates that Cu supplementation at 20 mg kg−1 of soil proved advantageous, however, 80 mg kg−1 of soil-applied Cu resulted in a toxic response for the overall growth and development of M. arvensis plants.