Plants respond to root temperature stresses by producing antioxidants as a defense mechanism. Since a number of these are phytochemicals with enhancing effects on human health, we examined the effects of 4 root-zone temperature (RZT) treatments (10, 20, 28, and 36 °C) on plant growth and the main bioactive compound concentrations in each organ of Agastache rugosa plants. We aimed to determine the optimal RZT treatment to increase bioactive compound concentrations with no deleterious effects on plant growth. Four-week-old seedlings were grown in a plant factory for 32 days. Nine plant growth parameters, namely, shoot and root fresh weights, stem and root lengths, leaf length and leaf width, leaf area, and shoot and root dry weights were significantly decreased at 10 and 36 °C compared with other treatments. A similar pattern was observed for the chlorophyll content and leaf gas exchange parameters. Of all the RZT treatments, RZT at 28 °C produced the significantly greatest accumulation of two major bioactive compounds, namely, rosmarinic acid (RA) and tilianin contents per the A. rugosa plant, and had no adverse effects on the overall growth of A. rugosa. This supports the use of 28 °C RZT to successfully improve the bioactive compounds with no adverse influence on plant growth or yield.

This study aimed to identify the optimal concentration of seaweed extract (SE) for enhancing growth, photosynthetic traits, antioxidant activity, and bioactive compound accumulation in Thai basil (Ocimum basilicum L.) plants cultivated in a fully controlled plant factory. Basil plants were foliar-sprayed twice weekly with five SE concentrations (0.5, 1.0, 1.5, 2.0, and 2.5 mL·L⁻¹), while untreated plants served as controls. After 28 days of transplanting, plant growth parameters, photosynthetic parameters, chlorophyll pigments, antioxidant activity, and the concentrations of phenolic acids and rosmarinic acid (RA) were analyzed. Moderate SE concentrations (1.0–2.0 mL·L⁻¹) significantly enhanced plant growth, chlorophyll a, carotenoid levels, DPPH radical scavenging, and total flavonoid content relative to control. The 2.0 mL·L⁻¹ treatment produced the highest total phenolic content (1.88-fold increase over the control) and was associated with elevated benzoic acid, rutin, quercetin, and kaempferol, along with reduced trans-cinnamic acid, indicating activation of the phenylpropanoid pathway. Moreover, all SE treatments significantly increased RA accumulation. These findings demonstrate that SE is an effective, sustainable biostimulant for Thai basil, with 2.0 mL·L⁻¹ as the optimal concentration for maximizing growth and phytochemical production.

Hemp (Cannabis sativa) has gained global attention since being legalized in the USA in 2018. The legalization of hemp is also underway in Korea; however, it requires facility cultivation and an agricultural technological system that can produce high-quality plants. This study investigated the changes in the growth and secondary metabolite content of female hemp following treatment with the plant growth retardant diniconazole (DIN). Treatment with DIN decreased the plant growth rate with increasing concentrations; however, at a concentration of 25 mg∙L⁻¹, it increased inflorescence biomass and apical inflorescence size. The high-performance liquid chromatograph analysis of major cannabinoids showed no statistically significant differences in total cannabidiol (CBD) and Δ9-tetrahydrocannabinol (Δ9-THC) contents among the treatment groups (25, 50, 100, 200, and 400 mg∙L⁻¹). However, the calculated production of CBD and THC per plant was significantly highest at DIN 25 mg∙L⁻¹. Overall, at a concentration of 25 mg∙L⁻¹, DIN treatment not only decreased the height of female hemp but also enhanced the production of female hemp inflorescences as well as major cannabinoids (CBD and Δ9-THC). Our results indicate that at a concentration of 25 mg∙L⁻¹, DIN is suitable for use in a vertical farming system. However, the Δ9-THC content needs to meet the 0.3% standard for industrial use. These findings can be applied in various fields that use hemp.

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.

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.