The Emerson enhancement effect and photosynthetic lighting
While it’s commonly known that there are a wide range of wavelengths absorbed and used by plants for photosynthesis, the enhancement effects of certain bands of the spectrum are more complex but still important to consider for indoor growers wanting to maximize photosynthetic growth effects from their lighting. Some of the shorter light wavelengths—when combined with longer wavelengths—act to boost photosynthesis more effectively than if either of the wavelengths was present alone. This is termed the ‘Emerson enhancement effect’ and it is an important aspect to take into consideration when deciding between different types and outputs of lamps and bulbs. This enhancement effect means there is a synergy between red and far red wavelengths and therefore a benefit to providing plants with both—even if the plants are not flowering.
Figure three below shows how the Emerson enhancement effect works—up at the 700 nm range, it appears as if photosynthesis drops off (this is called the ‘red drop off’), so it might appear that there is no point in providing plants with light in this waveband. However, when wavelengths in this far red range are combined with the shorter wavelengths of red light (680 nm), a photosynthetic enhancement effect occurs. This is why we have begun to see more lighting bulbs developed featuring output in this far red range, allowing indoor plants to take advantage of a fuller spectrum in the same way that outdoor plants have always been able to do.
Figure 3: The Emerson enhancement effect
Maximizing the photosynthetic potential indoors
Maximizing photosynthesis in an indoor garden is dependent on a number of factors: the correct wavelength spectrum (as explained earlier, these days that means full-spectrum lamp outputs), sufficient intensity of light for the stage of plant development, CO2 replacement or enrichment to levels over 1,000 ppm, sufficient warmth to maximize the rate of photosynthesis, good rates of water uptake and cell turgor, overall plant health and sufficient nutrition. Providing all these factors will allow plants to take full advantage of those cellular reactions which provide both energy and assimilate for maximum growth and development.
