• Journal of Bio-Environment Control
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• v.32 no.3
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• pp.217-225
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• 2023

This experiment was conducted to investigate the effects of microwave irradiation on the growth and secondary metabolite contents of lettuce seedlings. Seedlings at three weeks after sowing were treated by a microwave oven for 0, 4, 8, and 12 seconds with 200 W. After cultivation in a close plant production system for 4 weeks, plant growth measurements and secondary metabolite analysis were performed. The results showed that the fresh and dry weights of the shoot and root, leaf area, leaf length, and the number of leaves were decreased as increasing the microwave treatment times. Chlorophyll a and b, total carotenoids were increased and total phenolics were decreased at the 12-second treatment compared to the 4-second treatment. Total flavonoid contents were decreased at the 8-second treatment compared to the control. These results suggest that the changes in the levels of secondary metabolites were caused by oxidative stress. Although there was no significant difference in secondary metabolite contents excluding total flavonoid contents on the microwave treatments compared to the control, the significant difference suggests that the microwave treatment of 200 W and 2.45 GHz may alter secondary metabolite contents of lettuce after 4 weeks.