Hi,
That is not really an accurate statement. The peaks you refer to are simply individual frequencies that have the highest energy compared to the other frequencies across the bulbs output spectrum. This may produce what we perceive as the bulb's characteristic "color" but in reality the bulb emits energy in most or all of the other wavelengths. If you were to compare the energy of those peaks with the total energy of all wavelengths it would be a small ratio. It is the area under the curve that determines to total energy output of the bulb.

Based on the spectral quality of the light plants will produce various pigments to adapt to the conditions with very little loss of efficiency. This may be expressed as hue or color changes but other than that I don't believe there are any other differences in growth rates or other physiological differences as a function of frequency. Any differences are more likely to occur as a result of differences in CO2/nutrient availability or due to light intensity.

I've grown the same plants under different bulb types and have not observed any significant differences.

These examples aren't scientific by any means but more illustrative. The first image is L. aromatica grown under T5 Daylight + Interpet Triplus. The second image shows clippings from the first grown under Daylight + Osram 840 which is an orangy bulb found in office buildings. Other than minor color differences I saw no difference in form, such as internodal distances or leaf aspect ratio etc., or in growth rates. In fact, in both cases, for this plant internodal distances varied more significantly as the distance from the light increased. From a practical standpoint therefore you can simply get the bulb colors you find makes the plant most attractive.



Cheers,