1. Light intensity has a great impact on the seedling formation factors and leaf physiology and biochemistry of tobacco plants
1.Liu Guoshun et al. used gauze to shade tobacco seedlings in Xichang City, Sichuan, and showed that with the increase of shading, the photosynthesis of leaves decreased, the thickness decreased, the free water content increased, and the seedling formation factors weakened.
2.Zheng Ming found that the growth and development of Yunyan 87 and K326 and the leaf tissue structure of Yunyan 87 and K326 with different light intensities [4] showed that with the weakening of light intensity, the thickness of the upper and lower epidermis and mesophyll of the leaves decreased, the palisade tissue and tissue ratio increased, the contents of total sugar and reducing sugar decreased, and the contents of nitrogen, nicotine and potassium increased.
3.Yang Xingyou et al. found that shading would reduce the dry matter of tobacco plants and thin the leaves. Appropriately increase the light intensity of flue-cured tobacco, and the photosynthesis will be improved, which has the effect of increasing sugar and reducing nitrogen.
2. Light time has a great impact on the growth, development and quality of flue-cured tobacco leaves
Studies have shown that the annual sunshine hours are more than 2000h, and the leaf development is better for more than 8h during the growth period, and the study of the sunshine ratio during the harvest of flue-cured tobacco has found that the light ratio of % is the best, that is, the quality of tobacco leaves is the best for about 500h and 300h sunshine hours, and the quality of tobacco leaves below 200h becomes poor.
Wang Guangshan et al. found that the longer the irradiation time and the higher the light intensity, the increase of leaf thickness and the higher the nicotine content after curing [11-12]. Xie Jingming's study found that the increase of sunshine hours in the early stage of flue-cured tobacco growth was conducive to the accumulation of dry matter, and the reduction of sunshine hours in the later stage was conducive to the ripening of tobacco leaves.
3. Light quality will affect the photosynthetic rate, which in turn will affect leaf development
1.Lin Yechun et al. found that blue light was conducive to three-dimensional cultivation of strong seedlings, and the maximum net photosynthetic rate was ranked as blue light, white light, LED light, and red light, and the saturation point of flue-cured tobacco light was larger under blue light conditions, which was consistent with the higher absorption peak of blue-violet light by chlorophyll a and chlorophyll b.
2.Dai Mian et al. found that increasing the row spacing could improve the diffuse light environment of the middle and lower leaves, which provided a basis for changing the planting of double rows to single rows.
3.Shi Hongzhi et al. studied the effects of red light and blue light on the growth, carbon and nitrogen metabolism and quality of flue-cured tobacco, and found that short-wave light could promote leaf nitrogen metabolism, and long-wave light could promote carbon metabolism.
4.Jia Fangfang et al. found that changing the light quality increased the chlorophyll content, but the difference was that the nicotine content and total nitrogen content of the leaves increased and decreased under the yellow filter film, while the potassium content and decreased the carbohydrate and nicotine content under the red filter film.
5.Huang Yong et al. found that a certain amount of UV-B irradiation could make tobacco seedlings dwarf and thicken, reduce leaf area, and reduce photosynthesis, and a small amount of UV-B irradiation could effectively increase the chlorophyll content of seedlings and leaves.
Fourth, photoperiod as a signaling factor affects plant physiology and flower bud differentiation
1.In the 20s of the 20th century, American scholars discovered the photoperiod phenomenon of flue-cured tobacco by transplanting Maryland tobacco in different locations. Leaves are receptors of photoperiod, and only under certain conditions can leaves feel the stimulation of mosaic differentiation brought by photoperiod.
2.McDaniel's research has shown that tobacco leaves have the ability to sense photoperiod only when they are more than 10 cm long.
3.Xu Chaohua et al. used artificial light at night to prolong the light time, and found that prolonging the photoperiod of flue-cured tobacco could increase the maximum photosynthetic rate while keeping the respiration rate unchanged, and accelerate the photochemical reaction rate.