Abstract:

【Objective】 In order to provide a theoretical basis for optimization and perfection of curing technology, changes of cell ultrastructure and some physiological indexes and physical properties of tobacco leaves were studied during bulk-curing.【Method】 Changes of cell ultrastructure, some physiological indexes and physical properties were studied at key temperature points (fresh, 38℃, 42℃, 48℃, 54℃, dry sample) during flue-curing using the electric-heated flue-curing barn designed and made by Henan Agricultural University. 【Result】 The contents of the starch, chlorophyll and carotenoids of tobacco leaves changed greatly in the early yellowing stage. The differences of moisture content, thickness, density of tobacco leaves in the yellowing and leaf-drying stages were highly significant. The contents of the pectin and cellulose changed mainly in the leaf-drying stage, but leaf specific weight had a relatively small change during flue-curing. Cell ultrastructure observation indicated that cell wall, chloroplast and nucleus changed obviously, but mitochondrias were not easy to be found during flue-curing. The cell structure of the fresh leaves was normal, but chromatin decreased and part of the nuclear membrane disappeared at 38℃. Cells showed plasmolysis, chloroplast and other cellular organs freed to the central cell, chloroplast outer membrane and nuclear membrane fractured, most osmiophilic granules presented half-hollow state, grana lamella and most starch grains disappeared at 42℃. The obvious twist distortion of cell wall and nucleus pyknosis appeared at 48℃; Individual shapes of chloroplast were not apt to differentiate and the remains were basically osmiophilic materials of the weak electronic density after 54℃.【Conclusion】The changes of the cell ultrastructure of tobacco leaves were closely related to physical properties and physiological and biochemical reactions and extent of degradation and transformation of inclusion during flue-curing.

Key words: flue-cured tobacco, bulk flue-curing, physiological indexes, physical properties, ultrastructure