At Fractal AG we know that blue light can benefit the nutritional levels and coloring of the plant. We also understand that higher red and far-red ratios can help with leaf development and flowering. It’s why we developed the Fractal Savior. Because, by selecting the right quantities and types of red and blue chips and through our 6 channel tuning, our technology can impact chlorophyll pigments through the absorbtion of the light they need. Cannabis growers need to also consider the impact of UVB/blue spectrums for its various structural and THC-potency benefits. Therefore, far-red and red light is relatively more important to boost their yields. Other indoor growers are also experimenting with the controlled use of far-red spectrum, like salad leaf farmers for example. Plants associate this spectrum with shading from direct sunlight, which would happen lower down the canopy, causing leaf & stem stretching as the plant reaches out for sunlight.
Strategically, bigger leaves and flowering can occur without unnecessary stress to your crop. So, while there is no one specific light spectrum for any particular plant, the ratio of red to blue light is very important to maximize growth and the rate of photosynthesis.
Grow light spectrum refers to the electromagnetic wavelengths of light produced by a light source to promote plant growth. For the majority of the photosynthesis phase, plants use light in within the PAR (photosynthetic active radiation) wavelengths (400nm-700nm) humans only detect the visible light spectrum (wavelengths in the range of 380-740nm), on the other hand, plants detect and benefit from wavelengths beyond visable light spectrums including UV and Far Red spectrums
Typically, chlorophyll, the molecule in plants responsible for converting light energy into chemical energy, absorbs most light in the blue and red light spectrums for photosynthesis. Both red and blue light are found in the peaks of the PAR range. There are also advantages to the photosynthesis process outside the ranges of the PAR spectrums which has gone into the development of the Fractal Savior.
Every crop type is sensitive to different spectrums and quantities of light at different times throughout the day. This has a direct affect on the rate of photosynthesis and how much energy is needed and when light spectrums trigger growth phases in plants. Meaning, blue light spectrums will encourage vegetative and structural growth while red light promotes flowering, leaf growth, and stem elongation. .
We know that controlling light spectrums can have a significant impact on areas of a plants development like, growth, flowering, flavor, color, size and so on. However, it’s important to recognize that signaling specific growth factors is part of a much larger, complex cycle. Light intensity and efficacy, and photoperiod etc. Results also vary depending on the environment, the relative temperature/humidity, species types,
UV light spectrum, which is not visible to the human eye, is outside the PAR range (100nm-400nm). Around 10% of the sun’s light is ultraviolet, and like humans, plants can be harmed from overexposure to UV light. There are 3 catagories of UV, UV-A (315-400 nm), UV-B (280-315 nm), and UV-C (100-280 nm). While the benefits of ultraviolet light use in horticulture are still being researched, UV light is often associated with darker, purple coloring – in fact, small amounts can have beneficial effects on color, nutritional value, taste, and aroma.
Research shows environmental stress, fungus, and pests can also be reduced using controlled amounts of UV. Research has emerged that suggests an increase in cannabinoids like THC in Cannabis can be achieved using UV-B light (280nm – 315nm).
Blue light spectrum is widely responsible for increasing plant quality – especially in leafy crops. It promotes the stomatal opening – which allows more CO2 to enter the leaves. Blue light drives peak chlorophyll pigment absorption which is needed for photosynthesis.
It’s essential for seedlings and young plants during vegetative stages as they establish a healthy root and stem structure – and especially important when stem stretching must be reduced.
Green wavelengths have been somewhat written off as less important for plant photosynthesis given its (in)ability to readily absorb chlorophyll compared to red or blue light spectrums. Nonetheless, green is still absorbed and used for photosynthesis; in fact, only 5-10% is actually reflected – the rest is absorbed or transmitted lower down! This is due to green light’s ability to penetrate a plant’s canopy
In greenhouses, due to the presence of sunlight, supplementing the green light spectrum using LED grow lights would be less important compared to crops grown solely indoors – like Cannabis or vertical crop farming.
Red light is known to be the most effective light spectrum to encourage photosynthesis, as it sits in the peaks in chlorophyll absorption spectrum. Red light wavelengths around 660nm encourage stem, leaf, and vegetative growth, while also contributing to tall, stretching of leaves and flowers.
A balanced pairing with blue light will counteract any overstretching, like disfigured stem elongation. It’s important to consider that while red is the most responsive light spectrum for plants, its efficacy really steps in when in combination with other wavelengths found within the PAR range.
There are a few ways far-red can affect plant growth. First it can initiate a shade-avoidance response. At around 660nm a plant senses bright sunlight exposure. From 730nm and beyond – i.e. a higher ratio of far-red to red light, a plant will detect light “shade” from another plant or leaves higher up the canopy, so stretching of stems and leaves occurs.
Far-red can be very useful to promote flowering, and in certain plants, increase fruit yield. In short-day plants like Cannabis, which rely on longer periods of darkness, 730nm can be used at the end of a light cycle to promote flowering. Fractal technology allows growers to interrupting the dark cycle with bursts of red light to boost growth and flowering.
For photosynthesis to occur and chlorophyll to absorb the maximum amount of light for plant growth, plants use both blue and red light most efficiently. Other spectrums of light, like greens/yellows/oranges, are less useful for photosynthesis due to the amount of chlorophyll b, absorbed largely from blue light, and chlorophyll a absorbed largely from red and blue light.
It’s worth noting photosynthesis is more complex than just chlorophyll absorption, but it’s important to recognize the fundamental principles.
For growth, blue light is essential to help plants produce healthy stems, increased density, and established roots – all which occur in the early vegetative growth stages. Growth then continues with increased red light absorption, resulting in longer stems, increased leaf and fruit/flowering etc. It’s here that red light plays the dominating role in plant maturity and, therefore, size.
And finally, yield – this comes down to a combination of light spectrums and is often very unique to growers, including growers of several varieties of the same crop (like Cannabis). There’s no one single light spectrum that produces more of a crop – optimal lighting is very much a holistic, ever-changing process.
In some crops, blue light can benefit nutritional levels and coloring, and a higher red to far-red ratio can help with leaf size and flowering. It’s why today’s full-spectrum LEDs are so advanced – because by selecting the right quantities of red and blue light, chlorophyll pigments absorb more light they need. Cannabis growers – who pay attention to UVB/blue for its various structural and THC-potency benefits, which we’ll get into, are predominantly concerned with leaf size and flowering. Therefore, far-red and red light is relatively more important to boost their yields. Other indoor growers are also experimenting with the controlled use of far-red spectrum, like salad leaf farmers for example. Plants associate this spectrum with shading from direct sunlight, which would happen lower down the canopy, causing leaf & stem stretching as the plant reaches out for sunlight.
This means when used strategically, bigger leaves and flowering can occur without unnecessary stress. So while there is no specific LED grow light spectrum for any particular plant, the ratio of red to blue light is very important to maximize growth and the rate of photosynthesis
The grow light spectrum for Cannabis varies when compared to other plants as growers are focused on maximizing yields, controlling levels of THC and other cannabinoid production, increasing flowering, and to maintain overall uniformity. Aside from visible colors, Cannabis responds especially well to wavelengths just outside of the PAR range. Therefore, an added benefit of using full spectrum LEDs is the ability to use specific doses of ultra-violet wavelengths (100-400nm), and far-red wavelengths (700-850nm) outside of the PAR range.
For example, an increase in far-red (750nm-780nm) can help stimulate Cannabis stem growth and flowering – something growers want, whereas necessary blue light in minimal amounts, can prevent uneven elongation of stems and leaf shrinkage.
So, what’s the ideal light spectrum for Cannabis? There’s no single spectrum since varying light exposure promotes certain plant morphology during different stages of growth. The chart below explains the concept of outer-edge PAR light spectrum use.
First we must consider how specific plants use PAR-spectrum light for photosynthesis but also looking at wavelengths outside of the 400-700nm PAR range. This light is also know to help accelerate flowering, increase nutrition absorption while speeding up the rate of growth. If the light source is sole (indoors) or supplementary (greenhouses) also affects which grow light spectrums should be used.
Generally, photosynthetic efficiency occurs at the red and blue peaks which means plants absorb these spectrums most when growing. Sunlight produces a lot of greens, yellows, and oranges – they’re the most readily available spectrums of light. In fact, studies tell us how green light, while not absorbed by chlorophyll as well as red and blue, it’s absolutely critical for photosynthesis.
Light spectrums outside of blue and red wavelengths are used least by plants to grow as reds and blues are where most photosynthetic activity occurs. This is a big reason why full-spectrum tunable grow lights are incredibly efficient because a grower can get very specific in their spectrum selections and energy levels.
The above chart shows the PAR range – the spectrum of light plants use for photosynthesis. Grow light spectrum charts like this include both the PAR range and other spectrums as it’s been discovered that wavelengths outside of the PAR range are also helpful for plant growth.
The peak of photosynthetic efficiency (light absorption) falls in the red light and blue light spectrums of the PAR range. Red radiation (around 700nm) is considered most efficient at driving photosynthesis – especially in the flowering stage for biomass growth (important to Cannabis growers). Blue light is essential for both the vegetative and flowering stages of plant growth, but mainly for establishing vegetative and structural growth.