White (W) light-emitting diode (LED) light has been used as an efficient light source for commercial plant cultivation in vertical farming. This study aimed to examine the effect of W LED light sources on the growth and quality of butterhead and romaine lettuce. Three W LED light sources including normal W light (NWL) which has 450 nm as its pumping wavelength and two specific W lights (SWL1 and SWL2) with shorter blue peak wavelength (437 nm) were used to grow lettuce in comparison to a red (R) and blue (B) LED combination. As a result, SWL1 and SWL2 treatments with the same electrical power or photosynthetic photon flux density (PPFD) resulted in more growth of both lettuce cultivars compared to RB treatment. Some phenolic and flavonol contents were increased in the RB treatment, whereas SWL2 treatment stimulated the accumulation of other phenolic and flavonol compounds. Meanwhile, neither NWL nor SWL1 treatments increased the individual phenolic and flavonol contents in either cultivar (except for some flavonols in romaine lettuce in the SWL1 group). In addition, light and energy use efficiencies were also highest in the SWL1 and SWL2 treatments. These results illustrate the positive effects of specific W LED light on lettuce growth and quality, and suggest that the specific W LED light sources, especially SWL2, could be preferably used in vertical farming.

In this study, the primary (such as amino acids, fatty acids, and minerals) and secondary (including ginsenosides, phenolic acids, and flavonols) metabolites and antioxidant effects of Panax ginseng sprouts (PGSs) by different cultivation systems, such as soil–substrate cultivation (SSC) and deep-water cultivation (DWC), in a plant factory has been observed. There was no significant difference in the total fatty acid (FA) contents. Particularly, the major FAs of PGSs were palmitic acid (207.4 mg/100 g) of saturated FAs and linoleic acid (397.6 mg/100 g) and α-linolenic acid (222.6 mg/100 g) of unsaturated FAs in the SSC system. The values of total amino acids were all higher in SSC than in DWC. In the case of ginsenosides, the total protopanaxtriol product was 30.88 mg/g in SSC, while the total protopanaxdiol product was 34.83 mg/g in DWC. In particular, the values of total phenolic acids and total flavonols were 133.36 and 388.19 ug/g, respectively, and SSC had a higher content than DWC. In conclusion, the SSC system was shown to be higher in nutritional constituents and antioxidant activities in soil cultivation, suggesting that PGS with SSC has a positive effect on the quality of PGS in a plant factory.

This study analyzed growth patterns, biological compounds, antioxidant properties, ginsenoside contents, metabolites, and the annual net production of ‘Yunpoong’ and ‘K-1’ to find the optimal harvesting time of ginseng sprouts. One-year-old ginseng seedlings were cultivated in a container-type vertical farm under a temperature of 20 °C, a humidity of 60%, and average light intensity of 46.4 µmol m⁻² s⁻¹ (16 h photoperiod). Growth patterns at 2, 3, 4, and 5 weeks after transplanting (WAT) differed between cultivars. Regarding biological compounds and antioxidant properties, ‘Yunpoong’ took 5 WAT (43.59%; 2,2-diphenyl-1-picryl-hydrazine-hydrate radical scavenging activity, 1.47 OD_593nm; ferric reducing antioxidant power assay, 78.01%; 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging activity), and ‘K-1’ took 4 WAT (0.98 Re mg g⁻¹; total flavonoid contents, 35.93%; DPPH) to show a high content. Two cultivars showed the highest total ginsenoside contents at 5 WAT. Most of the analyzed metabolites had a higher content in ‘Yunpoong’ than in ‘K-1’. In both cultivars, it was confirmed that the longer the growth period (3 − > 5 WAT), the lower the yield and the annual ginsenoside net production. Therefore, ‘Yunpoong’ and ‘K-1’ cultivars should be grown as ginseng sprouts in the vertical farms for approximately 3 WAT and 4 WAT, respectively.

The objective of this study was to determine the efficiency of balloon flower sprout’s saponin production in a plant factory with artificial lighting (PFAL). Balloon flower has been traditionally used as herbal medicine and now, it is used as a medicinal plant as well as a functional food. It is important to establish the cultivation conditions for the stable production of high-quality balloon flower. Therefore, this study aimed to investigate the effects of culture systems and temperature conditions on the growth and saponin accumulation of balloon flower sprouts in controlled environment systems. One-year balloon flower roots were cultivated in soil and soilless culture systems at different temperature conditions (20, 25, and 30 °C) for 17 days. The results showed that the shoot fresh weight and shoot dry weight of the balloon flower sprouts grown in the soilless culture system at 25 °C were significantly increased by about 1.29 and 1.58 times, respectively, as compared with those of the sprouts grown in a soil culture system. Sprouts grown in the soilless culture system at 25 °C also recorded the highest root fresh weight, whereas there was no significant difference in root dry weight among the treatments. The plant height results showed an increased trend similar to that of the shoot fresh weight and shoot dry weight of the balloon flower sprouts. The concentrations of platycodin D3 (Pd-D3), polygalcin D (Pc-D), and total saponin in the shoot parts were highest in the soilless culture system at 20 and 25 °C. The root parts of sprouts grown in the soilless culture system at 30 °C also had higher deapioplatycodin D (Dpd-D) and total saponin concentrations. Overall, these results suggest that a soilless culture system with temperature conditions at 20 and 25 °C is suitable for improving the growth and saponin concentration of balloon flower cultivated in PFALs. Ultimately, our research should be a valuable resource for future research on the production of medicinal plants such as sprouts and should provide basic information to establish methods for enhancing the growth and bioactive compounds in balloon flower.

Achyranthes japonica Nakai (AJN) is a medicinal plant known to be beneficial for the joints. Since it takes at least two years from sowing to harvesting in an open field, new AJN cultivation strategies are needed to shorten the production period and improve quality. In this study, high-quality AJN is produced as microgreens in a vertical farm using a commercial ginseng soil mix (Myeongpum-Insamsangto, Shinsung Mineral Co., Ltd., Goesan, Republic of Korea) and controlled environmental conditions. The cultivation conditions included a temperature of 23 ± 2 °C, relative humidity of 50 ± 10%, and a photosynthetic photon flux density of 170 ± 15 µmol·m⁻²·s⁻¹. Pre-harvest intermittent UV-B exposure, with an intensity of 1.0 ± 0.3 W/m⁻², was applied for one day before harvest to evaluate its effects, using controlled environmental conditions in the vertical farm. Ultraviolet-B (UV-B) irradiation increases secondary metabolite levels in plants; however, the effect of UV-B on 20-hydroxyecdysone (20E), an indicator of AJN, is unclear. Therefore, we aimed to investigate whether UV-B treatment of AJN microgreens affected growth and secondary metabolites. The treatment group was set to 12 h of continuous UV-B treatment during the day, two 6 h UV-B treatments, and four 3 h UV-B treatments to confirm the effectiveness of regular and intermittent treatment and recovery. Short-term UV-B treatment before harvesting increased phenols, flavonoids, antioxidant capacity, and 20E levels without affecting AJN biomass. The intermittent 6 h UV-B irradiation with a 6 h recovery time stimulated 20E content by approximately 1.4 times compared to the control. These study findings indicate that short-term UV-B treatment before harvesting, an appropriate recovery time, and intermittent UV-B exposure are more effective at increasing 20E content than continuous treatment. This approach provides a promising strategy for improving the nutritional and health benefits of AJN microgreens in vertical farming systems.

Light is essential for plant production and has various effects on plant quality. Vertical farms typically use light-emitting diodes (LEDs) as light sources. However, the cost of LEDs varies with wattage and the initial installation costs are generally high. Therefore, to explore more cost-effective LED designs, we aimed to investigate the impact of red LED chips density on light distribution and plant growth under the same total electricity consumption. To this end, we exposed baby leaf soybean (Glycine max (L.) Merr.; 5 days) and kale (Brassica oleracea var. acephala; 18 days) to LEDs light with different arrangements of red and white chips. Plants were exposed to either 2 W chips with a red: white ratio of 4: 64 (2W4R treatment) or 1 W chips with a red: white ratio of 8: 64 (1W8R treatment) across the entire LED bar. We observed that the distribution of red light in the cultivation room differed depending on the density of the red LED chips. We found that arranging low-power red LED chips at narrow intervals resulted in uniform light distribution across the entire cultivation bed, positively affecting crop growth. Baby leaf soybean and kale exhibited uniform growth under 1W8R and growth was particularly enhanced in kale. This may be because of the dense leaf structure of kale, which promotes photosynthesis under a uniform light environment. The results of this study demonstrate that a favorable light environment can be created by altering the position and distribution of red LED chips, thereby inducing uniform growth in plants.