Lighting that influences mood is often confused with Human-Centric Lighting (HCL). However, lighting has a broader impact because it includes biologically effective light, which can be beneficial or harmful depending on how it's applied. Although the specific parts of the radiation spectrum may vary, illumination can have a clear and significant effect on both plants and animals.
The industry has conducted extensive research on plant growth and animal farming, sometimes even more than on human applications. This article explores the various biological effects of different wavelengths on plants, livestock, and humans, comparing current knowledge across species to inspire advancements in HCL.
**Current Status of Horticultural Lighting**
The use of bioactive spectral control is now common in plant cultivation. Industrial applications are expanding, and further research is expected. Today’s basic research focuses on how plants behave under different wavelengths.
Plants respond to light through photoreceptors like cryptochromes, phototropins, and phytochromes. Exposure to wavelengths below 400 nm (UV radiation) can lead to stronger leaves and greater stress resistance. These effects are not only seen with UV alone but also when combined with other wavelengths. Additionally, small amounts of UV can help prevent fungal infections.
Light in the 400–500 nm range helps reduce water loss in plants by decreasing transpiration. In household appliances, some refrigerators use blue light in vegetable compartments to keep produce fresh.
However, this wavelength range can also slow plant growth, causing leaf abnormalities. Using green light (600–700 nm) counteracts this effect and prevents such issues.
Red light (700–800 nm) encourages larger flowers and compact growth. It significantly affects the aroma of edible plants.
Combining these wavelengths allows for tailored lighting scenarios that improve crop quality and energy efficiency. By adjusting the spectrum, lighting can adapt to different growth stages. Multi-channel systems can suppress unwanted growth factors at any time. For example, early exposure to long-wave red light doesn’t help root length, but timely red light can help tomatoes ripen effectively, maximizing yield while ensuring ripeness.
However, defining light exposure solely by a single μmol value isn't sufficient. Without considering specific wavelengths, it's just a measure of output, not effectiveness. For practical use, it's better to split light into wavelength ranges and assign specific tasks to each.
**Current Status of Animal Husbandry Lighting**
In the field of animal farming, tunable spectral lighting is still in its early stages. While some effects have been observed, the underlying biological mechanisms are not fully understood. Artificial lighting in livestock facilities is becoming more common as more animals are raised indoors without natural sunlight. The global demand for meat, especially poultry, has risen sharply.
Poultry farming is fast and cost-effective, with chickens reaching 1.8 kg in just seven weeks. Based on current knowledge, certain lighting conditions are beneficial. Green light supports muscle development in the first weeks, while blue light increases hormone production. Yellow-white light improves food absorption. Red light can reduce aggression among chickens, helping manage cannibalism and reducing the need for antibiotics—though exact wavelength testing is still needed.
Chickens have a much wider visual spectrum than humans, making it difficult to assess lighting using standard V(λ) curves. The same applies to ducks, geese, and turkeys.
Interestingly, blue light at 480 nm keeps cows awake and boosts milk production by 8%. Cows cannot see beyond 640 nm.
A detailed assessment of lighting’s impact on pigs hasn’t been completed yet due to market conditions.
In such applications, operating technology plays a crucial role. Lighting must be highly resistant to flickering. Livestock and plants process visual stimuli faster than humans, so constant current operation is ideal for their health.
For dimming, simple PWM methods should be avoided. Instead, “clean†pulse control should be used, synchronized across multi-channel systems. If not properly managed, flicker can stress animals and negatively affect product quality.
**Simple Comparison of Plants, Animals, and Humans**
When comparing the known "plant spectrum" with current animal husbandry lighting, the dominant wavelengths are similar. However, the magnitude of the spectral composition remains unclear.
The effect of single wavelengths on human biology is still under study. Blue light at 480 nm inhibits melatonin production, marking an important step in HCL applications.
Plants and humans show similar sensitivity to wavelengths as chickens. Sunlight provides the foundation for all life, and its spectrum varies based on environment—forests, deserts, hills, valleys, land, and water.
Research across plants, animals, and humans reveals common wavelength-dependent effects. For example, red light reduces cortisol levels in chickens.
**Potential Consequences**
Properly naming these processes and measuring their effects remains challenging. Lux and lumens don’t apply to infrared or ultraviolet bands. The V(λ) curve doesn’t accurately represent melatonin inhibition at 480 nm. HCL doesn’t fit traditional lighting standards, and HCL-compatible luminaires may lose efficiency.
Since HCL impacts humans through exposure levels, the unit for measuring this range should be μmol for all organisms. Using species-specific sensitivity curves is already common in chicken farming. But can "chicken lux" work for all birds?
Stroboscopic effects on livestock are well-documented. Frequencies up to 1 kHz can harm animal health. Fast-responding organisms like plankton and algae are also affected. In general lighting, this issue shouldn’t be ignored. Constant-current multi-channel drivers can enhance desired outcomes by providing stable light.
**Conclusion**
In the future, standard lighting practices from the livestock sector may influence general lighting. This will also benefit HCL, as technical specifications can be adapted. To ensure safety, it’s essential to clarify product features.
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