Biochar is suggested as a conditioner for salt-affected soils for various crops. This study aimed to evaluate the effects of biochar on the growth and physiology of sugarcane under saline and non-saline conditions at an early growth stage. The experiment was conducted in pots in the greenhouses with three replications. Three biochar rates (0, 5, and 10 tons ha⁻¹) were applied before transplanting sugarcane seedlings into the pots. Four weeks after transplanting, plants were irrigated with 300 mL of 100 mM NaCl every two days for 2 weeks. Salinity significantly affected the growth and physiology of sugarcanes. The application of biochar increased plant height, shoot dry weight, root volume, root dry weight, Fv/Fm, and chlorophyll content while decreasing the water saturation deficit and the relative ion leakage in the leaves under both saline and non-saline conditions. Thus, biochar application has positive effects on the growth and physiology of sugarcane at an early growth stage under both saline and non-saline conditions. However, further study is suggested to investigate the effects of biochar on sugarcane under saline stress in the field at different growth stages.

In this study, an experiment was conducted to suggest optimal daytime temperature and light intensity for cucumber scion and rootstock production in a plant factory with artificial light. Plant growth of cucumber scions and rootstocks at a day/night temperature of 26/18 °C and photosynthetic photon fluxes of 50, 120, 190, 260, 330, and 400 μmol·m⁻²·s⁻¹ was investigated. Plant growth under daytime temperatures of 25/18, 26/18, 27/18, and 28/18 °C at a photosynthetic photon flux of 260 μmol·m⁻²·s⁻¹ was investigated. As the photosynthetic photon flux increased, hypocotyl length was shortened in cucumber scions and rootstocks, but Dickson quality index, compactness, and Seedling Health Index were improved. As the daytime temperature increased, the hypocotyl length of cucumber scions increased, but the quality of seedlings decreased. The root growth of scions decreased as the daytime temperature increased. As for the correlation between the major growth indicators, Dickson quality index, compactness, and Seedling Health Index showed a high correlation of more than 0.8 in stem diameter, leaf, and root weight. Therefore, it is judged that it is most efficient to maintain the photosynthetic photon flux at 260 μmol·m⁻²·s⁻¹ throughout the year and adjust the daytime temperature to 25 to 28 °C according to the season for farms and commercial nurseries that produce cucumber seedlings by installing plant factories with artificial light.

This study aimed to determine the feasibility of temperature difference as an overgrowth-prevention technique to influence plant height and internode length in a plant factory with artificial lighting. The control plants were grown in a commercial nursery greenhouse using a growth regulator (Binnari), and +DIF (25 °C/15 °C), 0DIF (20 °C/20 °C), and −DIF (15 °C/25 °C) were the treatments with different day/night temperatures and the same average temperature (20 °C). Cucumbers showed the strongest suppression under the −DIF treatment, with a dwarfism rate of 33.3%. Similarly, tomatoes showed 0.8% and 22.2% inhibition in the 0DIF and −DIF treatments, respectively. The F_V/F_M of cucumber was approximately 0.81 for all treatments. The OJIP changes differed for cucumbers; however, both cucumbers and tomatoes had similar OJIP curve patterns and no abnormalities. The relative growth rate of cucumbers at the growth stage was 1.48 cm·cm·day⁻¹ for days 6–9 in +DIF stage 3, which was the highest growth rate among all treatments, and 0.71 cm·cm·day⁻¹ for days 3–6 in −DIF stage 1, which was the most growth-inhibited treatment. In tomatoes, we found that days 3–6 of −DIF stage 1 had the most growth inhibition at 0.45 cm·cm·day⁻¹. For cucumber, −DIF days 3–6 had the most growth inhibition, with a relative growth rate of 0.71 cm·cm·day⁻¹, but the fidelity was significantly higher than the other treatments, with a 171% increase. The same was true for tomatoes, with days 3–6 of −DIF stage 1 showing the most inhibited growth at 0.45 cm·cm·day⁻¹ but a 200% increase in fidelity. Therefore, applying the −DIF treatment at the beginning of growth would be most effective for both cucumbers and tomatoes to prevent overgrowth through the DIF in a plant factory with artificial lighting because it does not interfere with the seedling physiology and slows down the growth and development stage.

This study provides basic data on the growth and production of seedlings produced in plant factories with artificial lighting by comparing seedling quality, growth and fruit characteristics, and production after transplanting cucumber seedlings according to environmental differences between plant factories with artificial lighting and conventional nurseries in greenhouse. The control group consisted of greenhouse seedlings (GH) grown in the conventional nursery before transplanting. Plant factory to greenhouse seedlings (PG) were grown for 9 days in a plant factory with artificial lighting and for 13 days in an conventional nursery. Plant factory seedlings (PF) were grown in a plant factory with artificial lighting for 22 days until planting. In terms of seedling quality, PFs had the highest relative growth rate and compactness and the best root zone development. After transplanting PFs tended to grow faster, the first harvest date was 2 days earlier than that of GHs, and the growing season ended 1 day earlier. The female flower flowering rate of the PFs was high, and the fruit set rate was of PF the lowest. The production per unit area was highest for PFs at 10.23kg Performance index on the absorption basis, the most sensitive chlorophyll fluorescence parameter, was highest at 4.14 for PFs at 4 weeks after transplantation. By comparing the maximum quantum yield of primary PS Ⅱ photochemistry and dissipated energy flux per PS Ⅱ reaction center electron at 4 weeks after transplantation, PFs tended to be the least stressed. PFs had the best seedling quality, growth, and production after planting, and fruit quality was consistent with that of greenhouse seedlings. Therefore, plant factory seedlings can be used in the field.

This study was carried out to balance the production and consumption of assimilates according to crop conditions as a basis to reduce the waste of assimilation through leaf and fruit control. There were four treatments: one fruit and two leaves (F1L2); two fruits and two leaves (F2L2); two fruits and three leaves (F2L3); and two fruits and four leaves (F2L4). This study showed that, as the number of leaves increased in Periods 1 and 2, the stem diameter and average weight decreased, with F1L2 having the highest stem diameter and average weight, although its numbers of leaves and fruits were the fewest. In the summer, Period 3, F1L2 production was the lowest due to increased rates of flower drop and fruit drop. In Period 4, when ambient temperature and light levels were decreased, the number of fruits was increased. However, the production was decreased. F1L2 and F2L4 showed significant decreases in production. Although F1L2 showed the highest average weight, it had a low production due to a decrease in the number of fruits. F2L4 showed weak generative growth due to an imbalance in growth over the summer. After reaching the last stage of development, the number of leaves showed the highest average weight and production in F2L4.