Last updated on October 23rd, 2023 at 08:58 pm
At the moment, everyone is retooling: Well-known manufacturers are installing one after the other. We are talking about COBs, which is short for chip on board. Several light-emitting diodes are mounted together on a ceramic field or other carrier and can thus be connected together.
The advantages are lower production costs, better heat dissipation, and less space consumption. These new COBs mostly shine in a white light that is very pleasing to the human eye, with only a few still shining in the familiar violet hue.
And here we come to a hotly debated topic: is an LED grow lamp that covers all spectrums of light and thus shines white, or an LED plant lamp that omits green and yellow light and thus shines mainly in the blue and red spectral range best suited for plant cultivation?
Here the opinions differ and we would like to present you the arguments of both sides.
The green gap
Surely you are familiar with the violet LED plant light. The light spectrum of the diodes installed in them usually corresponds to the results of the absorption curve, green and yellow light is completely omitted. However, the action spectrum, which is determined on the basis of the photosynthesis rate, shows that photosynthesis does not come to a standstill even in the green wavelength range from 500 to 600 nm, but only decreases. This means: plants can utilize green light and there is at least no green gap.
Difference between absorption rate and photosynthesis rate
Why the absorption rate and the photosynthesis rate are so far apart here is not quite clear. It seems carotenoids and other, partly still unknown photopigments are responsible. Also, the reflected green light hits lower-lying leaves and is partially absorbed there again and reflected further, even further down. So the difference between the two curves may also be due to only a superficial measurement. Finally, the green light penetrates deeper into the leaf surface and reaches photoreceptors on the underside of the leaf that are not reached by other light.
Research results confirm the effect of green light
This was already presented in 2009 in the journal Plant and Cell Physiologe. The main issue here is how the light is distributed in the plant leaf. Researchers found through experiments on sunflowers that when irradiated with white light, increasing the green component provided better photosynthetic performance than increasing the red component.
Researchers at Michigan State University grew plants under specific wavelengths in 2014 to observe their effect on plant growth. Again, green light was not useless, and when combined with red light, can even rival blue.
In production, blue LEDs are cheaper than green ones, and they also consume much less power, so blue LEDs continue to be installed in LED plant lamps.
Just a waste of energy?
The other party also has arguments. After all, a clear drop in the photosynthesis rate between 500 and 600 nm wavelength can also be seen in the action spectrum curve. Thus, it can be argued that only minimal green light can be useful, but a clear focus should be placed on blue and red light. At the most, white light is useful in cultivation and for seedlings, according to the manufacturer Platinum. In the following growth phases, the emphasis should be placed first on blue light and finally on red light during flowering. The green and yellow light only wasted energy. Here, the classic LED plant lamp with its different modes for the growth and flowering phases is pitted against the new white lamps.
The above-mentioned result of the researchers does not give clear information, because in the first experiment the green light was used in addition to white light. However, it indicates a benefit of green light. In the second experiment, it performed just as well as the blue light, but the power consumption of green LEDs is still significantly higher than that of blue LEDs.
Only the continued experimentation of researchers and users will show what works best for plants. At least for now, new models with COB technology are constantly being released. Personally, I find the white light simply more pleasing to the eyes, plus it allows for a clear, unobstructed view of the plant.
In the reports on our LED plant lamp test, the light spectrum of the grow lamps was also measured and shown in a spectral curve. This makes it easy to see what the focus of each lamp is.