关键词: 烤烟, 叶绿体, 叶绿素, 超微结构, SPAD值

Abstract: In order to clarify the change of pigment content and its relationship with chloroplast ultrastructure in the process of flue-cured tobacco ripening, three flue-cured tobacco varieties were used as experimental materials to measure the SPAD value of chlorophyll in vivo, the content of chlorophyll and the activity of chlorophyllase in the unripe, ripe and overripe middle leaves, and the ultrastructure of chloroplast was observed and analyzed. The results showed that the content of chlorophyll, the SPAD value of chlorophyll and the activity of chlorophyllase in the middle leaves of three flue-cured tobacco varieties decreased with the extension of maturity period. With the increase of maturity level, the structure of chloroplast changed from integrity to rupture, starch granules and eosinophil granules increased, the volume increased, the lamellar layer of basal granules changed from compact to loose, the structure was disordered and twisted, the boundary between the lamellar layer of matrix and the lamellar layer of basal granules also decreased significantly, starch granules and eosinophilic granules dissociated towards the middle of cell, and the membrane of chloroplast was damaged step by step. Correlation analysis showed that there was a strong correlation between pigment content and chloroplast ultrastructure in the middle leaf of flue-cured tobacco. This made it possible to determine maturity level from pigment and SPAD value, thus it was betterly understood the maturity of tobacco leaves, so as to harvest them in  optimal harvest period.

Key words: flue-cured tobacco, chloroplast, chlorophyll, ultrastructure, SPAD value