Design Suggestions for LED Plant Lighting

Light plays a key role in the process of plant growth. It is the best fertilizer to promote the absorption of plant chlorophyll and the absorption of various plant growth factors such as carrots. However, the determinant of plant growth is a comprehensive factor, not only related to light, but also closely related to the configuration of soil and water fertilizers, growth environmental conditions and comprehensive technical control.

In the past two or three years, there have been endless reports on the application of semiconductor lighting technology in three-dimensional plant factories or plant growth. But after reading it carefully, there is always some uneasy feeling. Generally speaking, there is no real understanding of what role light should play in plant growth.

It can be seen that the solar spectrum is a continuous spectrum, in which the blue and green spectrums are stronger than the red spectrum, and the visible light spectrum ranges from about 380 to 780 nm. The growth of natural organisms is related to the intensity of the spectrum. For example, most plants grow very fast in the area near the equator, and the growth size is also relatively large. However, the irradiation intensity of the sun is not as high as possible, and it is selective for the growth of animals and plants.

Several key auxins that affect plant growth have significantly different light absorption spectra. Therefore, the application of LED plant growth lights is not a simple matter, but very targeted. Here it is necessary to introduce the concept of the two most important photosynthetic plant growth factors.

chlorophyll

Chlorophyll is one of the most important pigments related to photosynthesis and is present in all organisms that can create photosynthesis, including green plants, prokaryotic blue-green algae (cyanobacteria) and eukaryotic algae. Chlorophyll absorbs energy from light, which is then used to convert carbon dioxide into carbohydrates.

Chlorophyll a mainly absorbs red light, and chlorophyll b mainly absorbs blue-violet light, mainly to distinguish shade plants from sun plants. The ratio of chlorophyll b to chlorophyll a of shade plants is small, so shade plants can strongly utilize blue light and adapt to grow in shaded places. Chlorophyll a is blue-green and chlorophyll b is yellow-green. Chlorophyll a and chlorophyll b have two strong absorption bands, one in the red region with a wavelength of 630-680 nm, and the other in the blue-violet region with a wavelength of 400-460 nm.

carotenoids

Carotenoids are a general term for a class of important natural pigments, commonly found in yellow, orange-red or red pigments in animals, higher plants, fungi, and algae. More than 600 kinds of natural carotenoids have been discovered so far.

Carotenoids absorb light in the OD303~505 nm range, which provides the color of food and affects the human body's intake of food; in algae, plants and microorganisms, its color cannot be presented because it is covered by chlorophyll. In plant cells, the produced carotenoids not only absorb and transfer energy to help photosynthesis, but also have the function of protecting cells from being damaged by excited one-electron bond oxygen molecules.