Closed Plant Factory Research Articles

Plant Factory Speed Breeding Significantly Shortens Rice Generation Time and Enhances Metabolic Diversity

Rice (Oryza sativa L.) plays a pivotal role in global food security, yet its breeding is constrained by its long generation time and seasonality. To enhance rice breeding efficiency and meet future food demands, we have developed a vertical hydroponic breeding system integrated with light-emitting diodes (LEDs) lighting in a closed plant factory (PF), which significantly accelerates rice growth and generation advancement. The results show that indica rice can be harvested as early as after 63 days of cultivation, a 50% reduction compared with field cultivation, enabling the annual harvesting of 5–6 generations within the PF. A hyperspectral imaging system (HSI) and attenuated total reflectance infrared (ATR-IR) spectroscopy were further employed to characterize the chemical composition of the PF- and field-cultivated rice. Metabolomics analysis with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and gas chromatography-mass spectrometry (GC-MS) revealed that, compared with the field-cultivated rice, the PF-cultivated rice exhibited an up-regulation of total phenolic acids along with 68 non-volatile and 19 volatile metabolites, such as isovitexin, succinic acid, and methylillicinone F. Overall, this study reveals the unique metabolic profile of PF-cultivated rice and highlights the potential of PFs to accelerate the breeding of crops such as rice, offering an innovative agricultural strategy to support food security in the face of global population growth and climate change.

Two-stage seedling cultivation method for sweet peppers combining closed plant factory and solar greenhouse

Two-stage seedling cultivation method for sweet peppers combining closed plant factory and solar greenhouse

High relative humidity improves leaf burn resistance in flowering Chinese cabbage seedlings cultured in a closed plant factory.

Plant factories that ensure the annual production of vegetable crops have sparked much attention. In the present study, thirty types of common vegetable crops from 25 species and eight families, were grown in a multi-layer hydroponic system in a closed-type plant factory to evaluate the adaptive performance. A total of 20 vegetable crops, belonging to 14 species and 4 families, unexpectedly exhibited different degrees of leaf margin necrosis in lower leaves firstly, then the upper leaves gradually. We defined this new physiological disorder as "leaf burn". It occurred more commonly and severely in cruciferous leafy vegetables. Two different light intensities (150 and 105 µmolm-2s-1 photosynthetic photon flux density (PPFD)), three photoperiod conditions (12, 10 and 8 hd-1) and two canopy relative air humidity (RH) (70% and 90% RH) were set to evaluate the suppression effects on leaf burn occurrence in two commercial flowering Chinese cabbage cultivars ('Sijiu' and 'Chixin'), the special cruciferous vegetable in South China. We discovered that changing light conditions did not fully suppress leaf burn occurrence in the cultivar 'Sijiu', though lower light intensity and shorter photoperiod partly did. Interestingly, the occurrence of leaf burn was completely restrained by an increased canopy RH from 70% to 90%. Specifically, the low RH-treated seedlings occurred varying degree of leaf burn symptoms, along with rapidly decreased water potential in leaves, while the high RH treatment significantly lessened the drop in leaf water potential, together with increased photosynthetic pigment contents, net photosynthetic rate, stomatal conductance and transpiration rate, decreased leaf stomatal aperture and density, and thus reduced the incidence of leaf burn in 'Sijiu' and 'Chixin', from 28.89% and 18.52% to zero, respectively. Taken together, high canopy RH may favor maintaining leaf water potential and improving photosynthesis performance, jointly regulating leaf burn incidence and plant growth.

Red and blue wavelengths affect the morphology, energy use efficiency and nutritional content of lettuce (Lactuca sativa L.)

Since red (R) and blue (B) LED light has different quantum efficiency and photoelectric conversion efficiency, mixed RB with different proportions of R and B results in varied energy consumption. In order to improve the energy use efficiency of the closed-type plant production systems, the effects of R and B proportions on the electric use efficiency (EUE), light use efficiency (LUE) as well as the quality of butter leaf lettuce were evaluated in this study. Lettuce seedlings were cultivated in a plant factory with artificial lighting (PFAL) and subjected to eleven combinations of R and B (100%R, 90%R, 80%R, 70%R, 60%R, 50%R, 40%R, 30%R, 20%R, 10%R, 0%R; the rest of the photons in each treatment were B) with the same total photosynthetic photon flux density (PPFD) and photoperiod (200 ± 3 μmol·m−2·s−1, 16 h) for 35 days. The results showed that palpable petiole distortion appeared when R proportion was more than 70% and the distortion was aggravated with the increase of R proportion. The highest EUE and LUE were both detected in lettuce under 90%R treatment, which were respectively 3.64% and 1.20%. The least number of photons and the least electricity amount required to produce 1 g dry weight of lettuce was respectively 2.92 mol and 1.67 MJ, which were both detected in lettuce treated with 90%R. The sucrose content in lettuce treated with more than 50%R was significantly higher than those treated with less than 50%R (50%R included). Lettuce treated with 80%R possessed the highest soluble sugar content as well as the lowest crude fiber and nitrate content (not significantly different with the minimum values). R proportion exceeding 50% in mixed RB light was beneficial to the accumulation of hexose and sucrose, as well as the decomposition of nitrate in lettuce. The vitamin C content in lettuce treated with 100%R was significantly higher than that in lettuce under other treatments in the study. On the whole, the study indicated that the proportions of R and B affected the energy use efficiency and quality of lettuce in closed plant factory, however the responses of plants to the proportions of R and B varied according to different indexes. Thus, some indexes of top priority should be determined before choosing the optimal proportions of R and B.

Experimental validation of CFD model with the air velocity and temperature in the plant factory

A computational fluid dynamics (CFD) model for the closed plant factory has been developed in this study, the experimental validation of CFD model with the air velocity value was compared with the measured air temperature value. The results showed that the mean relative error of validation with the air velocity was 15%, and comparable with experimentally observed air temperature profile inside the plant factory with RMSE of 3% which shows the utility of CFD to study plant factory microclimatic parameters.

Effects of Daily Light Integral and LED Spectrum on Growth and Nutritional Quality of Hydroponic Spinach

To achieve clean and high-quality spinach production, the effects of daily light integral (DLI) and light spectrum on growth, nutritional quality, and energy yield of hydroponic spinach (Spinacia oleracea L.) were investigated in a closed plant factory under light-emitting diode (LED) lighting. The hydroponic spinach plants were grown under 16 combinations of four levels of DLI (11.5, 14.4, 17.3, and 20.2 mol m−2 day−1) with four light spectra: LED lamps with ratio of red light to blue light (R:B ratio) of 0.9, 1.2, and 2.2 and fluorescent lamps with R:B ratio of 1.8 as control. The results show that total fresh and dry weights, energy yield, and light energy use efficiency (LUE) of harvested spinach were higher under D17.3-L1.2 treatment compared to other treatments. The higher net photosynthetic rates were shown at DLI of 17.3 mol m−2 day−1 regardless of light quality. Higher vitamin C contents of spinach in all LED treatments were obtained compared with the control. L1.2 treatments with higher fraction of blue light led to more vitamin C content, lower nitrate content, and higher LUE independent of DLI. L2.2 treatment with more fraction of red light was beneficial to reduce oxalate accumulation. Power consumption based on increased total fresh weight under LED lamps with R:B ratio of 1.2 in different DLIs was over 38% lower than that under the fluorescent lamps and 1.73 kWh per 100 g FW at DLI of 17.3 mol m−2 day−1. In conclusion, lighting environment in DLI of 17.3 mol m−2 day−1 using LED lamps with R:B ratio of 1.2 is suggested for the design of a LED plant factory for hydroponic spinach production.

Effects of Lettuce Cultivation Using Optical Fiber in Closed Plant Factory

본 연구는 태양광 기반으로 인공광 병렬 광공급 시스템을 개발하고 상추 재배효과를 구명하기 위하여 수행하였다. 태양광 기반으로 인공광원을 공급하는 장치는 광원 공급부, 전원공급부, 시스템 계측 및 제어부로 구성하였다. 광원공급부는 태양광 전송장치(광파이버)와 LED 램프(인공광)로 구성하였고, 태양광 전송장치는 광 전송률이 우수한 석영재질의 광섬유(Optical fiber)로 제작되었으며, 인공광은 LED 중 White 램프를 사용하였다. 전원 공급부는 누전 차단기, SMPS, LED 제어기 및 릴레이로 구성하였다. 시스템계측 및 제어부는 터치스크린과 지그비(ZigBee) 통신모듈, 광량센서로 구성하였다. 구성한 장치의 성능시험 결과 광량센서로 측정된 강도가 200µmol·m-2·s-1 이하가 되면 자동적으로 LED 램프가 작동되어 보광하는 것을 확인하였다. 또한 본 장치를 활용하여 상추를 재배한 결과, 엽장, 뿌리길이, 엽록소 함량 및 지하부 생체중이 LED 처리보다 큰 것으로 나타났다. 따라서 본 장치는 화석연료 고갈 등으로 전기 사용에 제한이 올 때 폐쇄형 식물공장 같은 시설에서 작물을 재배할 수 있을 것으로 판단된다.

Experimental verification of a CFD model for the closed plant factory under artificial lighting

A computational fluid dynamics (CFD) model for the closed plant factory under artificial lighting has been developed in this study, the experimental verification of CFD model with the air velocity value was compared with the measured air temperature value. The results showed that the mean relative error of validation with the air velocity was 15%, and comparable with experimentally observed air temperature profile inside the plant factory with RMSE of 3% which show the utility of CFD to study plant factory microclimatic parameters.

Effects of environment lighting on the growth, photosynthesis, and quality of hydroponic lettuce in a plant factory

Leafy vegetable production under controlled environment using artificial lighting has many advantages over conventional greenhouses and open-field production. However, high initial investment and operation costs are restricting the wide application of this technology. In order to design an optimal artificial lighting environment for lettuce production, effects of different combinations of light intensity, photoperiod, and light quality on growth, quality, photosynthesis, and energy use efficiency of lettuce (Lactuca sativa L. cv Ziwei) were investigated under a closed plant factory. Lettuce transplants were grown under photosynthetic photon flux density (PPFD) at 150 µmol/m2·s, 200 µmol/m2·s, 250 µmol/m2·s, and 300 µmol/m2·s provided by fluorescent lamps (FL) with a red to blue ratio (R:B ratio) of 1.8 and light-emitting diode (LED) lamps with R:B ratio of 1.2 and 2.2, in combination with photoperiod of 12 and 16 h/d. In order to examine the “long term” photosynthetic characteristics, net photosynthetic rates of hydroponic lettuce leaves were continuously measured for 2 days (15th and 16th day after transplanting) before harvest. There was no difference in leaf fresh weight (FW) between PPFD of 250 µmol/m2·s and 300 µmol/m2·s with photoperiod of 16 h/d, regardless of light quality, and same results showed in contents of nitrate, soluble sugar, and vitamin C, respectively. The results of continuous measurements of net photosynthetic rate of lettuce leaves before harvest indicated that plants grown at PPFD of 250 µmol/m2·s had consistently higher compared to those grown at PPFD of 300 µmol/m2·s. Combining the results from growth, photosynthesis, quality, and energy consumption, it can be concluded that PPFD at 250 µmol/m2·s with photoperiod of 16 h/d under LED with R:B ratio of 2.2 is a suitable light environment for maximum growth and high quality of commercial lettuce (cv. Ziwei) production under indoor controlled environment. Keywords: plant factory, daily light integral, artificial light, photosynthetic photon flux density, net photosynthetic rate, energy use efficiency DOI: 10.25165/j.ijabe.20181102.3420 Citation: Zhang X, He D X, Niu G H, Yan Z N, Song J X. Effects of environment lighting on the growth, photosynthesis, and quality of hydroponic lettuce in a plant factory. Int J Agric & Biol Eng, 2018; 11(2): 33–40.

Model-Based Design and Control of Closed Plant Factory

A closed type plant factory is a cultivation system that artificially supplies all kinds of substances such as gas, water and solution in addition to energy supply by LED and heat. In order to ideally design this plant factory based on the system theory and to stably control it, we propose various system models, basic ideas and policies of design and control.

完全人工光型植物工場を対象とした省エネ型植物栽培設備の開発研究 その1 省エネ型栽培設備内の気流及び濃度分布の解析と植物栽培実験結果及び電力消費量の比較

完全人工光型植物工場を対象とした省エネ型植物栽培設備の開発研究 その1 省エネ型栽培設備内の気流及び濃度分布の解析と植物栽培実験結果及び電力消費量の比較

A Combination of Downward Lighting and Supplemental Upward Lighting Improves Plant Growth in a Closed Plant Factory with Artificial Lighting

“Plant factory with artificial lighting” (PFAL) refers to a plant production facility that can achieve mass production of vegetables year round in a controlled environment. However, the high-density planting pattern in PFALs causes low light conditions in the lower canopy, leading to leaf senescence in the outer leaves and thus to reductions in plant yields. In the present study, the effect of supplemental upward lighting underneath the plants on photosynthetic characteristics and plant yield was examined in lettuce, in comparison with supplemental downward lighting from above the plants at the same light intensity. Supplemental upward lighting increased the curvature factor of the photosynthetic response to light from above the plants. Moreover, supplemental upward lighting significantly enhanced the lettuce yield by retarding the senescence of the outer leaves. Here, we propose a novel cultivation system with a combination of downward lighting and supplemental upward lighting that can effectively increase plant growth and yield in PFALs.

Theoretical Design for the Production of Quinoa (Chenopodium quinoa Willd.) in a Closed Plant Factory

Quinoa (Chenopodium quinoa Willd.) is a grain crop with high nutritional value. The leaves and sprouts of quinoa can also be consumed either raw or cooked, providing considerably nutritional value as well as high antioxidant and anticancer activities. This study was carried out to obtain basic data to assist in the practical design of a plant factory with artificial lighting for the cultivation of quinoa as a leafy vegetable. We estimated the energy content of the quinoa and the electrical energy required to produce this crop. The yield was 1,000 plants per day, with a planting density and light intensity of 0.015 m2 (15 × 10 Cm) and 200 μmol·m-2·s-1, respectively. The total number of plants, cultivation area, and electricity consumption were estimated to be 25,000, 375 m2, and 93,750 μmol·s-1, respectively. White fluorescent lamps were used at a power of 20.4 kW from 1,857 fluorescent lamps (FL, 55 W), and the cost for electricity was approximately 1,820 dollars (exchange rate of $1 = 1,200 won) per month. For a daily harvest of 1,000 plants per day in a closed plant factory, the estimated light installation cost, total installation cost, and total production cost would be 15,473, 46,421, and 55,704 dollars, respectively. The calculated production cost per plant, including labor costs, would be 27 cents for the 25-day cultivation period, with a marketable ratio of 80%. Considering the annual total expenses, income, and depreciation costs, the selling price per plant was estimated to be approximately 56 cents.

Development of an Android-tablet-based system for analyzing light intensity distribution on a plant canopy surface

An Android application system for the simple and real-time estimation of light intensity distribution on a plant canopy surface was developed, and its usefulness was tested under artificial lighting. The application system was designed to semi-automatically analyze the photosynthetic photon flux density (PPFD) distribution on the canopy from a reflection image acquired by the tablet. A single manual measurement by a quantum sensor at a point on the canopy was performed to build a regression model that estimated the PPFD on leaves from the pixel values of the image. Measured and estimated PPFD histograms, as well as parameters derived from histograms, were compared at three different growth stages of a plant canopy in a closed plant factory with artificial lighting. The measured and estimated histograms exhibited a similar pattern at each growth stage with close values of the parameters. The results suggested that the reflection-image-based estimation system developed in this study was a useful method for analyzing the light conditions under artificial lighting. Although the developed system will require additional improvements in automation and performance before it can be applied to actual cultivation-management procedures, this simple method for estimating the light intensity distribution is expected to help improve the efficiency and reproducibility of light control methods used for plant production.

Utilization Technique of Artificial Light in a Closed Plant Factory

Utilization Technique of Artificial Light in a Closed Plant Factory

IMPACT OF LIGHT INTENSITY ON FLUCTUATIONS IN GROWTH AND NUTRIENT CONTENT OF LEAFY VEGETABLES UNDER ARTIFICIAL CONDITIONS

The impact of variability in light intensity (photosynthetic photon flux, PPF) at a closed plant factory with artificial light on fluctuations in growth and nutrient content (ascorbic acid, β-carotene, calcium and iron) of 3 types of leafy vegetables was investigated to examine the possibility of nutritional labeling for leafy vegetables. Chingensai (Brassica rapa L. var. chinensis), Komatsuna (Brassica rapa L. var. peruviridis), and Rocket (Eruca vesicaria L.) were cultivated in a hydroponic culture system under artificial conditions (white fluorescent lamps as light source). Four test treatments were established with PPF values of 160, 200, 240, and 280 μmol m-2.s-1. Fresh and dry weights were greater with higher PPF values for all plant species. However, no impact of PPF was observed on the dry matter ratio or the proportion of the fresh weight of leaf blades in relation to the total fresh weight of plants. Except for ascorbic acid concentration in Chingensai and β-carotene and iron concentrations in Rocket, no significant differences in nutrient concentrations (fresh or dry weight basis) were revealed in relation to PPF. The coefficient of variation for nutrients was relatively smaller than that of fresh and dry weight in all crops. There were only small fluctuations in nutrient concentrations attributable to variation in PPF in these leafy vegetables, particularly in Chingensai and Komatsuna, which have a uniform shape and growth rate. Thus, nutritional labeling in leafy vegetables cultivated in plant factories is considered possible.

On application of a new hybrid maximum power point tracking (MPPT) based photovoltaic system to the closed plant factory

Photovoltaic (PV) generation systems have been shown to have a promising role for use in high electric-load buildings, such as the closed plant factory which is dependent upon artificial lighting. The power generated by the PV systems can be either directly supplied to the buildings or fed back into the electrical grid to reduce the high economic costs and environmental impact associated with the traditional energy sources such as nuclear power and fossil fuels. However, PV systems usually suffer from low energy-conversion efficiency, and it is therefore necessary to improve their performance by tackling the energy loss issues. The maximum power point tracking (MPPT) control technique is essential to the PV-assisted generation systems in order to achieve the maximum power output in real time. In this study, we integrate the previously proposed direct-prediction MPP method with a perturbation and observation (P&O) method to develop a new hybrid MPPT method. The proposed MPPT method is further utilized in the PV inverters in a PV system installed on the roof of a closed plant factory at National Taiwan University. The tested PV system is constructed as a two-stage grid-connected photovoltaic power conditioning (PVPC) system with a boost-buck full bridge design configuration. A control scheme based on the hybrid MPPT method is also developed and implemented in the PV inverters of the PVPC system to achieve tracking of the maximum power output of the PV system in real time. Based on experimental results obtained in an outdoor environment over a period of one year, the hybrid MPPT method not only decreases energy loss but also increases power utilization. These results demonstrate the applicability of the PV system to a closed plant factory for saving energy consumption and reducing CO2 emissions.

Effects of Salinity and Nutrients in Seawater on Hydroponic Culture of Red Leaf Lettuce

Among various environmental factors, the effects of light quality and quantity on growth of vegetables and ornamental plants were investigated thoroughly in closed plant factories, whereas how solutes and minerals in hydroponics affect on growth of vegetables were poorly understood. In this study, we investigated the effects of salinity and nutrients on the growth of red leaf lettuce (Lactuca sativa L. cv. Mother-red). A closed plant factory with hydroponic cultures supplemented with sodium salt (NaCl) or seawater was employed for cultivation of lettuce. The fresh weight of lettuce grown in culture with NaCl was dramatically reduced when compared to those grown in standard culture or culture with seawater. The lettuces grown in the culture with NaCl or seawater contained higher amounts of sugar and anthocyanin, and the lettuce plants grown in the culture with seawater accumulated highest levels of photosynthetic pigments, chlorophylls and carotenoids. These results indicate that the addition of some solutes (e.g. NaCl) to the culture medium affect the size of plant as well as the levels of sugars and pigments in the plant, and suggest that the addition of seawater (20%) to the medium is effective to produce lettuces with higher quality and nutritional value.

The Optimal Harvesting Time of Vaccine-Producing Transgenic Lettuce Cultivated in a Closed Plant Factory

The Optimal Harvesting Time of Vaccine-Producing Transgenic Lettuce Cultivated in a Closed Plant Factory

Effect of Artificial Light Sources on Growth and Quality Characteristics of Leaf Lettuce in Closed Plant Factory System

The growth and quality of lettuce were evaluated in a plant factory system with three types of artificial lights including fluorescent lamp (FL), light-emitting diode (LED) and external electrode fluorescent lamp (EEFL). Air temperature, relative humidity, CO2 concentration, and wind velocity in the plant factory system were maintained at about 25°C, 60%, 400 ppm, and 0.5 m·s, respectively. The photosynthetic photon flux densities (PPFD) of FL, LED, EEFL 7000K, EEFL 9000K and EEFL 12000K were 200, 300, 215, 265, and 235 μmol.m-2.s-1, respectively, with all same 24 hour photoperiod per day. Among lettcue cultivar ‘Manchudae' plants grown for three weeks under different artificial lights, plants under LED showed the highest fresh weight, followed *Corresponding author: Yeong Cheol Um Tel: +82-31-240-3657 Fax: +82-31-240-3669 E-mail: ycum0403@korea.kr 24 ... Journal of Agriculture & Life Science 47(6) by those under EEFL 9000K. In contrast, the lowest fresh weight was observed in plants grown under FL. The number of leaves showed the same trend as fresh weight. There was no significant difference in both leaf area and photosynthetic rate among plants grown in different light sources, although they were relatively low in those under FL. The contents of phenolic compound and total flavonoid were highest in plants under FL and LED but lowest in those under EEFL. In conclusion, the EEFL promoted growth in lettuce compared to FL although the growth response varied depending on the types of EEFL. Thus, EEFL can replace FL considering production-cost and energy saving in closed-type plant factories. Further studies are needed on the growth conditions such as temperature, light intensity, and relative humidity to increase antioxidant chemicals in lettuce grown in plant factories.