The following section highlights several peer-reviewed research papers on microgreens lighting. This is a chance to see the variation of lighting that is used in microgreens research as well as a chance to practice recognizing the lighting terms we introduced in this blog series.

Effect of Low Light Intensity With Supplemental Far‐Red Light on Growth, Yield and Quality of Broccoli Microgreens (Link to Article)

Abstract

One of the main obstacles to indoor agriculture is the high expense of lighting energy. The purpose of this study was to investigate how to grow broccoli microgreens under low light with higher yield and better quality. Broccoli seedlings were exposed to different photosynthetic photon flux densities (PPFD) ranging from 50 to 150μmol/m2 s, along with supplemental far-red (FR) light (20% of total photon flux density (TPFD)) at 50 and 75μmol/m2 s. Broccoli grown under 50, 75, and 100μmol/m2 s exhibited the highest fresh weight. As light intensity decreased, the hypocotyl length of broccoli microgreens increased. High chlorophyll, carotenoid, and anthocyanin contents were observed at 100 and 150μmol/m2 s, while ascorbic acid and total phenolics were higher at 50 and 75μmol/m2 s. The addition of FR light resulted in increased plant height, fresh weight, and antioxidant concentration. However, there was a significant decrease in total phenolic content. These results indicate that broccoli microgreen can adapt to low light with high yield and quality. Addition of FR under low light can further increase microgreen yield and plant height. Furthermore, post-harvest quality and shelf-life of microgreens under 50 and 75μmol/m2 s were better than those under 100 and 150μmol/m2 s. This research provides the platform for further managing microgreen growth under low light to reduce energy consumption for controlled environment agriculture (CEA)

The impact of light heterogeneity in controlled environment agriculture on biomass of microgreens (Link to Article)

(AI-generated Summary)

This study looked at how different types and amounts of light affect how well microgreens grow in a vertical farm. Instead of setting up a controlled experiment, the researchers used the natural variation in lighting already present in the farm. This allowed them to test many light conditions at once without needing extra space or equipment.

The team grew kale, radish, and sunflower microgreens in 256 different spots in the farm. Each tray was divided into small sections, and each spot got slightly different light. They measured the light intensity (PAR) and light quality (amounts of red, blue, and far-red light) at each spot before planting.

Plants were grown on Growfelt wool mats using an aeroponic system. The radish was harvested after 5 days, and kale and sunflower were harvested after 7 days. After harvesting, the fresh biomass was weighed to see how well each plant grew under different light conditions.

The experiment was done at the Grow It York vertical farm in central York. The farm used Vertically Urban LED lights above each of four stacked growing beds. Each bed had four trays, and each tray had 16 growing spots used in the study. Due to space constraints, the lights weren’t evenly placed—two were at the front and one at the back—causing uneven light levels across the trays. This unevenness created the perfect setting to study how different light zones affect plant growth.

The results showed that light quality was more important than just total light intensity. Blue light helped growth, while too much red light often led to lower yields. The ratio of red to far-red light (R:FR) was especially important—but different crops reacted differently. For example, a high R:FR ratio was good for radish but not for kale.

Each microgreen variety responded in its own way to light, so the study confirmed that there’s no one-size-fits-all light recipe. The findings suggest that small vertical farms can use the natural differences in their lighting to learn what works best—without needing complicated or expensive experiments.

This approach could help farmers boost yields, lower energy use, and grow more consistent crops, especially in tight spaces like shipping containers or indoor urban farms.

Effect of different times of exposure to LED treatment on microgreens of arugula and radish (Link to Article)

(AI-Generated Summary)

This study explored how different daily light exposure times (photoperiods) using white LED lights influenced the growth and nutritional quality of arugula (Eruca sativa) and radish (Raphanus sativus) microgreens. The goal was to find the ideal light duration and harvest timing to increase health-promoting compounds like chlorophyll, flavonoids, and anthocyanins.

Researchers used arugula cv. “Surya” and radish cv. “Indra” seeds. The microgreens were grown in small plastic containers filled with commercial substrate. Seeds were first kept in the dark for 2 days to improve germination. After that, they were exposed to white LED lighting for 10, 12, 14, 16, or 18 hours per day, with total growth lasting 7 days. The growth chamber was lined with reflective foil and kept at 25°C with 60–70% humidity. The team measured a range of factors, including chlorophyll, carotenoids, flavonoids, anthocyanins, moisture, pH, acidity, ash content, and plant height.

Chlorophyll a and b, important for photosynthesis and green color, increased naturally as the plants developed but actually decreased when exposed to longer light periods. The highest chlorophyll levels were found with 16 hours of light on the 6th day after planting. Carotenoids, another type of pigment, also dropped off as light hours increased, but they built up steadily over the week, especially at 12–16 hours of light by day 7.

In terms of flavonoids, which have antioxidant benefits, radish plants responded positively to both longer light exposure and later harvests—levels were highest with 16–18 hours of light. Arugula, on the other hand, peaked at 12 hours of light on day 7. Anthocyanin levels varied by crop. In radish, they dropped off with more light, while in arugula, they increased with longer photoperiods. Optimal anthocyanin levels for both species were seen at 14–16 hours of light on day 6 or 7.

Other physical traits like moisture, pH, acidity, and ash content were mostly unaffected by lighting. Plant height in both crops was shorter than the typical commercial standard, likely because only basic white LED lighting was used instead of full-spectrum or red-blue light recipes.

In conclusion, the study recommends using 16 hours of LED light per day, with a harvest on day 6 after planting, to maximize nutritional value in arugula and radish microgreens. This setup provided the best balance of high pigment content and efficient growth, making it a practical and energy-conscious choice for both home growers and vertical farms.

Harvest time, photoperiod and white light irradiance on yield of red cabbage microgreens in plant factory (Link to Article)

(AI-Generated Summary)

This study focused on how different light conditions affect the growth and yield of red cabbage microgreens in a controlled indoor environment, also known as a plant factory. The researchers tested three key factors: how long the lights were on each day (photoperiods of 12, 16, or 20 hours), how strong the light was (irradiance levels of 150, 250, 350, or 450 μmol m²/s), and when to harvest (after 4 or 6 days of light exposure).

The microgreens were grown under white LED lights, which had a broad light spectrum—a mix of blue (25%), green (24%), yellow/orange (21%), red (27%), and a small amount of far-red (2%). These lights were used because they’re affordable and offer a balanced light recipe that supports healthy plant growth.

Results showed that early harvest (4 days) led to shorter plants, smaller cotyledon areas (leaf size), and lower yields compared to harvesting at 6 days. However, harvesting early allows more production cycles per year—up to 91 vs. 60—and therefore can lead to 26–27% higher annual yields even if individual crops are smaller.

Longer daily light exposure (especially 20 hours) helped increase cotyledon size and total yield, though it slightly reduced stem length (hypocotyl). Higher light intensity (up to 315 μmol m²/s) also improved growth and yield but began to reduce stem length at the very highest level tested (450 μmol m²/s).

The best yield (8.2 kg per m²) was reached with 20 hours of light and 315 μmol m²/s, and no visual or physiological damage was seen under these intense conditions. Plant quality stayed high across all treatments, with no stress detected in the plants’ photosystems.

In conclusion, while longer photoperiods and higher light intensity improve growth and yield, growers must balance energy use and cycle length. A shorter 4-day cycle with moderate lighting may be more efficient for maximizing total yearly production, even if each individual harvest is slightly smaller.

More to come!!