| According to the studies on TSNA of flue-cured tobacco leaf under the different nitrogen nutrition in the field and curing conditions, there are conclusions asbellow:1 .The nitrate content, nitrite content and TSNA content increase with the nitrate nitrogen content increasing in the fertilizer. The sort order of nitrate content, nitrite content and TSNA different positions is cutters >upper leaf >lower leaf. The nitrogen compounds such as total nitrogen, protein and nicotine have the same order. The results of experiments indicate that different blend of nitrate nitrogen and nitrite nitrogen in the fertilizer can decrease the nitrate content and nitrite content, then get the goal of decreasing TSNA in the flue-cured tobacco through the technique of fertilization in the field. As to the whole quality of tobacco leaf, the blend 50%: 50% of nitrate nitrogen and nitrite nitrogen is the advisable choice.2.During the process of flue-curing, the nitrate content, nitrite content and TSNA content increase from the fresh leaf to the yellowing stage, decrease from the yellowing stage to the color-fixing stage, and hold stable change during the color-fixing stage to the stem drying stage; These contents in leaf after flue-curing process are higher than those in leaf before flue-curing process. This is connected with the nitrate content and nitrite content in tobacco leaf. And during the yellowing process, the relative low temperature, relative high humidity and the enhancement of membrane penetration make the penetrating quantity of electrolyte increases. Every material in cell is combined with enzymes and oxygen, cooperated with each other, expedite transformation from nitrate content to nitrite content, then has the result of high TSNA content in tobacco leaf after curing. So. the perfect control of temperature and humidity during the flue-curing process can prolong the destruction of cytoplasm and construction of membrane, then decrease TSNA content in the end.3.Under the condition of low temperature yellowing and period prolonging conditions, the nitrate content, nitrite content and TSNA content are higher; under the low temperature yellowing condition, these contents are high; under the high temperature yellowing condition, these contents are the lowest. The temperature during yellowing stage influences the action of enzymes and the operation period, and then influences the huge molecular materials such as carbohydrate, nitrogen compounds and pigment. The period of low temperature and high humidity is longer, the accumulation of nitrate content and nitrite content which is the degradation of nitrogen compounds is easier; and then has the result of high TSNA content in the end.4.There are different nitrate content, nitrite content and TSNA content between different curing barns. These contents are higher in bulk curing barn; then, high in stand type barn; and low in cement slab surface plate type barn. This is connected with the temperatureand humidity of different barns. The relative humidity is high in the bulk curing barn, the yellowing period is long. So, the TSNA content of tobacco leaf is higher. The relative temperature is not well proportioned in the stand type barn, the yellowing period is different. So, the TSNA content of tobacco leaf is high. Therefore, the flue-curing barn can be used to decrease TSNA content and should pay attention to the proportion changes of temperature and humidity in barn and reasonable reduce of period of low temperature during yellowing period.5.The nitrate content, nitrite content and TSNA content in the tobacco leaf can be decreased by microwave treatment on fresh mature leaf, leaf during yellowing stage and leaf starting color fixing. The discrepancy of TSNA content is the biggest in the microwave treatment of leaf starting color fixing. In the treatments of leaf starting color fixing, the result of the microwave treatment which prolongs 90s. But when it accesses 90s, tobacco leaf has not flue-curing value because of huge damage. As to the compositive qual...
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