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Plant lighting – the difference between white and purple/pink light
Plant lighting - the difference between white and purple/pink light
Today I’d like to discuss the topic of lighting our plants. It may be helpful for many of you who are considering choosing your first grow light or for those who want to understand the difference between lighting plants with white and violet light. You may have wondered why LED grow lights offer models with different light color, what is full-spectrum light and what is corner light? How can you tell the difference? If you want to learn which light is best for your plants, I invite you to read on.
HOW DOES FULL SPECTRUM (WHITE LIGHT) AFFECT PLANTS AND HOW DOES CORNER SPECTRUM (PURPLE/PINK LIGHT) AFFECT PLANTS?
Illuminating plants with full-spectrum LED lamps allows you to fully utilize the genetic potential of plants because the plant is exposed to all seven basic colors of visible light as well as invisible light such as infrared and ultraviolet (you can read about the benefits of each color below).
Beyond the efficiency and energy efficiency of LED light, the spectrum used is paramount when growing plants. Some colors work together and stimulate plants solely through their mutual presence, so plants benefit from all wavelengths, not just two.
Full-spectrum LED lamps imitate sunlight much better and allow plants to grow in their full growth cycle, not just in specific phases (germination, growth, flowering or fruiting).
Illuminating plants with LED lamps with a corner light spectrum combines red and blue LEDs in various combinations, ranging from 75 to 90% red LEDs and 10 to 25% blue LEDs. This ratio of both colors is based primarily on research. Plants derive the most photosynthesis from red and blue, so red and blue LEDs are very efficient at illuminating plants, converting absorbed electrical energy into light photons for our plants without significant losses. This is a very energy-efficient solution, but it does have its drawbacks.
First of all, illuminating plants with light with a corner spectrum is recommended primarily in a greenhouse or on a windowsill indoors. Why? Because in places with access to sunlight (i.e., full-spectrum sunlight) this is the best combination for plants. In addition to the light they receive from outside, they also receive light that most impacts their photosynthesis and stimulates their rapid growth.
Using lamps with a corner light spectrum without access to full-spectrum light can expose them to so-called “rapid growth,” and although red and blue colors are very efficient, illuminating plants with only this type of light for a longer period of time can cause the plant to elongate towards the light and become limp.
This effect is called the etiolic effect. It refers to excessive elongation and slackness of plant shoots, which is the result of insufficient blue light. Excessive exposure to red light from LED lamps can lead to this effect, as plants require a specific balance of different light colors for proper growth and development.
WHITE LIGHT VS PURPLE LIGHT - WHICH IS BETTER FOR GROWING PLANTS?
Full spectrum diodes
White diodes are actually not white at the initial stage of production, they are blue. Covering the blue diode with a phosphor layer allows for combining red, green and blue light into one color, which is perceived by the eye as white.
White diodes are therefore diodes with a full spectrum of light, illuminating plants with lamps that have white diodes can be called lamps with FULL SPECTRUM light.
Although white LEDs are not as effective as blue or red LEDs, apart from the efficiency and energy saving of LED light, the spectrum used in the lamp is of greatest importance for plant cultivation, and only then the efficiency of the diodes.
Other advantages of illuminating plants with full-spectrum lamps:
– Pleasant effect on the surroundings in the autumn-winter season, light color that does not tire the eyes.
– Possibility of observing plants, ease of spotting pests, fungi and nutritional problems.
6500K - cool white
3500K - warm white
The spectrum of our lamp is warm with the addition of red, infrared and ultraviolet colors
Corner spectrum diodes
Lamps with a violet light color have a very high luminous efficiency. The light they generate immediately affects plants and allows for increased growth, flowering, and fruiting in a short period of time. This acts as a stimulant. Using a lamp with this light spectrum with blue-red LEDs works very well in the initial growth phase of a plant or when it is about to produce a crop.
Examples of spectrograms of lamps with red-blue and red-blue-infrared diodes
INFLUENCE OF OTHER WAVELENGTHS ON PLANT LIGHTING
1. Ultraviolet – It stimulates the production of secondary compounds that protect against oxidative stress, pathogens, and pests. Ultraviolet radiation improves plant health, influences growth and root development, increases flowering and fruiting, and brings out the depth of plant color.
2. Blue color – It plays a very important role in the photosynthesis process of plants by activating chlorophyll A. Blue light is very important for the growth and development of plants, especially in the initial stages of their life, promoting the growth of young and more compact plant shoots.
3. Green color – It influences the shape and size of leaves, normalizes their spatial arrangement in the plant, regulates the opening and closing time of stomata in leaves, penetrates the lower parts of leaves and improves their photosynthesis.
4. Yellow color – It is of great importance for the perception of light by plants, regulating their orientation towards the light source.
5. Red color Red light is a key factor in activating photosynthesis. Chlorophyll a and b, which absorb red light, are within this spectrum. Absorption of this light leads to energy production, the synthesis of organic compounds, growth, seed germination, shoot and root formation, and leaf angle. Red light regulates the flowering and fruiting processes and can accelerate the flowering of short-day plants.
6. Infrared color “Infrared light is beyond the visible range of the human eye, and its role in plant physiology is still being discovered. Infrared light generates heat, thus influencing plant thermoregulation and their response to changes in ambient temperature. Using infrared light can trigger a perceptual process in plants – plants using infrared wavelengths will detect neighbors and competitors, which can influence their growth strategies. Infrared light also affects plant stretching, shortens the time required for flowering (in some cases from 44 to 34 days), and improves leaf shape and size.”
COMBINATION OF SEVERAL WAVELENGTHS AND THEIR EFFECT ON PLANTS
1. Red and infrared light – Red and infrared light interact through the pigment phytochrome (photoreceptor). By absorbing the appropriate wavelength (red or infrared), the phytochrome transforms into one form, and the reaction is reversed by the other wavelength. This allows for regulating the plant’s circadian cycle, determining day and night, and influencing flowering through the appropriate ratio of red and infrared LEDs in the lamp. Furthermore, using red and infrared simultaneously can cause the plant to exhibit a response called “shade avoidance.” Shade avoidance is simply the plant’s elongation (through stems and leaves) in search of light. The more infrared, the greater this effect. Applying a small amount of infrared, on the other hand, will keep the plant compact and in good shape.
2. Combination of warm light (3500k) and cold light (6000k) – Combining light with different color temperatures simulates seasonal changes, influencing plant growth, flowering, and fruiting. Warm and cool light used simultaneously effectively balances photosynthesis and plant growth.
3. Warm and/or cool white ultraviolet light – Adding ultraviolet light stimulates the production of light-receiving receptors, allowing the plant to receive more light and increasing its resistance to stress related to its lack, drying out or nutritional deficiencies.
EXPERIMENTAL EXAMPLES
In the first control test Lettuce under full-spectrum light was 16% smaller than under red-only light, but its weight was 28% greater than under red-blue light (89% red + 11% blue). Compared with red-blue light with a ratio of 67% red and 33% blue, lettuce was 29% smaller. In contrast, under red-blue light with a ratio of 44% red and 56% blue, lettuce weight was 50% lower than under full-spectrum light. Lettuce size decreased when the amount of blue in the light was higher.
In the second control test Lettuce under full-spectrum light and under red-only light (100%) weighed similarly. Lettuce under red-blue light (89% + 11%) was 26% smaller than lettuce under full-spectrum light, while lettuce under blue-only light (100%) was 63% smaller.
In the third control test (the fertilizer dose was changed) lettuce under full spectrum light was 33% larger than under red-blue light (67% + 33%), infrared light was added to the illumination of subsequent plant samples, compared to full spectrum light lettuce with red-blue-infrared light was 20% smaller (3rd sample), very similar (4th sample), and 45% larger (5th sample), in the case of using more infrared diodes.
The third sample in the third control sample contained: blue – 22%, infrared – 11%, red 67%
The fourth sample in the third control sample contained the following amounts: blue – 11%, infrared – 22%, red – 67%
The fifth sample in the third control sample contained the following amounts: red – 67%, infrared – 33%
CONCLUSIONS
Red-blue or violet light is not the “best” when compared to white/full spectrum light, lighting of lettuce plants has shown that under full spectrum light the plant is at least 26% larger than under red-blue light.
Plants prefer all light spectrums (full spectrum) in appropriate proportions, and each color is important throughout their lifespan. Plants have different photoreceptors adapted to receive different colors of light. Different colors of light are responsible for photosynthesis or biological development, making them crucial not only for growth but also for plant health.
Blue-red LED lighting is perfect for greenhouses or industrial production where plant lighting consumes large amounts of energy and sunlight is present. It is a combination of energy saving and high efficiency ensuring very good plant growth.
Research on full-spectrum lights and their impact on plant growth shows that plants benefit from a variety of wavelengths, not just the two most common. Full-spectrum LED lights with the addition of infrared and ultraviolet diodes are believed to provide the spectrum closest to the sun.
