Application of 730nm far-red light in LED plant lighting

Light plays a particularly important role in the growth and development of plants, and it affects almost all growth stages of plants.

The effect of light on plants is mainly manifested in two aspects: one is to provide radiant energy for plant photosynthesis; the other is to regulate many physiological processes throughout the plant cycle as a signal. Effects of light on plant growth - photosynthesis and phytochromes. Usually the growth and development of plants depends on sunlight, but the factory production of vegetables, flowers and other economic crops, tissue culture and the propagation of test-tube seedlings also need artificial light sources to supplement light to promote photosynthesis.

Photosynthesis refers to the process by which green plants use light energy through chloroplasts to convert carbon dioxide and water into organic matter that stores energy and release oxygen. A key player in this process is the chloroplast inside the plant cell. Under the action of sunlight, the chloroplast converts the carbon dioxide entering the interior of the leaves through the stomata and the water absorbed by the roots into glucose, and at the same time releases oxygen. .

Analysis and explanation of plant lamp manufacturers: The photosystem in which the light reaction occurs is composed of a variety of pigments, such as chlorophyll a (Chlorophylla), chlorophyll b (Chlorophyllb), and carotenoids (Catotenoids). The main absorption spectra of chlorophyll a, chlorophyll b and carotenoids are concentrated at 450nm and 660nm. Therefore, in order to promote photosynthesis, 450nm deep blue LEDs and 660nm ultra-red LEDs are mainly used, and some white LEDs are combined to achieve high efficiency. LED plant fill lighting, shown: In order to perceive the light intensity, light quality, light direction and photoperiod of the surrounding environment and respond to their changes, plants have evolved photoreceptor systems (photoreceptors). Photoreceptors are the key for plants to sense changes in the external environment. In plant light reactions, the main photoreceptors are phytochromes that absorb red/far-red light. Phytochromes are a class of pigment proteins that have a reversal effect on the absorption of red and far-red light, participate in photomorphogenesis, and regulate plant development. It plays an important regulatory role in the entire growth and development process from germination to maturity.

Phytochromes in plants exist in two stable states: red light absorbing type (Pr, lmax=660nm) and far-red light absorbing type (Pfr, lmax=730nm). The two light-absorbing types can be reversed to each other under the irradiation of red and far-red light. Phytochrome-related studies have shown that the effects of phytochromes (Pr, Pfr) on plant morphology include seed germination, detoxification, stem elongation, leaf expansion, shade avoidance, and flowering induction. Therefore, a complete LED plant lighting solution requires not only 450nm blue light and 660nm red light, but also 730nm far-red light. Deep blue light (450nm) and ultra-red light (660nm) provide the spectrum required for photosynthesis, and far-red light (730nm) controls the entire process of plants from germination to vegetative growth to flowering. The right combination of deep blue (450nm), ultra-red (660nm) and far-red (730nm) provides better chromatographic coverage and growth patterns.

Two major effects of 730nm far-red LEDs on plants.

1. The shade-avoidance effect of 730nm far-red light

One of the main effects of 730nm far-red illumination on plants is shade avoidance. If the plant is only irradiated by the deep red light of 660nm, the plant will feel that it is under direct sunlight and grow normally. If the plant is mainly irradiated by the far-red light of 730nm, the plant will feel as if the direct light of the sun is blocked by another taller plant, so the plant will grow harder to break through the blocking, that is, there is Helps plants grow taller, but doesn't necessarily mean more biomass.

2. The flowering induction effect of 730nm far-red light

Another important role of 730nm far-red light in horticultural lighting applications is that the cycle of flowering can be controlled by 660nm and 730nm illumination without relying only on the influence of seasons, which is of great value for ornamental flowers. The conversion of the phytochrome Pr to Pfr is mainly induced by deep red light at 660 nm (representing sunlight during the day), while the conversion of Pfr to Pr usually occurs naturally at night, and can also be excited by irradiation with far-red light at 730 nm. It is generally believed that the control of plant flowering by phytochromes mainly depends on the ratio of Pfr/Pr, so we can control the Pfr/Pr value by irradiating far-red light at 730nm, thereby controlling the flowering cycle.

3. Customized light formula for LED plant lighting LED is used for horticultural lighting, which can increase the growth rate of plants by 40% or flexibly control the flowering period. Since the individual LEDs are independent of each other, the performance can be easily illuminated in the greenhouse.

The photosynthetic photon flux (PPF) efficiency of the LED itself is very high. The typical PPF luminous efficiency of deep blue (450nm) and far-red (730nm) LEDs is about 2.3 μmol/J, and the typical PPF of ultra-red (660nm) LEDs is about 2.3 μmol/J. The light efficiency is about 3.1μmol/J, and the wavelengths of these LEDs match the absorption spectra of chlorophyll a/b, carotenoids and phytochrome Pr/Pfr, which can achieve lighting and energy consumption. LEDs do not emit heat in the lighting direction and do not damage plants, making them suitable for overhead lighting, interior lighting and multi-layer cultivation. The R/FR ratio is the ratio of the intensity of red light (660nm) to far-red light (730nm). The R/B ratio is the ratio of the intensity of red light (660nm) to blue light (450nm). Through the control of R/FR ratio and R/B ratio, customized light formulations for various plants can be realized. ---- Plant lamp manufacturers