高垣 美智子

Since the introduction of LED lamps a decade ago, the plant factory with artificial lighting (PFAL) has been expected to be a savior that overcomes the food crisis, brings food safety, and enhances environmental friendliness. Despite such high expectations, the diffusion of commercial crop production in PFALs has been slow. It has been said that the main reason for this is the huge initial investment required to construct PFALs. This situation has attracted studies to access the economic feasibility of the crop production in PFALs. One thing strange in these studies is that they pay little attention to the scale of their PFALs. PFALs are factories so that they would be subject to economies of scale. If so, the scale of PFALs is an important factor that determines the economic feasibility of plant production in PFALs. However, no study has thus far attempted to examine whether economies of scale exist in the construction of PFALs. To fill this gap, this paper tries to examine, based on the data on the investment cost of PFAL construction collected from various countries and regions in the world, whether economies of scale exist in PFAL construction and, if yes, how it affects the economic viability of the plant production in PFALs by searching for the minimum scale that ensures PFAL crop production economically viable. The results show that economies of scale exist in PFAL construction, and that the production of lettuce, PFALs’ most popular crop, is now well on a commercial basis with the technology level of the most advanced PFAL operators, but strawberries has not reached that stage yet. It is also shown that crop production in PFALs is highly sensitive to changes in the yield and the price of the crops: A 30% decline either in the yield or the price of lettuce would easily bring PFALs bankruptcy. It is discussed that the optimum scale of PFALs would depend not only on the economies of scale but also on the transaction costs, such as the costs of searching and keeping a sufficient number of buyers who offer good and stable crop prices.

Quantitative nutrient management has advantages, such as saving resources and improving nutrient utilization, compared with the conventional electrical conductivity management method. The growth and nutrient utilization of vegetables are affected by the integrated environmental conditions such as nutrient supply and light spectrum. This study investigated the effects of applied nutrient quantity (ANQ) (0.5, 1, 2, and 4 times (T) the absorption quantity of nutrients determined in the preliminary experiment, indicated by 0.5T, 1T, 2T, and 4T, respectively) in nutrient solution and red:blue ratio (R:B = 3:7, 7:3, and 9:1, indicated by RB3:7, RB7:3, and RB9:1, respectively) on the growth and nutrient utilization of basil plants in a plant factory with artificial lighting. Results demonstrated that the nutrient use efficiency (NUE) and the nutrient absorption efficiency (NAE) were significantly increased by the ANQ of 0.5T compared with the treatments of 1T, 2T, and 4T, irrespective of R:B ratios. Furthermore, under the ANQ of 0.5T, RB7:3 significantly increased the yield and the absorption of N and K of the basil plant compared with other R:B ratios. Therefore, the ANQ of 0.5T combined with RB7:3 was considered the optimal combination to improve the yield, NUE, and NAE of basil plants in the present study.

Hydroponic cultivation using nutrient solution (NS) is the main cultivation method employed by plant factories with artificial lighting (PFALs). The electrical conductivity (EC) of NSs influences the yield and quality of vegetables. The purpose of this study was to optimize the yield and antioxidant accumulation of basil in a PFAL by EC management. In experiment 1, basil plants were grown under four different ECs (0.5, 1.0, 3.0, and 5.0 dS m−1) after transplanting. At 18 days after treatment, the highest levels of shoot fresh and dry weights, leaf fresh and dry weights, and leaf area were observed at an EC of 3.0 dS m−1. However, low-EC treatments (0.5 and 1.0 dS m−1) generated total phenolic content (TPC) and antioxidant capacities that were higher than those of other EC treatments (3.0 and 5.0 dS m−1). In experiment 2, basil plants were grown at an EC of 3.0 dS m−1 for 13 or 15 days, then treated with water or NS with low ECs (0.5 and 1.0 dS m−1) for 5 or 3 days before harvest. The short-term low-EC treatments, especially, water for 3 days and 0.5 dS m−1 for 5 days, significantly increased the TPC and antioxidant capacity of leaves without significantly decreasing the yields of basil, compared with the control. In conclusion, yield of basil was optimized with an EC of 3.0 dS m−1; however, the TPC and antioxidant capacity of basil were significantly increased by low ECs of 0.5 and 1.0 dS m−1. Short-term low-EC treatments (0.5 dS m−1 for 5 days or water for 3 days) could be used to promote the TPC and antioxidant capacity in leaves without sacrificing yield of basil significantly.

<title>Abstract</title>The color and nutritional quality of vegetables directly affect the choices of consumers and thus affect the commercial value of the vegetable products. Green light can penetrate the outer leaves and reach the inner leaves to promote photochemical reaction of the overlapping leaves of head vegetables. However, whether this promotion can increase the nutritional components and change the color of the inner leaves of head cabbages, which is one of the major head vegetables largely produced worldwide, remains unclear. Therefore, we investigated the changes in the colors and the concentrations of chlorophyll (Chl) and carotenoid of the inner leaves of two types of cabbages by externally irradiating the cabbage with green light. The results showed that a short-term (48 h) irradiation with low light intensity (50 μmol m⁻² s⁻¹) of green light enhanced the Chl concentration and colors of the inner leaves of cabbages, and the positive changes of these indicators increased as the leaf layers approached the head center of the cabbage. Simultaneously, we also establish a method to effectively estimate the Chl concentration using luminosity (<italic>L*</italic>) and greenness (<italic>− a*</italic>) when the Chl concentration is so low that it is difficult or not possible to be measured by SPAD meter. Our findings demonstrated that green light, as a new tool, can be used to control the colors and nutritional components of the inner leaves of cabbages. The discoveries will help produce head vegetables with the preferred phenotype desired by consumers using a plant factory with artificial lighting.

Nasturtium (Tropaeolum majus L.), as a medicinal plant, has a high phenolic content in its leaves and flowers. It is often used in salads as a dietary vegetable. Attracting strong demand, it could be a good candidate crop for a plant factory with artificial lighting (PFAL) that can achieve the mass production of high-quality crops with high productivity by regulating environmental conditions such as light. In this study, two experiments were conducted to investigate the effects of continuous lighting (CL) and different daily light integrals (DLIs) under CL on the growth, secondary metabolites, and light use efficiency (LUE) of nasturtium, all of which are essential in the successful cultivation in PFALs. In Experiment 1, two lighting models, the same DLI of 17.3 mol m-2 d-1 but different light periods (24 and 16 h) with different light intensities (200 and 300 µmol m−2 s−1, respectively), were applied to nasturtium. The results showed that leaf production, secondary metabolites, and LUE were higher under the 24-h CL treatment than under the 16-h non-CL treatment. In Experiment 2, three DLI levels (17.3, 25.9, and 34.6 mol m-2 d-1) under the CL condition were applied. The results showed that the growth parameters were positively correlated with the DLI levels under CL. The lowest DLI had the highest LUE. We conclude that the mass production of nasturtium under CL in PFALs is feasible, and the yield increases as DLI increases from 17.3 to 34.6 mol m-2 d-1 under CL without causing physiological stress on plants.

Nasturtium is a popular herbal plant, widely cultivated as culinary and medicinal plants all over the world. However, the seed propagation of nasturtium is inefficient, and in-vitro propagation is sophisticated and high-cost. In this study, the cutting propagation method was employed to produce nasturtium seedlings. We aimed to determine the optimal conditions for cutting propagation of nasturtium seedlings by investigating the effects of node position and electric conductivity (EC) of nutrient solution on the root formation of the cuttings. Cuttings from five node positions (apical bud, 2nd node, 3rd node, 4th node, and 5th node) were subjected to water and five EC (1.0, 2.0, 3.0, 4.0, and 5.0 dS m−1) treatments with a hydroponic cultivation system in a plant factory. Results showed that all cuttings rooted successfully within two weeks. The cuttings from the apical bud position rooted earliest and produced the most roots regardless of EC level. Cuttings from other node positions produced longer roots and heavier root fresh and dry weights than those from the apical bud position. The cuttings under EC of 1.0 dS m−1 had the greatest root number, the longest root length, and the heaviest root fresh and dry weights regardless of node positions. The EC of 1.0 dS m−1 is considered the best condition for nasturtium cuttings for the range of EC tested in this study, and the cuttings from all the five node positions can be used as seedling materials.

Population growth and increased stress caused by urbanization have led to social problems that are predicted to intensify in the future. In these conditions, the recently established ”nature therapy” has revealed that an environment rich in various plant life significantly contributes to the relief of physical and mental stress. Meanwhile, from the perspective of reduction in the energy required for transportation and the retention of plant freshness, urban horticulture, in which plant life exists harmoniously with the city, has attracted considerable attention. Interactions between humans and plants in urban horticulture are considered to contribute to the good health and wellbeing of people. Therefore, we incorporate human-centered thinking based on nature therapy into horticultural produce-centered thinking based on conventional urban horticulture. By introducing a pioneering urban horticulture plant factory as an example, we propose the possibility of sustainable urban horticulture based on nature therapy.

The demand for high-nutrient and fresh vegetables, including coriander, has been growing rapidly. A plant factory with artificial lighting enables the application or suppression of stress conditions to plants for producing high-quality vegetables. This study aimed to determine a suitable root-zone temperature (RZT) treatment for enhancing the biomass and secondary metabolite content of hydroponic coriander plants. The combination of a mid-RZT (25 °C) pre-treatment with low (15 °C or 20 °C) or high (30 °C or 35 °C) RZT for a short period (3 or 6 days) was applied to the plants before harvesting. The fresh weights of the coriander plants were reduced under RZT stress. By contrast, the content of secondary metabolites, including ascorbic acid, carotenoids, phenolic compounds, chlorogenic acid, and the antioxidant capacity of the plants were enhanced by the combination of the lowest or highest RZT (15 °C or 35 °C) and the longer stress period (6 days). Growing coriander under an RZT of 30 °C for 6 days can produce large amounts of bioactive compounds and water, whereas growing coriander at an RZT of 15 °C for 6 days can produce high dry biomass and secondary metabolite content.

A comprehensive analysis of multiple aspects of food production is needed to address related concerns, such as the use of nitrogen, phosphorus, and potassium fertilizers, the consumption of water, the occupation or transformation of land, and greenhouse gas emissions. We examine the environmental properties of plant factories with sunlight and plant factories with artificial light, comparing them with conventional Japanese horticulture systems. Process conditions and inventory data were extracted from demonstration factories in Chiba, Japan. We found that these plant factories reduced the use of irreplaceable resources for food production, i.e., phosphorus, water, and land area, at the expense of additional energy consumption compared with conventional Japanese horticulture systems. By employing emerging energy technology options, energy consumption can be reduced sufficiently to be competitive with that of conventional horticulture systems. The results indicate that plant factories could become a viable or competitive production technology, changing the slope factors in the nexus of food, energy, and water systems.

The global demand for medicinal plants is increasing. The quality of plants grown outdoors, however, is difficult to control. Myriad environmental factors influence plant growth and directly impact biosynthetic pathways, thus affecting the secondary metabolism of bioactive compounds. Plant factories use artificial lighting to increase the quality of medicinal plants and stabilize production. Photosynthetic photon flux density (PPFD) and electrical conductivity (EC) of nutrient solutions are two important factors that substantially influence perilla (Perilla frutescens, Labiatae) plant growth and quality. To identify suitable levels of PPFD and EC for perilla plants grown in a plant factory, the growth, photosynthesis, and accumulation of secondary metabolites in red and green perilla plants were measured at PPFD values of 100, 200, and 300 mu mol m(-2) s(-1) in nutrient solutions with EC values of 1.0, 2.0, and 3.0 dS m(-1). The results showed significant interactive effects between PPFD and EC for both the fresh and dry weights of green perilla, but not for red perilla. The fresh and dry weights of shoots and leafy areas were affected more by EC than by PPFD in green perilla, whereas they were affected more by PPFD than by EC in red perilla. Leaf net photosynthetic rates were increased as PPFD increased in both perilla varieties, regardless of EC. The perillaldehyde concentration (mg g(-1)) in red perilla was unaffected by the treatments, but accumulation in plants (mg per plant) was significantly enhanced as the weight of dry leaves increased. Perillaldehyde concentrations in green perilla showed significant differences between combinations of the highest PPFD with the highest EC and the lowest PPFD with the lowest EC. Rosmarinic acid concentration (mg g(-1)) was increased in a combination of low EC and high PPFD conditions. Optimal cultivation conditions of red and green perilla in plant factory will be discussed in terms of plant growth and contents of medicinal ingredients.

Greenhouses with sophisticated environmental control systems, or so-called plant factories with solar light, enable growers to achieve high yields of produce with desirable qualities. In a greenhouse crop with high planting density, low photosynthetic photon flux density (PPFD) at the lower leaves tends to limit plant growth, especially in the winter when the solar altitude and PPFD at the canopy are low and day length is shorter than in summer. Therefore, providing supplemental lighting to the lower canopy can increase year-round productivity. However, supplemental lighting can be expensive. In some places, the cost of electricity is lower at night, but the effect of using supplemental light at night has not yet been examined. In this study, we examined the effects of supplemental LED inter-lighting (LED inter-lighting hereafter) during the daytime or nighttime on photosynthesis, growth, and yield of single-truss tomato plants both in winter and summer. We used LED inter-lighting modules with combined red and blue light to illuminate lower leaves right after the first anthesis. The PPFD of this light was 165 mu mol m(-2) s(-1) measured at 10 cm from the LED module. LED inter lighting was provided from 4:00 am to 4:00 pm for the daytime treatments and from 10:00 pm to 10:00 am for the nighttime treatments. Plants exposed only to solar light were used as controls. Daytime LED inter-lighting increased the photosynthetic capacity of middle and lower canopy leaves, which significantly increased yield by 27% in winter; however, photosynthetic capacity and yield were not significantly increased during summer. Nighttime LED inter-lighting increased photosynthetic capacity in both winter and summer, and yield increased by 24% in winter and 12% in summer. In addition, nighttime LED inter-lighting in winter significantly increased the total soluble solids and ascorbic acid content of the tomato fruits, by 20 and 25%, respectively. Use of nighttime LED inter-lighting was also more cost-effective than daytime inter-lighting. Thus, nighttime LED inter-lighting can effectively improve tomato plant growth and yield with lower energy cost compared with daytime both in summer.

This study aimed to evaluate the environmental burden of three hydroponic tomato production systems using partial life cycle assessment (LCA). System-1 was modified nutrient film technique (NFT), in which the solution does not flow longitudinally but rather horizontally and it secures an even nutrient solution to each plant. System-2 was traditional NFT system in which the nutrient solution was recirculating the whole day continuously. System-3 was a tray that had 10 growing pots of 250 mL volume. These pots were filled with granulated rock wool and used a drip-irrigation system activated by a solar radiation threshold. All inputs and outputs of each hydroponic system were classified into structural materials, cultivation inputs and waste. The analysis shows that the environmental burden from cultivation was significantly higher for all three systems than the environmental burden from structural materials and waste. Among inputs considered under cultivation, the environmental burden from fertilizer was the highest as a result of production. However, use emissions were not considered as all systems were closed loops. System 2 had a high total environmental impact because of its considerably higher resource consumption compared to others. Water had significantly a lower environmental burden in all systems. However, all systems had different water consumptions and System-3 was the lowest for water consumption. The environmental burden from fertilizer could be minimized by a proper fertigation schedule and it needs to be examined in more detail and improved as it is the most visible environmental burden. An efficient irrigation schedule would also directly minimize the overall environmental burden due to its direct relation with all inputs used during cultivation.

Recently, the so-called "plant factory with artificial lighting" (PFAL) approach has been developed to provide safe and steady food production. Although PFALs can produce high-yielding and high-quality plants, the high plant density in these systems accelerates leaf senescence in the bottom (or outer) leaves owing to shading by the upper (or inner) leaves and by neighboring plants. This decreases yield and increases labor costs for trimming. Thus, the establishment of cultivation methods to retard senescence of outer leaves is an important research goal to improve PFAL yield and profitability. In the present study, we developed an LED lighting apparatus that would optimize light conditions for PFAL cultivation of a leafy vegetable. Lettuce (Lactuca sativa L.) was hydroponically grown under white, red, or blue LEDs, with light provided from above (downward), with or without supplemental upward lighting from underneath the plant. White LEDs proved more appropriate for lettuce growth than red or blue LEDs, and the supplemental lighting retarded the senescence of outer leaves and decreased waste (i.e., dead or low-quality senescent leaves), leading to an improvement of the marketable leaf fresh weight.

In greenhouses during the winter season, a high vapor pressure deficit (VPD), particularly due to air exchange during midday period, can limit plant biomass and yield. Thus, the VPD control in greenhouses is of immense importance for cultivating plants. In the present study, the effects of VPD controlled by a fogging system on greenhouse environment and tomato plant growth were studied during a winter season. The VPD was effectively reduced by the fogging system from 1.4 to 0.8 kPa on average in the midday during the entire winter season. Maintaining a lower VPD in the midday increased tomato leaf stomatal index and stomatal conductance during the major part of the day, which led to increase in net photosynthetic rate. Furthermore, maintaining a lower VPD increased mean tomato biomass and yield by 17.3% and 12.3%, respectively. Thus, it is concluded that the VPD control via the fogging system promotes plant growth and productivity by improving photosynthesis during the winter season. (C) 2015 Elsevier B.V. All rights reserved.

In order to increase the efficiency of nutrient utilization in solution culture systems, it is indispensable to understand how plants absorb nutrients. A series of experiments were conducted using hydroponic culture system in the first to third experiments and soil culture system in the fourth experiment in a greenhouse in Okinawa, Japan. In the first experiment, changes in NO3-N absorption were measured every three hours during a 24-hour period on 40 days after transplanting (DAT) in cucumber. In the second experiment, daytime and nighttime NO3-N absorption were measured from 45 to 48 DAT in five crops including cucumber. In the third experiment, NO3-N, NH4-N, and K absorption in daytime, nighttime and shaded conditions were determined from 30 to 34 DAT in bitter gourd, a substitute crop for cucumber, and water spinach. In the fourth experiment, daytime and nighttime (NH4)(2)SO4-N-15 absorption rates were measured from 9 to 12 DAT in cucumber. The results showed that daily NO3-N absorption in cucumber peaked twice, just before midday and again just after the nightfall. The corresponding fluctuation pattern was observed in all other tested crops, with 20-41% of the total absorption occurring at night. Absorption rate of 15N in cucumber cultivated in soil also increased in daytime and decreased at night, with the nighttime rate accounting for 39-40% of the daily total absorption. The average nighttime NO3-N, NH4-N, and K absorption percentages of the daily total before shading the plant were 34-35%, 49-51%, and 33-49%, respectively. During the shaded period, these nutrient absorption rates dramatically decreased, except for NH4-N which was not affected by shading. Across all experiments, 20-51% of total absorption took place at night, the majority of which may concentrate around the early nighttime. Furthermore, the absorption rates may be influenced by photosynthetic products.

© 2015 by the authors; licensee MDPI, Basel, Switzerland.In recent times, attention has been focused on the role of urban green spaces in promoting human health and well-being. However, there is a lack of evidence-based research on the physiological effects of walking in urban green areas. This study aimed to clarify the physiological and psychological effects of walking in urban parks during fall. Twenty-three males (mean age 22.3 ± 1.2 years) were instructed to walk predetermined 15-min courses in an urban park and in a nearby city area (control). Heart rate and heart rate variability were measured to assess physiological responses, and the semantic differential method, Profile of Mood States, and State-Trait Anxiety Inventory were used to measure psychological responses. We observed that walking in an urban park resulted in a significantly lower heart rate, higher parasympathetic nerve activity, and lower sympathetic nerve activity than walking through the city area. In subjective evaluations, participants were more “comfortable,” “natural,” “relaxed,” and “vigorous” after a walk in the urban park. Furthermore, they exhibited significantly lower levels of negative emotions and anxiety. These findings provide scientific evidence for the physiological and psychological relaxation effects of walking in urban parks during fall.

Some residents living in urban areas with little chance to grow plants outdoors have recently started enjoying indoor farming using a household plant factory with artificial light (PFAL) or micro-PFAL in Japan, Taiwan, and China and a few other Asian countries. In addition, mini-PFALs have been set up for various purposes at restaurants, cafés, shopping centers, schools, community centers, hospitals, etc. Such micro- and mini-PFALs and their networks could help bring new lifestyles related to local production for local consumption, food, health, ecology, the environment and the Internet to people living in urban areas. This chapter describes the characteristics, functions, and examples of micro- and mini-PFALs.

The Center for Environment, Health, and Field Sciences, Chiba University and the Japan Plant Factory Association are using five greenhouses (semi-closed system) with an environmental control system and three plant factories with artificial lighting (total 10,845m2) on the campus of Chiba University for research, education, and training. Annually, over 5000 people visit the facilities to learn about and understand plant factories. This education program on plant factories has been carried out since 2011 for the graduate school students of Chiba University and short-stay (70-90 days) students from sister universities. Intensive business forums on plant factories have been held since 2010, covering the information, science, business, and operation of plant factories. Intensive plant factory business workshops have been held on a wide range of issues for business people by planning workshops, excursions, and instructor dispatches on a monthly basis since 2009.

The physiological and psychological relaxation effects of viewing a kiwifruit (Actinidia deliciosa Hayward') orchard landscape were investigated. Seventeen Japanese adult females (46.1 +/- 8.2 years) viewed a kiwifruit orchard landscape or a building site (control) for 10 min. The heart rate variability and heart rate were determined. The modified semantic differential method and the short-form Profile of Mood States were used to assess the psychological effects. Compared with viewing the building site, viewing the kiwifruit orchard landscape resulted in a significant increase in the parasympathetic activity, a marginally significant decrease in the heart rate, a significant increase in comfortable, relaxed and natural feelings and a significant improvement in mood states.

Protected cultivation, especially in Asia, is operated at a small scale (&lt;0.1 ha) using a relatively low-cost structure. This type of operation is a low-input, low-output system with low resource use efficiency, while larger industrial operations (&gt;1 ha) with high-input, high-output systems that adopt modern high technologies have increased in number during the past few decades. In contrast, technology-intensive indoor agriculture operations (i.e., plant factories with artificial lighting or PFALs) in urban/suburban areas are steadily increasing in number. Such operations are a potential driving force for the development of resource-efficient technology to enhance the sustainability of both small- and large-scale protected cultivation. This paper focuses on recently developed controlled-environment technologies for these contrasting but technologically complementary applications. We discuss: A) low-cost intelligent environment controllers suitable for small-scale greenhouses; B) the concept and methodology of variable rate control; and C) closed plant production system (CPPS) and PFALs. Topic A includes intelligent controllers that can be used independently at a cost of around 100 Euro, and can also be used as a distributed environmental controller connected with an integrative environment control system for a large-scale greenhouse. Examples include controllers for: 1) null balance CO2 enrichment; 2) variable-rate fogging; and 3) multi-purpose heat pumps.

Background: It is widely believed that contact with the natural environment can improve physical and mental health. Urban green spaces may provide city residents with these benefits; however, there is a lack of empirical field research on the health benefits of urban parks. Methods: This field experiment was performed in May. Seventeen males aged 21.2 +/- 1.7 years (mean +/- standard deviation) were instructed to walk predetermined 15-minute courses in an urban park and a nearby city area (control). Heart rate and heart rate variability (HRV) were measured to assess physiological responses. The semantic differential (SD) method, Profile of Mood States (POMS), and State-Trait Anxiety Inventory (STAI) were used to measure psychological responses. Results: Heart rate was significantly lower while walking in the urban park than while walking in the city street. Furthermore, the urban park walk led to higher parasympathetic nervous activity and lower sympathetic nervous activity compared with the walk through the city street. Subjective evaluations were generally in accordance with physiological reactions, and significantly higher scores were observed for the 'comfortable', 'natural', and 'relaxed' parameters following the urban park walk. After the urban park walk, the score for the 'vigor' subscale of the POMS was significantly higher, whereas that for negative feelings such as 'tension-anxiety' and 'fatigue' was significantly lower. The score for the anxiety dimension of the STAI was also significantly lower after the urban park walk. Conclusions: Physiological and psychological results from this field experiment provide evidence for the physiological and psychological benefits of urban green spaces. A brief spring-time walk in an urban park shifted sympathetic/parasympathetic balance and improved mood state.