UV spectrum (100 – 400 nm)
The ultraviolet spectrum invisible to the human eye is outside the par range (100 nm-400 nm). About 10% of the sunlight is ultraviolet. Like humans, plants will be damaged by excessive exposure to ultraviolet light. There are three types, UV-A (315-400 nm), UV-B (280-315 nm) and UV-C (100-280 nm).
Although the benefits of UV in Horticulture are still being studied, UV usually brings a deeper purple - in fact, a small amount of UV can have a beneficial effect on color, nutritional value, taste and aroma.
Studies have shown that the use of controlled amounts of UV can also reduce environmental stress, fungi and pests. Studies have shown that the use of UV-B light (280 nm to 315 nm) can increase cannabinoids such as tetrahydrocannabinol in cannabis.
Blue spectrum (400 – 500 nm)
Blue light spectrum is widely responsible for improving plant quality - especially in leaf crops. It promotes stomatal opening - allowing more carbon dioxide to enter the leaves. Blue light drives the peak of chlorophyll pigment absorption required for photosynthesis.
This is essential for seedlings and seedlings at the vegetative stage because they establish healthy root and stem structure - especially when stem extension must be reduced.
Green spectrum (500 – 600 nm)
Compared with the red or blue spectrum, the green wavelength is less important for plant photosynthesis because it absorbs chlorophyll easily. Nevertheless, green is still absorbed and used for photosynthesis. In fact, only 5-10% is actually reflected - the rest is absorbed or transmitted to a lower place! This is because green light can penetrate the plant canopy
In greenhouse, due to the presence of sunlight, the importance of using LED growth lights to supplement the green light spectrum is lower than that grown indoors (such as hemp or vertical crops).
Red spectrum (600 – 700 nm)
As we all know, red light is the most effective spectrum to promote photosynthesis because it is highly absorbed by chlorophyll pigment. In other words, it is located at the peak of chlorophyll absorption. The wavelength of red light (especially around 660nm) promotes the growth of stems, leaves and general nutrients - but the most common is the tall extension of leaves and flowers.
It must be paired with the blue light balance to counteract any excessive stretching, such as deformed stem elongation. It is important to consider that although red is the most sensitive spectrum to plants, its efficacy will really play a role when combined with other par wavelengths.
Far red spectrum (700 – 850 nm)
Far red affects plant growth in several ways - one is to start the shade avoidance response. At about 660nm (crimson), plants feel bright sunlight. From 730 nm and above - that is, the ratio of far red light to red light is higher, the plant will detect the light "shadow" from another plant or leaves higher in the canopy, so the stretching of stems and leaves will occur.
Far red is very useful for promoting flowering and can increase fruit yield in some plants. In short day plants such as marijuana that rely on longer dark times, 730nm can be used to promote flowering at the end of the photoperiod. Many growers are trying to interrupt the dark cycle with bursts of red light to promote growth and flowering.