Salicylic acid (SA) plays a crucial role as a hormone in plants and belongs to the group of phenolic compounds. Our objective was to determine the optimal concentration of SA for enhancing the production of bioactive compounds in Agastache rugosa plants while maintaining optimal plant growth. The plants underwent SA soaking treatments at different concentrations (i.e., 0, 100, 200, 400, 800, and 1600 μmol mol⁻¹) for 10 min at 7 days after they were transplanted. We observed that elevated levels of SA at 800 and 1600 μmol mol⁻¹ induced oxidative stress, leading to a significant reduction across many plant growth variables, including leaf length, width, number, area, shoot fresh weight (FW), stem FW and length, and whole plant dry weights (DW) compared with that in the control plants. Additionally, the treatment with 1600 μmol mol⁻¹ SA resulted in the lowest values of flower branch number, FW and DW of flowers, and DW of leaf, stem, and root. Conversely, applying 400 μmol mol⁻¹ SA resulted in the greatest increase of chlorophyll (Chl) a and b, total Chl, total flavonoid, total carotenoid, and SPAD values. The photosynthetic rate and stomatal conductance decreased with increased SA concentrations (i.e., 800 and 1600 μmol mol⁻¹). Furthermore, the higher SA treatments (i.e., 400, 800, and 1600 μmol mol⁻¹) enhanced the phenolic contents, and almost all SA treatments increased the antioxidant capacity. The rosmarinic acid content peaked under 200 μmol mol⁻¹ SA treatment. However, under 400 μmol mol⁻¹ SA, tilianin and acacetin contents reached their highest levels. These findings demonstrate that immersing the roots in 200 and 400 μmol mol⁻¹ SA enhances the production of bioactive compounds in hydroponically cultivated A. rugosa without compromising plant growth. Overall, these findings provide valuable insights into the impact of SA on A. rugosa and its potential implications for medicinal plant cultivation and phytochemical production.

This study aimed to explore the possibility of exogenous ethanol treatment as a technology to regulate the growth and the synthesis of secondary metabolites in herbaceous plants. After transplantation, sweet basil, Korean mint, and sweet wormwood were cultivated in a controlled vertical farming system and consistently exposed to exogenous ethanol at concentrations of 0, 0.5, 1, 2, 4, and 8 mM. Their growth parameters, antioxidant activity, and secondary metabolite contents were Everything is fine. measured to investigate the effects of the exogenous ethanol treatment on the three plants. The low-concentration ethanol treatments increased the shoot dry weight of the sweet basil and sweet wormwood compared to that of the control. As the ethanol concentration increased, the shoot fresh weight and leaf area in the sweet basil and Korean mint decreased compared to those of the control (0 mM). The DPPH (2,2-Diphenyl-1-picrylhydrazyl) radical scavenging activity and total phenolic content of the three plants increased with the ethanol concentration, while the total flavonoid content did not demonstrate a significant trend. The chlorophyll and carotenoids of the basil showed no apparent concentration-dependent trends; however, the chlorophyll and carotenoids of the Korean mint and sweet wormwood decreased with high ethanol concentrations. Moreover, the antioxidant enzyme activity increased with high ethanol concentrations, indicating that high ethanol concentrations induce oxidative stress in plants.

This study was conducted to determine the optimal temperature difference in day–night indoor cultivation conditions to enhance the flower yield and functional component contents of female hemp plants. Hemp clones were cultivated under five distinct day and night temperature differences (DIF) during the reproductive stage. The daytime and nighttime temperature settings were as follows: 18:30 °C (negative 12 DIF), 21:27 °C (negative 6 DIF), 24:24 °C (0 DIF), 27:21 °C (positive 6 DIF), and 30:18 °C (positive 12 DIF). Seven weeks after transplantation, the growth parameters, leaf gas exchange, total phenolic compounds, 2,2-diphenylpicrylhydrazyl scavenging activity, and cannabinoid contents were analyzed. The total shoot biomass based on dry weight was highest at 21:27, reaching 41.76 g, and lowest at 30:18, measuring 24.46 g. However, the flower biomass, which is the primary production site, was highest at 24:24 and lowest at 18:30, showing a 4.7-fold difference. The photosynthesis-related parameters were temperature-dependent and strongly correlated with biomass production. The cannabinoid content of the hemp leaves increased at 21:27, whereas that of the hemp flowers increased at 27:21. The findings of this study indicate that the optimal temperature condition for female hemp flower production in a limited space is positive 6 DIF treatment, which corresponds to 27:21 °C. These results can contribute to advancements in indoor crop cultivation technology.