Application of LED fill light in facility horticulture and its effect on crop growth
The effects of light on plant growth and development include seed germination, stem elongation, leaf and root development, phototropism, chlorophyll synthesis and decomposition, and flower induction. The lighting environment elements in the facility include light intensity, light cycle and spectral distribution, and artificial light supplementation can be used to adjust its elements without being restricted by weather conditions.
Plants have the characteristic of selective absorption of light, and light signals are sensed by different photoreceptors. At present, there are at least three types of photoreceptors in plants, photosensitisers (absorbing red and far red light), and cryptochrome (absorbing blue light Near-ultraviolet light) and ultraviolet light receptors (UV-A and UV-B). The use of a specific wavelength light source to irradiate crops can improve the photosynthesis efficiency of plants, accelerate the establishment of their light forms, and promote the growth and development of plants. Plant photosynthesis mainly uses red-orange light (610-720 nm) and blue-violet light (400-510 nm). Using LED technology, it can radiate monochromatic light (such as red light with a peak of 660nm and blue light with a wavelength of 450nm) that meets the chlorophyll's strongest absorption band, and the spectral range is only ± 20 nm. At present, it is believed that the red-orange light will significantly accelerate the development of plants, promote the accumulation of dry matter, the formation of bulbs, tubers, leaf bulbs and other plant organs, cause the plants to flower and set earlier, and play a leading role in plant color enhancement; Blue and purple light can control the phototropism of plant leaves, promote stomatal opening and chloroplast movement, inhibit stem elongation, prevent plant length, and delay plant flowering, and promote the growth of vegetative organs; the combination of red and blue light LEDs can make up for both colors. The lack of light forms a spectral absorption peak that basically matches the photosynthesis and morphology of the crop. The light energy utilization rate can reach 80% to 90%, and the energy saving effect is significant.
Equipped with LED fill light in facility gardening can achieve a very significant increase in production. Studies have shown that the number of fruits, total yield and fruit weight of cherry tomatoes under 300 ol / (m2 · s) LED strip and LED tube 12h (8: 00 ~ 20: 00) supplementary light are significantly increased, of which the supplementary light of LED lamps increased by 42.67%, 66.89%, and 16.97%, and the supplementary light of LED lamps increased by 48.91%, 94.86%, and 30.86%, respectively. LED light supplement during the whole growth period [Red-blue light quality ratio is 3: 2, light intensity is 300 ol / (m2 · s)] Treatment can significantly increase the single fruit quality and yield per unit area of ??zucchini and eggplant, and zucchini improves 5.3%, 15.6%, eggplant increased by 7.6%, 7.8%. Through the LED light quality, intensity, and duration of air conditioning in the whole growth period, it can shorten the plant growth cycle, improve the commercial output, nutritional quality, and morphological value of agricultural products, and achieve efficient, energy-saving, and intelligent production of facility horticultural crops.