Research Article

Korean Journal of Horticultural Science and Technology. 31 December 2022. 586-594
https://doi.org/10.7235/HORT.20220053

ABSTRACT


MAIN

  • Introduction

  • Materials and Methods

  •   Plant Materials and Growth Conditions

  •   Growth Characteristics

  •   Anthocyanin Content

  •   Statistical Analyses

  • Results and Discussion

  • Conclusions

Introduction

Due to increased demand for high-quality agricultural products and environmental changes, it has become difficult to maintain stable production (Jeong et al., 2020). To solve this problem, interest in crop cultivation using plant factory with artificial lighting (PFAL) is increasing (Um et al., 2010). Research on crop cultivation using PFAL has increased in Asia (Korea, Japan, Taiwan, China), Europe (Netherlands, United Kingdom), the Middle East, and the United States of America due to unstable crop productivity and the sharp increase in vegetable prices (Choi et al., 2014).

A PFAL is an automated agricultural system that can produce crops in planned production, as with industrial products, regardless of season and location by artificially controlling an environment (light, temperature, CO2, and nutrition) suitable for plant production in a closed facility (Takatsuji, 2008). PFAL can cultivate uniform, high-quality crops with increased yields and phytochemicals compared to open-field cultivation products by establishing an optimal cultivation environment (Goto, 2012). In addition, PFAL has several advantages, such as producing uniform plants, higher annual yield, saving resources, and short production cycles (Heo et al., 2012). Therefore, many studies have been conducted on the commercial use of PFAL, which are widely used for academic purposes (Kim et al., 2021).

For the precise control of the environment, various artificial light sources are used in PFAL. These include high- pressure sodium lamps, metal halide lamps, fluorescent lamps, and light-emitting diodes (LEDs) (Park et al., 2012; Kim et al., 2021). Among them, LEDs are the most studied and used because they can light of various wavelengths, emit less heat that can damage plants, and save installation space owing to their small size (Lee et al., 2015; Bae et al., 2017; Kim et al., 2021). LEDs also have a long lifespan, high light efficiency, and low power consumption; therefore, they are commonly used in PFAL as artificial light sources (Choi et al., 2014). However, even if LEDs are used, artificial light sources still incur the highest cost in the operation of PFAL (Cha et al., 2012). Therefore, it is important to determine an appropriate light intensity and photoperiod for plant growth to improve the economic efficiency of PFAL and its products.

Light is an important environmental factor that affects the growth and development of plants. Dorais et al. (1991) reported that tomato yield increased under high light intensity (150 µmol·m-2·s-1). Plants grown under high light intensity show higher dry weight and growth (Park et al., 2012). The photoperiod affects the flowering response, growth, and development of plants (Salisbury and Ross, 1992). Chrysanthemum plant height increased as the photoperiod increased (Berghage et al., 1991). It has also been reported that the fresh and dry weights of various lettuce varieties increase as the photoperiod increases (Koontz and Prince, 1986). In PFAL, many studies have been conducted to change plant growth by controlling the light intensity and photoperiod using LEDs. Hwang et al. (2016) reported that when white dandelion (Taraxacum coreanum Nakai) was grown in PFAL, the yield increased when the photoperiod was longer than 12 h but decreased at light intensities above 150 µmol·m-2·s-1. Yan et al. (2019) reported that lettuce yield increased as the photoperiod increased (16 h), but under high light intensity (above 200 µmol·m-2·s-1), the yield decreased. Therefore, because the suitable light intensity and photoperiod for plant growth differ among plant species, it is important to determine the optimal light intensity and photoperiod to increase the yield of crops in PFAL.

Brassica juncea L. (red mustard), along with lettuce and pak choi, is one of the major leafy vegetables consumed in Korea (Lee et al., 2012). Red mustard is a suitable crop for PFAL because of its short growth period, plant height, and wide edible area (Lee et al., 2010). In addition, red mustard has been used worldwide as a model plant suitable for research on the response of plants to light in facilities (Dougher and Bugbee, 2001; Kim et al., 2004; Park et al., 2012). However, studies on photoperiod and light intensity effects on red mustard in a PFAL are insufficient.

Therefore, this study was conducted to investigate the effects of light intensity and photoperiod on the growth and anthocyanin content of red mustard in a PFAL.

Materials and Methods

Plant Materials and Growth Conditions

Red mustard (Brassica juncea L., Danong Co. Ltd., Namyangju, Korea) was sown on a urethane sponge. After sowing, germination, and seedling nurseries were carried out in a PFAL with RGB LEDs (red:green:blue = 7:1:2, ES LEDs Co. Ltd., Seoul, Korea) at a temperature of 20 ± 1°C, light intensity of 180 ± 10 µmol·m-2·s-1 photosynthetic photon flux density (PPFD), and photoperiod 12/12 (light/dark) for 9 days. Thereafter, a similar cultivation environment was maintained; however, the light intensity was 150 or 300 µmol·m-2·s-1 PPFD, the photoperiod was 8/16, 12/12, and 16/8 (light/dark), and the daily light integral (DLI) of each treatment was calculated using the formula (LEDTonic, 2019) below (Table 1).

Daily light integral (mol·m-2·d-1) = light intensity (µmol·m-2·s-1) × photoperiod (h) × 0.0036

Light intensity was measured at the upper part of the red mustard using a photometer (HD2101.1, Delta OHM Co. Ltd., Padova, Italy), and the light wavelength was measured using a spectroradiometer (ILT950, International Light Co. Ltd., MA, USA). Hoagland nutrient solution (Hoagland and Anon, 1950) at pH 6.0 and EC 1.5 dS·m-1 was supplied using the closed hydroponic culture.

Table 1.

Light intensity, photoperiod, and daily light integral (DLI) value of each treatment in the experiment

Light intensity (µmol·m-2·s-1) Photoperiod (h) DLIz (mol·m-2·d-1)
150 8 4.3
12 6.5
16 8.6
300 8 8.6
12 13.0
16 17.2

zDLI, total light amount of light PPFD integrated during a day; and DLI = light intensity (µmol·m-2·s-1) × photoperiod (h) × 0.0036.

Growth Characteristics

The fully grown red mustards were harvested and leaf length, leaf width, number of leaves, leaf area, chlorophyll content (SPAD), fresh and dry weights of the shoots and roots, and chlorophyll fluorescence (Fv/Fm) were measured. Shoot and root weights for each treatment were measured using an electronic scale (EW 220-3 NM, Kern and Sohn GmbH., Balingen, Germany). Shoots and roots were dried in a drying oven (Venticell-222, MMM Medcenter Einrichtungen GmbH., Munich, Germany) at 70°C for 72 h and then measured. Chlorophyll content was expressed as the SPAD value and was measured using a portable chlorophyll meter (SPAD-502, Konica Minolta Inc., Tokyo, Japan). Chlorophyll fluorescence was measured at the growth point of the second leaf using a portable chlorophyll fluorescence analyzer (FluorPen FP100, Photon Systems Instruments spol. Brno, Czech Republic). L* and a* were measured using a colorimeter (CR-200, Minolta Co., Japan). A higher value of L* indicates a brighter color, and a positive a* value indicates a red color. Dry matter was calculated using the following formula:

Dry matter (%) = plant dry weight / plant fresh weight × 100

The photosynthetic rate was measured from the growth point of the fifth fully developed using a portable photosynthetic meter (CIRAS-3, PP Systems International Inc., MA, USA). Measurement conditions were controlled at an air volume of 150 mL·min-1, a leaf area of 4.5 mm2, a leaf temperature of 25°C, a CO2 concentration of 500 µmol·mol-1, and light intensities of 150 and 300 µmol·m-2·s-1 PPFD.

Anthocyanin Content

Red mustard leaves were frozen in liquid nitrogen and stored at –72°C (NF140SF, Nihon Freezer Co. Ltd., Japan) until analysis. To determine the total anthocyanin content, 2 g of sample was collected from the second leaf at the growth point of the red mustard leaf, and 2 mL of a 95% ethanol and 1.5 N HCl mixed at 85:15 (v/v) was added to a mortar and ground. After transferring 1 mL of the ground sample to a microtube, it was stored in the dark at 4°C for 24 h, and then centrifuged at 13,000 rpm for 20 min. The obtained 1 mL of supernatant was diluted. The total anthocyanin content was calculated by measuring the absorbance at 535 nm using a spectrophotometer (Libra S22, Biochrom Co., Ltd., UK) (Fuleki and Francis, 1968).

Statistical Analyses

Experimental treatments were performed using a randomized complete block design. Each treatment group consisted of 30 plants. A total of 10 plants were used per replicate, and the replication was completed three times. Statistical analyses were performed using statistical analysis software (SAS 9.4, SAS Institute Inc., Cary, NC, USA). The experimental results were analyzed using analysis of variance (ANOVA), Tukey’s multiple range test, and Fisher’s least significant difference test. Differences were considered significant at p < 0.05. The graph was plotted using SigmaPlot software package (SigmaPlot 12.5, Systat Software Inc., San Jose, CA, USA).

Results and Discussion

The growth of red mustard increased with high light intensity and a long photoperiod (Table 2 and Fig. 1). Leaf length, leaf width, and leaf area showed higher values as the photoperiod increased. Dry matter (%) increased with high light intensity and long photoperiod. High light intensity and long photoperiods can increase the photosynthetic rate of crops, causing the accumulation of assimilation products in the leaves (Gardner et al., 2020a). Park et al. (2012) and Kim et al. (2016) reported that the growth of lettuce and Ixeris dentata (Thunb.) Nakai increased as the photoperiod increased. Therefore, it is presumed that the growth of red mustard was improved by the accumulation of assimilation products due to higher photosynthesis rates at a high light intensity and a long photoperiod.

Table 2.

Growth characteristics of red mustard (Brassica juncea L.) as affected by different light intensities and photoperiods at 16 days after transplanting

Treatment Leaf
length
(cm)
Leaf
width(
cm)
Number of
leaves
Leaf area
(cm2)
Fresh weight
(g/plant)
Dry weight
(g/plant)
Dry matter
(%)
Light intensity
(µmol·m-2·s-1) (A)
Photoperiod
(h) (B)
Shoot Root Shoot Root
150 8 19.0 cz 10.0 c 6.7 a 424.30 d 21.03 d 2.23 c 0.90 d 0.10 c 4.53 bc
12 19.4 bc 10.2 c 6.8 a 454.71 d 22.82 cd 3.32 c 0.98 d 0.14 c 4.29 c
16 22.4 ab 12.4 b 6.4 a 654.54 bc 38.98 b 6.29 b 2.08 c 0.32 b 5.35 ab
300 8 22.3 ab 12.3 b 6.4 a 635.61 c 31.87 bc 4.06 c 1.80 c 0.19 c 5.70 a
12 23.4 a 13.4 ab 7.1 a 804.94 ab 49.62 a 7.50 b 2.90 b 0.35 b 5.68 a
16 25.2 a 15.2 a 7.0 a 881.46 a 58.27 a 10.20 a 3.82 a 0.49 a 6.21 a
F-test A ******NS******************
B *****NS****************
A × B NSNSNSNSNSNSNSNSNS

zMean separation within columns by Duncan’s multiple range test at p < 0.05 (n = 9).

NS,*,**,***Nonsignificant or significant at p < 0.05, 0.01 or 0.001, respectively.

https://static.apub.kr/journalsite/sites/kshs/2022-040-06/N0130400602/images/HST_40_06_02_F1.jpg
Fig. 1.

Growth of red mustard (Brassica juncea L.) as affected by different light intensities and photoperiods at 16 days after transplanting.

Under high light intensity and longer photoperiod, red mustard showed a dark red color (Fig. 2). The higher the L* value, the brighter the color; the higher the a* value, the higher the red color. The L* value decreased as the photoperiod increased and the a* value increased as the photoperiod increased. Plants under high light intensity had low brightness and high saturation owing to their active pigment synthesis (Rezai et al., 2018). The stronger the dark red color in red mustard, the higher its marketability (RDA, 2018). Therefore, high light intensity and a longer photoperiod are more advantageous for producing high-quality red mustard.

https://static.apub.kr/journalsite/sites/kshs/2022-040-06/N0130400602/images/HST_40_06_02_F2.jpg
Fig. 2.

The L* (A) and a* (B) values of red mustard (Brassica juncea L.) as affected by different light intensities and photoperiods at 16 days after transplanting. Vertical bars represent the standard deviation of the mean (n = 9). Different letters in the same column indicate significant differences based on Duncan’s multiple range test (p < 0.05). A higher L* value indicates a brighter color, and a positive a* value indicates a red color.

The photosynthetic rate increased at 300 µmol·m-2·s-1, which was the highest light intensity treatment, and there was no significant difference depending on the photoperiod (Fig. 3). SPAD increased as the photoperiod increased, regardless of the light intensity. Photosynthesis is generally higher under high light intensity, and continues to increase until it reaches the photosaturation point when the CO2 concentration is saturated (Gardner et al., 2020b). Lee et al. (2012) reported that the photosynthetic rate increased with increasing photoperiod in red mustard and pak choi. Kim et al. (2016) reported that the SPAD of leafy vegetables (i.e., Ixeridium dentatum) increased as the photoperiod increases. Therefore, photosynthesis and SPAD of red mustard increased due to active photosynthesis and pigment synthetase under high light intensity and a long photoperiod.

https://static.apub.kr/journalsite/sites/kshs/2022-040-06/N0130400602/images/HST_40_06_02_F3.jpg
Fig. 3.

Photosynthetic rate (A) and SPAD (B) of red mustard (Brassica juncea L.) as affected by light intensities and photoperiods at 16 days after transplanting. Vertical bars represent the standard deviation of the mean (n = 6). Different letters in the same column indicate significant differences based on Duncan’s multiple range test (p < 0.05).

The anthocyanin content of red mustard increased as the light intensity and photoperiod increased (Fig. 4). Anthocyanins are purple-colored pigments that act as antioxidants, which protect plants from abiotic stress (Islam et al., 2002; Ma et al., 2021). The higher the color value, the greater the amount of anthocyanin in the leaves (Shimizu and Nakamura, 1993; Islam et al., 2002), and the crops with distinct colors are highly estimated for their commercial value (Ferrante et al., 2008). In this study, the color value of red mustard grown under high light intensity and a long photoperiod was high (Fig. 2). Light is one of the most factors involved in the anthocyanin biosynthesis pathway, when organs absorb light, the organ part of absorbing light, light intensity, light quality determines the quantity of the anthocyanins (Ma et al., 2021). Park and Lee (1999) reported that the anthocyanin content of leafy vegetables increased under high light intensity. In addition, the activity of enzymes and genes related to anthocyanin synthesis increases when crops are continuously irradiated by high light intensity (Sato et al., 1996; Guo et al., 2022). Therefore, it is considered that the activity of anthocyanin synthetase increases under high light intensity and long photoperiods, which causes an increase in anthocyanin content.

https://static.apub.kr/journalsite/sites/kshs/2022-040-06/N0130400602/images/HST_40_06_02_F4.jpg
Fig. 4.

Total anthocyanin content of red mustard (Brassica juncea L.) as affected by light intensities and photoperiods at 16 days after transplanting. Vertical bars represent the standard deviation of the mean (n = 6). Different letters in the same column indicate significant differences based on Duncan’s multiple range test (p < 0.05).

The DLI is the level of photosynthetically active radiation delivered over 24 h (Faust et al., 2005). As the DLI increased, the fresh weight and the total anthocyanin content showed a positive correlation (Fig. 5). The 150 µmol·m-2·s-1 with 16/8 photoperiod (low light intensity with long photoperiod) and 300 µmol·m-2·s-1 with 8/16 photoperiod (high light intensity with short photoperiod) had the same DLI, and fresh weight and total anthocyanin content showed no significant differences. He et al. (2020) reported that the quantum energy reaching photosystem II in plants under the same DLI conditions was similar. However, under the same DLI, the morphology and color can be different according to the change of photoperiod and light intensity. Kitaya et al. (1998) reported that at the same DLI, the longer photoperiod increased hypocotyl length and leaf area of ‘Summer-green’ lettuce. Kelly et al. (2020) reported that in ‘Rex’ and ‘Rouxai’ lettuce, there was no morphological change at the same DLI, but the color value was changed. In this study, at the same DLI, there is no difference in leaf area, fresh weight, and dry weight, but the color value and SPAD showed a difference (Table 2, Figs. 2 and 3B). Furthermore, DLI can act as an important indicator for establishing a strategy to control the operating cost of plant factory. The electricity cost has a large portion of the operating cost of a plant factory for using the light source (Kozai and Niu, 2019). Some countries, including Korea, the industrial electricity using the TOU (Time of usage) method, which electricity costs vary by season and time of day (Park et al., 2021). Therefore, by controlling the photoperiod while maintaining the same DLI, it is possible to save the electricity cost of the plant factory, and the results of this study can be used as an indicator to save operating costs in the production of plant factories of red mustard.

https://static.apub.kr/journalsite/sites/kshs/2022-040-06/N0130400602/images/HST_40_06_02_F5.jpg
Fig. 5.

Relationships between shoot fresh weight (A) and total anthocyanin content (B) of red mustard (Brassica juncea L.) with the daily light integral 16 days after transplanting.

Conclusions

This study investigated the growth and anthocyanin content of red mustard under various light intensities and photoperiods in a PFAL. Leaf length, leaf width, leaf area, fresh and dry weights, and anthocyanin content of crops were the greatest at a light intensity of 300 µmol·m-2·s-1 and a 16/8 photoperiod. Fresh weight and total anthocyanin content increased as the DLI increased. There was no significant difference between the fresh weight and the anthocyanin content when the DLI was the same, even if the light intensity and photoperiod were different. In conclusion, shoot growth and anthocyanin content of red mustard increased as the light intensity and photoperiod increased. This study can be used as basic data to control the production and anthocyanin content of red mustard in a PFAL using DLI.

References

1
Bae JH, Park SY, Oh MM (2017) Supplemental irradiation with far-red light-emitting diodes improves growth and phenolic contents in Crepidiastrum denticulatium in a plant factory with artificial lighting. Hortic Environ Biotechnol 58:357-366. doi:10.1007/s13580-017-0331-x 10.1007/s13580-017-0331-x
2
Berghage RD, Erwin JE, Heins RD (1991) Photoperiod influences leaf chlorophyll content in chrysanthemum grown with a negative DIF temperature regime. HortScience 26:92
3
Cha MK, Kim JS, Cho YY (2012) Growth response of lettuce to various levels of EC and light intensity in plant factory. Protected Hortic Plant Fac 21:305-311. doi:10.12791/KSBEC.2012.21.4.305 10.12791/KSBEC.2012.21.4.305
4
Choi MK, Baek GY, Kwon SJ, Yoon YC, Kim HT (2014) Effect of LED light wavelength on lettuce growth, vitamin C and anthocyanin contents. Protected Hortic Plant Fac 23:19-25. doi:10.12791/KSBEC.2014.23.1.019 10.12791/KSBEC.2014.23.1.019
5
Dorais M, Gosselin A, Trudel MJ (1991) Annual greenhouse tomato production under a sequential intercropping system using supplemental light. Sci Hortic 45:225-234. doi:10.1016/0304-4238(91)90067-9 10.1016/0304-4238(91)90067-9
6
Dougher TAO, Bugbee B (2001) Differences in the response of wheat, soybean and lettuce to reduced blue radiation. Phytochem. Photobiol. 73:199-207. doi:10.1562/0031-8655(2001)073&lt;0199:DITROW&gt;2.0.CO;2 10.1562/0031-8655(2001)073<0199:DITROW>2.0.CO;211272735
7
Faust JE, Holcombe V, Rajapakse NC, Layne DR (2005) The effect of daily light integral on bedding plant growth and flowering. HortScience 40:645-649. doi:10.21273/HORTSCI.40.3.645 10.21273/HORTSCI.40.3.645
8
Ferrante A, Incrocci L, Serra G (2008) Quality changes during storage of fresh-cut or intact swiss chard leafy vegetables. J Food Agric Environ 6:132-134
9
Fuleki JE, Francis FJ (1968) Quantitative methods for anthocyanins. 1. Extraction and determination of total anthocyanin in cranberries. J Food Sci 33:72-77. doi:10.1111/j.1365-2621.1968.tb00887.x 10.1111/j.1365-2621.1968.tb00887.x
10
Gardner FP, Pearce RB, Mitchell RL (2020a) Photosynthesis and respiration. In RGB Press, ed, Physiology of crop plants, Translated by Nam SY, Ed 1, Seoul, Korea, pp 101-135
11
Gardner FP, Pearce RB, Mitchell RL (2020b) Photosynthesis and respiration. In RGB Press, ed, Physiology of crop plants, Translated by Nam SY, Ed 1, Seoul, Korea, pp 120-126
12
Goto E (2012) Plant production in a closed plant factory with artificial lighting. VII International Symposium on Light in Horticultural Systems 956:37-49. doi:10.17660/ActaHortic.2012.956.2 10.17660/ActaHortic.2012.956.2
13
Guo X, Shakeel M, Wang D, Qu C, Yang S, Ahmad S, Song Z (2022) Metabolome and transcriptome profiling unveil the mechanisms of light-induced anthocyanin synthesis in rabbiteye blueberry (vaccinium ashei: Reade). BMC Plant Biol 22:223-236. doi:10.1186/s12870-022-03585-x 10.1186/s12870-022-03585-x35488209PMC9052483
14
He D, Yan Z, Sun X, Yang P (2020) Leaf development and energy yield of hydroponic sweetpotato seedlings using single-node cutting as influenced by light intensity and LED spectrum. J Plant Physiol 254:153274-153282. doi:10.1016/j.jplph.2020.153274 10.1016/j.jplph.2020.15327432961477
15
Heo JW, Kang DH, Bang HS, Hong SG, Chun C, Kang KK (2012) Early growth, pigmentation, protein content, and phenylalanine ammonia-lyase activity of red curled lettuces grown under different lighting conditions. Hortic Sci Technol 30:6-12. doi:10.7235/hort.2012.11118 10.7235/hort.2012.11118
16
Hoagland DR, Aron DI (1950) The water-culture method for growing plants without plant. 3rd ed. Univ. Calif. Agric. Exp. Stat. Circular 347, CA, USA
17
Hwang YH, Park Jem Chang YH, An JU, Yoon HS, Hong KP (2016) Effects of LED (Light Emitting Diode) photoperiod and light intensity on growth and yield of Taraxacum coreanum Nakai in a plant factory. Protected Hortic Plant Fac 4:232-239. doi:10.12791/KSBEC.2016.25.4.232 10.12791/KSBEC.2016.25.4.232
18
Islam MS, Yoshimoto M, Terahara N, Yamakawa O (2002) Anthocyanin compositions in sweetpotato (Ipomoea batatas L.) leaves. Biosci Biotechnol Biochem 66:2483-2486. doi:10.1271/bbb.66.2483 10.1271/bbb.66.248312506993
19
Jeong HK, Sung JH, Lee HJ (2020) Analysis of social demand for countermeasures in response to extreme weather events in Korean agricultural sector. J Climate Change Res 11:235-246. doi:10.15531/KSCCR.2020.11.4.235 10.15531/KSCCR.2020.11.4.235
20
Kelly N, Choe D, Meng Q, Runkle E (2020) Promotion of lettuce growth under an increasing daily light integral depends on the combination of the photosynthetic photon flux density and photoperiod. Sci Hortic 272:109565-109579. doi:10.1016/j.scienta.2020.109565 10.1016/j.scienta.2020.109565
21
Kim HH, Goins GD, Wheeler RM, Sager JC (2004) Green-light supplementation for enhanced lettuce growth under red- and blue-light-emitting diodes. HortScience 39:1617-1622. doi:10.21273/HORTSCI.39.7.1617 10.21273/HORTSCI.39.7.161715770792
22
Kim HM, Kang JH, Jeong BR, Hwang SJ (2016) Light quality and photoperiod affect growth of sowthistle (Ixeris dentata Nakai) in a closed-type plant production system. Hortic Sci Technol 34:67-76. doi:10.12972/kjhst.20160005 10.12972/kjhst.20160005
23
Kim YG, Kim HM, Kim HM, Lee HR, Jeong BR, Lee HJ, Kim HJ, Hwang SJ (2021) Growth and phytochemicals of ice plant (Mesembryanthemum crystallinum L.) as affected by various combined ratios of red and blue LEDs in a closed-type plant production system. J Appl Res Med Aromat Plants 20:100267-100274. doi:10.1016/j.jarmap.2020.100267 10.1016/j.jarmap.2020.100267
24
Kitaya Y, Niu G, Kozai T, Ohashi M (1998) Photosynthetic photon flux, photoperiod, and CO2 concentration affect growth and morphology of lettuce plug transplants. HortScience 33:988-991. doi:10.21273/HORTSCI.33.6.988 10.21273/HORTSCI.33.6.988
25
Koontz HV, Prince RP (1986) Effect of 16 and 24 hours daily radiation (light) on lettuce growth. HortScience 21:123-124
26
Kozai T, Niu G (2019) Criticisms of PFALs and responses to them. K Toyoki, N Genhua, T Michiko, eds, Plant factory: an indoor vertical farming system for efficient quality food production, Ed 2, Academic press, Cambridge, USA, pp 21-30
27
LEDTonic (2019) DLI (daily light integral) chart - understand your plants' PPFD & photoperiod requirements. Available via https://www.ledtonic.com/blogs/guides/dli-daily-light-integral-chart-understand-your-plants-ppfd-photoperiod-requirements Accessed 02 September 2022
28
Lee JG, Oh SS, Cha SH, Jang YA (2010) Effects of red/blue light ratio and short-term light quality conversion on growth and anthocyanin contents of baby leaf lettuce. J Bio-Env Cont 19:351-359
29
Lee MJ, Park SY, Oh MM (2015) Growth and cell division of lettuce plants under various ratios of red to far-red light-emitting diodes. Hortic Environ Biotechnol 56:186-194. doi:10.1007/s13580-015-0130-1 10.1007/s13580-015-0130-1
30
Lee SG, Choi CS, Lee JG, Jang YA, Nam CW, Yeo KH, Lee HJ, Um YC (2012) Effects of different EC in nutrient solution on growth and quality of red mustard and pak-choi in plant factory. J Bio-Env Cont 21:322-326. doi:10.12791/KSBEC.2012.21.4.322 10.12791/KSBEC.2012.21.4.322
31
Ma Y, Ma X, Gao X, Wu W, Zhou B (2021) Light induced regulation pathway of anthocyanin biosynthesis in plants. Int J Mol Sci 22:11116-11131. doi:10.3390/ijms222011116 10.3390/ijms22201111634681776PMC8538450
32
Park JE, Park YG, Jeong BR, Hwang SJ (2012) Growth and anthocyanin content of lettuce as affected by artificial light source and photoperiod in a closed-type plant production system. Korean J Hortic Sci Technol 30:673-679. doi:10.7235/hort.2012.12020 10.7235/hort.2012.12020
33
Park MH, Lee YB (1999) Effects of light intensity and nutrient level on the growth and quality of leaf lettuce in a plant factory. J Bio-Env Con 8:108-114
34
Park MW, Kang MS, Yun YW, Hong SR, Bae KY, Baek JB (2021) Particle swarm optimization-based peak shaving scheme using ESS for reducing electricity tariff. J Inst Korean Electr Electron Eng 25:388-398
35
RDA (Rural Development Administration) (2018) Baby leaf vegetables. In RDA Press, ed, Leafy vegetables, Ed 4, Seoul, Korea, pp 256-257
36
Rezai S, Etemadi N, Nikbakht A, Yousefi M, Majidi MM (2018) Effect of light intensity on leaf morphology, photosynthetic capacity, and chlorophyll content in sage (Salvia officinalis L.). Hortic Sci Technol 36:46-57. doi:10.12972/kjhst.20180006 10.12972/kjhst.20180006
37
Salisbury FB, Ross CW (1992) Plant physiology. 4th ed. Wadsworth, Belmont, CA, USA, pp 27-65
38
Sato K, Nakayama M, Shigeta J (1996) Culturing conditions affecting the production of anthocyanin in suspended cell cultures of strawberry. Plant Sci 113:91-98. doi:10.1016/0168-9452(95)05694-7 10.1016/0168-9452(95)05694-7
39
Shimizu T, Nakamura M (1993) Purple sweetpotato color. In Natural food colorants, ed. Fuji, M. Kohrin Corp., Tokyo, Japan, pp. 224-225
40
Takatsuji M (2008) Plant factory. World Science Publishment, Seoul, Korea, pp 8-13
41
Um YC, Oh SS, Lee JG, Kim SY, Jang YA (2010) The development of container-type plant factory and growth of leafy vegetables as affected by different light sources. J Bio-Environ Con 19:333-342
42
Yan Z, He D, Niu G, Zhai H (2019) Evaluation of growth and quality of hydroponic lettuce at harvest as affected by the light intensity, photoperiod and light quality at seedling stage. Sci Hortic 248:138-144. doi:10.1016/j.scienta.2019.01.002 10.1016/j.scienta.2019.01.002
페이지 상단으로 이동하기