| During the year from 2006 to 2008, the large-scale experiment in the field was made in Xinchang in Zhejiang province. The effect of different amounts of nitrogenous fertilizer on the physiological characteristics of the oriental tobacco, the changes of the endogenous hormone content, as well as the physical properties, the inherent chemical composition, and the comment on the cigarettes'quality through smoking of the modulated tobacco were studied; the impact of different topping periods on the main compounds containing the Nitrogen and the effect production in the leaves of oriental tobaccos were also studied. The more reasonable fertilizing way and the topping period to produce the high quality oriental tobacco were explored. According to the results of testing and analysis, the following conclusions were obtained:1. The effect of the amount of Nitrogen on the dry weight accumulation of the various parts of the oriental tobacco in the growth period.The amount of Nitrogen had a great impact on the dry weight accumulation of the various parts of tobacco plants. The dry weight accumulation of the leaves and stems transplanted after 45-75d was increased with the raising of the amount of Nitrogen, and the influence of the amount of Nitrogen on the dry weight of leaves was greater than the tobacco stems. With the promoting of reproductive age, the disparity of various dry weight that was done with N3, N4 and N1, N2 was gradually widened, but the difference that was processed by N3 and N4 was not very distinct, which on the one hand showed that the seedling N4 was affected by the early flower phenomenon, on the other hand, which explained that the excessive nitrogen was hard to the accumulation of the dry weight.2. The effect of the amount of Nitrogen on the related physiological indexes of the oriental tobacco in the reproductive age.The research was indicated that with the increasing amount of nitrogenous fertilizers, the activity of the glutamine synthetase (GS), invertase (INV), sucrose synthase, sucrose phosphate synthase, phenylalanine ammonia-lyase of leaves was raised, the transformation from the Nitrogen metabolism to Carbon metabolism was delayed, and both the maturity of the tobacco and the accumulation of carbohydrates were blocked; Furthermore, with the increasing amount of nitrogenous fertilizers, the total nitrogen and nicotine content of leaves were augmented, and the total Carbon and sugar content of leaves were reduced. The total Nitrogen and chlorophyll content of leaves were added with the enhancement of the Nitrogen application levels.3. The effect of the amount of Nitrogen on the endogenous hormone content of the oriental tobacco in the reproductive age.Due to the increasing amount of nitrogenous fertilizers, IAA, ZR and GA were increased while ABA was decreased. The correlative analyses showed that the content of nitrogenous and chlorophyll had a significantly positive coefficient with GA and ZR; IAA had a significantly positive coefficient with ABA, GA and ZR; ABA had a significantly negative coefficient with ZR. The study showed that the growth and development of the leaves, the content and balance of the endogenous hormone were closed with the level of the Nitrogen application. The content of endogenous hormone of leaves could be control as the result of the improving amount of the nitrogen fertilizer in turn affecting the growth and development of the leaves.4. The effect of the amount of Nitrogen on the quality of the modulated tobaccoThe amount of Nitrogen had greater influence on the yield and quality of the oriental tobacco. The results presented that the yield and quality of the tobacco were expanded with the increase of Nitrogen; The total Nitrogen, protein and nicotine content of leaves were increased with the improving of the nitrogen application level while the total sugar content was lowered, and the chemical composition was imbalanced; The big leaf blades, the rough organization, the thick leaves but the lower of recurrence pairs of leaf quality, the weakening characteristics of the tobacco aroma, the poor quality of the aroma, the extending miscellaneous gas and stimulating, the bitter aftertaste, the lower overall quality were made by the excessively high Nitrogen Therefore, it was beneficial for improving the quality and overall efficiency of the tobacco to appropriately control the amount of the Nitrogen. The appropriate amount of Nitrogen was obtained in 67.5-112.5kg/hm~2.As far as the same Nitrogen application level, the content of the total Nitrogen, nicotine and protein of the upper leaves were higher than the middle's. The contents of the comment on the cigarettes'quality through smoking were highest when the middle and upper leaves were deal with the low Nitrogen and middle Nitrogen5. The effect of different topping periods on the growth and development of the oriental tobaccoThe study manifested that the topping period had a marked effect on the endogenous hormone content of the oriental tobacco. The ZR content was dropped, the ABA content was raised, the activity of the leaf blades glutaminase (GS) and asparagine synthetase (AS) were lowered, the Nitrogen metabolism intensity of the upper leaves was weakened, the content of compounds containing the Nitrogen was decreased and the process of the leaf senescence was speeded up on account of the delayed topping.6. The effect of the different topping period on the quality of the modulated oriental tobaccoThe research demonstrated that the enlargement of the nutrient consumption, the thickness of leaf blades, the falling of the leaf quality and the single-leaf weight, the less substantial material in tobaccos, the reducing of the yield and quality would be produced owning to the postponed topping period (A1-level leaf ratio). Particularly in the green fruit topping period, the tobacco aroma was weakened. According to the cost-effectiveness, physical properties, chemical composition and sensory quality of the tobacco, the suitable topping period was in the bud and boosting flowers stage.
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