4 points misunderstanding should be avoided when you choose or design LED Grow Light.
1-Red blue wavelength ratio of light wavelength
As the two main absorption areas of plant photosynthesis, the spectrum of LED plant lamp should be dominated by red and blue light. However, it cannot be simply measured by the ratio of red to blue. For example, the ratio of red to blue is 4:1, 6:1, 9:1 and so on.
Plant species vary greatly, with different habits, and different growth stages also have different lighting needs. The spectrum required for plant growth should be a continuous spectrum with a certain distribution width. It is obviously inappropriate to use the light source made of two specific wavelength chips of red and blue with very narrow spectrum. In the experiment, it is found that plants will have yellowish, light leaves and stems, thin leaves and stems and so on. There have been a lot of studies on the response of plants to different spectra abroad, such as the effect of infrared part on photoperiod, the effect of yellow and green part on shielding effect, the effect of purple part against diseases and pests, nutrients and so on.
In practical application, the seedlings are often burned or withered. Therefore, the design of this parameter must be targeted according to the plant species, growth environment and conditions.
2. Ordinary white light and all-optical spectrum
The effect of light “seen” by plants is different from that of human eyes. Our commonly used white light lamps can not replace the light of the sun, such as the three primary color white light tubes widely used in Japan. The use of these spectra has a certain effect on the growth of plants, but the effect is not as good as the light source made by LED.
For the fluorescent tubes dominated by three primary colors widely used in previous years, although white is synthesized, the red, green and blue spectra are discrete, and the spectral width is very narrow. The spectral intensity of the continuous part is relatively weak. At the same time, the power is relatively large compared with LED, with 1.5 ~ 3 times of energy consumption. The LED full spectrum specially designed for plant lighting optimizes the spectrum. Although the visual effect is still white, it contains the important light required for plant photosynthesis.
3. Light intensity parameter PPFD
Photosynthesis flux density (PPFD) is an important parameter to measure the light intensity of plants. It can be expressed not only by light quanta, but also by radiant energy. It refers to the effective radiation luminous flux density of light in photosynthesis, and represents the total number of light quanta incident on plant leaves and stems in the wavelength range of 400 ~ 700 nm per unit time and unit area. Its unit is μ E·m-2·s-1（ μ mol·m-2·s-1）。 Photosynthetic effective radiation (PAR) refers to the total solar radiation with a wavelength in the range of 400 ~ 700 nm.
General positive plants PPFD > 50 μ Mol · m-2 · S-1 can start the mechanism of photosynthesis; The shade plant PPFD only needs 20 μ mol·m-2·s-1。 Therefore, when installing the LED plant lamp, it can be installed and set according to this reference value, select the appropriate installation height, and realize the ideal PPFD value and uniformity on the leaf surface.
4. Light formula
Light formula is a new concept recently proposed, which mainly includes three factors: light quality, light quantity and duration. Simply understand, light quality is the most suitable spectrum for plant photosynthesis; The amount of light is the appropriate PPFD value and uniformity; Duration is the cumulative value of exposure and the ratio of day to night time. Dutch agronomists have found that plants judge the change of day and night by the ratio of infrared and red light. At sunset, the proportion of infrared increases significantly, and plants respond and go to sleep quickly. In the absence of this process, plants take hours to complete the process.
In practical application, we need to accumulate experience through testing and select the best combination.