WHY FULL SPECTRUM?

Update time : 2021-08-31 08:59:00

When most people think about LEDs being used for horticulture lighting, the first thing that comes to mind is a purple glow being emitted from a fixture consisting of red and blue diodes. This purple glow may be the industry standard for horticulture LEDs, but have you ever wondered why red and blue diodes have historically been the semiconductors of choice by lighting manufacturers? Many manufacturers reference the absorption spectrum of chlorophyll a and b (which peaks in the blue and red regions of the electromagnetic spectrum) as the main reason for providing a purple spectrum (Figure 1).

The absorption spectrum of Chlorophyll a and b measured in vitro.

Figure 1

At first glance, this seems legitimate since chlorophyll drives photosynthesis after all, but have you considered how the absorption spectrum of chlorophyll is measured? Additionally, have you considered if the absorption spectrum of chlorophyll directly correlates to photosynthesis and plant growth, and what happens if you only target a sole pigment and neglect other pigments responsible for plant growth and development? This article will discuss the differences between absorption spectrum and action spectrum, and (spoiler alert) dispel the myth that “plants don’t utilize green light” to promote plant growth and development.

ACTION SPECTRUM

The action spectrum of photosynthesis was created from research that was performed in the 1970s by Drs. McCree and Inada and this work was fundamental in defining the range of photosynthetically active radiation (PAR). Prior to this research, very little work had been performed to determine how varying wavelengths of light influenced photosynthesis and plant growth. These researchers utilized filters to create monochromatic wavebands to determine the influence of light spectra on photosynthesis of single leaves using an assimilation chamber. If you see figure 2, you will notice that plants do in fact utilize green light for photosynthesis, quite efficiently in fact (figure 2).

Figure 2

Figure 2. The action spectrum of photosynthesis as determined by Drs.
McCree and Inada.

So why is there such a difference between the absorption spectrum and the action spectrum if chlorophyll is responsible for photosynthesis? The answer is simple: Chlorophylls are not the only photoreceptors that are responsible for photosynthesis. There are other types of antenna photoreceptors (mainly carotenoids) which also promote photosynthesis, and by utilizing narrow band red/blue LEDs in sole-source lighting conditions these pigments are not able to optimize their light harvesting cap abilities. Also, it should be noted that green light does in fact promote photosynthesis in chlorophylls, quite efficiently in fact. Recent work has shown that green light is able to penetrate deeper into leaf surfaces to drive photosynthesis in chloroplast located towards the bottom surface of the leaf, in fact, more efficiently than red light at high PPFD. As PPFD increases, light energy that is absorbed in the upper chloroplasts tends to be dissipated as heat, while penetrating green light increases photosynthesis by exciting chloroplasts located deep in the mesophyll (Terashima et. al., 2009). Additionally, green light penetrates through leaf surfaces much better than red or blue light to reach the lower canopy, which is extremely important in dense canopy production techniques which are common in controlled environment agriculture.

CONCLUSION

So, what does this all mean for the grower? While we are still in the early-stages of understanding how plants use light and we are still working to understand how different photoreceptors function and interact with one another, the bottom line is that plants absolutely do utilize green light. If your horticulture lighting system is delivering a spectrum which neglects photoreceptors that absorb light in the 500-600 nm region (especially in sole-source lighting applications) you will not be optimizing your growing environment.

Previous : 5 COMMON MISCONCEPTIONS

Next : What Is PAR, PPF And PPFD?

Why 3-Channel Spectrum Works Best for High-Value Medicinal Crops？

Apr .15.2026

Many growers mistake dimming for "light recipe" control. In 2026, true control means independent spectrum management. Using the Hortibest OG8 Tri-channel led grow light as a case study, we explore how separating Blue(450nm) ,Deep Red (660nm) and White+FR (380-730nm) Full Spectrum channels directly impacts yield, terpene profiles, and plant morphology.

How to increase basil yield in greenhouse

Apr .08.2026

Basil is an essential crop for the food service industry and essential oil production. While its market price remains stable, it has a high barrier to entry—it is extremely demanding in terms of light spectrum and intensity. If even one step is mishandled, it can quickly turn from a “high-profit crop” into a “money-losing venture.”

Day-by-Day Watering Schedule for Seedlings (First 30 Days & Beyond)

Apr .02.2026

Overwatering plants is the mistake that beginner plants growers make. No more! Follow this easy plants seedling watering schedule for happy plants seedlings that quickly grow into thriving plants.

Preparing for the 420 Season: Why Inter-Lighting Is the Yield Key for High-Value Crops？

Mar .27.2026

Commercial greenhouse growers are gearing up for one of the most demanding production cycles of the year. For those cultivating high-value flowering crops, achieving consistent quality and maximizing yield requires more than just standard overhead lighting. The key lies in strategic inter-lighting—placing light sources directly within the plant canopy to reach the lower branches that overhead lights often miss.

Visit us

2817 N. Classen Blvd, Oklahoma City, OK 73106

Call us

405-493-9315

sales@hortibest.com

Info sales

Leave a message

Language / Currency

Language

Currency

WHY FULL SPECTRUM?