Influence Of Different Topping Stages And A-NAA Application On Yield And Quality Of Flue-cured Tobacco

A split block experiment with completely random design was adopted, with topping stage as main factor A and different concentrations of a-NAA as deputy factor B,9treatments altogether, to analyze the effect of different treatments on tobacco agronomic traits, physiological and biochemical indexes and yield and quality of flue-cued tobacco, the main results are as follows:1. At the first week after topping, there were no significant differences in agronomic characters among different treatments; At the second week after topping, the stem circumference showed some differences, treatment7(10.99cm) significantly higher than treatment1(10.06cm).2. During a month after topping, the nitrate reductase activity of flue-cured tobacco leaf was decreasing. At the second week after topping, nitrate reductase activity in tobacco leaf decreased slowly, then, decreased obviously.3. A month after topping, invertase activity of flue-cured tobacco leaf among different treatments showed an overall declining trend. During the first week to second week after topping, treatment7was the highest; at the third week, treatment6was the highest; at the fourth week, treatment3was the highest.4. The treatments without topping and topping at full blooming stage in addition to the concentration of200mg/kg a-NAA application can reduce nicotine content in upper leaves to some extent;nicotine content of middle leaves generally moderate, the nicotine values were within the suitable range. Total potassium content in tobacco leaves showed as Lower leaves’>middle leaves’>upper leaves’. The treatments without topping or200mg/kg a-NAA application can improve the potassium content in upper leaves. The total nitrogen content in upper leaves is slightly larger than that of the middle leaves and lower leaves, total nitrogen content of middle leaves and lower leaves had little difference. Effects of topping time on total sugar content in tobacco leaves is more obvious, the earlier the topping stage, the higher the total sugar content. The treatment with a-NAA application has very little effect on the content of total sugar. There was no significant difference in reducing sugar content among different treatments.5. There were obvious differences in yield and output value of flue-cured tobacco between different treatments. Of which the control (A0B0) was the lowest, and the higher in the treatments topping at squaring stage than in the treatments topping at full blooming stage. Topping treatments improved the yield, output value and the quality of flue-cured tobacco obviously. The effects of topping treatments were better than that of auxin application.6. In conclusion, the best treatment was A2B2.