Photosynthesis, Maximized
Photosystems 1 and 2, and the Emerson Enhancement Effect
Net Effect
Photosystem II
Photosystem I
Absorption / Activity
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 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
300
400
500
600
700
800
Wavelength (nm)
Figure 3: The Emerson enhancement effect
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.
Maximizing the
photosynthetic
potential
indoors
Maximizing photosynthesis in an indoor garden is dependent on a number
of factors: the correct wavelength spec-
trum (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. MY
References
Hashimoto, T., 1994, “Requirements of
Blue, UV-A, and UV-B Light for Normal
Growth of Higher Plants, as Assessed by
Action Spectra for Growth and Related
Phenomena”, International Lighting in
Controlled Environments Workshop, T.W.
Tibbits, Editor.
Kim, H. H., Goins, G. D., Wheeler, R. M.
and Sager, J.C., 2004, “Green Light Supplementation Enhances Lettuce Growth
under Red and Blue Light Emitting Diodes”, HortScience, Volume 39, pages 1617
through 1622.
Kim H. H., Goins, G. G., Kagie, H. R,
Wheeler, R. M. and Sager, J. C., 2001,
“Improving Spinach, Radish and Lettuce
Growth under Red Light Emitting Diodes (LEDs) with Blue Light Supplementation”, HortScience, Volume 38, pages 380
through 383.
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Maximum Yield USA | March 2012