Seedlings are the first major source of plant seedlings. Explore the influence of light environment on physiological characteristics and nutritional quality of seedlings, provide theoretical support for the regulation of light environment of high-quality and high-yield seedlings, and provide reference for the regulation of light environment of protected seedlings.
light intensity
Cai Zhiquan et al. (2003) studied the fluorescence characteristics and active oxygen metabolism of seedlings of Gareimia hanhuryi, a woody plant in Xishuangbanna tropical rainforest, after being treated with 4 ℃ at night under two different growth light intensities. The results showed that low temperature made the photosynthetic mechanism PSII primary light energy conversion efficiency (Fv/Fm) and the quantum efficiency of PSII acyclic electron transfer（ Φ PSII), non photochemical quenching coefficient (NPQ) decreased, and primary fluorescence (F0) increased.
After the elimination of low temperature stress, Fv/Fm and FO of Garcinia tenuifolia leaves grown at 50% light intensity could not be completely recovered after 3 days, while Fv/Fm and FO of Garcinia tenuifolia leaves grown at 8% light intensity basically recovered, indicating that low temperature made the PSII reaction center of the photosynthetic organs of Garcinia tenuifolia grow at 8% light intensity reversible inactivated, while the photosynthetic organs of Garcinia tenuifolia grown at 50% light intensity were damaged by oxidation.
With the extension of low temperature stress time, although the activities of active oxygen protective enzymes (SOD, CAT, APX) in the leaves of two species of Garcinia fortunei increased, the production rate of active oxygen and the accumulation of H2O2 and MDA content increased. In the recovery stage, the content of active oxygen in garlic yellow leaves growing at 8% light intensity decreased faster than that growing at 50% light intensity, further indicating that plants growing at high light intensity were more vulnerable to low temperature than those growing at low light intensity.
When transplanting single year old flower bed plant seedlings or plug seedlings, they are compact and fully rooted, with high stem diameter and more root biomass, and are considered to be high-quality seedlings. In the greenhouse of northern latitude, they rely on HPS light supplement to obtain high-quality plug seedlings in winter. LED provides high energy efficiency, long operating life, accurate wavelength specificity, and can eliminate the light quality of wavelengths that are considered invalid. Randall and Lopez (2014）.
Under 85:15 red and blue light IED cultivation, the plant height of Changchun flower, cockscomb flower, impatience, petunia, marigold, sage and violet decreased by 31%, 29%, 31%, 55%, 20%, 9% and 35%, respectively, compared with that under HPS light. However, the stem diameter of snapdragon, geranium and marigold increased by 16%, 8% and 13%, while the plant quality index (QI) of impatiens, geranium and marigold was similar.
However, compared with HPS, petunia, sage and violet have larger plant height under the LEDs of 85:15, 70:30 and 100:0 in red and blue light. These results showed that the quality of most seedlings under red and blue LED was similar or higher than that under HPS lamp.
Plant seedling breeding and its light environment regulation（一）
Seedlings are the first major source of plant seedlings. Explore the influence of light environment on physiological characteristics and nutritional quality of seedlings, provide theoretical support for the regulation of light environment of high-quality and high-yield seedlings, and provide reference for the regulation of light environment of protected seedlings.
light intensity
Cai Zhiquan et al. (2003) studied the fluorescence characteristics and active oxygen metabolism of seedlings of Gareimia hanhuryi, a woody plant in Xishuangbanna tropical rainforest, after being treated with 4 ℃ at night under two different growth light intensities. The results showed that low temperature made the photosynthetic mechanism PSII primary light energy conversion efficiency (Fv/Fm) and the quantum efficiency of PSII acyclic electron transfer（ Φ PSII), non photochemical quenching coefficient (NPQ) decreased, and primary fluorescence (F0) increased.
After the elimination of low temperature stress, Fv/Fm and FO of Garcinia tenuifolia leaves grown at 50% light intensity could not be completely recovered after 3 days, while Fv/Fm and FO of Garcinia tenuifolia leaves grown at 8% light intensity basically recovered, indicating that low temperature made the PSII reaction center of the photosynthetic organs of Garcinia tenuifolia grow at 8% light intensity reversible inactivated, while the photosynthetic organs of Garcinia tenuifolia grown at 50% light intensity were damaged by oxidation.
With the extension of low temperature stress time, although the activities of active oxygen protective enzymes (SOD, CAT, APX) in the leaves of two species of Garcinia fortunei increased, the production rate of active oxygen and the accumulation of H2O2 and MDA content increased. In the recovery stage, the content of active oxygen in garlic yellow leaves growing at 8% light intensity decreased faster than that growing at 50% light intensity, further indicating that plants growing at high light intensity were more vulnerable to low temperature than those growing at low light intensity.
When transplanting single year old flower bed plant seedlings or plug seedlings, they are compact and fully rooted, with high stem diameter and more root biomass, and are considered to be high-quality seedlings. In the greenhouse of northern latitude, they rely on HPS light supplement to obtain high-quality plug seedlings in winter. LED provides high energy efficiency, long operating life, accurate wavelength specificity, and can eliminate the light quality of wavelengths that are considered invalid. Randall and Lopez (2014）.
Under 85:15 red and blue light IED cultivation, the plant height of Changchun flower, cockscomb flower, impatience, petunia, marigold, sage and violet decreased by 31%, 29%, 31%, 55%, 20%, 9% and 35%, respectively, compared with that under HPS light. However, the stem diameter of snapdragon, geranium and marigold increased by 16%, 8% and 13%, while the plant quality index (QI) of impatiens, geranium and marigold was similar.
However, compared with HPS, petunia, sage and violet have larger plant height under the LEDs of 85:15, 70:30 and 100:0 in red and blue light. These results showed that the quality of most seedlings under red and blue LED was similar or higher than that under HPS lamp.