Lipoxygenase activity and antioxidant capacity in pepper (Capsicum annum) exposed to high concentration of copper sulphate

Abstract

Excess Cu causes negative effects on plant growth and development by affecting important physiological processes in plants. In this study, the effect of high concentration of copper sulphate (CuSO₄) on lipoxygenase (LOX) activity, lipid peroxidation and antioxidant activity in pepper was investigated. The highest amount of LOX activity increase and lipid peroxidation in pepper seedlings’ leaves exposed to CuSO₄ was detected 24 h following the application. An early antioxidant response to CuSO₄ application occurred, and the highest 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity was detected 3 h after the application and the highest reducing power after 12 h. The increase in malondialdehyde of leaf samples taken 1.5 h and 3 h after the application, along with the increase in LOX activity, reducing power and DPPH scavenging activity (%), showed that CuSO₄ stimulates the defence system in a short time. The increased lipid peroxidation, despite generally decreased DPPH fragmentation activity and reducing power in samples taken after 6 h showed that 0.5 M CuSO₄ caused high oxidative stress. This result revealed that high CuSO₄ concentrations may also disturb the non-enzymatic antioxidant capacity.