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● Power consumption (watts): 0 - 100
● Electrical efficiency (μmol/J): 2.23
● Spectrum: Phytochrome Based (''Far Red - 730nm'')
● Dimensions: 21,6 x 21,6 x 10,16 cm (8,5'' x 8,5'' x 4'')
● Coverage Area Bloom: Optimal: 120 x 120 cm (4' x 4') | Maximum: 150 x 150 cm (5' x 5')
● Coverage Area VEG: 150 x 150 cm (5' x 5')
Figure 1: Far Red wavelengths: 730nm
● Fixture Weight: 4 kg (7 Lbs)
● Auto voltage: 90 - 277 V
● Maximum current: 0.83 A @ 120V | 0.41 A @ 240 V
● Operating Temperature: 0 - 41.7°C (0 - 107 F)
● Frequency: 50 - 60 Hz
● Full Warranty: 3 years
● Limited Warranty: 5 years
● LED lifetime rating: 50.000+ hours
● Cord length: 180 cm (6')
● Certifications: UL & CE
● Thermal Management: Active (Fans)
What Effect Does Far-Red Light have on Plants?
It’s intimidating to choose the best lighting for growing cannabis, especially when there are so many factors to consider, like spectrum, lumens, PPFD, CRI, CCT, and more! Don’t know what those terms mean? We’ve already covered the basics of horticultural lighting, so read that first if you haven’t already. We are going to dive deeper into one of those factors – spectrum. Plants use photosynthetically active radiation (PAR; 400 – 700 nm) to drive photosynthesis. But plants use wavelengths outside of the PAR range – mainly UV and far-red light to understand and respond to their environment. Far-red light is radiation with wavelengths between 750 and 850 nm and it falls between the red and infrared regions of the spectrum.
Plants sense signals from their environment, such as light, that cause them to change their growth. Light is sensed using photoreceptors, like phytochrome. Phytochrome has an inactive (red light absorbing) and active form (far-red light absorbing), and it switches between the two forms based on the light conditions. The light conditions are often quantified by looking at the ratio of red light to far-red light (usually shortened to “R:FR”). How much red (R) and far-red (FR) light is needed to make phytochrome switch back and forth? Well, it depends on many different factors, such as the species, growing conditions, and light intensity. In one often-used lab species, Arabidopsis, a R:FR of ~2 will switch phytochrome from inactive to active. A R:FR of ~0.25 will switch it back. Via phytochrome, far-red light controls seed germination, stem elongation, and flowering time.
Far-Red Light and Seed Germination
Far-red light mediates seed germination in some species. It’s important that a seed germinates in a good growing environment – one that has lots of light and isn’t too shaded. If a seed germinates in a shady spot, it can be detrimental to the plant because it will not get enough light to grow. Shade environments are enriched in far-red wavelengths compared to other colors of light (Figure 1), so high amounts of far-red radiation can prevent seeds from germinating. Germination rate drops by about 30% when R:FR changes from 1.1 to 0.62. For this reason, seeds should be germinated under bright lights that have high amounts of red light and low amounts of far-red light. Far-red wavelenghts can trick a seed into thinking that it is in a shaded environment, and it is less likely to germinate.
Figure 2: When full-spectrum light hits the leaves of a plant, the photosynthetic pigments absorb much of the red and blue light. Therefore, the light reaching the lower leaves of the canopy is enriched in green and far-red light. Photoreceptors in the lower leaves receive this altered spectrum and signal to the lower leaves that they are being shaded.
Far-Red Light and Vegetative Growth
The R:FR also impacts vegetative growth in plants. High amounts of far-red light can cause stems to elongate and leaves to get longer and wider. This is because the plant is trying to stretch up in hopes of reaching more sunlight. As a result, a plant can look “stretched out” and these long skinny stems are sometimes too weak to hold up heavy cannabis flowers. High amounts of far-red light can also decrease the amount of chlorophyll, anthocyanins, and antioxidants in the plant. Chlorophylls and anthocyanins are pigments that make a plant colorful, which can factor into the novelty and value of the harvest. Antioxidants protect against harmful free radicals – both for the plant and the humans consuming it! Ideally, a grower wants a plant with vibrant color and high antioxidant levels. To produce plants with strong stems and a vibrant color, they should be given high amounts of red light and low amounts of far-red light. This is especially true if the plants are being grown at high-density.
Far-Red Light and Flowering
By this point, you might be starting to notice a trend: plants associate far-red light with shade. Thus, if you give a plant too much far-red light, they will think they are in a shady environment. Too much shade can be stressful to a plant, so it takes precautionary measures to avoid these conditions. Seeds will avoid germinating and stems will stretch out to reach more light. In response to too much shade, a plant will often start flowering. Flowers are the reproductive tissues of a plant and if a plant thinks there is a risk of death (from too much shade), it begins reproducing ASAP so that it may pass its genetics to the offspring. High amounts of far-red light accelerate flowering in many species – tomato, potato, cucumber, beans, wheat, mustard, and many ornamental flowers. In some species, far-red light also increases the number of flowers produced.
As growers, we can use this knowledge to our advantage. If we wish a plant to begin flowering (such as a stubborn cannabis plant that refuses to bud out), we can give it high amounts of far-red light. Far-red light should be applied for a short period to induce flowering, and stopped once buds begin to appear. Small amounts of far-red light applied at nighttime (~2 μmol s-1 m-2) is also effective at accelerating flowering and increasing flower number.
For most stages of plant growth, a grower should maintain a high R:FR ratio. In other words, plants should be provided with high amounts of red light (and other colors of light, like blue and green light) and low amounts of far-red light. If a grower wishes to induce flowering, they can provide a plant with high amounts of far-red light (either during the day or night) for a short period. Once flowering starts, the plants should be returned to their regular lighting conditions. When choosing a light for growing cannabis, look for a horticultural light that has high amounts of red and blue light, moderate amounts of other colors (green, yellow, and orange), and low amounts of far-red and UV light. When used for an extended period, far-red light can be detrimental to plant growth, so it should be avoided when purchasing a grow light. Far-red light causes plants to stretch out and reduces the amount of chlorophyll (which is essential for plant growth) in leaves. When used for a short period, far-red light can stimulate flowering, which can be advantageous if you have a stubborn plant that refuses to flower.
The light cycle of cannabis ?
To keep a plant in the vegetative stage, it needs atleast 13 hours of light per day. Most growers mimic the conditions of long summer days, where it gets the most light.
Setting your lights to an 18-hour light cycle will give them plenty of light to grow fast and strong. Some growers will even go for constant light, keeping them lit for 24-hours-a-day. During the flowering stage, where our beautiful flowers are produced, the light cycle is reduced to a 12-on/12-off in order to mimic fall, where the days grow shorter, and the plants grow female flowers to attract pollen and produce seeds. But while light is vital for growth, it is the uninterrupted periods of darkness that really tell the plant what to do.
But while light is vital for growth, it is the uninterrupted periods of darkness that really tell the plant what to do.
Why the dark is just as vital
It is natural in the great outdoors for clouds to cover the sky and rainy days to limit light at times. Similarly, when growing cannabis indoors, it is okay to turn your lights off for short periods of time to do maintenance on your grow space, replace bulbs, etc. But ask any veteran grower, and they will tell you that you never want light to leak into the grow space while the plants are sleeping. Why? A host of reasons.
But ask any veteran grower, and they will tell you that you never want light to leak into the grow space while the plants are sleeping. Why? A host of reasons.
First, it is the length of darkness that a plant is exposed to that signals its system on which stage of life it should be in. Longer nights mean it is time to grow buds. Short nights mean it is time to just grow mass. Like car headlights in your bedroom window, letting light in disturbs this cycle, and messes with their biological clock.
A strong enough exposure during their night cycle can trigger them to stop growing buds and revert back to vegetative growth.
The second reason is even more vital. Just like you or me, when our sleep gets interrupted, we get cranky. For plants, the stress can cause them to react far worse than we do. They can spontaneously become hermaphrodites, and even one hermie in your grow could ruin all your hard work by pollinating the females and making the whole crop go to seed.
More information coming soon!