This page will help growers understand the important roles that different wavelengths of light play in plant development, specifically red, far-red, blue, and green light. The current range of Telos Grow Lights have been specially designed to make full use of a light spectrum optimised for promoting the plants’ natural photosynthetic behaviours and even growth.
Telos have developed two spectra for their grow lights: one for indoor growing and one for growing in greenhouses. Both are full spectrum, meaning they emit all wavelengths of light in the 400-700nm PAR range. The indoor spectrum has been carefully balanced to drive photosynthesis while ensuring other pigments are not compromised. The greenhouse spectrum has been designed with more blue light than the indoor spectrum to off-set plant stretching which often occurs in greenhouses due to high levels of far-red light. If you are running a commercial facility and are interested in purchasing a light with our greenhouse spectrum, please contact us.
Many companies focus their spectrum on delivering the optimal light for photosynthesis. Traditionally this meant using light solely from the blue and red part of the spectrum, as studies showed that these are the wavelengths most absorbed by chlorophyll A and B and therefore are drivers of photosynthesis. Chlorophyll A is the main pigment involved in photosynthetic behaviour, while chlorophyll B assists in this process by collecting and transporting the energy absorbed from light used by chlorophyll A. However, chlorophyll A and B absorption is not the only factor in photosynthesis.
The McCree Curve illustrates the relationship between different regions of the light spectrum and their effectiveness in promoting a plant’s photosynthetic behaviours. This curve typically covers the wavelength range from 400 to 700nm, which corresponds to the visible light spectrum.
Many lighting companies misuse the McCree curve, viewing it as a blueprint for ideal spectral power distribution. This is not correct for a few reasons:
While little is known about the potential role green light plays in photomorphogenesis, there are other benefits to having green light in a grow light’s spectrum. Studies show that green light is efficient at penetrating through canopies, increasing photosynthesis beneath the canopy and increasing yields. Adding green light to grow light spectra will also increase the colour rendering index of the light, providing a more natural white light which will make it easier to inspect crops.
Photomorphogenesis is plant development that is triggered by light, such as seed germination, seedling development, and flowering in photoperiod crops— defined as plants whose developmental processes synchronise with a specific time of year and the different levels of light exposure associated with various times of year. This development is triggered by photoreceptors in the plant that respond to absorbing certain wavelengths of light. Typically, plants contain phytochromes, which are photoreceptors that respond to red and far-red light, and cryptochromes that respond to blue light.
Red and far-red light triggers many developmental processes in plants. Phytochromes are responsible for processes such as flowering in short- and long-day plants, stem elongation in response to shade, and the production of flavonoids such as anthocyanin (blue-purple plant pigment). There are two forms of phytochromes: red light absorbing, known as phytochrome red (Pr) and far-red light absorbing, known as phytochrome far-red (Pfr).
Pr converts into Pfr after absorbing red light and Pfr converts into Pr after absorbing far-red light. Red light is generally available to plants during the daytime, and far-red light is available in the shade and during the night, therefore plants use Pfr and Pr levels to determine when there are changes in the length of daylight and when they are in the shade.
Blue light is responsible for similar processes to red and far-red light. One of the differences is that cryptochromes (which absorb blue light) can inhibit stem elongation. This means that adding more blue light to a spectrum could be ideal for growers looking to offset the stretch that can be caused by far-red light (shade response). This often occurs in greenhouses where there is an abundance of far-red light. Blue light is also the trigger for phototropism where plants move and grow towards the light.
