Closed Transplant Production System Research Articles

Root Architecture, Growth and Photon Yield of Cucumber Seedlings as Influenced by Daily Light Integral at Different Stages in the Closed Transplant Production System

Optimizing light conditions for vegetable seedling production in a closed transplant production system is critical for plant growth and seedling production. Additionally, energy use efficiency should be considered by growers when managing the light environment. In the present study, cucumber seedlings (Cucumis sativus L. cv. Tianjiao No. 5) were grown under six different daily light integrals (DLIs) at 8.64, 11.52, 14.40, 17.28, 23.04, and 28.80 mol m−2 d−1 created by two levels of photosynthetic photon flux density (PPFD) of 200 and 400 μmol m−2 s−1 combined with photoperiod of 12, 16 and 20 h d−1 provided by white light-emitting diodes (LEDs) in a closed transplant production system for 21 days. Results indicated that quadratic functions were observed between fresh and dry weights of cucumber seedlings and DLI at 6, 11, 16, and 21 days after sowing. Generally, higher DLI resulted in longer root length, bigger root volume and root surface area accompanied with shorter plant height and hypocotyl length; however, no significant differences were observed in root length, root volume, and root surface area as DLI increased from 14.40 to 28.80 mol m−2 d−1. Photon yield based on fresh and dry weights decreased with increasing DLI. In conclusion, increased DLI resulted in compact and vigorous morphology but reduced photon yield of cucumber seedlings produced in a closed transplant production system. In terms of plant growth and energy use efficiency, DLI at 14.40–23.04 mol m−2 d−1 was suggested for cucumber seedling production in the closed production system. Additionally, different control strategies should be applied at different growth stages of cucumber seedlings.

The Combined Conditions of Photoperiod, Light Intensity, and Air Temperature Control the Growth and Development of Tomato and Red Pepper Seedlings in a Closed Transplant Production System

Understanding environmental factors is essential to maximizing the biomass production of plants. There have been many studies on the effects of the photosynthetic photon flux (PPF), photoperiod and air temperature as separate factors affecting plants, including under a closed transplant production system (CTPS). However, few studies have investigated the combined effects of these factors on plant growth. Germinated tomato and red pepper seedlings were transferred to three different photoperiods with five different photosynthetic photon fluxes (PPFs) at an air temperature of 25/20 °C to investigate plant growth under a different daily light integral (DLI). Three different air temperatures, 23/20, 25/20, and 27/20 °C (photo/dark periods), with five different PPFs were used to examine plant growth under different DIFs (difference between the day and night temperature). Increasing the DLI from 4.32 to 21.60 mol·m−2·d−1, either by increasing the photoperiod or PPF, improved the growth of seedlings in both cultivars. However, when comparing treatments that provided the same DLI, tomato seedlings had s significantly higher growth when grown under longer photoperiods and s lower PPF. Even in higher DLI conditions, reduced growth due to higher PPF indicated that excessive light energy was a limiting factor. At 23 and 25 °C, tomato seedlings showed similar correlation curves between growth and PPF. However, at the higher temperature of 27 °C, while the slope of the curve at low PPFs was similar to that of the curves at lower temperatures, the slope at high PPFs was flatter. On the other hand, red pepper seedlings displayed the same correlation curve between growth and PPF at all tested temperatures, and red pepper plants accumulated more dry weight even at higher temperatures. These results suggested that the combination effect was more useful to observe these overall tendencies, especially in reacting to a second factor. This will provide us with more information and a deeper understanding of plant characteristics and how they will behave under changing environments.

Changes in Transpiration Rates and Growth of Cucumber and Tomato Scions and Rootstocks Grown Under Different Light Intensity Conditions in a Closed Transplant Production System

Changes in Transpiration Rates and Growth of Cucumber and Tomato Scions and Rootstocks Grown Under Different Light Intensity Conditions in a Closed Transplant Production System

Growth and Development of Grafted Cucumber Transplants as Affected by Seedling Ages of Scions and Rootstocks and Light Intensity during Their Cultivation in a Closed Production System

The objective of this study was to determine the effects of seedling ages of scions and rootstocks for grafting and light intensity during their cultivation in a closed transplant production system on the growth and development of grafted cucumber transplants. Cucumber scions and rootstocks were cultivated under 5 photosynthetic photon flux (PPF) levels: 100, 140, 180, 230, and <TEX>$280{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$</TEX> in a closed transplant production system. The scions were grafted onto the rootstocks at 8, 9, 10, 11, and 12 days after sowing (DAS). Hypocotyl length of scions and rootstocks decreased significantly as PPF increased, and an increase in dry weight with increasing PPF was more pronounced in scions. After grafting, cucumber transplants were grown in a greenhouse until 22 DAS and were then transplanted for investigation of their growth and development. Plant height, leaf area, and fresh weight of cucumber transplants grafted at 8, 9, and 10 DAS were greater, but light intensity during cultivation of scions and rootstocks did not significantly affect the early growth of cucumber transplants after grafting. The number of female flowers in grafted cucumber after transplanting was highest when scions and rootstocks were cultivated under PPF 140 and <TEX>$180{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$</TEX> and were grafted at 8 DAS. These results indicate that controlling environmental conditions in a closed transplant production system during the production of scions and rootstocks can advance grafting time and promote the growth and development of grafted cucumber transplants.

Root-zone cooling affects growth and development of paprika transplants grown in rockwool cubes

The possibility of improving the efficiency of transplant production during a summer season was studied by applying partial cooling of the root-zone during the cultivation of paprika transplants in a greenhouse. Paprika seedlings produced in a closed transplant production system were transferred to rockwool cubes, and cool-water circulation systems using plastic and stainless pipes were tested in a greenhouse during a summer season. The root-zone temperature of rockwool cubes and growth and development of paprika transplants as affected by root-zone cooling were investigated. When plastic pipes were used, the cooling efficacy by circulation of cool water (17°C) was the greatest and the temperature of rockwool cubes decreased by 3.6°C during the day time on a sunny day. Partial cooling of the root-zone enhanced root growth and increased number of flowers as compared with the transplants grown on uncooled rockwool cubes. The results indicate that partial cooling of the root-zone can alleviate damages to transplants commonly caused under high air temperature conditions, which could efficiently improve the paprika transplant production efficiency in greenhouses during the summer season.

Effects of Planting Density and Air Current Speed on the Growth and Uniformity of Qing-geng-cai and Spinach Plug Seedlings in a Closed Transplant Production System

Qing-geng-cai (Brassica chinensis L., cv. Seitei) and spinach (Spinacia oleracea L., cv. Sunlight) seedlings were grown in plug trays at 3 planting densities and 2 air current speeds either in a closed transplant production system (CTPS) or in a greenhouse in which the air current speed was not controlled. The growth parameters such as dry mass, plant height, and leaf area; uniformity of qing-geng-cai; and growth of spinach seedlings decreased with the increase in planting density in the CTPS. At higher air current speeds, the growth of the qing-geng-cai seedlings decreased. However, the growth of the spinach seedlings was not affected by the air current speed. Based on these results, the differences in the extent of mutual shading and space in the seedling populations caused by the differences in canopy height and leaf angle appear to be responsible for differences in the effect of air current speed on the growth of seedlings of each species. The growth and uniformity of qing-geng-cai and the growth of spinach seedlings were greater in the CTPS than in the greenhouse. Based on the abovementioned results, we conclude that growth in the CTPS facilitates denser seedling production and shorter production period in comparison to that in the greenhouse.

閉鎖型苗生産システム内のトマト苗の成長に及ぼす高級脂肪族アルコール溶液処理の影響

閉鎖型苗生産システム内のトマト苗の成長に及ぼす高級脂肪族アルコール溶液処理の影響

Effects of Planting Density and Air Current Speed on the Growth and That Uniformity of Tomato Plug Seedlings in a Closed Transplant Production System

閉鎖型システムにおいて, 栽植密度および気流速度を変えてトマト実生苗を育成して, 成長量およびその均一性を調査した. また, 温室にて育成した苗との比較も行った.閉鎖型システムにおいて栽植密度が高いほど苗は徒長し, 乾物重や生体重が減少し, 成長量の均一性は低くなった. また, 気流速度が高い方が乾物重や生体重が増大した. 徒長, および成長量の均一性は気流速度による有意な影響を受けなかった. これらの結果から, 気流速度を高めれば, 栽植密度が高くとも, 苗を徒長させず, かつ成長量の均一性を保持したまま生育の促進が行えることが示された.閉鎖型システムの苗は温室よりも栽植密度を高くしても徒長せず, 乾物重が大きく, 成長量が均一な品質の高い苗であることが示された.以上から, 閉鎖型システムを用いて気流速度を調節することで, 温室などの育苗施設よりも, 更なる密植育苗もしくは育苗期間の短縮ができることが示された.

CO2 and Water Utilization Efficiencies of a Closed Transplant Production System as Affected by Leaf Area Index of Tomato Seedling Populations and the Number of Air Exchanges

The closed transplant production system is defined as a transplant production system covered with opaque and insulated walls, where the energy and mass transfer between inside and outside the system is controlled and/or restricted, and using artificial lights. CO2 utilization efficiency of a closed transplant production system, CUE, was defined as the ratio of the amount of CO2 fixed by plants to that supplied into the system. Water utilization efficiency of the system, WUE, was defined in the same way as CUE. Tomato seeds were sown on plug trays and grown for 20 days in the system. CUE and WUE increased with increasing leaf area index (LAI) and decreasing the number of air exchanges. Maximum CUE (0.93) and WUE (0.95) during the present study were obtained at maximal LAI of 1.2 and minimal number of air exchanges of 0.02 h-1. Results suggest that a high LAI and a low number of air exchanges provide high CUE and WUE values.

閉鎖型苗生産システムにおけるサツマイモ増殖体生産数と電気エネルギ消費量に及ぼすトレイのセル容積の影響

Reduction in electric energy consumption is important for minimizing resources used for sweetpotato propagule production in a closed transplant production system. The objective of this study was to test whether or not an increase in cell volume of a tray can reduce electric energy consumption for sweetpotato (Ipomoea batatas (L.) Lam.) vegetative propagation in a closed transplant production system. Single node cuttings each with one unfolded leaf were used as propagules and grown for 18 days at cell volumes of 20, 40, 60 or 80 mL with the same planting density of 643 m-2 in all treatments (number of cells per tray was 98) . The number of harvestable propagules per stock plant did not differ significantly among cell volumes 6 and 10 days after planting, but increased with increasing cell volume 14 and 18 days after planting. The electric energy consumption per propagule for cell volumes of 20, 40, 60 and 80 mL was 0.54, 0.42, 0.34 and 0.26 MJ, respectively, corresponding to electricity costs of 2.2-2.4, 1.7-1.8, 1.4-1.5 and 1.0-1.1 Japanese Yen, respectively, 18 days after planting. Thus, increasing the cell volume of a tray is a useful method for reducing electric energy consumption per propagule for sweetpotato vegetative propagation in a closed transplant production system.

閉鎖型苗生産システムにおけるトマト実生個体群の葉面積指数がエネルギ利用効率に及ぼす影響

PUEP and PUEL, photosynthetically active radiation (PAR) energy utilization efficiencies were calculated by dividing the chemical energy fixed in plants by the PAR energy measured at the top of plant populations and by the theoretical value of total PAR energy on lamp surfaces, respectively. EUE, electric energy utilization efficiency of a closed transplant production system, was also calculated using the total electric energy consumed in the system as a denominator. Tomato seedlings on plug trays were grown for 20 days in the closed system in which air current speed and CO2 concentration were controlled at 0.53±0.07ms-1 and 1040±50 μmol mol-1, respectively, and the effect of leaf area index (LAI) of tomato seedling populations on PUEP, FUEL and EUE were investigated. The maximal values of PUEP, FUEL, and EUE during the present study were 0.10, 0.075 and 0.015, respectively, which were obtained when the LAI reached the maximal value of 2.4. The maximal value of PUEP (0.10) obtained in the present study was greater than the theoretical maximal value that Beadle and Long (1985) reported for C3 plants grown under ambient CO2 concentration. Results suggest that a closed system is energy efficient for transplant production and the efficiency could be even higher with a greater planting density and optimized air current speed and CO2 concentration.

閉鎖型苗生産システムにおけるサツマイモ増殖体生産速度と消費電力量に及ぼす栽植密度の影響

Multiplication ratio (number of average of harvestable propagules per stock plant, M) and electric energy consumption per propagule (Ep) at four levels of planting density (59, 118, 236 and 473 m-2) were investigated for sweetpotato (Ipomoea batatas (L.) Lam.) vegetative propagation in a closed transplant production system. After n multiplication cycles, total number of harvestable propagules (Nn) and electric energy consumption per propagule (Ep, n) in the system were estimated by using mathematical models. Single nodal cuttings were used as propagules and grown to 14 days under photosynthetic photon flux of 140, 200 and 320μ mol·m-2·s-1 during 1 to 5, 6 to 10 and 11 to 14 days after planting, respectively. Other environmental conditions included photoperiod of 16 h·d-1, air temperature of 29°C, and CO2 concentration of 920μmol·mo1-1. At the planting densities of 59, 118, 236 and 473 m-2, M were 5.9, 6.4, 3.8 and 2.3, respectively, and Ep, 1 were 0.41, 0.19, 0.16 and 0.13 kWh (electricity cost : 6.2, 2.9, 2.4 and 2.0 Yen), respectively. Results suggest that production can be optimized and electricity cost can be reduced by manipulating planting densities.

閉鎖型苗生産システムにおけるサツマイモ増殖体生産速度と消費電力量に及ぼす増殖法の影響

Multiplication ratios (average number of harvestable propagules per stock plant) and electric energy consumption per harvestable propagule (single nodal cutting with an unfolded leaf, SNC) as affected by two propagation methods, propagation method using SNC only as propagules and propagation method using both SNC and stock plant base with an unfolded leaf (SPB) as propagules were investigated for sweetpotato (Ipomoea batatas (L.) Lam.) vegetative propagation in a closed transplant production system. Total number of harvestable propagules and electric energy consumption per harvestable propagule n multiplication cycles after the start of propagation (P (n) and Ep (n), respectively) were simulated for the two propagation methods, based on the results of the experiment : multiplication ratios were 1.8 and 3.7 for SNC and SPB, respectively, when a multiplication cycle was 12 d. P (10) were 89 to 197 times greater in the propagation method using both SNC and SPB than in the propagation method using SNC only. E (n) five or more multiplication cycles after the start of propagation in the propagation method using both SNC and SPB were reduced by 40% compared with those in the propagation method using SNC only. Results show that propagation method using both SNC and SPB as propagules in the system reduces the electricity cost and shortens the multiplication period.

実用規模閉鎖型苗生産システムのエネルギ収支

The energy balance of a commercial scale closed transplant production system was investigated to estimate the energy consumed by the system and to find the optimal strategies of environmental control of the system. The system consisted of a transportation/irrigation machine, four basic modules and thermal insulation wall. The basic module consisted of shelves, lamps, air conditioners, fans and a humidifier. Sweetpotato (IPomoea batatas (L.) Lam. cv. Beniazuma) transplants were grown for 15 days under conditions of 140/200/320μ molm-2s-1 (1-5/6-11/12-15 days after planting, respectively) photosynthetic photon flux with 16h d-1 photoperiod, 28°C air temperature, 74% relative humidity and 990μmol mol-1CO2 concen-tration in the system. The total electric energy consumed by the system during 15 days when four basic modules operated was 764 MJ m-2. The system's lamps, air conditioners, fans, humidifiers and transportation/irrigation machine consumed 78.4%, 10.6%, 7.1%, 0.7% and 3.2% of the total electric energy consumed by the system, respectively. The electric energy cost per transplant, depending on the seasonal electric energy charge, was 2.5-2.6 Yen. The ratio of net chemical energy fixed by transplants to the total electric energy consumed by the system was estimated at 0.006 when the transplants grew normally. The coefficient of performance of the system was 8.0 and about 2 times higher than that described in the catalog of the air conditioner. The maximum percentage of heat energy transported by ventilation and penetra-ted through walls and floor to the cooling load of the system was estimated at 0.18% in summer and -25% in winter.

International Symposium on Transplant Production in Closed Systems for Solving the Global Issues on Environmental Conservation, Food Resources, and Energy

This symposium, with the longest name of those I have ever attended, was certainly not stretched out in time. It was a compact, very well organized meeting with 50 presentations in 3 days covering a wide range of plant transplant technology. Having participated in a symposium in Yokohama 8 years ago, at which I was impressed with the presentations on somatic embryogenesis, I was anxious to go to this meeting. Not many of the 150 participants came from Europe; however 13 countries were present, most from the eastern latitudes, with a number of American and Canadian scientists also present. The symposium started with an opening address by the legendary Dr. Atsushi Komamine. He explained that this symposium is a part of the outcome of the Japanese Research for the Future Program, started in 1996 with a budget of 2.4 billion yen for 4 years, dealing with the expected crisis in the biosphere on earth sometime in the 21st century. He stressed that the application of different biotechnologies should prevent this crisis. Genetic engineering for tolerance to environmental stress, molecular approaches for improvement of productivity, and production of resistant plants may form part of the solution. Another part is thought to be mass propagation of (woody) plants in an economically reliable way. Concepts and technologyfor closed plant production systems. The USA experts Drs. Giacomelli and Ting, and a major contributor to the symposium, Dr. Kozai from Japan, covered the first introductory session on concepts and technology. The application of machines equipped with vision technology for intensive seedling production becomes routine in a fast way. However, the environment still greatly affects seedling growth habit, final seedling quality, and ultimately the quality of the mature plant. Developments were presented of precise and uniform plant environments within closed low-mass systems with a recirculating atmosphere. The importance of this was demonstrated by the selection of morphologically similar seedlings (by radicle length and leaf size) leading to improved mature plant quality. Of the batches selected, measuring net photosynthesis and leaf temperature may lead to real-time plantbased (micro)-environmental control. 'Phytomation' is the word for this technology, leading to plant factories and biomass production units for space journeys as carried out by NASA. Theoretical studies to effectively describe the components of closed plant production systems have led to a set of 'foundation classes', resulting in a first version of a Java-based computer model describing a crop production system for long-duration human exploration of space. No-w ste systems? The necessity of closed systems for (tissue culture) transplants will, according to Dr. Kozai, become more serious in the coming decades because limitations will be set to the polluting open systems. Resources such as heating, cooling, vessels, trays, gar, water and labor will become more expensive, and thus wa e has to be minimized. A photoautotrophic closed tissue culture productio system reduces this waste and increases the final quality of the plants, compared to some traditional systems, by at least 30%. A closed transplant production system is defined as a tran plant production system covered with opaque walls, with minimized or controlled ventilation rates, using artificial lighting. So with this system, photoperiod, light intensity and quality, air temperature, humidity, C02 concentration and air current speed can be completely controlled. Photoautotrophic micropropagation and scaling-up. A historical overview of the evolution of vessels used in tissue culture shows a