Studies On Alkaloid Characteristic And Agronnmic Regulation Measures Of Nicotine Content Of Burley Tobacco In Enshi

178 burley tobacco samples from 2007 to 2009 were used as materials to analyze the variation of alkaloid-content among different regions, different stalk positions and different years in Enshi areas. The changes of main chemical components and aroma matters were studied under different alkaloid contents, and the effects of agronomy measures such as nitrogen fertilizer, topping stage and harvest period on nicotine content were also analyzed. In addition, the second national soil survey data were used as reference to analyze the distribution of total nitrogen and available nitrogen content of the tobacco growing soil in Enshi. The results showed that:1. The content of total nitrogen and available nitrogen in Enshi tobacco growing soil were both high. There were 90.74% samples of which total nitrogen content exceeds 1.50%, and 83.33% samples of which available nitrogen content more than 120mg/kg. The contents of total nitrogen and available nitrogen were high in Cuiba, Banqiao and Hongtu, but low in Baiguo, Xintang and Taiyang.2. The average nicotine content was 3.59%. Samples of which nicotine content less than 2.50% took 33.15%, between 2.50% and 4.00% took 26.79%, and more than 4.00% took 39.89%. The average nornicotine content was 0.25%; samples of which nornicotine content less than 0.15% took 27.53%; between 0.15% and 0.25% took 28.09%, and more than 0.25% took 44.38%. The anatabine content were 0.28±0.12%, with large coefficient of variation and less stable.3. The nicotine content had the trend of decreasing year by year, and had significant difference at 0.05 level among different years. The nicotine content was higher in Banqiao, Hongtu, Baiguo than that in Shadi, Xintang and Taiyang. There existed significant difference of nicotine content among different stalk positions in burley tobacco, and the nicotine content increasing with the position increased.4. With the increasing of nicotine content, total nitrogen and petroleum ether extract content increased; the total sugar content increased firstly and then decreased, but reducing sugar, potassium, chloride and starch content gradually decreased. With the increasing of nornicotine content, potassium and chlorine content increased; the reducing sugar and total sugar content increased firstly and then decreased. The total nitrogen, starch and petroleum ether extract content had a decreasing trend. With the increasing of anatabine content, the reducing sugar, total sugar, starch and petroleum ether extract content had the trend of increasing, but total nitrogen, potassium and chlorine content gradually decreased.5. The cluster analysis showed that the nicotine content in each group was 1.59%, 3.57% and 5.51%, and nornicotine content in each group was 0.13%, 0.26% and 0.43%, with anatabine content of 0.15%, 0.28% and 0.44%. There existed high significant difference among different groups based on nicotine, nornicotine, and anatabine contents.(1) In the groups of low, middle and high levels of nicotine content, the content of heptanoic acid and iso-nicotinic acid were also at low, medium, and high level, while the content of caproic acid were at high, medium, and low level as for acidic aroma components. In the groups of low, middle and high level nornicotine content, the content of valeric acid showed low, medium, and high. Heptanoic acid and caprylic acid were higher in the low anatabine group. The content of valeric acid, isovaleric acid and pelargonic acid were higher in the middle anatabine group. In the high anatabine content group, butyric acid and hexanoic acid were also at a high level.(2) In the groups of low, middle and high levels of nicotine content, the content of pyrazine was also at low, medium, and high levels for alkaline aroma components. In the group of low nicotine content, 3-methylpyridine and 2-acetylpyrrole contents were also at a low level. In the group of medium nicotine content, 3-methylpyridine and pyridine content were at a high level, while 2-acetylpyrrole and indole contents were lower. In the group of low nornicotion content, pyrazine and pyridine content were at a high level. In the group of high nornicotion content, 3-methylpyridine and indole contents were at a high level. In the group of low anatabine content, 2-acetylpyrrole and indole contents were higher; while in the group of medium anatabine content, pyrazine and 3-methylpyridine contents were higher, and the variation of pyridine was contrary to anatabine in groups.(3) With the increasing of nicotine and anatabine content, neutral aroma components were slso increased. With the increasing of nornicotine content, carotenoid degradation products and aromatic amino acids were increased, while products degraded by cembrane, maillard reaction and neophytadiene content were decreased.6. With the increasing of nitrogen fertilizer, the nicotine content increased in different stalk positions of burley tobacco. As for Enshi area, nitrogen fertilizer was suitable for 13kg/667m2~15kg/667m2. Topping can significantly affected nicotine content in burley tobacco. The nicotine content was decreased with the delaying of topping time. The nicotine content was suitable when topping between initial flowering stage and full-bloom stage. The accumulation of nicotine content was a dynamic process, and the nicotine content was less than 1% before topping, but rapidly accumulated after topping. The nicotine content reached a maximum value after topping 28 days, and then gradually decreased.