Vertical farm research shows increased nutrient density with amber LED exposure

The impact of amber LEDs (light emitting diodes) on Brassica microgreens highlights the potential for year-round nutrient-dense vertical greenhouse growth in food security-challenged areas. 

“By increasing amber-blue LED lights while decreasing red, microgreens showed increased production of antioxidants, particularly the carotenoid nutrient,” said Dr. Xiuming Hao, Agriculture and Agri-Food Canada (AAFC) research scientist.

Why it matters: Increasing the nutrient value of crops by altering light could make for healthier food and potential for higher-value crops for farmers.

Carotenoid is a nutrient responsible for plant-based Vitamin A production and antioxidants crucial in age-related macular degeneration reduction.

The two-year AAFC study looked at several combinations and ratios of amber-blue and red LED (abrLED) and how they affected the yield, quality and antioxidant levels in eight types of Brassica plants in a vertical greenhouse production setting.

The results showed abrLED activated genes responsible for carotenoid antioxidant production in the eight (mostly cabbage) varieties of Brassica microgreens.

Hao said there were significant increases in the collective and individual carotenoid production, from 20 to 44 per cent and 10 to 55 per cent, respectively.

Hao, who works out of the Harrow Research and Development Centre (HRDC), specializes in sustainable greenhouse and indoor crop production systems and is optimistic abrLED research will open opportunities for affordable, accessible and nutrient-dense crops within a sustainable vertical greenhouse system.

“This discovery shows that there is great potential for LED lights to improve the nutritional quality of plants and therefore, increase options for growers, consumers and northern communities that depend on indoor food production systems,” Hao said.

Research is ongoing to optimize the environment, light, temperature, humidity and nutrition of vertical greenhouse operations to increase yield and quality while lowering energy, fertilizer and water.

The research involved fellow AAFC research scientists Dr. Rong Cao, a phytochemical antioxidant specialist, and technicians from the Guelph Research and Development Centre, Massimo F. Marcone, with University of Guelph’s Department of Food Science, Hao, the team and the greenhouse workers at Harrow.

Hao said the lab analysis from the study is complete, but researchers will continue to investigate more energy-efficient lighting software for vertical indoor production.

“We (are trying) to find a way also to improve the lighting efficiency, the energy efficiency to reduce the cost for the farmer.”

Hao said remote or northern communities often have leafy green or microgreen accessibility challenges due to short growing seasons, unproductive land or lack of sufficient sunlight.

Indoor production systems that use artificial light could provide affordable, sustainable and consistent access to nutrient-dense leafy greens or microgreens loaded with antioxidants to improve overall health, he said.

“This kind of research can expand easily to leafy greens like arugula, spinach and lettuce. Then the next step is you could get into the fruit vegetable, which is a little more challenging, like peppers or tomato, because they are bigger.”

However, until dwarf varieties of strawberries, tomatoes and peppers are developed to grow efficiently and quickly in a multi-layer system using artificial light, the development will likely stall at the leafy green level. Hao is optimistic these varieties will be available within the next five to 10 years as researchers and producers invest more time and finances in vertical greenhouse production to address food insecurity and affordability within Canada.

“We will be there in the five-to-10-year time frame of seeing feasible year-round vertical farming,” he said.