Effect of short-duration microwave treatments on flower development and secondary metabolite production in Agastache rugosa

TL;DR

Short microwave treatments improved flower growth and increased valuable plant compounds in Agastache rugosa.

Contribution

Short microwave exposure is shown to enhance flower development and secondary metabolite production in Agastache rugosa.

Findings

Microwave exposure increased flower biomass and branch number by 9–24% and 9–15%, respectively.

Photosynthesis, chlorophyll, and antioxidant enzyme activities were significantly elevated.

Key phytochemicals like chlorogenic acid increased up to 7.3-fold with microwave treatment.

Abstract

This study investigated the effects of short-duration microwave (MW) exposure on growth, photosynthesis, antioxidant activity, and secondary metabolite accumulation in Agastache rugosa cultivated in a deep flow technique hydroponic system. Plants at 14 and 18 days after transplanting were exposed to MW radiation at 200 W for 5, 10, 15, 20, and 25 s, with untreated plants serving as the control. While most vegetative growth parameters were unaffected, MW exposure for 15–25 s significantly increased flower branch number by 9–15% and flower biomass by 9–24% compared with the control. These treatments also enhanced net photosynthetic rate (by up to 53%), chlorophyll a content (by 12%), and total phenolics (by 43–85%) compared with the control. Antioxidant enzyme activities were markedly elevated, with SOD, POD, and CAT increasing by up to 66%, 49%, and 103%, respectively. MW exposure also promoted phytochemical accumulation: total flavonoids increased by 7–11%, and key bioactive compounds such as chlorogenic acid (up to 7.3-fold), tilianin (up to 53%), and rosmarinic acid (up to 42%) were significantly enhanced. These results indicate that short MW exposures of 15–25 s act as an effective elicitation strategy to improve flower development and phytopharmaceutical quality of A. rugosa under controlled cultivation conditions.

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