Effect of Different Levels of Soil Applied Copper on the Morpho-physiological, Photochemical, and Antioxidant System of Brassica juncea

Purpose Copper (Cu) is an essential micronutrient prerequisite for various metabolic processes in plants. At optimum concentration, it performs a vital role in plant growth and development, while as at supra-optimal levels, it disturbs the normal growth in plants. Due to its dual behavior (vital and harmful), the present experiment was designed to assess the potential role of different Cu concentrations (30, 60, and 90) on Brassica juncea cv. Varuna plants. Method The experiment was set up in a randomized block design, and various physiological, biochemical, microscopic, and histochemical parameters were assessed at 30, 45, and 60 days after sowing. Result According to our findings, Cu inhibits growth at all concentrations over the control. The maximum reduction was reported in plants cultivated on Cu 90 mg kg(-1) of soil. Cu inhibits the chlorophyll content, RUBISCO activity, photosynthetic parameters, PSII activity, electron transport, and maximum quantum yield, at all concentrations. Cu stress decreases nitrate reductase and carbonic anhydrase activity as well as reduction in relative water content and carbohydrate levels in treated plants. Cu levels induced oxidative stress molecules like reactive oxygen species and malondialdehyde content in test plants, due to which the enzymatic antioxidants (catalase, superoxide-dismutase, and peroxidase) as well as non-enzymatic antioxidants (glutathione, proline), were unregulated. Excess Cu level disturbs the essential nutrient and decreases the levels of nitrogen, phosphorus, and potassium while elevated levels of Cu were observed in test plants. Conclusion From the above findings, we conclude that Cu displayed a toxic effect at all the concentrations and reduced growth, photosynthetic parameters, and biochemical parameters in Brassica juncea.