Effects Of Topping Stages On The Metabolism, Yield And Quality Of Flue-cured Tobacco

The field experiment was conducted in Jinyeyuan of Fangcheng in 2008, seven treatments were designed, which were T1: topping at buttoning stage; T2: topping at the early bloom; T3: topping in early flower; T4:one day after topping in early flower;T5,topping at full blooming stage;T6: one week after topping in early flower;T7,not topping. The experiment designed with single factor randomized block, effects of different topping stages on the growth, development, yields and quality were researched, and the results were as follows:1 Effects of topping stages on the metabolism of flue-cured tobacco leaves:The root activity of all treatments except the T7 increased firstly and decreased then, T1,T2,T3 and T4 tended to be its own biggest value at 77th day after transplanting, and T1 was the highest; T5 and T6 tended to be their own biggest value at 87th after transplanting, while their highest extent was far less than the earlier topping treatment; so far as the biggest value, the root activity decreased gradually with the stages of topping delaying. The nicotine content increased gradually with the growth period prolonged, the upper leaves of tobacco was influenced most greatly by topping, and nicotine content in the upper leaves was decreased with the delayed topping stages. The total nitrogen contents decreased gradually with the growth period after topping, and the size order of the nitrogen during different parts of tobacco leaves was that: the upper leaves>the middle leaves>the lower leaves, and there were little differences between the same parts and different treatments, and there was no obervious changing tendency. The protein content of upper leaves were influenced greatest, and the differences in all treatments were relatively large, it decreased gradually with the growth period, and protein content in topping tobacco leaves was higher than that which has no topping leaves, there was no obvious changing tendency in all treatments .2 Effects of topping stages on economic properties of flue-cured tobacco leaves:There was little difference during the average prices of T2,T3,T4 and T5 , and T6 took second place. The average price of T1 was lower than T6, and T7's was the lowest. The yield of tobacco increased firstly but decresed then with the topping stage delayed, T4's yield was the highest but T7's was the lowest, in which the changing tendency was accordance with the production value of tobacco in all treatments.3 Effects of topping stages on physical characteristics of flue-cured tobacco leaves: The filling values of upper leaves of tobacco was increased at first and decreased then, increased and decreased with the topping stages delayed, T7's filling value was the minimum while T2's was the maximum, and the middle leaves'filling value increased firstly but decreased then, T3's was the biggest, and T7's was the smallest.The differences during leaf thickness of upper leaves of tobacco in which threre were not significant from T1 to T4, whereafter, the leaf thickness decreased gradually with the topping stages delayed, T7's was the minimum, the leaf thickness of middle leaves were decreased gradually from T1 to T7, T1's was the maximum, and T7's was the minimum. The leaf specific weight of upper leaves of tobacco in all treatments was increased at first and decreased with the topping time delayed, while the leaf specific weight of middle leaves were decresed gradually except T5's, T1's was the maximum and T7's was the minimum.4 Effects of topping stages on chemical constituents of flue-cured tobacco leaves:The rank of the influenced extent of different topping stages to the total sugar content of leaves from different parts of tobacco was : the upper leaves>the middle leaves>the lower leaves, and the total sugar content increased firstly and then decreased, T3's was the most, T7's was the least, while T4's was the least during the lower leaves. The reducing sugar content was consistent with the variation of the total sugar content, while T4's was the highest during the upper leaves, the size order of reducing sugar content during different parts of tobacco leaves was the middle leaves > the upper leaves=the lower leaves. The size order of starch content during different parts of tobacco leaves was as follows: the upper leaves > the middle leaves >the lower leaves, and there was no obervious changing tendency of the starch content in the lower leaves, while the starch content in the upper and the middle tobacco leaves increased firstly and then decreased, and T4's was the highest, T7's was the lowest. The total nitrogen content decreased gradually with the topping time delayed, T1's was the highest and T7's was the lowest, the size order during different parts of tobacco leaves was that: the upper leaves > the lower leaves >the middle leaves. The nicotine content of the upper and the middle leaves decreased gradually with the topping stages delayed, T1's was the maximum, while the nicotine content in the lower leaves increased firstly and then decreased, T3's and T4's were the maximum, T7's was the minimum. The size order of protein content during different parts of tobacco leaves was the upper leaves > the lower leaves >the middle leaves, the protein content decreased gradually with the delaying topping stages. The potassium content was relatively lower, the calcium content was relatively higher, the contents of potassium and calcium increased firstly and then decreased with the topping time delayed, the potassium of T4 was the highest, and the size order during different parts of tobacco leaves was that: the lower leaves > the middle leaves>the upper leaves. T4's calcium was the highest, and T3's took second palce and T1's was the lowest. The contents of B and Mn increased and later decreased, T4's was the highest, the size order of B content and Cu content was as follows: the upper leaves > the middle leaves> the lower leaves.5 Effects of topping stages on the content of the neutral aroma components of flue-cured tobacco leaves:The contents of carotenoids and the cembranenoides content of the neutral aroma components in flue-cured tobacco leaves which of different stages topped tobacco were relatively higher, the browning recration produces took second place, the content of the pheny lalamines content was the lowest. There was no obervious changing tendency in all treatments except the content of the cembranenoides content,the other neutral aroma components increased firstly and decreased later, T2's and T3's were significantly greater than the other treatments, T6's and T7's were the lowest. 6 Relationship during root activity, chemical constituents and the neutral aroma components in all treatments.The relativity between root activity and chemical constituents was obvious, so the topping stage which had the most exuberant root activity at 73rd or 83rd days after transplantings, that is T1,T2,T3 and T4 were the optimal topping stages.Comperhensive analysis showed that,integrating production and quality od early flower treatment was the apporpriate topping stage.