Impact of Different LED Light Types on Microgreens Cultivation: Growth, Weight, and Micronutrient Content
Thanks to one of our friends Lucia Jasenovska and her study over microgreens, we are smarter today for some very important information about effects of various light spectra on microgreens species which we want and will talk about in this article. We want to thank you from this place for using the seeds from us, making the experiment from them and adding so much value into the microgreens world and horticultural district.
Thank you, Lucia!
In these article we will go over:
1. How does light in general influence microgreens cultivation?
2. Why are we using LED lamps in microgreens farming?
3. How was the experiment made?
3.1. Conditions
3.2. Which varieties of microgreens were checked in the experiment?
3.3. What was measured in microgreens in the experiment?
4. Table with General results
5. How do white, blue, and red lights affect microgreens' fresh weight?
6. How do white, blue, and red lights affect microgreens concentration of flavonoids and anthocyanins?
6.1 What are Flavonoids and anthocyanins and why are they important for human health and microgreeners?
6.2. How LED lamp colors affect the concentration of flavonoids on microgreens-examples?
6.3. How LED lamp colors affect the concentration of anthocyanins on microgreens-examples.
7. How LED lamp colors affect the concentration of microgreens colors, chlorophyll and carotenoids?
8. Conclusion in points
1. How does light in general influence microgreens cultivation?
It's well known that light significantly influences plant growth, and this applies to microgreens too. Different types of light and lighting durations can affect:
- Growth Speed: Plants can grow faster or slower depending on the light.
- Nutritional Content: Light can influence the amount of vitamins and other nutrients in the plants.
- Metabolism: The metabolic processes in plants are affected by light.
- Appearance: Light affects the height, weight, and color of the plants.
This is especially important today as many people grow plants indoors using LED lamps, whether at home, in urban farms, or in hydroponic systems. Understanding how light affects microgreens is crucial for us, the microgreen growers.
2. Why are we using LED lamps in microgreens farming?
Microgreens are typically grown in artificial and controlled environments, with artificial light being a key factor. Light-emitting diodes (LEDs) are frequently used in indoor farming for several reasons:
- Availability and Cost: LEDs are easily accessible and affordable.
- Ease of Use and Optimization: They are simple to operate and can be optimized for different growing needs.
- Energy Efficiency: LEDs are highly energy-efficient.
- Addressing Land and Climate Issues: They help mitigate land scarcity and climate change impacts by reducing the human footprint, ensuring year-round food availability, and enhancing food production.
- Improved Cultivation and Quality: LEDs offer opportunities to improve the cultivation process and the quality of microgreens.
Photo from the experiment documentation⬇️
3. How was the experiment made?
By choosing the right LEDs, we can enhance the production and quality of microgreens.
While some effects of different light spectra are known, there is limited information about how different plant species and genotypes respond.
This study was about investigating how red, blue, and white LED lights affect the growth and pigment composition of microgreens, including non-invasive assessments of anthocyanin and flavonoid contents.
Photo 1 from the experiment documentation⬇️
3.1 Conditions:
- The study was made February to June 2023
- in IPES SUA NITRA in Slovakia,
- with regulated and recorded conditions:
- 20 degrees in the night and 23 degrees during the day,
- with humidity 60-80%.
- Each part of the seeds from the same variety was divided and treated with different light.
- MP SEEDS seeds were used in the experiment.
- It was used 3 types of lamps: polychromatic warm-white LEDs, monochromatic red LEDs (peak at 660 nm) and monochromatic blue LEDs (peak at 470 nm).
- The light intensity in all three light compartments was set to have similar energy output (~60 W · m−2, which represents PPFD of app. ~160 μmol photons · m−2 for blue light, ~175 μmol photons · m−2 for white light and up to ~200 μmol photons · m−2 for red light)
- Schedule of lightning: 14/10 (day/night)
Photo 2 from the experiment documentation
3.2. Which varieties of microgreens were checked in the experiment?
- Amaranth
- Cabbage
- Kohlrabi
- Arugula
- Lettuce
- Cress
- Radish Red Rambo
- Radish Rose
- Mustard
- Spinach
- Fenugreek
- Pak Choi
- Mizuna
- Komatsuna
- Kale
- Broccoli
- Beet Red
- Beet Yellow
- Basil Italian
- Basil Red Opal
- Onion
3.3 What was measured in microgreens in the experiment?
At the end of each growing cycle, they took samples of individual plants and immediately measured their fresh weight.
Then, they put the samples in paper bags and dried them in an oven at 75°C for 2 days until their weight stayed the same. After that, they measured their dry weight.
Samples were taken from each pot with microgreens, weighed, packed into bags, frozen, and placed in a deep freezer at -81°C. The samples were then extracted and blended.
The mixture was diluted with 80% acetone, poured into tubes with a conical bottom, and centrifuged. They measured the absorbance with a spectrophotometer and calculated the chlorophyll and carotenoid contents.
- Parameters measured with a multispectral fluorimeter:
To measure chlorophyll, flavonoid, and anthocyanin fluorescence from the top of the plants without touching them. Three fluorescence excitation ratios (FERs) were calculated as follows.
Small translation from professional language to farmer's language (will be needed later on):
- FERR/UV: This is FR divided by FUV. FR is the fluorescence intensity after red light, and FUV is the fluorescence intensity after UV light. This ratio estimates flavonoid content.
- FERR/G: This is FR divided by FG. FR is the fluorescence intensity after red light, and FG is the fluorescence intensity after green light. This ratio estimates anthocyanin content.
- Single Fluorescence Ratio (SFR): This is F735 divided by F685. F735 is the fluorescence intensity after blue light in the far-red zone, and F685 is the fluorescence intensity after blue light in the red zone. This ratio estimates surface chlorophyll concentration.
4. Charts with Average experiment results
In the charts, each point (x) represents the mean value, the line represents the median, and the margins of the box correspond to quartiles. The points illustrate the overall distribution of the values.
In next chapters we will go over subjective conclusions, examples which are important for us as microgreeners and may be implemented in microgreens farms.
How different colors of LED lamps influence microgreens- Table with results. Source: study of Lucia Jasenova. ⬇️
The effect of different light spectra on various parameters in all species and genotypes examined:
(A) Fresh weight (FW) of individual plants
(B) Total chlorophyll content in leaves
(C) Total carotenoid contents in leaves
(D) Fluorescence excitation ratio R/UV (FERR/UV) related to flavonoid content
(E) Fluorescence excitation ratio R/G (FERR/G) related to anthocyanin content
(F) Simple fluorescence ratio (SFR)
5. How do white, blue, and red lights affect microgreens' fresh weight?
Fresh weight indicator is crucial for us in the microgreens business because it determines how much we can harvest, price, and sell.
What we can read from charts, microgreens grown under white light yield the highest weight, followed by red light and then blue light.
Specific Examples from the experiment:
- Amaranth micorgreens grown under blue light weighs almost 5 times less than under white light (Blue: 0.510 g, Red: 1.450 g, White: 2.440 g).
- Radish Red Rambo microgreens grown under white light weighs more than twice as much compared to under blue light (White: 5.330 g, Blue: 2.430 g).
- Cress microherbs grows heaviest under white light and lightest under blue light. Red light is also good but not as impressive.(White: 3.0 g, Blue: 0.660, Red:1.830 g).
- Pak Choi microherbs grown under red and white LED lights has almost the same weight , while under blue light it gained less weight(White: 2.0 g, Blue: 1.300 g, Red: 1.990 g).
In summary:
- white LED light generally produces the heaviest microgreens, making it the best choice for maximizing yield and profitability.
- On the other hand blue LED light makes microgreens of “higher quality”, if we are speaking about nutritional benefits but slow down the growth.
- This information is valuable for optimizing growth conditions to achieve the best harvest and market value.
6. How do white, blue, and red LED lights affect microgreens concentration of flavonoids and anthocyanins?
Flavonoids and anthocyanins are natural compounds found in plants, including microgreens, that offer health benefits. Its concentration can be an important competitive advantage today and even more so in the future, especially as the microgreens market becomes increasingly saturated. Its concentration may be influenced by the color of the LED lamps under which they are grown.
6.1 What are Flavonoids and Anthocyanins and why are they important for human health and microgreeners?
Flavonoids:
- are a type of antioxidant commonly found in: fruits, vegetables, and herbs.
- They help protect plants from environmental stresses and are beneficial for human health.
- Flavonoids have anti-inflammatory and antioxidant properties, which may help reduce the risk of chronic diseases such as heart disease, cancer, and neurodegenerative disorders.
- They can also support immune function and promote overall health.
Anthocyanins:
- are a subgroup of flavonoids responsible for the red, purple, and blue colors in many fruits and vegetables.
- They act as powerful antioxidants, helping to protect cells from damage caused by free radicals.
- Anthocyanins have been associated with improved cardiovascular health, enhanced cognitive function, and anti-inflammatory effects.
- They may also contribute to better eye health and help regulate blood sugar levels.
In the context of microgreens, these compounds are concentrated forms of nutrients due to their young and tender nature. When microgreens are harvested early, they tend to have higher levels of flavonoids and anthocyanins compared to their mature counterparts. That is why they are so healthy.
The concentration of these substances is crucial for urban farming, especially when promoting healthy living and providing information to our customers who are very interested in this.
6.2. How LED lamp colors affect the concentration of flavonoids on microgreens-examples?
It is proven that light type, and color significantly affects the content of anthocyanins and flavonoids in microgreens. Previous studies showed an increase in phenolic content under blue LED lighting for Chinese cabbage and buckwheat sprouts.
Blue light has the most positive effect on flavonoid content.
What about growing under other colors? Plants grown under blue light have the highest flavonoid levels, followed by white light, and then red light.
Specific Examples from the experiment:
- Mizuna: Highest flavonoid concentration under blue light (1.370 g) compared to red (1.590 g) and white (1.580 g) light.
- Kale: Flavonoid concentration under red light (1.070 g), blue light (0.990 g), and white light (1.090 g).
- Amaranth: Flavonoid concentration under red light (1.080 g), blue light (0.960 g), and white light (1.020 g).
- Beet Red: Flavonoid concentration under red light (1.240 g), blue light (1.060 g), and white light (1.220 g).
- Cabbage Red microgreens has highest cointains of flavonids when grown under the white light. (Blue: 1,370 g, Red: 1,140g, White: 1,230 g).
Variations Among Species from the experiment:
- Most microgreens showed higher flavonoid levels under blue light compared to both: red or white light.
- In some species like lettuce, kale, and beets, white light with blue component was enough to match the flavonoid levels of blue light.
In conclusion, blue light generally enhances flavonoid content in microgreens more effectively than red or white light, although some species respond differently.
In our opinion the differences between white and blue light are not so big so the perfect match is to use white with blue addition LED lamps or white lamps, as they improve microgreens weight.
6.3. How LED lamp colors affect the concentration of anthocyanins on microgreens-examples?
Light quality affects anthocyanin content, similar to flavonoids, but with some unique responses. Blue light generally increases anthocyanin levels in green-leafed microgreens (the increase in anthocyanins under blue light is linked to blue light receptors in plants).
However the response of red-leafed species to light spectra varies more than green-leafed species.
Specific Examples from the experiment:
- Amaranth (red-leafed): Regarding anthocyanins in Amaranth, the concentration varies under different light conditions: under red light, it is 1.950 g, under blue light, it is 2.480 g, and under white light, it is 1.240 g.
- Other red-leafed species: Minimal effect of light spectra on anthocyanin content.
- Green-leafed species: Generally, blue light increases anthocyanin content, with exceptions like mustard, where blue light does not increase anthocyanins.
- Radish, onion, and broccoli: No significant response in anthocyanin content to different light spectra.
- Red-leafed species like mizuna and red basil did not show the expected increase in anthocyanins with blue light, which is unusual and requires further study.
In conclusion, blue light generally enhances anthocyanin content in green-leafed microgreens, but the response in red-leafed species varies and needs more investigation.
7.How LED lamp colors affect the concentration of microgreens colors, chlorophyll and carotenoids?
7.1 Chlorophyll contains in microgreens after using different LED lamps colors
The color of LED light significantly influences the concentration of chlorophyll and carotenoids in microgreens. Blue and white light tend to increase chlorophyll and carotenoid levels compared to red light. Blue light is particularly effective at enhancing the genes involved in chlorophyll synthesis, while red light can reduce the concentrations of chlorophyll precursors when used at high intensities.
Specific examples from the experiment:
- Mizuna microgreens showed similar chlorophyll levels under blue (0.800 g) and white light (0.800 g), slightly higher than under red light (0.780 g).
- Kale had the highest chlorophyll concentration under red light (0.590 g), with lower levels under blue light (0.430 g) and white light (0.570 g).
- Amaranth microgreens exhibited the highest chlorophyll concentration under white light (1.810 g), with lower concentrations under blue light (1.150 g) and red light (1.340 g).
- Beet Red microgreens showed consistent chlorophyll concentrations across all light types, slightly higher under white light (0.138 g) compared to blue (0.111 g) and red light (0.134 g).
- Cabbage Red microgreens has more or less same amount of chlorophyll when grown under the blue and white light. (Blue: 0,800 g, Red: 0,610 g, White: 0,850 g).
Photo with comparison of growing the same varieties under different light (Cabbage Red)⬇️
7.2. Carotenoids concentration in microgreens after using different LED lamps colors
Carotenoid content shows similar trends to chlorophyll. Blue light positively impacts carotenoid levels in microgreens, as seen in lettuce where blue light promotes carotenoid accumulation.
However, the effect can vary among different plants.
For instance, spinach did not show the same increase under blue light. Also, the faster growth under white and red light compared to blue light can lead to a dilution effect, where the biomass increases faster than pigment synthesis, reducing pigment concentration per unit of biomass.
Therefore, the choice of LED light color plays a crucial role in determining the concentration of chlorophyll and carotenoids in microgreens, with blue light generally providing the most significant.
Photo with comparison of growing the same varieties under different light (Amaranth and Mustard Red Giant)⬇️
8. Conclusion in points:
- The study clearly demonstrated that light spectra significantly affect the growth and pigment content in microgreens.
- The experiments, conducted with 21 genotypes under red, blue, and white LED lights, showed that white light generally resulted in higher fresh weight compared to monochromatic lights, particularly blue light.
- In general, white LEDs supported the best growth and had positive effects on most parameters across various species. This highlights the advantage of using broad-spectrum white LEDs over monochromatic LEDs.
- However, certain species showed a higher preference for blue light (e.g., basil genotypes, mizuna, and kale) or red light (e.g., mustard and pak choi).
- The study confirmed that manipulating light spectra can enhance both the quantity and quality of microgreens, particularly in terms of flavonoid and anthocyanin content. However, these responses are genotype-specific, indicating that the optimal light conditions should be tailored for each species.
- Most species benefited from blue and white light in terms of chlorophyll and carotene concentrations compared to red light.
- Blue light was especially effective in increasing flavonoid and anthocyanin levels, though it sometimes suppressed growth.
- In conclusion, while multispectral white LEDs positively influenced most quantitative and qualitative traits in microgreens, blue light improved quality but sometimes reduced growth.
- These findings underscore the importance of optimizing light conditions to enhance the production and nutritional value of microgreens.
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