Effects Of Different Flue-curing Technologies on Micro- scopic Structure of Flue-cured Tobacco Leaves

摘要

[Objective]This study aimed to compare the effects of Chinese quality-improving fragrance-increasing tobacco flue-curing technology,Chinese threestage tobacco flue-curing technology and Zimbabwean tobacco flue-curing technology on microscopic structure of flue-cured tobacco leaves to provide theoretical basis for tobacco flue-curing. [Method]Middle leaves of tobacco cultivar K326 were collected in Pengshui County of Chongqing City for flue-curing experiment using three flue-curing technologies. Leaf samples were collected regularly in the flue-curing process,to investigate the microscopic structure of flue-cured tobacco leaves.[Result]During three flue-curing processes,leaves,palisade tissues and sponge tissues shrank gradually. Three flue-curing processes exhibited significant differences in the peak of tissue shrinkage: microscopic structure of flue-cured tobacco leaves in Chinese three-stage tobacco flue-curing process shrank earliest,follower by Chinese quality-improving fragrance-increasing tobacco flue-curing process; flue-cured tobacco leaves in Zimbabwean tobacco flue-curing process presented the latest shrinkage. At 84 h post-curing,leaf thickness in three flue-curing processes showed a descend order of Chinese three-stage tobacco flue-curing process >Chinese quality-improving fragrance-increasing tobacco flue-curing process > Zimbabwean tobacco flue-curing process. Upper and lower epidermal cells in Zimbabwean tobacco flue-curing process ruptured earlier than other two flue-curing processes; eventually,the majority of cells ruptured and mixed with palisade tissues and sponge tissues. In Chinese quality-improving fragrance-increasing tobacco flue-curing process,only a small number of epidermal cells in dried leaves ruptured.Among three flue-curing technologies,Zimbabwean tobacco flue-curing technology exhibited the greatest damage to epidermal cells,followed by Chinese three-stage tobacco flue-curing technology; Chinese quality-improving fragrance-increasing tobacco flue-curing technology had the minimum damage to epidermal cells. Mesophyll cross-section exhibited significant morphological changes in stomata. To be specific,at 0- 12 h post-curing,stomata of tobacco leaves closed with slightly prominent stomatal apparatuses on upper and lower epidermis; at 24- 72 h post-curing,stomata of tobacco leaves changed gradually from opening to closure with significantly prominent stomatal apparatuses on upper and lower epidermis; at 84 h post-curing,stomata of tobacco leaves closed,and the majority of stomatal apparatuses were significantly prominent. In Chinese quality-improving fragrance-increasing tobacco flue-curing process,only a small number of epidermal cells ruptured at 84 h post-flue-curing; palisade tissues and sponge tissues shrank almost simultaneously. Significant gaps were observed between palisade tissues and between palisade tissues and sponge tissues. Chinese quality-improving fragrance-increasing tobacco flue-curing technology exhibited lower disorder level compared with other two flue-curing technologies. [Conclusion]Chinese quality-improving fragrance-increasing tobacco flue-curing technology was conducive to maintaining the microscopic structure integrity of flue-cured tobacco leaves and obtaining high-quality flue-cured tobacco leaves.