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[Objective] The present paper aimed to clarify the curing characteristics of different quality upper leaves, such as green tobacco leaves, few rainy sunshine tobacco and multi-fermented tobacco leaves. [Method]A dark box and an electric oven were used to study the yellowing characteristics and water loss characteristics of the upper leaves of different qualities and dynamic changes of moisture, color and pigment and activity of polyphenol oxidase in flue cured tobacco during curing of Hong-hua-da-jin-yuan. [Result]In dark box and curing test, the yellowing speed of more fertilizer and turn green tobacco leaves was slower, the water loss speed was faster, the yellowing speed of rainy sunshine tobacco leaves was faster, and the water loss speed was slower;during the curing process, the degradation rate of the pigments in the turn green and more fertilizer tobacco leaves was slower, and the degradation rate of the pigments in the rainy sunshine tobacco leaves was faster;starch content was more fertilizer> turn green> rainy sunshine;polyphenol oxidase activity was rainy sunshine> more fertilizer>turn green;after curing, the proportion of ash and black bad smoke was relatively high, and rainy sunshine and more fertilizer tobacco leaves’ proportion of turn green tobacco leaves was higher, the percentage of baked green tobacco leaves was relatively high. [Conclusion] The turn green tobacco leaves are less roasting and have good curing resistance, rainy sunshine tobacco leaves are easy to roast and have poor roasting resistance, more fertilizer tobacco leaves is difficult to turn yellow, easy to brown, easy to roast and roasting resistance are poor, in the actual production process, the curing process should be adjusted according to its curing characteristics, to improve the quality of the roasted tobacco leaves. [ABSTRACT FROM AUTHOR]

[Objective] The changes of lignin and water holding capacity of different flue-cured tobacco varieties during ripening were analyzed in order to provide theoretical support for revealing the characteristics of flue-cured tobacco varieties. [Method]The contents of lignin in tobacco leaves of Qinyan 96, K326 and middle tobacco 100 were measured and the relative metabolic enzymes (phenylalanine aminotransferase (PAL), cinnamic acid 4-hydroxylase (C4H), 4-coumaryl CoA ligase (4CL), 4-hydroxybenzohydroxylase (C3H) and cinnamic alcohol dehydrogenase (CAD) were measured. The activity and the change of water holding capacity and relative water content of tobacco leaves. [Result] The results showed that the water retention and relative water content of different varieties of tobacco leaves were the highest in the period of ripening and relative water content, 96 times of Qin tobacco and 100 of middle tobacco, and the content of lignin in the mature process of different varieties of flue cured tobacco in the process of topping was the highest, the content of K326 was the highest, and the 96 times of Qin tobacco 96 times. In the middle tobacco 100, the PAL activity of different varieties of tobacco leaves in the process of ripening was first slowly and then decreased, and the activity of C4H, 4CL and CAD decreased slowly and then then decreased, and the activity of C3H was reduced and then increased, and the content of lignin and water retention in tobacco leaves were reduced. There was a significant positive correlation with relative water content, and the activity of PAL, C4H and (LAD had a significant positive correlation with lignin content, and there was no significant correlation between the activity of 4CL and (3H and the content of lignin. [Conclusion] The results showed that high activity of PAL and (LAD was the basis for the increase of lignin content, and the content of tobacco lignin could be an indicator to measure the water retention ability of flue-cured tobacco. [ABSTRACT FROM AUTHOR]