Light Spectrum: A look at what wavelengths are most utilized.
Each unit of light has a different wavelengths. As humans, our eyes interpret these varying wavelengths as different colors of light. An important concept when talking about the light spectrum is this. If a plant is green it'll reflect large amounts of green light. If a plant is red it'll reflect large amounts of red light. The other spectrums of light will be absorbed at a higher rate compared to the color of the plant. This is why as light intensity increases, plants will often turn bright red to protect against heavy red and blue light and intense par output.
Plant species reflect different spectrums depending on the leaf coloration. This is one of the reasons a full spectrum of light is important for plant health and growth. This allows them to utilize a wide range of light spectrums at varying rates. Most plants are green, meaning they'll reflect a large percentage of the green light that they are exposed to. Other spectrums such as red and blue wavelengths will be absorbed at a higher rate.
An experiment was done by isolating various photosynthetic pigments such as chlorophyll A, and chlorophyll B for the most part, though others were measured. First, we will explain what was learned from this. It was found that Chlorophyll A developed a massive spike in photosynthesis at around the 650 nm wavelength, this equates to bright, deep red color.
There was another slightly smaller but wider spike in the 400 to 430 nm range. This equates to the color violet and blue for light spectrums. Now for chlorophyll B and where it has photosynthesis spikes. The largest spike for chlorophyll B starts rising in the 400 nm range and then around 470 nm it maxes out and spikes significantly. 400 nm is the end of the visible light spectrum and it would appear a dark violet color. While 470 nm appears to be a bright blue and almost blue-green spectrum. Then a significantly smaller spike is seen around the 590 to 640 nm range. These wavelengths equate to white, yellow, and orange light. Since chlorophyll A and B are responsible for the majority of photosynthesis in plants, we can reasonably say that the violet and blue colors of the 400 to 470 nm range are one of the spectrums that create the highest rate of photosynthesis in plants.
To add to that, the red and orange color at the 590 to 640 nm range has a similarly high rate of photosynthesis in these two types of chlorophyll. Though some of the green light is reflected, it is still very important to photosynthesis for many reasons. Shorter wavelengths like violet, blue, and green store more energy and as a result penetrate deeper into the plant tissue, which results in more photosynthetic cells being stimulated. On the other end of the spectrum, long wavelength light like white, yellow, orange, and red carry far less energy. The result is even though the red spectrum stimulates the highest rate of photosynthesis for both chlorophyll A and B, its shorter wavelength can only penetrate the plant’s tissue so deep and will stimulate fewer photosynthetic cells than blue or green spectrum light.
Though red and blue spectrums trigger the highest rate of photosynthesis within chlorophyll A and B cells, the other light spectrums are still important. In part for aquarium aesthetics, having a pink aquarium isn't the best way to showcase your aquatic plants. By adding large amounts of white light you both increase the PAR output and allow better color rendition for the plants you are growing. Having a full spectrum of light is also very important for the health of the plants. Without the blue spectrum, you'd be missing out on photosynthetic cells deeper in plant tissue, and without the red spectrum the upper layer of photosynthetic cells will be significantly less dense since red spectrum light accumulates in the upper layers for the leaf and blue spectrum light has more energy and will stimulate deeper photosynthetic cells.
To get the best color rendition and health for your aquarium plants, choose a full spectrum light with a good balance of white, red, and blue.
Written by Jacob Thompson
Imagery by AquaticMotiv Llc