The Emerson Effect: Unlocking Maximum Photosynthesis with Far-Red Light

For decades, commercial growers have focused entirely on Photosynthetically Active Radiation (PAR)—the visible light spectrum spanning from 400nm to 700nm. While optimizing PAR is critical for plant growth, modern LED technology has unlocked access to a biological phenomenon that pushes photosynthetic efficiency beyond standard limits: The Emerson Effect.

By stepping just outside the traditional PAR range and introducing Far-Red light (700nm–750nm) in combination with deep red light, cultivators can trick their crops into a state of hyper-efficient energy production. Here is a breakdown of the science behind the Emerson Effect and how you can leverage it to increase biomass and maximize yields in your facility.

What is the Emerson Effect?

In 1957, scientist Robert Emerson made a groundbreaking discovery regarding how plants process light. He observed the rate of photosynthesis in plants exposed to different wavelengths of light.

• When plants were exposed only to Deep Red light (680nm), photosynthesis occurred at a baseline rate.
• When exposed only to Far-Red light (700nm+), the rate of photosynthesis was extremely low.
• The Breakthrough: When plants were exposed to both wavelengths simultaneously, the rate of photosynthesis was significantly higher than the sum of the two individual rates.

The Science: Photosystem I and Photosystem II

To understand why this happens, we have to look at the protein complexes inside the chloroplasts of the plant, known as Photosystems.

Under standard grow lights that lack Far-Red spectrums, Photosystem II works overtime, but Photosystem I creates a bottleneck. When you supplement your lighting with Far-Red (700nm–750nm), you provide the exact energy Photosystem I needs. This removes the bottleneck, allowing the two systems to work in perfect, rapid harmony, drastically increasing carbon assimilation and overall growth rates.

Applying the Emerson Effect in Commercial Cultivation

Integrating the Emerson Effect into your lighting strategy is not just about growing faster; it is about steering crop morphology and maximizing the efficiency of your facility.

1. Increased Biomass and Yield: By optimizing the electron transport chain between PSI and PSII, plants can convert CO2 and water into sugars at a much higher rate, leading to denser, heavier flowers and accelerated vegetative growth.
2. Enhanced Canopy Penetration: Far-Red light has a longer wavelength, allowing it to penetrate deeper into the plant canopy than blue or green light. This stimulates photosynthesis in the lower leaves that typically get shaded out, increasing your overall usable yield.
3. The "Sleep" Trigger: In nature, as the sun sets, the ratio of Red to Far-Red light drops significantly. Blasting your plants with pure Far-Red light for 10-15 minutes at the end of your photoperiod rapidly converts phytochrome proteins (Pr/Pfr), signaling to the plant that it is night. This puts the plant to sleep faster, accelerating the onset of the flowering cycle and potentially shaving days off your harvest time.

Light Spectrum Impact Comparison

Here is a quick reference guide on how different spectrums interact with plant biology when optimizing for the Emerson Effect:

Upgrade Your Yields with Precision Lighting

The days of measuring grow lights solely by standard PAR are ending. To stay competitive in commercial indoor agriculture, utilizing the full extended spectrum (ePAR) to trigger physiological advantages like the Emerson Effect is a necessity.