During seedling production, growth control of seedlings is an important problem because the overgrowth of seedlings causes a decrease of seedling quality and has disadvantages after transplanting. In this study, we aim to evaluate the possibility of replacing chemical plant growth regulators using light quality in a closed-type plant production system (CPPS) for cucumber seedling production. We used various light treatments, such as monochromatic or combined red (R) and blue (B), and combined R and B with UV-A or Far-red (Fr) light, to compare with a chemical plant growth regulator conventionally using in nursery farms. The combined R and B treatment decreased stem elongation and increased dry matter and compactness. UV-A treatment increased compactness but did not significantly affect the stem elongation or dry matter. Fr increased stem elongation and stem diameter and decreased compactness and dry matter. In leaf growth, combined R and B treatments and UV-A treatments increased leaf area, specific leaf weight, and SPAD value, and decreased leaf shape index. Fr treatments increased leaf area and leaf shape index and decreased specific leaf weight (SLW) and SPAD values. Cucumber seedlings have many different morphological changes, and R5B5 light quality was more effective in growth control due to higher compactness than chemical plant growth regulators. Also, R5B5 light quality has increased seedling quality, such as dry matter and SLW compared with fluorescent lamps. Thus, the use of light quality is a possible alternative to a chemical plant growth regulator.

To produce a high quality crop, light is an essential environmental factor in greenhouse cultivation. In the winter season, solar radiation is weak than other season. Therefore, using supplemental light during a low radiation period can increase the crop growth and yield. This study was conducted to select the economical supplemental light source for greenhouse cultivation in pepper during the low radiation period. The green pepper (Capsicum annuum 'Super Cheongyang') was transplanted on 5 September 2019. Supplemental lighting treatment was conducted from 1 January 2020 to 31 March 2020. RB LED (red and blue LED, red:blue = 7:3), W LED (white LED, R:G:B = 5:3:2), and HPS (high-pressure sodium lamp) were used as the supplemental light source. Non-treatment was used as the control. The plant height, SPAD, and number of nodes of pepper plants have no significant differences by supplemental light sources. However, the number of ramifications plants was the greatest in RB LED light source. Moreover, supplemental lighting increased photosynthesis of the pepper plant, and especially, the RB LED had the highest photosynthesis rate during supplemental lighting period. Also, the yield of pepper increased in the supplemental lighting treatment than in the control, and the RB LED had the greatest yield than other light sources. The electricity consumption was the highest in W LED and the lowest in HPS light. Through the economic analysis, the RB LED had high economic efficiency. In conclusion, these results suggest that using RB LED for supplemental light source during low radiation in pepper greenhouse increase the yield and economic feasibility.

The forced cultivation of strawberries (Fragaria × ananassa Duch.) requires fast flower bud differentiation. Using temporary nutrient-withholding periods is a common management practice for inducing flower bud differentiation at strawberry nurseries in the Republic of Korea. After the temporary nutrient-withholding period, nutrient solution resupply can advance both flower bud growth and fruit yield. This study aims to determine the optimal nutrient solution resupply period with anatomical analysis in order to find a method for fast flower bud differentiation in the early harvest period. Here, the runner plants were divided into 5 groups, each receiving a treatment period of watering (W) and nutrient solution (N) (W40 + N0 (control), W30 + N10, W20 + N20, W10 + N30, and W0 + N40; each number represents the days of the treatment period). The nutrient solution treatments were supplied using a strawberry nutrient solution developed by Gyeongsangnam-do Agricultural Research and Extension. Rapid flower bud differentiation was found for W20 + N20 via anatomical analysis. When the temporary nutrient-withholding period was decreased, the T-N (total nitrogen), P, K, and S concentrations showed a tendency to increase. The C/N ratio showed a tendency to decrease when the nutrient solution resupply period was increased. The W20 + N20 group showed faster flower bud development than the other groups at 10 days before transplanting and on the day of transplanting (2.2 and 5.5), 6 days in a primary cluster budding ratio, and 16 days in flowering plants. No differences in fruit characteristics were observed for the different treatments. In conclusion, the W20 + N20 treatment, which maintains fast flowering, seems to be appropriate for nutrient solution resupply treatment for “Maehyang” strawberries during the nursery period.

This study was conducted to investigate the effect of different NaCl concentrations and treatment timing on growth and bioactive compound content in Glehnia littoralis Fr. Schmidt ex Miquel. In the first experiment, seedlings were transplanted and grown during 30 days into a deep floating technique system (DFT system) on Hoagland solution (EC 1.5 dS•m -1 and pH 6.5) with 40, 80, 120, 160, and 200 mM NaCl in a greenhouse. In the second experiment, G. littoralis was grown during 50 days into DFT system, and treated 50, 100, 150, and 200 mM NaCl at 5 and 10 days before harvest (DBH), respectively. In both experiments, non-treatment was set as the control. Plant growth and photosynthetic characteristic, total phenolic contents, total flavonoid contents, and antioxidant activity were measured. When NaCl concentration was higher than 80 mM, growth of G. littoralis Fr. Schmidt ex Miquel was decreased. In the second experiment, growth characteristics, such as number of leaves, leaf area, dry weights of shoot and root were the highest in the 50 mM NaCl with 10 DBH. The photosynthetic rate was observed the highest in the control and 50 mM treatments, and significantly decreased in the NaCl concentration of more than 100 mM regardless of NaCl treatment timing. In addition, visible leaf injury was observed in the NaCl concentrations of more than 100 mM. The total phenolic and flavonoid concentrations were the highest in the 200 mM with 5 DBH treatment. However, antioxidant activity was the highest in the control and 50 mM with 10 DBH treatment. In conclusion, these results suggest that the application of 50 mM NaCl with 10 DBH on nutrient solution will be effective for cultivation of high quality and bioactive compound content of G. littoralis in a hydroponic system.

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