The light plays a key role in the process of plant growth, which is the best fertilizer to promote the absorption of chlorophyll and the growth of various plant growth qualities such as carrots. However, the determinants of plant growth are a combination of factors, not only with light, but also inseparable relationship with soil and water distribution, growth conditions and comprehensive technical control.
The last two or three years, there are endless reports about the semiconductor lighting technology in the three-dimensional plant or plant growth applications. But carefully read down, there is always some uneasy feeling. In general, it is the problem of not really able to understand the role of application of light on plant growth.
Semiconductor lighting has shown great advantages in terms of energy saving and light selectivity and light coordination. However, from the rapid development of these two years, it is a lot of errors of light design and application, mainly in the following aspects of the embodiment.
① as long as a certain wavelength of red, blue chip in accordance with a certain proportion of the combination can be applied to the cultivation of plants, such as red and blue ratio of 4: 1, 6: 1, 9: 1 and so on.
② as long as the white light can replace the sun's light, such as Japan's widely used three-color white light tube, etc., the use of these spectra for the growth of plants have a certain effect, but the effect is not as good as the LED light source.
③ as long as the light of an important parameter PPFD (light quantum flux density) to a certain index on it, but when in the use of this indicator must pay attention to the shady plants or raw plants, to find these the light compensation point of plants, also known as light compensation point. In the actual application of the seedlings are often burned or withered, so the design of this parameter must be based on plant species, the growth of the environment and conditions, then to design targeted.
With regard to the first aspect, it has been introduced that the spectrum required for plant growth should be a continuous spectrum with a certain distribution width, and the light source made from two specific wavelength chips with very narrow spectrum of red and blue is not appropriate, found in the experiment. The plant will occur yellowish, and leaf stem is very light, leaf stem is very thin and so on.
For the previous years it is widely used to three primary colors of the fluorescent tube. Although the synthesis of white, the red, green and blue spectra are discrete (Figure 3 (b)), and the width of the spectrum is very narrow. The following continuous part of the spectral intensity is relatively weak, while the power relative to the LED is still too large, 1.5 to 3 times the energy consumption. Therefore, the use of the effect is not as good as LED lights.
PPFD is the quantum flux density of light, which refers to the effective radiated flux density of light in photosynthesis, which represents the total number of photons per unit time, the unit area is in the range of 400 ~ 700 nm. And photosynthetic active radiation (PAR) is the wavelength of 400 ~ 700 nm in the total solar radiation. It can be expressed in light quantum or radiant energy.