The seasonal variation of redox status in komatsuna (Brassica rapa var. perviridis) leaves

• Hydrogen peroxide was higher in komatsuna leaves harvested in summer season than that in winter.
• The activity of superoxide dismutase was significantly higher in the leaves harvested in summer season than that in winter.
• Komatsuna leaves harvested in winter had higher activities of antioxidant-related enzymes than that in summer.
• Seasonal conditions influenced the antioxidant metabolism of komatsuna leaves varies at different times of the year.

The objective of this research was to evaluate seasonal variations in antioxidant metabolism of komatsuna leaves. Komatsuna, cv. ‘Hitomi’, was harvested in summer and winter seasons. The level of hydrogen peroxide, a preventive ROS, was significantly higher in the summer leaves. Meanwhile, the activity of superoxide dismutase (SOD) was significantly higher in the summer leaves. On the other hand, the levels of ascorbate, reduced glutathione and total antioxidant capacity (TAC) were significantly higher in the winter leaves. Meanwhile, similar trends were observed in the activities of antioxidant-related enzymes including catalase (CAT), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR) as well – higher in the winter leaves. These results indicate that the antioxidant metabolism of komatsuna leaves responded differently to the high summer temperature, and low winter temperature stresses.