Next Article in Journal
Blue Light Upregulates Auxin Signaling and Stimulates Root Formation in Irregular Rooting of Rosemary Cuttings
Previous Article in Journal
Nitrogen Effects on the Essential Oil and Biomass Production of Field Grown Greek Oregano (Origanum vulgare subsp. hirtum) Populations
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Agronomy
Volume 11
Issue 9
10.3390/agronomy11091724
agronomy-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Influence of Green Light Added with Red and Blue LEDs on the Growth, Leaf Microstructure and Quality of Spinach (Spinacia oleracea L.)

by
Thi-Phuong-Dung Nguyen
1,†,
Dong-Cheol Jang
2,†,
Thi-Thanh-Huyen Tran
3,
Quang-Thach Nguyen
4,
Il-Seop Kim
2,
Thi-Lan-Huong Hoang
5 and
Ngoc-Thang Vu
1,*
1
Faculty of Agronomy, Vietnam National University of Agriculture, Hanoi 131000, Vietnam
2
Department of Horticulture, Kangwon National University, Chuncheon 200-701, Korea
3
Faculty of Biology, Hanoi National University of Education, Hanoi 131000, Vietnam
4
Institute of Agrobiology, Vietnam National University of Agriculture, Hanoi 131000, Vietnam
5
Plant Resources Center, Vietnam Academy of Agricultural Sciences, Hanoi 131000, Vietnam
*
Author to whom correspondence should be addressed.
†
These authors contribute equally to this paper.
Agronomy 2021, 11(9), 1724; https://doi.org/10.3390/agronomy11091724
Submission received: 31 July 2021 / Revised: 26 August 2021 / Accepted: 27 August 2021 / Published: 28 August 2021
Browse Figures
Versions Notes

Abstract

:
The aim of this study was to investigate the effects of green light, added with red and blue LEDs, on the growth, leaf microstructure and quality of spinach plants. Plants were transplanted and grown hydroponically for 30 days under different combinations of red:blue with a 4:1 ratio (R4B1), red:blue:green with a 5:2:3 ratio (R5B2G3) and red:blue:green with a 1:1:1 ratio (R1B1G1), at a 190 µmoL m−2·s−1 photosynthetic photon flux density (PPFD). The results showed that green light, added to red and blue LEDs at a reasonable ratio, could reduce the growth, leaf microstructure and quality of spinach plants, but not the organic acid content. The highest values for the growth parameters, photosynthetic pigments, leaf structure characteristics and quality of the spinach plant were observed for the R4B1 treatment, but not for the organic acid content. Therefore, our results suggest that green light added to red and blue LEDs at a reasonable ratio is not suitable for the growth of spinach.

1. Introduction

Light regulates a variety of plant development pathways, from germination to the induction of flowering and fruit development [1]. As an important part of the light spectrum for normal plant growth, red light affects plant morphogenesis by inducing transformations in phytochromes and is crucial in the development of the photosynthetic apparatus, as well as the regulation of the synthesis of phytochemicals such as phenolics and oxalate [2,3,4]. Blue light is effective in the stimulation of photomorphogenesis and adaptive phenomena such as the regulation of stoma opening/closing, as well as biomass accumulation and chlorophyll and anthocyanin biosynthesis [5,6,7,8,9].
However, it has been reported that monochromatic red or blue light cannot satisfy the requirements for normal plant growth. For example, plants under red light alone displayed an abnormal morphology and reduced net photosynthetic rates (Pn) compared to those under white light or red light supplemented with blue light [10,11,12]. Blue light alone, or a constant illumination with high amounts of blue light, might have negative effects, such as reduced Pn, in many species, due to chloroplast avoidance responses [13,14] and impaired mesophyll conductance [15]. Therefore, previous studies have shown that a combination of blue and red light in the visible light spectrum is ideal for photosynthesis and the normal growth of different crops [16,17,18]. Additionally, the combination of red and blue light resulted in increased Pn and shoot biomass compared to monochromatic red or blue light [19,20,21,22].
Recently, it has been reported that green light plays an important role in light absorption, similar to blue light [23,24]. Green light is also known to stimulate deeper photosynthesis in the canopy and improve photosynthesis and plant growth, such as extending the stem height, inducing morphological changes, improving the leaf anatomy and enhancing the antioxidant activity, antioxidant content and aromatic compounds in leaves [16,25,26]. Green light can participate in photosynthesis through proteins that receive photosynthetic pigments, such as phytochromes and cryptochromes; therefore, it can affect plant growth and development. Green light regulates leaf expansion, stem stretching and stomatal conductance. Moreover, it has been shown that green light leads to greater dry mass accumulation and growth stimulation [27]. However, green light alone is not enough to support plant growth. However, when used in combination with red, blue and far-red light, it results in some important physiological reactions. Terashima et al. [28] stated that green light supplemented with strong white light made photosynthesis more effective than red light in sunflower leaves. As Kim et al. [29] pointed out, green light combined with red and blue LED light that can promote plant growth.
Recently, greenhouse spinach production has emerged as an alternative to traditional tomato production because it allows the production of many shorter cycles in a year and thus faster economic returns than the tomato crop [30]. Moreover, spinach has a high content of protein, vitamins, carotenoids, organic acids and alkaline mineral constituents, as well as antioxidants [31,32]. Thus, the objective of this study was to investigate whether adding green light to red and blue LEDs would affect the growth, leaf microstructure and quality of hydroponically cultivated spinach plants.

2. Materials and Methods

2.1. Plant Materials and Growth Conditions

This experiment was conducted in an indoor system at the Institute of Agrobiology, Vietnam National University of Agriculture. These methods draw upon our previous work [33,34]. The room temperature and humidity were maintained at 27 ± 0.5 °C and 65 ± 5%, respectively. Heat-treated F1 seeds of the PD512 spinach variety (Spinacia oleracea L.) were provided by Phu Dien Trading & Production Co. Ltd., Hanoi, Vietnam. The seeds were sown in 128-cell plug trays (Bumnong, Jeongeup, Korea) that had been filled with commercial growing substrate (Klasmann TS-2, Germany). Ten days after germination, seedlings of the same size were transplanted into plastic in the circulating hydroponic system. The experiment was conducted in 9 indoor hydroponic systems, where one system has 4 layers (three hydroponic systems for one light quality treatment). Each layer has got 5 rows and 9 plant sites per one row. Every hydroponic system was equipped with light of a separate quality (at the same PPFD = 190 µmoL m−2·s−1). Light was supplied by red LEDs (R) with peak wavelengths of 660 nm, by blue LEDs (B) with a peak wavelength of 445 nm and by green LEDs (G) with a peak wavelength of 550 nm. The three light qualities were created from a ratio of R:B that was 4:1 (R4B1), R:B:G that was 5:2:3 (R5B2G3) and R:B:G that was 1:1:1 (R1B1G1), at the same intensity of 190 µmoL m−2·s−1.
The LEDs were manufactured and supplied by the Rang Dong Light Source & Vacuum Flask Joint Stock Company, Hanoi, Vietnam. The plants were grown under a 12/12 h light/dark photoperiod cycle. The harvest time was 30 days after transplanting.
A solution based on Hoagland’s nutrient solution was used in the experiment [35]. The pH and EC of the nutrient solutions were maintained at 6.0–6.5 and 1200 µS/cm, respectively, by changing the solutions in the hydroponic containers every 7 days.

2.2. Growth Parameters

Specific leaf area (SLA) (cm2/g) = leaf area/leaf dry weight.
The relative growth rate (RGR) was calculated using the following equation of Hoffmann and Poorter [36]:
RGR = (lnW2 − lnW1)/(t2 − t1)
The net assimilation rate (NAR) was calculated using the following equation of Radford [37]:
NAR = [(W2 − W1)/(t2 − t1)] × [(lnA2 − lnA1)/(A2 − A1)]
where:
ln = the natural logarithm;
t1 = time one (in days); W1 = the dry weight of the plant at time one (in grams);
t2 = time two (in days); W2 = the dry weight of the plant at time two (in grams);
A1 = the leaf area of the plant at time one; A2 = the leaf area of the plant at time two (in square meters).

2.3. Photosynthetic Pigments

The chlorophyll and carotenoid concentrations were determined by Lichtenthaler and Wellburn’s method. Then, the pigment contents in the fresh leaves were converted to mg/g [38].

2.4. Anatomical Features of Leaves

The anatomical features of the mesophyll cells in the spinach leaves were determined using Clark’s method [39]. Cross-sections were cut by hand. The leaf compactness was calculated using the following formula:
Leaf compactness = Palisade tissue length/Leaf thickness
The ratio of the thickness of the palisade to that of the spongy tissue (PT/ST) was calculated as follows: PT/ST = Palisade tissue length/Spongy tissue length [40].

2.5. Stomatal Traits

For epidermal studies, leaves were soaked in absolute ethanol for 24 h and then transferred to 80% acetone for 2–4 h. The leaf samples were immersed in NaOH/ethanol (1:5 mM NaOH/absolute ethanol). Next, the samples were placed on a glass slide with lactic acid and kept overnight [41].
The leaf cross-section and stomatal microphotographs were taken using an electron microscope (Nikon Eclipse 80i, Japan) coupled with a digital microscope camera and filar micrometer. The images were processed and analyzed with ImageJ software (National Institutes of Health, USA). The size and density of the stomata and epidermal cells were calculated for both the adaxial and abaxial epidermal surfaces.

2.6. Quality Parameters

The total organic acid content, fiber content and total polyphenol content were determined at the Vietnam National University of Agriculture. The total acid content was determined by the titration method, according to Horwitz [42]. The crude fiber content was measured by the digestion and gravimetric technique according to Antial et al. [43]. The total polyphenol content was determined by the colorimetric method using Folin–Ciocalteu reagent, in accordance with Singleton and Rossi [44].

2.7. Statistical Analysis

Statistical analyses were conducted with Excel and R software. Data were analyzed by analysis of variance (ANOVA), and the differences between means were tested using Duncan’s test (p ≤ 0.05).

3. Results

3.1. Effect of Light Quality on Growth Parameters of Spinach Plant

The hydroponically cultivated spinach grown under various light qualities showed significant differences in growth characteristics (Table 1). The relative growth rate (RGR), net assimilation rate (NAR), fresh weight (FW) and dry weight (DW) of the spinach plant decreased with a decrease in the ratio of red light. The highest values of RGR, NAR and FW of the whole plant were observed in the R4B1 treatment; the lowest values of the RGR, NAR and FW for the whole plant were observed for the R1B1G1 treatment. The DW for the R1B1G1 treatment was not statistically significantly different to that for the R5B2G3 treatment. However, the highest specific leaf area (SLA) was observed for the R5B2G3 treatment.

3.2. Effect of Light Quality on Photosynthetic Pigments of Spinach Plant

The highest values of the photosynthetic pigment content were observed for the R4B1 treatment, followed by the R5B2G3 and R1B1G1 treatments, except for the Chla/chlb ratio. However, there were no statistically significant differences in the Chla content and Chla/Chlb ratio between the R5B2G3 and R1B1G1 treatments. There were no statistically significant differences in the Chlb and Chl(a + b) contents, Chla/Chlb ratio and carotenoids between the R5B2G3 and R4B1 treatments (Table 2).

3.3. Effect of Light Quality on Leaf Structure Characteristics of Spinach Plant

3.3.1. Anatomy of the Leaf Cross-Sections

The highest values of the palisade tissue length, spongy tissue length, leaf thickness and ratio of palisade tissue length/spongy tissue length were observed for the R4B1 treatment, followed by the R5B2G3 and the R1B1G1 treatments. There was no statistically significant difference in leaf compactness between the R4B1 and R5B2G3 treatments, but the highest value of leaf compactness was also observed for the R4B1 treatment (Table 3 and Figure 1).

3.3.2. Characteristics of Stomata Cells

The characteristics of the responses of the stomatal cells in the adaxial epidermis to the light treatments are shown in Figure 2, Figure 3 and Figure 4. The highest values of the stomatal length and stomatal width/length ratio were observed for the R4B1 treatment, followed by the R1B1G1 and the R5B2G3 treatments. However, there was no statistically significant difference in stomatal length between the R1B1G1 and R5B2G3 treatments. The highest values of stomatal width and stomatal density were observed for the R4B1 treatment, followed by the R5B2G3 and R1B1G1 treatments.
The highest values of the stomatal length, stomatal length/width ratio and stomatal density in the abaxial spinach epidermis leaves were observed for the R4B1 treatment, followed by the R5B2G3 and R1B1G1 treatments. However, there was no statistically significant difference in the stomatal length/width ratio between the R1B1G1 and R5B2G3 treatments. The highest value of the stomatal width was observed for the R5B2G3 treatment, followed by the R4B1 and R1B1G1 treatments (Figure 5 and Figure 6).

3.4. Effect of Light Quality on Nutrition Content and Quality of Spinach Plant

The highest values of the crude fiber content and total polyphenol content were observed for the R4B1 treatment, while the lowest values were observed for the R1B1G1 treatment. However, there was no statistically significant difference in the crude fiber content and total polyphenol content between the R1B1G1 and R5B2G3 treatments (Figure 7). The highest organic acid content was observed for the R5B2G3 treatment, followed by the R1B1G1 and R4B1 treatments. However, there was no statistically significant difference in the organic acid content between the R1B1G1 and R5B2G3 treatments, or between the R4B1 and R5B2G3 treatments (Figure 7).

4. Discussion

Current LED-based artificial lights for crop cultivation consist of red and blue lights, because their spectra effectively promote leaf photosynthesis. Red and blue light are the most important light regions, necessary for plant growth and development [9]. The combination of red and blue light resulted in increased photosynthesis and biomass of the plant compared to monochromatic red or blue light [12,19,20,21,22]. However, it has recently been reported that green light plays an important role in light absorption, similar to blue light [23,24]. Green light is also known to stimulate deeper photosynthesis in the canopy, and improve photosynthesis and plant growth, such as extending the stem height, causing morphological changes, altering the leaf anatomy and enhancing the antioxidant activity, antioxidant content and aromatic compounds in leaves [16,25,26]. Green light can participate in photosynthesis through proteins that receive photosynthetic pigments, such as phytochromes and cryptochromes; therefore, it can affect plant growth and development. Kim et al. [29] grew lettuce under blue:red and blue:green:red and found that plants grown under 24% green had a greater fresh mass, dry mass and leaf area than plants grown under blue:red. However, in our study, the green light, when added with red and blue LEDs, resulted in decreased growth parameters for the spinach plant compared to the red and blue light combination. This result is similar to the result of Hernández and Kubota [45], who reported that the addition of green to the spectrum did not have any influence on cucumber plants. However, Wollaeger and Runkle [46] also found that tomato, impatiens and salvia transplants had the same shoot dry weights when grown under combination LED lights of green:red, blue:green:red and blue:red. Therefore, Hernández and Kubota [46] suggested that the effect of green light on a plant’s growth rate is species-specific.
Blue and red LEDs are commonly used for plant growth, as chlorophyll a and b efficiently absorb blue and red wavelengths in the ranges of blue (maximum absorption at 430 and 453 nm) and red (maximum absorption at 663 and 642 nm) [47]. On the other hand, Wollaeger and Runkle [46] suggested that light quality is an important factor for photosynthetic pigments, and red light has a greater influence than other light spectra. Therefore, in our study, the photosynthetic pigment content decreased with a decrease in the ratio of red light. The highest values of the photosynthetic pigment content were observed in the R4B1 treatment, followed by the R5B2G3 and R1B1G1 treatments. This result is similar to the result of Terashima et al. [28], who suggested that the light in the red and blue regions of the spectrum is mainly absorbed by photosynthetic pigments.
The combination of red and blue light is effective for photosynthesis and the normal growth of different plants [16,17,18]. Changes in the light spectrum strongly influence plant growth and quality [48]. In our study, the anatomical structure of the spinach leaves decreased with a decrease in the ratio of red light. The highest values for the anatomical structure of the spinach leaves were observed for the R4B1 treatment, followed by the R5B2G3 and R1B1G1 treatments. The results also presented similarities with those of the study of Stryjewski et al. [49] on the anatomical structure of spinach leaves exposed to different qualities of light, which showed that the leaf thickness, palisade tissue length and spongy tissue length were larger with a 660 nm red-light-supplemented 470 nm blue light LED treatment than with others (690, 700 and 725 nm combined with 470 nm) [49].
The ratio of blue and red LEDs was important for the morphology, growth and phenolic compounds with antioxidant properties in two lettuce varieties [50]. Accordingly, in our study, the highest values for crude fiber content and total polyphenol content were observed with the R4B1 treatment. Our results for the phenolic content also slightly differ from those of Samuoliene et al. [51]. The authors demonstrated that the phenol concentration in red leaf lettuce increased by 52.7 and 14.5%, respectively, when red–blue LEDs were used 16 h before harvest. However, the highest organic acid content in our study was observed with the R5B2G3 treatment, followed by the R1B1G1 and R4B1 treatments. The change in organic acid content was also similar to the findings of Viršilė et al. [52]. Light (green 510 nm, 595 nm orange) supplementary to the LED light (435 nm blue LED, 627 nm and 660 nm and 735 nm red LEDs) at PPFD 300 µmoL m−2 s−1 did not affect the growth of lettuce; however, it had a pronounced effect on the organic acid content. Orange and green light had a different effect on the metabolism of red and green leaf lettuce, correlating with the nutritional and safety values in lettuce production. The metabolic reactions were characteristic of the plant varieties; however, green light had a reasonable impact on the levels of primary metabolites in red and green leaf lettuce [52].

5. Conclusions

The ratio of red, blue and green LEDs was an important factor in the growth, photosynthesis and biosynthesis of metabolites in spinach plants. The combination of red and blue light at a 4:1 ratio had higher values of the growth parameters, photosynthetic pigments, leaf structure characteristics and quality of the spinach plant than combinations of red:blue:green with 5:2:3 and 1:1:1 ratios. Green light, when added to red and blue LEDs at a reasonable ratio, could reduce the growth, leaf microstructure and quality of spinach plants, but not the organic acid content.

Author Contributions

Conceptualization, T.-P.-D.N. and N.-T.V.; methodology, T.-P.-D.N., D.-C.J., Q.-T.N. and N.-T.V.; software, T.-P.-D.N., N.-T.V. and T.-L.-H.H.; validation, Q.-T.N., T.-T.-H.T. and N.-T.V.; formal analysis, T.-P.-D.N., D.-C.J. and N.-T.V.; investigation, Q.-T.N. and T.-T.-H.T.; resources, Q.-T.N. and T.-T.-H.T.; data curation, T.-P.-D.N., D.-C.J. and N.-T.V.; writing—original draft preparation, T.-P.-D.N. and N.-T.V.; writing—review and editing, T.-P.-D.N., D.-C.J., T.-T.-H.T., Q.-T.N., I.-S.K., T.-L.-H.H. and N.-T.V.; project administration, D.-C.J. and I.-S.K. All authors have read and agreed to the published version of the manuscript.

Funding

This work was partially funded by the Korea Ministry of Agriculture, Food and Rural Affairs, Technical commercialization support project (Task Number: 821045-3).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Jiao, Y.; Lau, O.S.; Deng, X.W. Light-regulated transcriptional networks in higher plants. Nat. Rev. Genet. 2007, 8, 217–230. [Google Scholar] [CrossRef]
  2. Choi, H.G.; Moon, B.Y.; Kang, N.J. Effects of LED light on the production of strawberry during cultivation in a plastic greenhouse and in a growth chamber. Sci. Hortic. 2015, 189, 22–31. [Google Scholar] [CrossRef]
  3. Qi, L.D.; Liu, S.Q.; Xu, L. Effects of light qualities on accumulation of oxalate: Tannin and nitrate in spinach. Trans. Chin. Soc. Agric. Eng. 2007, 4, 201–205. [Google Scholar]
  4. Saebo, A.; Krekling, T.; Appelgren, M. Light quality affects photosynthesis and leaf anatomy of birch plantlets in vitro. Plant Cell Tissue Organ Cult. 1995, 41, 177–185. [Google Scholar] [CrossRef]
  5. Cosgrove, D.J. Rapid suppression of growth by blue light. Plant Physiol. 1981, 67, 584–590. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  6. Senger, H. The effect of blue light on plants and microorganisms. Phytochem. Photobiol. 1982, 35, 911–920. [Google Scholar] [CrossRef]
  7. Giliberto, L.; Perrotta, G.; Pallara, P.; Weller, J.L.; Fraser, P.D.; Bramley, P.M.; Fiore, A.; Tavazza, M.; Giuliano, G. Manipulation of the blue light photoreceptor cryptochrome 2 in tomato affects vegetative development, flowering time, and fruit antioxidant content. Plant Physiol. 2005, 137, 199–208. [Google Scholar] [CrossRef] [Green Version]
  8. Li, Q.; Kubota, C. Effects of supplemental light quality on growth and phytochemicals of baby leaf lettuce. Environ. Exp. Bot. 2009, 67, 59–64. [Google Scholar] [CrossRef]
  9. Chen, X.L.; Yang, Q.C.; Song, W.P.; Wang, L.C.; Guo, W.Z.; Xue, X.Z. Growth and nutritional properties of lettuce affected by different alternating intervals of red and blue LED irradiation. Sci. Hortic. 2017, 223, 44–52. [Google Scholar] [CrossRef]
  10. Goins, G.D.; Yorio, N.C.; Sanwo-Lewandowski, M.M.; Brown, C.S. Life cycle experiments with Arabidopsis under red light-emitting diodes (LEDs). Life Support Biosph. Sci. 1998, 5, 143–149. [Google Scholar] [PubMed]
  11. Wang, X.Y.; Xu, X.M.; Cui, J. The importance of blue light for leaf area expansion, development of photosynthetic apparatus, and chloroplast ultrastructure of Cucumis sativus grown under weak light. Photosynthetica 2015, 53, 213–222. [Google Scholar] [CrossRef]
  12. Hogewoning, S.W.; Trouwborst, G.; Maljaars, H.; Poorter, H.; van Ieperen, W.; Harbinson, J. Blue light dose-responses of leaf photosynthesis, morphology, and chemical composition of Cucumis sativus grown under different combinations of red and blue light. J. Exp. Bot. 2010, 61, 3107–3117. [Google Scholar] [CrossRef] [PubMed]
  13. Wada, M.; Kagawa, T.; Sato, Y. Chloroplast movement. Annu. Rev. Plant Biol. 2003, 54, 455–468. [Google Scholar] [CrossRef] [PubMed]
  14. Kim, S.J.; Hahn, E.J.; Heo, J.W.; Paek, K.Y. Effects of LEDs on net photosynthetic rate, growth and leaf stomata of chrysanthemum plantlets in vitro. Sci. Hortic. 2004, 101, 143–151. [Google Scholar] [CrossRef]
  15. Loreto, F.; Tsonev, T.; Centritto, M. The impact of blue light on leaf mesophyll conductance. J. Exp. Bot. 2009, 60, 2283–2290. [Google Scholar] [CrossRef]
  16. Bian, Z.; Yang, Q.; Li, T.; Cheng, R.; Barnett, Y.; Lu, C. Study of the beneficial effects of green light on lettuce grown under short-term continuous red and blue light-emitting diodes. Physiol. Plant. 2018, 164, 226–240. [Google Scholar] [CrossRef] [Green Version]
  17. Viršilė, A.; Olle, M.; Duchovskis, P. LED Lighting in Horticulture. In Light Emitting Diodes for Agriculture; Springer: Berlin/Heidelberg, Germany, 2017; pp. 113–147. [Google Scholar]
  18. Wang, J.; Lu, W.; Tong, Y.; Yang, Q. Leaf morphology, photosynthetic performance, chlorophyll fluorescence, stomatal development of lettuce (Lactuca sativa L.) exposed to different ratios of red light to blue light. Front. Plant Sci. 2016, 7, 250. [Google Scholar] [CrossRef] [Green Version]
  19. Brown, C.S.; Schuerger, A.C.; Sager, J.C. Growth and photomorphogenesis of pepper plants under red light-emitting diodes with supplemental blue or far-red lighting. J. Am. Soc. Hortic. Sci. 1995, 120, 808–813. [Google Scholar] [CrossRef] [Green Version]
  20. Ohashi-Kaneko, K.; Matsuda, R.; Goto, E.; Fujiwara, K.; Kurata, K. Growth of rice plants under red light with or without supplemental blue light. Soil Sci. Plant Nutr. 2006, 52, 444–452. [Google Scholar] [CrossRef]
  21. Nanya, K.; Ishigami, Y.; Hikosaka, S.; Goto, E. Effects of blue and red light on stem elongation and flowering of tomato seedlings. Acta Hortic. 2012, 956, 261–266. [Google Scholar] [CrossRef]
  22. Li, H.; Tang, C.; Xu, Z. The effects of different light qualities on rapeseed (Brassica napus L.) plantlet growth and morphogenesis in vitro. Sci. Hortic. 2013, 150, 117–124. [Google Scholar] [CrossRef]
  23. Cui, J.; Ma, Z.; Xu, Z.; Zhang, H.; Chang, T.; Liu, H. Effects of supplemental lighting with different light qualities on growth and physiological characteristics of cucumber, pepper and tomato seedlings. Acta Hortic. Sin. 2009, 36, 663–670. [Google Scholar]
  24. Bantis, F.; Smirnakou, S.; Ouzounis, T.; Koukounaras, A.; Ntagkas, N.; Radoglou, K. Current status and recent achievements in the field of horticulture with the use of light-emitting diodes (LEDs). Sci. Hortic. 2018, 235, 437–451. [Google Scholar] [CrossRef]
  25. Bian, Z.H.; Cheng, R.F.; Yang, Q.C.; Wang, J.; Lu, C. Continuous light from red, blue, and green light-emitting diodes reduces nitrate content and enhances phytochemical concentrations and antioxidant capacity in lettuce. J. Am. Soc. Hortic. Sci. 2016, 141, 186–195. [Google Scholar] [CrossRef] [Green Version]
  26. De Keyser, E.; Dhooghe, E.; Christiaens, A.; Van Labeke, M.C.; Van Huylenbroeck, J. LED light quality intensifies leaf pigmentation in ornamental pot plants. Sci. Hortic. 2019, 253, 270–275. [Google Scholar] [CrossRef]
  27. Kim, H.H.; Wheeler, R.; Sager, J.; Norikane, J. Photosynthesis of lettuce exposed to different short-term light qualities. Environ. Control Biol. 2005, 43, 113–119. [Google Scholar] [CrossRef] [Green Version]
  28. Terashima, I.; Fujita, T.; Inoue, T.; Chow, W.S.; Oguchi, R. Green light drives leaf photosynthesis more efficiently than red light in strong white light: Revisiting the enigmatic question of why leaves are green. Plant Cell Physiol. 2009, 50, 684–697. [Google Scholar] [CrossRef] [Green Version]
  29. Kim, H.H.; Goins, G.D.; Wheeler, R.M.; Sager, J.C. Green-light supplementation for enhanced lettuce growth under red-and blue-light-emitting diodes. HortScience 2004, 39, 1617–1622. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  30. Brandenberger, L.; Cavins, T.; Payton, M.; Wells, L.; Johnson, T. Yield and quality of spinach cultivars for greenhouse production in Oklahoma. HortTechnology 2007, 17, 269–272. [Google Scholar] [CrossRef] [Green Version]
  31. Lisiewska, Z.; Kmiecik, W.; Gębczyński, P.; Sobczyńska, L. Amino acid profile of raw and as-eaten products of spinach (Spinacia oleracea L.). Food Chem. 2011, 126, 460–465. [Google Scholar] [CrossRef]
  32. Lisiewska, Z.; Gębczyński, P.; Bernaś, E.; Kmiecik, W. Retention of mineral constituents in frozen leaf vegetables prepared for consumption. J. Food Compos. Anal. 2009, 22, 218–223. [Google Scholar] [CrossRef]
  33. Nguyen, T.P.D.; Tran, T.T.H.; Dong, C.J.; Kim, I.S.; Nguyen, Q.T. Effects of supplemental green LEDs to red and blue light on the growth, yield and quality of hydroponic cultivated spinach (Spinacia oleracea L.) in plant factory. Prot. Hortic. Plant Fact. 2020, 29, 171–180. [Google Scholar] [CrossRef]
  34. Nguyen, T.P.D.; Tran, T.T.H.; Nguyen, Q.T. Effects of light intensity on the growth, photosynthesis and leaf microstructure of hydroponic cultivated spinach (Spinacia oleracea L.) under a combination of red and blue LEDs in house. Int. J. Agric. Technol. 2019, 15, 75–90. [Google Scholar]
  35. Hoagland, D.R.; Arnon, D.I. The water culture method for growing plants without soil. Calif. Agric. Expt. Stat. Circ. 1950, 347, 1–32. [Google Scholar]
  36. Hoffmann, W.A.; Poorter, H. Avoiding bias in calculations of relative growth rate. Ann. Bot. 2002, 90, 37–42. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  37. Radford, P. Growth analysis formulae-their use and abuse. Crop. Sci. 1967, 7, 171–175. [Google Scholar] [CrossRef]
  38. Lichtenthaler, H.K.; Wellburn, A.R. Determinations of total carotenoids and chlorophylls a and b of leaf extracts in different slovents. Biochem. Soc. Trans. 1983, 11, 591–592. [Google Scholar] [CrossRef] [Green Version]
  39. Clark, G. Staining Procedures, 4th ed.; Williams and Wilkins: London, UK, 1981; pp. 325–326. [Google Scholar]
  40. Yao, X.Y.; Liu, X.Y.; Xu, Z.G.; Jiao, X.L. Effects of light intensity on leaf microstructure and growth of rape seedlings cultivated under a combination of red and blue LEDs. J. Integr. Agric. 2017, 16, 97–105. [Google Scholar] [CrossRef]
  41. Tuan, T.A.; Valya, V.; Petar, P.; Petrova, P.L. Cadmium-induced structural disturbances in Pisum sativum leaves are alleviated by nitric oxide. Turk. J. Bot. 2013, 37, 698–707. [Google Scholar] [CrossRef]
  42. Horwitz, W. Official Methods of Analysis of the Association of Official Analytical Chemists; Association of Official Analytical Chemists: Washington, DC, USA, 1980. [Google Scholar]
  43. Antial, B.S.; Akpanz, E.J.; Okonl, P.A.; Umorenl, I.U. Nutritive and anti-Nutritive evaluation of sweet potatoes. Pak. J. Nutr 2006, 5, 166–168. [Google Scholar] [CrossRef]
  44. Singleton, V.L.; Rossi, J.A.J. Colorimetry of total phenolics with phosphomolybdic-phosphotungstic acid reagents. Am. J. Enol. Viticult. 1965, 16, 144–158. [Google Scholar]
  45. Hernández, R.; Kubota, C. Physiological responses of cucumber seedlings under different blue and red photon flux ratios using LEDs. Environ. Exp. Bot. 2016, 121, 66–74. [Google Scholar] [CrossRef]
  46. Wollaeger, H.M.; Runkle, E.S. Growth and acclimation of impatiens, salvia, petunia, and tomato seedlings to blue and red light. HortScience 2015, 50, 522–529. [Google Scholar] [CrossRef] [Green Version]
  47. Hopkins, W.G.; Huner, N.P.A. Introduction to Plant Physiology, 3rd ed.; John Wiley and Sons: Hoboken, NJ, USA, 2004. [Google Scholar]
  48. Macedo, A.F.; Leal-Costa, M.V.; Tavares, E.S.; Lage, C.L.S.; Esquibel, M.A. The effect of light quality on leaf production and development of in vitrocultured plants of Alternanthera brasiliana Kuntze. Environ. Exp. Bot. 2011, 70, 43–50. [Google Scholar] [CrossRef]
  49. Stryjewski, E.; Goins, G.; Kelly, C. Quantitative morphological analysis of spinach leaves grown under light-emitting diodes or sulfur-microwave lamps. In Proceedings of the 31st International Conference on Environmental Systems, Orlando, FL, USA, 9–12 July 2001; SAE International: Warrendale, PA, USA, 2001. [Google Scholar] [CrossRef]
  50. Son, K.H.; Oh, M.M. Leaf shape, growth, and antioxidant phenolic compounds of two lettuce cultivars grown under various combinations of blue and red light-emitting diodes. HortScience 2013, 48, 988–995. [Google Scholar] [CrossRef]
  51. Samuolienė, G.; Brazaitytė, A.; Sirtautas, R.; Sakalauskienė, S.; Jankauskienė, J.; Duchovskis, P.; Novičkovas, A. The impact of supplementary short-term red led lighting on the antioxidant properties of microgreens. Acta Hortic. 2012, 956, 649–655. [Google Scholar] [CrossRef]
  52. Viršilė, A.; Brazaitytė, A.; Vaštakaitė-Kairienė, V.; Miliauskienė, J.; Jankauskienė, J.; Novičkovas, A.; Laužikė, K.; Samuolienė, G. The distinct impact of multi-color LED light on nitrate, amino acid, soluble sugar and organic acid contents in red and green leaf lettuce cultivated in controlled environment. Food Chem. 2019, 301, 125799. [Google Scholar] [CrossRef]
Agronomy 11 01724 g001 550
Figure 1. Anatomy of the spinach leaf cross-section at different light qualities: (a) R4B1, (b) R5B2G3 and (c) R1B1G1. Scale bar is 50 µm.
Figure 1. Anatomy of the spinach leaf cross-section at different light qualities: (a) R4B1, (b) R5B2G3 and (c) R1B1G1. Scale bar is 50 µm.
Agronomy 11 01724 g001
Agronomy 11 01724 g002 550
Figure 2. Adaxial epidermis (a) and abaxial epidermis (b) of hydroponically cultivated spinach leaves under R5B2G3 treatment. Scale bar is 50 µm.
Figure 2. Adaxial epidermis (a) and abaxial epidermis (b) of hydroponically cultivated spinach leaves under R5B2G3 treatment. Scale bar is 50 µm.
Agronomy 11 01724 g002
Agronomy 11 01724 g003 550
Figure 3. The adaxial epidermis of spinach leaves at different light qualities: (a) R4B1, (b) R5B2G3 and (c) R1B1G1. Scale bar is 50 µm.
Figure 3. The adaxial epidermis of spinach leaves at different light qualities: (a) R4B1, (b) R5B2G3 and (c) R1B1G1. Scale bar is 50 µm.
Agronomy 11 01724 g003
Agronomy 11 01724 g004a 550Agronomy 11 01724 g004b 550
Figure 4. Characteristics of the stomatal cells in the adaxial spinach epidermis leaves for the different light qualities. The error bars show the standard errors. Data were analyzed by R software. Different letters indicate a significant difference among treatments (p ≤ 0.05).
Figure 4. Characteristics of the stomatal cells in the adaxial spinach epidermis leaves for the different light qualities. The error bars show the standard errors. Data were analyzed by R software. Different letters indicate a significant difference among treatments (p ≤ 0.05).
Agronomy 11 01724 g004aAgronomy 11 01724 g004b
Agronomy 11 01724 g005 550
Figure 5. The abaxial epidermis of spinach leaves at different light qualities: (a) R4B1, (b) R5B2G3 and (c) R1B1G1. Scale bar is 50 µm.
Figure 5. The abaxial epidermis of spinach leaves at different light qualities: (a) R4B1, (b) R5B2G3 and (c) R1B1G1. Scale bar is 50 µm.
Agronomy 11 01724 g005
Agronomy 11 01724 g006a 550Agronomy 11 01724 g006b 550
Figure 6. Characteristics of the stomatal cells in the abaxial spinach epidermis leaves for the different light qualities. The error bars show the standard errors. Data were analyzed by R software. Different letters indicate a significant difference among treatments (p ≤ 0.05).
Figure 6. Characteristics of the stomatal cells in the abaxial spinach epidermis leaves for the different light qualities. The error bars show the standard errors. Data were analyzed by R software. Different letters indicate a significant difference among treatments (p ≤ 0.05).
Agronomy 11 01724 g006aAgronomy 11 01724 g006b
Agronomy 11 01724 g007a 550Agronomy 11 01724 g007b 550
Figure 7. Effects of LEDs with a different light quality at the same intensity on some nutritional parameters of hydroponically cultivated spinach (30 DAT). The error bars show the standard errors. Data were analyzed by R software. Different letters indicate a significant difference among treatments (p ≤ 0.05).
Figure 7. Effects of LEDs with a different light quality at the same intensity on some nutritional parameters of hydroponically cultivated spinach (30 DAT). The error bars show the standard errors. Data were analyzed by R software. Different letters indicate a significant difference among treatments (p ≤ 0.05).
Agronomy 11 01724 g007aAgronomy 11 01724 g007b
Table
Table 1. Effects of different light qualities on the growth characteristics of hydroponically cultivated spinach (30 DAT).
Table 1. Effects of different light qualities on the growth characteristics of hydroponically cultivated spinach (30 DAT).
TreatmentSLA (cm2/g)RGR (g/day)NAR (g/m2/day)FW of Whole Plant (g/Plant)DW of Whole Plant (g/Plant)
R4B12.99 c0.140 a5.56 a74.69 a4.20 a
R5B2G34.08 a0.132 b5.35 b53.57 b2.45 b
R1B1G13.57 b0.121 c5.22 c36.31 c2.19 b
CV%4.402.711.142.766.90
LSD0.050.310.0070.123.020.36
DAT: Days after transplanting; SLA: Specific leaf area; RGR: Relative growth rate; NAR: Net assimilation rate; FW: Fresh weight; DW: Dry weight. Different lowercase letters in the same column indicate significant differences among treatments (p ≤ 0.05; n = 3).
Table
Table 2. Effects of different light qualities on the photosynthetic pigments of hydroponically cultivated spinach (30 DAT).
Table 2. Effects of different light qualities on the photosynthetic pigments of hydroponically cultivated spinach (30 DAT).
TreatmentChla (mg/g)Chlb (mg/g)Chl(a + b) (mg/g)Chla/ChlbCarotenoids (mg/g)
R4B10.290 a0.522 a0.812 a0.555 a0.183 a
R5B2G30.274 b0.515 a0.789 a0.532 ab0.181 a
R1B1G10.268 b0.498 b0.766 b0.538 b0.169 b
CV%1.681.511.381.602.34
LSD0.050.0090.0150.0220.0170.008
DAT: Days after transplanting; Chl: Chlorophyll. Different lowercase letters in the same column indicate significant differences among treatments (p ≤ 0.05; n = 3).
Table
Table 3. Effects of different light qualities on the anatomical structure of hydroponic spinach leaves (30 DAT).
Table 3. Effects of different light qualities on the anatomical structure of hydroponic spinach leaves (30 DAT).
TreatmentPalisade Tissue Length (µm)Spongy Tissue Length (µm)Leaf Thickness (µm)PT/STLeaf Compactness
R4B178.31 a253.00 a382.43 a0.310 a0.205 a
R5B2G365.00 b218.59 b320.92 b0.297 b0.203 a
R1B1G146.91 c163.48 c251.88 c0.287 c0.186 b
CV%2.340.710.592.512.15
LSD0.051.361.381.740.0070.004
DAT: Days after transplanting; PT/ST: ratio of palisade tissue length/spongy tissue length. Different lowercase letters in the same column indicate significant differences among treatments (p ≤ 0.05; n = 3).
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Nguyen, T.-P.-D.; Jang, D.-C.; Tran, T.-T.-H.; Nguyen, Q.-T.; Kim, I.-S.; Hoang, T.-L.-H.; Vu, N.-T. Influence of Green Light Added with Red and Blue LEDs on the Growth, Leaf Microstructure and Quality of Spinach (Spinacia oleracea L.). Agronomy 2021, 11, 1724. https://doi.org/10.3390/agronomy11091724

AMA Style

Nguyen T-P-D, Jang D-C, Tran T-T-H, Nguyen Q-T, Kim I-S, Hoang T-L-H, Vu N-T. Influence of Green Light Added with Red and Blue LEDs on the Growth, Leaf Microstructure and Quality of Spinach (Spinacia oleracea L.). Agronomy. 2021; 11(9):1724. https://doi.org/10.3390/agronomy11091724

Chicago/Turabian Style

Nguyen, Thi-Phuong-Dung, Dong-Cheol Jang, Thi-Thanh-Huyen Tran, Quang-Thach Nguyen, Il-Seop Kim, Thi-Lan-Huong Hoang, and Ngoc-Thang Vu. 2021. "Influence of Green Light Added with Red and Blue LEDs on the Growth, Leaf Microstructure and Quality of Spinach (Spinacia oleracea L.)" Agronomy 11, no. 9: 1724. https://doi.org/10.3390/agronomy11091724

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop