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Yuki Sago and Airi Shigemura

Environmentally controlled closed cultivation systems with artificial lighting, such as plant factories, are becoming important for stable vegetable production because they allow continuous cultivation of crops and protect crops from the weather and

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Ming Li, Toyoki Kozai, Katsumi Ohyama, Shigeharu Shimamura, Kaori Gonda and Tetsuo Sekiyama

facility respire CO 2 into the air, was analyzed. Materials and Methods Commercial closed system with artificial lighting. The cultural room of the commercial CSAL (hereafter referred to as commercial CSAL) developed by Mirai Co., Ltd. (Japan) was 21 m

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Jyotsna Joshi, Geng Zhang, Shanqi Shen, Kanyaratt Supaibulwatana, Chihiro K.A. Watanabe and Wataru Yamori

“Plant factories with artificial lighting” are a new type of facility that can produce high yield with high quality all year round in a controlled environment (e.g., lighting, temperature, CO 2 concentration, and nutrients) ( Kozai, 2013a ; Yamori

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Hyeon-Hye Kim, Changhoo Chun, Toyoki Kozai and Junya Fuse

Spinach (Spinacia oleracea L.) was chosen to demonstrate that value-added transplant can be relatively easily produced under artificial light in a closed system. Transplant production under artificial light was divided into three periods, and the photoperiod during each period was varied. It was found that the rate of floral development could be controlled by photoperiod treatments, although floral initiation itself could not be manipulated. Short photoperiod treatments retarded floral development and stem elongation. This occurred even when the transplants were transferred for transplanting to natural conditions with long days and high temperatures. In conclusion, by providing the short photoperiod during the transplant production process, marketable plants with negligible bolting can be produced under natural long-day conditions. Moreover, the production cost per transplant in summer could be reduced by using a combination of natural and artificial lighting during the transplant production process. These results open the possibility to produce value-added transplants of different species under artificial lighting conditions and control their floral development and/or stem elongation for a timely and profitable harvest.

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Hyeon-Hye Kim, Changhoo Chun, Toyoki Kozai and Junya Fuse

Spinach (Spinacia oleracea L.) was chosen to demonstrate that the respective vegetative or reproductive conditions of transplants can be controlled in their early stages of development under artificial light in a closed system. Transplant production under artificial light was divided into three growth phases and the photoperiod during each of these phases was varied. The rate of floral development was controlled by photoperiod, but floral initiation itself was not affected. Short photoperiod treatments (8 or 12 hours/day) retarded floral development and stem elongation (bolting). This delay continued even after the transplants were transferred to natural long-day (15.5 hours/day on average) conditions with high temperatures (17 and 37 °C minimum and maximum). We concluded that by using short photoperiods during transplant production, marketable plants with reduced bolting could be produced under natural long-day conditions. In Japan, spinach with this rosetting capacity would be of greater value. Further, this concept opens the possibility of producing better quality transplants of several species under artificial lighting conditions of appropriate length, and thereby controlling their floral development and/or bolting.

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Johshin Tsuruyama and Toshio Shibuya

growing demand, a high-performance production system based on seed-propagated strawberry plugs will be required. Here, the authors focus on indoor transplant production systems using artificial lighting ( Kozai, 2007 ; Kozai et al., 2006 ), which are used

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Yuki Sago

in a plant factory equipped with artificial lighting at the Faculty of Agriculture, Yamaguchi University, Japan. The room had two air conditioners (SZYA50CAV; Daikin Industries Ltd., Japan), a dehumidifier (MJ-180JX; Mitsubishi Electric Corp., Japan

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Haijie Dou, Genhua Niu, Mengmeng Gu and Joseph G. Masabni

( Liaros et al., 2016 ; Saha et al., 2016 ). Indoor vertical farming, also known as “plant factory,” is a highly controlled environmental system for plant production that uses multiple-layer culture shelves with artificial lighting ( Despommier, 2010

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Hiromi Toida, Katsumi Ohyama, Yoshitaka Omura and Toyoki Kozai

The light and dark periods can be easily controlled by the use of artificial lighting. To understand the effects of alternation of light and dark periods on plant growth and development, we studied the growth and development of tomato (`Momotaro') seedlings under nonperiodic alternation of light and dark periods. Tomato seedlings grown under two nonperiodic alternation treatments of NF (NF-1 and NF-2) were compared with seedlings grown under a periodic alternation treatment (P treatment) with 12-hour light and dark periods. In all treatments, photosynthetic photon flux (PPF) during the light period was maintained at 280 μmol·m-2·s-1; the sum of each light period and the following dark period was 24 hours; and each of the integrated light and dark periods was 132 hours during 11 days of the experiment. In NF-1, the initial light and dark periods were 7 and 17 hours, respectively, and the light period was extended 1 hour per day, while in NF-2, they were initially 17 and 7 hours, respectively, and the light period was shortened 1 hour per day. At the end of the experiment, dry weight per seedling was greater and flower-bud initiation of the first flower truss was earlier in NF-1 than in NF-2 and P, even though the integrated PPF during the experiment was the same in all treatments. These results demonstrate that growth and development of tomato seedlings can be enhanced without any increase in electric energy consumption for lighting by gradually extending the light period or shortening the dark period.

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Noriko Ohtake, Masaharu Ishikura, Hiroshi Suzuki, Wataru Yamori and Eiji Goto

Plant factories with artificial lighting have been developed for efficient production of food crops and are now used for the commercial production of leafy greens and herbs in many countries ( Kozai, 2013 ). As the demands for year-round production