Plant Factories With Artificial Lighting Research Articles

Vegetable Production in PFALs: Control of Micro-Environmental Factors, Principal Components and Automated Systems

Plant factories with artificial lighting (PFALs) are indoor crop production systems aiming at the growth of high-value products in terms of yield and quality, while maximizing resource use efficiency. The emergence of PFALs opened a new world for crop production and offered an option to tackle problems related to climate change, land availability, and urban/peri-urban farming. This was made possible upon major technological advancements and extensive research in the field of controlled environment agriculture, which paved the way for the establishment of such cost-efficient and climate-unaffected modules of vegetable and other crops’ production. In the present review, we have examined the recent research achievements regarding the micro-environmental factors, the principal components, as well as the automated systems used for plant production in PFALs. Ultimately, we provide the reader with a number of future perspectives that can be considered for indoors cultivation in the following years.

Transcriptome-Based Identification of Candidate Flowering-Associated Genes of Blueberry in a Plant Factory with Artificial Lighting (PFAL) under Short-Day-Length Conditions.

In blueberry (Vaccinium corymbosum L.), a perennial shrub, flower bud initiation is mediated by a short-day (SD) photoperiod and buds bloom once the chilling requirement is satisfied. A plant factory with artificial lighting (PFAL) is a planting system that can provide a stable and highly efficient growing environment for blueberry production. However, the characteristics of bud differentiation of blueberry plants inside PFAL systems are poorly understood. To better understand flower bud initiation and the flowering mechanism of blueberry in PFAL systems, the anatomical structure of apical buds under SD conditions in a PFAL system was observed using the southern highbush cultivar 'Misty' and a transcriptomic analysis was performed to identify the candidate flowering genes. The results indicated that the apical bud of 'Misty' differentiated gradually along with SD time course and swelled obviously when chilling was introduced. A total of 39.28 Gb clean data were generated, and about 20.31-24.11 Mb high-quality clean reads were assembled, yielding a total of 17370 differentially expressed genes (DEGs), of which 9637 were up-regulated and 7733 were down-regulated. Based on the functional annotation, 26 DEGs were identified including 20 flowering-related and 6 low-temperature DEGs, out of which the expressive level of four flowering-related DEGs (VcFT2, VcFPA, VcFMADS1, and VcCOP1) and two low-temperature-induced DEGs (VcTIL-1 and VcLTI 65-like) were confirmed by qRT-PCR with a good consistency with the pattern of transcriptome. Functional analysis indicated that VcFT2 was highly conserved with nuclear and cytoplasmic subcellular localization and was expressed mainly in blueberry leaf tissue. In Arabidopsis, ectopic overexpression of VcFT2 results in an early flowering phenotype, indicating that VcFT2 is a vital regulator of the SD-mediated flowering pathway in blueberry. These results contribute to the investigation of photoperiod-mediated flowering mechanisms of blueberry in PFAL systems.

Yield and Photosynthesis Related to Growth Forms of Two Strawberry Cultivars in a Plant Factory with Artificial Lighting

Appropriate growth forms for strawberry production in a plant factory with artificial lighting (PFAL), which is a recently developed production system, remain undetermined. Improving strawberry productivity in a PFAL requires insights into the interplay between production characteristics (growth and photosynthesis) and growth forms, such as plant height and leaf area (LA), which are major determinants of crop yield. Growth status, yield, and photosynthetic characteristics of the two cultivars of strawberries (Fragaria ×ananassa Duch. Tochiotome and Koiminori) with different growth forms were examined. ‘Koiminori’ exhibited a 1.9-fold higher yield and a 2.0-fold greater total dry weight of respective organs compared with ‘Tochiotome’. The single-plant photosynthetic rate (AP), serving as an index for both cultivars, was 2.2-times higher for Koiminori than for Tochiotome. The photosynthetic rates of a single leaf (AL) and LA were also analyzed as important factors that influence the AP. The AL for ‘Koiminori’ surpassed that of ‘Tochiotome’ by 1.4 times. This was attributed to the elevated photosynthetic photon flux density received by the upper leaves of Koiminori, which is a consequence of its higher plant height in proximity to the light source. Evaluation of four photosynthetic capacities, maximum rate of carboxylation, maximum rate of electron transport, photosynthetic rate under saturating light, and light utilization efficiency, which are potential factors that affect AL, revealed no differences in these capacities between cultivars. ‘Koiminori’ exhibited a significantly larger LA (2.3- to 3.1-times) than ‘Tochiotome’, indicating that the former’s higher AP resulted mainly from its higher AL and larger LA. Thus, strawberry production in a PFAL can be improved by growing cultivars with growth forms such as higher plant height and larger LA.

Effects of Supplemental Red and Far-Red Light at Different Growth Stages on the Growth and Nutritional Properties of Lettuce

The understanding of the supplementation scheme of red (R) and far-red (FR) light in the cultivation of leafy vegetables in plant factories with artificial lighting (PFALs) is still limited. This study investigated the effects of supplemental R and FR light at different plant growth stages on the morphology, growth characteristics, and nutritional properties of lettuce. Supplemented R + FR throughout the entire growth stages was beneficial for the growth of lettuce, for which the total fresh weight was increased by 53.76%, and it also enhanced the content of soluble sugars by 39.98% and vitamin E by 34.21%. The pre-supplementation of FR light followed by supplementation of R light at various growth stages not only increase the total fresh weight of lettuce by 26.10% but also ensured that most nutritional indices did not decrease, and it even increased the content of soluble sugars by 35.24% while decreasing the nitrate content by 31.52%. The scheme of pre-supplementation of R light followed by the supplementation of FR light promoted a more upright plant architecture in lettuce, which was advantageous for improving the cultivation density of lettuce in plant factories with artificial lighting, thereby enhancing the yield/m2. Moreover, it could increase the vitamin E content of lettuce. The growth and nutritional properties of lettuce exhibit significant effects under different supplementation methods of R and FR light. In PFALs, the selection of different light supplement schemes also requires a careful balance between yield and quality. From an energy-saving perspective, the pre-supplementation of FR light followed by supplementation of R light at various plant growth stages is beneficial for lettuce production in PFALs.

Side Lighting of Red, Blue and Green Spectral Combinations Altered the Growth, Yield and Quality of Lettuce (Lactuca sativa L. cv. "Yidali") in Plant Factory.

A plant factory with artificial lighting (PFAL) usually uses top lighting for cultivation. The light from the upper part of the canopy cannot penetrate the entire lettuce canopy, however, resulting in uneven vertical spatial light in the canopy, and accelerating the senescence of both the bottom and side leaves of the plant canopy. Therefore, in this study, the performance of lettuce in hydroponics was investigated upon supplemental side lighting with different spectral LEDs in a PFAL. A set of short-term side lighting treatments, including no side lamps (CK), red (R), blue (B), red + blue (RB), and red + blue + green (RGB) LED lamps (150 μmol·m-2·s-1, respectively), was employed for an additional 2 h per day after normal top lighting for 6 days before harvest. The results showed that the lettuce canopy was relatively loose and had a large crown size under side lighting compared with CK. Side lighting, irrespective of spectral qualities, significantly increased the fresh weight, and the R, B, RB, and RGB treatments increased the shoot fresh weight of lettuce plants by 34%, 19%, 31%, and 34%, and increased the fresh weight of leaf layer 2 by 50%, 17%, 44%, and 48%, respectively. The side lighting of different spectral qualities had a significant impact on the nutritional quality of the first row of lettuce at the edge of the top lighting illuminated area. Treatment B significantly promoted the chlorophyll content of leaf layer 3; the soluble sugar contents from leaf layer 1, 2, and 3; the starch contents in leaf layers 2 and 3; and the content of phenolics in the leaf layers 3; and significantly reduced the nitrate content in leaf layers 2 and 3. RGB significantly increased soluble sugar content by 91%, and the starch content in leaf layer 1, as well as the leaf chlorophyll and flavonoid content of leaf layer 3, while R had opposite effect completely. RB significantly increased the leaf chlorophyll content of leaf layer 3 and the nitrate content in leaf layer 1, but the overall effect was lower than that of RGB. In summary, side lighting of any type could effectively improve lettuce yield, solve the problem of inconsistent lettuce plant size caused by the edge effect of top lighting, and affect the nutritional quality of lettuce. B and RGB performed best. There was spatial response diversity of lettuce plants to side lighting spectral qualities.

Growth and Photosynthetic Responses to Increased LED Light Intensity in Korean Ginseng (Panax ginseng C.A. Meyer) Sprouts

Compared to the traditional production of ginseng roots, Panax ginseng sprouts (PGSs) are currently regarded as a substitute due to the relatively short-term culture but still high nutrition. However, the optimal light intensity for the growth ability of PGSs and the characterizations of the responses of PGSs to the light intensity have been largely neglected. This study aimed to determine the influences of the light intensity on the growth, morphogenesis, and photosynthetic responses in PGSs. To this end, two-year-old ginseng rootlets were subjected to one of six light intensities (from 30 to 280 PPFD with 50 PPFD intervals) in a plant factory with artificial lighting (PFAL) via LED light for 10 weeks. On the whole, the recorded parameters of the PGSs showed gradually decreasing trends in response to the increasing light intensities. However, the 80 PPFD-treated PGSs possessed similar or greater root dry weights, leaf areas, carotenoids levels, and photosynthesis (the maximal PSII quantum yield) compared to those in the 30 PPFD regime. Additionally, photoinhibition symptoms as evidenced by chlorosis, necrosis, and stunted growth were observed as the light intensity attained 180 PPFD. Thus, 130 PPFD could be considered a safe point for the appearance of photoinhibition in PGSs. Taken together, we show that the light intensity range of 30–80 PPFD is suitable for maximizing the production of PGSs in PFALs.

Response of Flavor Substances in Tomato Fruit to Light Spectrum and Daily Light Integral.

Light-emitting diodes (LEDs) have been widely used as light sources for plant production in plant factories with artificial lighting (PFALs), and light spectrum and light amount have great impacts on plant growth and development. With the expansion of the product list of PFALs, tomato production in PFALs has received attention, but studies on fruit quality influenced by artificial light are lacking. In this study, precisely modulated LED light sources based on white light combined with additional red, blue, and green lights were used to investigate the effects of light spectrum and daily light integral (DLI) on the main quality indicators and flavor substances of "Micro-Tom" tomato fruits. The highest sugar-acid ratio was obtained under the white light with addition of red light with high DLI and blue light with low DLI. The contents of β-carotene, lycopene, and lutein were significantly increased by higher DLI conditions except for under the blue light treatment, and the cross-interactions between the light spectrum and DLI were observed. The accumulation of the main flavor substances in tomato fruits was decreased by addition of green light with a high DLI and red light with a low DLI; notably, the percentage of 2-isobutylthiazole, which is associated with fresh tomato aroma, was decreased by green light. This study provides insights for improving tomato fruit quality and flavor by regulating light conditions in PFALs.

Yield, Quality, and Resources Use Efficiency of Wild Rocket Baby Leaves Grown under Different Controlled Environment Systems and Various Growing Seasons

Wild rocket is a leafy vegetable with economic interest as a consequence of baby leaf ready-to-eat salads. The climate crisis is expected to influence wild rocket production, but these effects could be confronted with cultivation in greenhouses and plant factories with artificial lighting (PFALs). Climate responses are related to growing seasons. Our objective was to test the impact of two growing seasons, winter and summer, on the growth and physiology of wild rocket baby leaves in different controlled environment systems (greenhouse and PFAL). The growth cycle was reduced by 27% in the PFAL compared to the greenhouse during winter. Summer yield was greater in the greenhouse, but leaf number and area were greater in the PFAL. The lowest water use efficiency was recorded in the greenhouse during summer. Energy use efficiency was lower in PFAL compared to the greenhouse. Land use efficiency was not affected by the growing system, but in PFALs it is able to increase it by growing in vertical layers. Relative chlorophyll content and total soluble solids were enhanced in the greenhouse. The photosynthetic efficiency evaluation showed considerable stress in summer-grown plants in the greenhouse, as shown by PIABS and φP0. In general, the production was similar in the PFAL regardless of seasons.

Effects of Nutrition and Light Quality on the Growth of Southern Highbush Blueberry (Vaccinium corymbosum L.) in an Advanced Plant Factory with Artificial Lighting (PFAL)

A plant factory is a highly developed product system that can produce higher yields and better quality plants under controlled conditions. However, knowledge of blueberry cultivation in plant factories is limited. This study established an advanced plant factory with artificial lighting (PFAL) and investigated the effects of nutrition supply and light qualities on the growth performance of blueberries. Different nutrition treatments affected the vegetative growth of blueberries in PFAL, especially the new shoot length and number. Exogenous fertilization significantly promoted the uptake of N, P, and K elements, and a nutrition solution with N:P:K = 2:1:1 was suggested to be superior for blueberries in PFAL. Red light facilitated vegetative growth to some degree, and the blue light was conducive to increased chlorophyll and anthocyanin content. The Pn value was significantly enhanced under 60% red plus 40% blue light. Combining red and blue light is more beneficial to blueberry growth and might be a preferential strategy in PFAL. This study is the first to investigate the growth performance of blueberries cultivated in PFAL, which can provide an important theoretical database for blueberry cultivation in a plant factory with artificial lighting.

Multi-objective optimal regulation model and system based on whole plant photosynthesis and light use efficiency of lettuce

Lettuce growth and light energy consumption in a plant factory with artificial lighting (PFAL) were studied, and whole plant photosynthetic rate (ACO2) and light use efficiency (LUE) data were obtained on different days after planting (DAP) under different photosynthetic photon flux densities (PPFDs). Genetic algorithm‐support vector regression (GA-SVR) was used to construct the ACO2 and LUE prediction models. The coefficient of determination (R2) between the predicted and measured values of the ACO2 model was 0.97 and the root mean square error (RMSE) was 0.42 μmol·mol−1·plant−1·min−1, and R2 between the predicted and measured values of the LUE model was 0.97 and RMSE was 0.36%. The ACO2 and LUE prediction models were used as the objective functions, and multi-objective search was performed by the non-dominated sorting genetic algorithm II (NSGA-II) and the distance-based knee point detection method were used to obtained the optimal equilibrium solution for different DAPs. The optimal equilibrium solutions were used as the basis to establish the light regulation model based on lettuce DAP with R2 of 0.99. To validate the effect of model regulation, a lettuce light regulation system was built using an artificial climate chamber for a 30-day system validation. The results showed that compared with the traditional quantitative light supplementation method, the dry matter of model regulation significantly increased by 39.23% and 29.48% compared with quantitative PPFD150 (μmol·m−2·s−1) and PPFD200 (μmol·m−2·s−1). Model regulation increased the number of total light quanta consumed by 1.39% over PPFD150 and decreased by 23.96% over PPFD200; however, plant productivity increased by 35.35% and 33.14%, respectively. Model regulation significantly reduced the number of light quanta consumed per unit mass of lettuce production by 24.35% for PPFD150 and 41.54% for PPFD200, and LUE of light-emitting diode energy into dry matter was significantly increased by 33.49% and 75.09%. Therefore, the light regulation model based on multi-objective optimization in this study could improve crop yield and increase LUE.

Analyzing the effect of light on lettuce Fv/Fm and growth by machine learning

Varied plant growth cultivations require different light conditions. To explore them with lettuce (Lactuca sativa L. cv. ‘Hong Kong glass’), five photosynthetic photon flux density (PPFD, 50, 150, 300, 450 and 600 μmol·m−2·s−1) levels were set in completely controlled circumstances. Using ordinary least squares (OLS), the appropriate PPFD was determined depending on the dark fluorescence characteristics. Following 14 h of treatment, a new PPFD of 200 μmol·m−2·s−1 was employed to monitor the adaptation process obtained using the genetic algorithm-support vector regression (GA-SVR) model. The results showed that Fv/Fm declined as PPFDs increased except for L50, and OLS with R2 and RMSE of 0.9710 and 0.0416 suggested 140.80 μmol·m−2·s−1 was the ideal PPFD. Little changed in the new PPFD adaptation procedure for, L50, L150, and L300. During 42 h of adaptation, the discretized curves of Fv/Fm using the GA-SVR model at various PPFDs revealed that Fv/Fm increasingly approached and eventually reached the same level. The quick change was in [290, 480] μmol·m−2·s−1 depending on the probability density distributions. The difference in change rates between the two PPFD treatments decreased, indicating that lettuce's light tolerance improved after the two phases. The largest sum Fv/Fm in L150 indicated a maintained growth state. Full-cycle cultivation revealed that 150 and 250 μmol·m−2·s−1 had the highest fresh biomass. In conclusion, in [290, 480] μmol·m−2·s−1, short-term high light could improve plant light adaptability in variable light. In the constant light of the plant factory with artificial lighting (PFAL), it was recommended to utilize the light intensity of 140.80 μmol·m−2·s−1, which can both maintain growth and save light energy. A more suitable solution might be chosen depending on the cultivation requirements.

Economies of scale in constructing plant factories with artificial lighting and the economic viability of crop production.

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.

Current Situation, Direction, Policy Support, and Challenges of Plant Factories with Artificial lighting (PFAL) in Thailand

One of the greatest challenges in the 21st century is how to sufficiently and sustainably feed the world population with nutritional and safe food. Plant factory with artificial lighting (PFAL) is a closed plant production system. Regardless of environments outside, PFAL is considered as an alternative technology for food and feed production with high efficiency, high quality and low risk to health of customers. Therefore, the aim of this review is to provide the basic information on the current situation, direction, government policy and support and challenges of PFAL technology in Thailand.

Physiological responses, yield and medicinal substance (andrographolide, AP1) accumulation of Andrographis paniculata (Burm. f) in response to plant density under controlled environmental conditions.

Agricultural practice in adjusting planting density and harvest date are important factors for plant development and crop improvement, reaching maximum yields and enhancing the production of secondary metabolites. However, it is unclear as to the optimal planting densities during mass production that encourage consistent, high yield secondary metabolite content. For this, controlled environment, crop production facilities such as plant factories with artificial lighting (PFAL) offer opportunity to enhance quality and stabilize production of herbal plants. This study assessed the effect of plant density and harvest date on physiological responses, yield and andrographolide (AP1) content in Andrographis paniculata (Andrographis) using hydroponic conditions in a PFAL system. Andrographis, harvested at vegetative stage (30 days after transplanting; 30 DAT) and initial stage of flowering (60 DAT) exhibited no significant differences in growth parameters or andrographolide accumulation according to planting densities. Harvest time at flowering stage (90 DAT) showed the highest photosynthetic rates at a planting density of 15 plants m-2. Highest yield, number of leaves, and Andrographolide (AP1) content (mg per gram of DW in m2) were achieved at a more moderate planting density (30 plants m-2). Finally, five out of seventeen indices of leaf reflectance reveal high correlation (r = 0.8 to 1.0 and r = -0.8 to -1.0, P<0.01) with AP1 content. These results suggest that a planting density of 30 plants m-2 and harvest time of 90 DAT provide optimal growing condition under the hydroponic PFAL system.

Intracanopy lighting strategies to improve green bush bean (Phaseolus vulgaris) compatibility with vertical farming

Now that multi-tiered plant factories with artificial lighting (PFALs) have demonstrated sufficient proof of concept for leafy green and microgreen production; the next challenge is to determine the optimal environment conditions and horticultural management practices required to produce nutrient-dense plant-based protein (PBP) crops within these advanced controlled environment systems (CES). Sole-source lighting within PFALs is energetically and economically expensive, as such, optimizing light distribution through intracanopy lighting could be a key factor in expanding the number of crops compatible with PFAL production. An ideal PBP PFAL crop will have a compact morphology (height, area, volume), be compatible with low-light environments, be self-pollinating, and have a relatively short life cycle. The objectives of this study were to 1) evaluate a selection of green bush bean cultivars (Phaseolus spp.) within a CES to determine which currently available cultivar is most compatible with PFAL production and 2) determine if the addition of intracanopy LED lighting could further improve cultivar compatibility with PFAL systems. The bush bean cultivar “Bronco” was selected after a 40-day flowering and 60-day fruiting trial for its compact morphology and yield (count, fresh weight). Intracanopy LED lighting trials on “Bronco” demonstrated a reduced shoot height (16%), increased bean count (22%), and increased fresh bean weight (17%) relative to plants produced with overhead lighting alone. While intracanopy lighting improved green bush bean compatibility with PFAL production, the additional light applied within the canopy increased the cost of production.

English

In recent years, plant factories have developed rapidly and played an important role in modern agricultural production. Finding the best lighting formula has become the most basic and important research topic for the industrialization of the plant factory with artificial lighting (PFAL) hydroponic Cichorium endivia L. In this paper, the LED plant growth lamp with adjustable ratio of red, blue and white light intensity was used as the light source for the growth of C. endivia L., with 5R:8B:7W, 6R:7B:7W, 5.5R:8B:6.5W as the treatment group and white LED as the control group, the growth characteristics and nutritional quality of the grown plants of C. endivia L. were compared and analyzed through experiments. It was found that under the combined illumination of 5.5R:8B:6.5W, the leaves of C. endivia L. had the largest number, and the contents of VC (Vitamin C) and carotene were the highest. Under 6R:7B:7W illumination, the content of chlorophyll and soluble sugar was the highest. The combination illumination with the ratio of blue and white light slightly larger than that of red light was the most suitable illumination for hydroponic cultivation of C. endivia L. in PFAL. Key words: Light formula, hydroponic cultivation, plant lighting, plant industrialized production, modern agriculture.

Online recognition and yield estimation of tomato in plant factory based on YOLOv3

In order to realize the intelligent online yield estimation of tomato in the plant factory with artificial lighting (PFAL), a recognition method of tomato red fruit and green fruit based on improved yolov3 deep learning model was proposed to count and estimate tomato fruit yield under natural growth state. According to the planting environment and facility conditions of tomato plants, a computer vision system for fruit counting and yield estimation was designed and the new position loss function was based on the generalized intersection over union (GIoU), which improved the traditional YOLO algorithm loss function. Meanwhile, the scale invariant feature could promote the description precision of the different shapes of fruits. Based on the construction and labeling of the sample image data, the K-means clustering algorithm was used to obtain nine prior boxes of different specifications which were assigned according to the hierarchical level of the feature map. The experimental results of model training and evaluation showed that the mean average precision (mAP) of the improved detection model reached 99.3%, which was 2.7% higher than that of the traditional YOLOv3 model, and the processing time for a single image declined to 15 ms. Moreover, the improved YOLOv3 model had better identification effects for dense and shaded fruits. The research results can provide yield estimation methods and technical support for the research and development of intelligent control system for planting fruits and vegetables in plant factories, greenhouses and fields.

Optimization of Cultivation Type and Temperature for the Production of Balloon Flower (Platycodongrandiflorum A. DC) Sprouts in a Plant Factory with Artificial Lighting

The objective of this study was to determine the efficiency of balloon flower sprout’s saponin production in a plant factory with artificial lighting (PFAL). Balloon flower has been traditionally used as herbal medicine and now, it is used as a medicinal plant as well as a functional food. It is important to establish the cultivation conditions for the stable production of high-quality balloon flower. Therefore, this study aimed to investigate the effects of culture systems and temperature conditions on the growth and saponin accumulation of balloon flower sprouts in controlled environment systems. One-year balloon flower roots were cultivated in soil and soilless culture systems at different temperature conditions (20, 25, and 30 °C) for 17 days. The results showed that the shoot fresh weight and shoot dry weight of the balloon flower sprouts grown in the soilless culture system at 25 °C were significantly increased by about 1.29 and 1.58 times, respectively, as compared with those of the sprouts grown in a soil culture system. Sprouts grown in the soilless culture system at 25 °C also recorded the highest root fresh weight, whereas there was no significant difference in root dry weight among the treatments. The plant height results showed an increased trend similar to that of the shoot fresh weight and shoot dry weight of the balloon flower sprouts. The concentrations of platycodin D3 (Pd-D3), polygalcin D (Pc-D), and total saponin in the shoot parts were highest in the soilless culture system at 20 and 25 °C. The root parts of sprouts grown in the soilless culture system at 30 °C also had higher deapioplatycodin D (Dpd-D) and total saponin concentrations. Overall, these results suggest that a soilless culture system with temperature conditions at 20 and 25 °C is suitable for improving the growth and saponin concentration of balloon flower cultivated in PFALs. Ultimately, our research should be a valuable resource for future research on the production of medicinal plants such as sprouts and should provide basic information to establish methods for enhancing the growth and bioactive compounds in balloon flower.

Variation in terpenoids in leaves of Artemisia annua grown under different LED spectra resulting in diverse antimalarial activities against Plasmodium falciparum

BackgroundProductivities of bioactive compounds in high-value herbs and medicinal plants are often compromised by uncontrollable environmental parameters. Recent advances in the development of plant factories with artificial lighting (PFAL) have led to improved qualitative and/or quantitative production of bioactive compounds in several medicinal plants. However, information concerning the effect of light qualities on plant pharmaceutical properties is limited. The influence of three different light-emitting diode (LED) spectra on leaf fresh weight (FW), bioactive compound production and bioactivity of Artemisia annua L. against the malarial parasite Plasmodium falciparum NF54 was investigated. Correlation between the A. annua metabolites and antimalarial activity of light-treated plant extracts were also determined.ResultsArtemisia annua plants grown under white and blue spectra that intersected at 445 nm exhibited higher leaf FW and increased amounts of artemisinin and artemisinic acid, with enhanced production of several terpenoids displaying a variety of pharmacological activities. Conversely, the red spectrum led to diminished production of bioactive compounds and a distinct metabolite profile compared with other wavelengths. Crude extracts obtained from white and blue spectral treatments exhibited 2 times higher anti-Plasmodium falciparum activity than those subjected to the red treatment. Highest bioactivity was 4 times greater than those obtained from greenhouse-grown plants. Hierarchical cluster analysis (HCA) revealed a strong correlation between levels of several terpenoids and antimalarial activity, suggesting that these compounds might be involved in increasing antimalarial activity.ConclusionsResults demonstrated a strategy to overcome the limitation of A. annua cultivation in Bangkok, Thailand. A specific LED spectrum that operated in a PFAL system promoted the accumulation of some useful phytochemicals in A. annua, leading to increased antimalarial activity. Therefore, the application of PFAL with appropriate light spectra showed promise as an alternative method for industrial production of A. annua or other useful medicinal plants with minimal environmental influence.

Optimization of the Yield, Total Phenolic Content, and Antioxidant Capacity of Basil by Controlling the Electrical Conductivity of the Nutrient Solution

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.