Studies On Regulation Mechanism Of Chemicals And Reducing Techniques To Flue-cured Tobacco Nicotine Content

The appearance qualities of flue-cured tobacco leaves in china go near to the standards of international high quality tobacco leaves. Because of their high nicotine contents, the tobacco leaves lack of the harmonization of chemical components, especially the middle and upper leaves. That reduced tobacco leaf usability in cigarette manufacture. For decreasing nicotine content, harmonizing chemical contents and improving tobacco leaf usability, 54 different kinds of chemical materials were used to treat van K326 plants, a variety of flue-cured tobacco. On the premise of not affecting the growth and development, yield and quality of tobacco leaves, treatments that can decrease the nicotine content of tobacco leaves will be expected to screen out from those above. Then corresponding cultivation techniques of them will be also studied. The biological mechanism of nicotine biosynthesis that regulated by the chemical selected will be probed into by comparing the difference of precursor, intermediate product contents and activities of enzymes involved. The results were as follows:1. The treatments that sprinkling 50μM α-NAA, 3μM GA₃, 1.25mM ethephon, 1mM CuSO₄, 1mM ZnSO₄on tobacco leaves or watering 100μM α-NAA at tobacco root could decrease nicotine contents in middle, upper leaf and the whole leaves significantly. While sprinkling 0.15μM BR on tobacco leaves or watering 2mM MnSO₄, 3mM MnSO₄ at tobacco root could increase nicotine contents significantly. The differences of growth, development and structure of tobacco leaves among the 54 treatments were analyzed. The results showed: growing days, leaf area, ratio of dry weight to fresh weight, leaf thickness, ratio of sponge tissue thickness to fence tissue thickness, fence tissue cell number, tomenta density and epidermal hair number of tobacco leaves of the treatment sprinkling 50μM a-NAA on leaves had no difference with those of the control. Both of the results of principal component analysis and stepwise regression analysis indicated that nicotine content changes correlated with that of growing days, leaf area, ratio of dry weight to fresh weight, leaf thickness, ratio of sponge tissue thickness to fence tissue thickness and fence tissue cell number after treated with different chemical materials. Changes of the 6 indexes could represent that of the effect of growth, development and structure of tobacco leaves treated with chemical materials. After analyzing the chemical contents of cured leaves of the 6 treatments above, the results showed that the harmonization of chemical components of leaves sprinkling 50μM α-NAA on leaf accorded with that of the high quality leaves, and their usability were the highest.2. The biological mechanism of nicotine biosynthesis that regulated by the 9 different treatments by regulating precursor, intermediate product contents and activities of enzymes involved were obviously different. The main probable pathway included that: (1)...