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The Benefits of Using Blue LED Lighting at the End of Production Cycles

LED Grow Light Pigmentation
Recent research demonstrates of using blue LED lights at the end of the production cycle for lettuce.

While indoor farming offers distinct benefits when compared to outdoor agricultural production, certain plants do not develop sufficient pigments to provide the plants the colors consumers expect. New research finds using red-blue LED lighting at the end of the production cycle overcomes this obstacle.  

Even economists who monitor agricultural markets now recognize the advantages of greenhouse and indoor hydroponic crop production. Many of these benefits stem from the ability to control growing conditions, such as the quality, quantity, and duration of light exposure, temperature, carbon dioxide and relative humidity levels, and the amount of water and nutrients provided to the plants. Until recently, greenhouse growers who relied on ambient sunlight for illumination faced a significant challenge – the glazing on the glass and the structure of their grow facilities blocked as much as 50 percent of photosynthetic producing light. As a result, certain types of produce, such as red leaf lettuce, do not develop pigments that give the vegetables the characteristic color consumers expect. Fortunately, horticulturalists working at Purdue University recently published their research findings that provide a solution – exposing plants to blue and red LED lights at the end of the production cycle spurs the synthesis of the pigments that give plants the color consumers demand.

The Benefits of LED Lighting as a Sole Source of Illumination

The scientists based their research on previous studies demonstrating the advantages of using red-blue LED grow lights as the sole lighting source in indoor farming environments. Some examples of the benefits include the following:

  • Plants contain higher levels of chlorophyll, which allows the plants to capture more energy for photosynthesis
  • The plants grown using LED lighting produced more phenols, flavonoids, and antioxidants than those grown using other light sources.
  • Plants produced using LED grow lights have better leaf structure and greater size when compared to plants grown using other types of illumination.

What effects did using different spectrums of LED lighting at the end of the production cycle have on plants?

Exposure to LED Lighting Improves Plant Color

The research team at Purdue compared the levels of the pigment anthocyanin, which gives plants a reddish hue, in red leaf lettuce grown with different end of production lighting sources. The five different lighting conditions included the following:

  • A control condition with no supplemental lighting at the end of the production cycle.
  • High-Pressure Sodium (HPS) lighting used as a supplemental lighting source applied at the end of the growth cycle.
  • An experimental group using only monochromatic red LED grow lights at the end of production
  • An experimental group using only monochromatic blue LED lighting
  • A group of plants exposed to a combination of red and blue LED grow lights

The picture below illustrates the color differences in the red leaf lettuce varietals grown in each of the lighting conditions.

Growth study - LEDs


The findings of this study are as follows:

  • Plants exposed to LED lighting for as few as three days at the end of the production cycle had deeper red leaves than those not exposed to LED lights.
  • The maximum improvement in leaf color occurred seven days earlier in plants exposed to a 50:50 mix of red and blue LED lights throughout the growth cycle.
  • Monochromatic blue lights increased anthocyanin seven days sooner than plants in the monochromatic red condition, which emphasizes the importance of light in the blue area of the spectrum for the production of this pigment.

If you are considering making a switch to LED grow lights, this research demonstrates a way to make the transition incrementally if you are not in a place to equip your entire indoor grow operation at one time.

Do you want to know the LED light mix that is best for your crops? Our LED light experts are available for free consultations. Call or email your questions to our team today!



N.A. (2010).  Anthocyanins. Phytochemicals.

N.A. (2014). The Light Fantastic. The Economist.

Owen, W.G. & R.G. Lopez.(2015). End-of-production Supplemental Lighting with Red and Blue Light-emitting Diodes (LEDs) Influences Red Pigmentation of Four Lettuce Varieties. Horticultural Science, 50 (5): 676-684.  


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