Understanding the Light Spectrum
Light is made of up particles known as photons. When you turn on a light bulb it starts emitting photons which our eyes can detect. The color of light we see is determined by the wavelength of the photons being emitted. Photons with shorter wavelengths (450-490 nm) create blue light, while longer wavelengths (635-700 nm) result in red light. When we look at light with the human eye, we only perceive it as being one color. In reality, light it almost never made up of photons that are all the same wavelength and is typically a combination of many different wavelengths. The combination of wavelengths and the number of photons at each wavelength is known as light’s spectrum.
How A Light’s Spectrum Affects Plant Growth
Light is obviously a critical component in growing plants, but it’s about quality as much as it is quantity. Plants can only absorb and utilize certain spectrums of light. The spectrum of light that plants use is known as Photosynthetically Active Radiation (PAR) and includes wavelengths from 400-700 nm. So, the light produced that doesn’t fall within this range cannot be absorbed by the plants and utilized for growth. Additionally, different wavelengths of light can trigger different responses in the plant. For example, red light is effective for increasing the total size of a plant, but when used alone can result in “stretched” plants that are tall with thin leaves. That is why have a “full-spectrum” light that includes many different wavelengths of light is important.
Depending on the stage of growth your plant is in, increasing the number of certain colors of light can help your plant grow how you desire. For example, during the vegetative state increasing the amount of blue light can result in more compact, stockier plants which creates a more even canopy height and ensure plants receive equal amounts of light. Then during the flowering stage, adding more red light increases the growth rate of the plant and “stretches” it resulting in larger yields. This is because in nature the spectrum of light a plant receives indicates certain environmental conditions, like what season it is, and trigger responses in the plant.
Spectrum of LED Grow Lights
When LED grow lights were first introduced in the market, they only included produced light in the red and blue wavelengths which led to them being known as “smurf” lights. The focus on red and blue light came from the idea that the cells in plants absorbed these spectrums far better than they do green light. While this is true, more recent studies have shown that adding green light to an LED grow light actually increases crop yields compared to fixtures focused entirely on red and blue light. Researchers believe that because plant cells don’t absorb green light as easily, it is able to penetrate deeper into the canopy before being absorbed. This provides light to plant cells that were being blocked from receiving red/blue photons by cells higher in the canopy, thus allowing them to contribute to photosynthesis and increasing the plant’s total yield. They have also found that green light can result in a healthier plant structure.
The focus on red and blue light is one of the suspected reasons why earlier generations of LED grow lights struggled to match the production of traditional HID light using High-Pressure Sodium (HPS) lamps. Modern LED grow lights producing a white, full-spectrum light are now capable of matching and even exceeding the yields of crops cultivated under HPS grow lights. VOLT has worked to optimize the spectrum of our LED grow light fixtures to maximize both the yield and quality of crops.