Effects of Light Intensity on Photosynthetic Characteristics and Neutral Aroma Constituents of Burley Tobacco

To identify the effects of light intensity on photosynthesis of burley tobacco leaves during field stages, and explore the distribution differences of main neutral aroma constituents in cured burley tobacco leaves of different light intensities treatment, artificial shade experiment with 3 light transmittance level (100%, 80%, 60%) from rosette stage to maturation stage was carried out by using Eyan 6 as test material. The results indicated that leaf source capacity per unit area of 80% transmittance level was higher than the other two levels. In the early stage of the shade, light intensity was the major controlling factor, net photosynthetic rate under shading treatment were lower than that under full sunlight (100%>80%>60%); In the later period, environment temperature under shading treatment was lower, air humidity and CO₂ concentration was relatively high in the air, and stomatal conductance and transpiration rate increased, and net photosynthetic rate was higher than CK(100% transmittance level), but the intercellular CO₂ concentration decreased. Tobacco leaves had a strong adaptability to light, and long-term shade could stimulate its absorption and conversion efficiency of weak light. Neutral aroma constituents, sense quality, activities of peroxidase and superoxide dismutase were better than those of 100% full natural light as a whole. But 100% natural light intensity was more advantageous to the increasing of content of soluble sugar, and absorption of water-soluble chloride and potassium in burley tobacco leaves. Through comprehensive analysis, tobacco leaves in 80% transmittance level have better quality and meet the formula requirements of the industrial enterprises.