Objective The study was conducted to explore the controlled factors of the stable carbon isotope composition in tobacco leaves with a view to provide a new theoretical basis for the improvement of tobacco planting evaluation index system and the study of ecological adaptability mechanism.
Method The stable carbon isotope composition(δ13C)analysis was carried out on tobacco leaves which were collected during the mature stage from four major first class tobacco growing areas in China, namely, Southwest China, Southeast China, upper and middle reaches of the Yangtze River and Huanghuai area.
Result The δ13C values of tobacco leaves ranged from -27.76 ‰ to 25.39 ‰, with an average value of -26.46‰. The δ13C values decreased with longitude significantly, with a rate of 0.09‰, and the values showed a quadratic parabola relationship with latitude. In addition, there were significant differences in δ13C values in different leaf positions, and the results showed as upper leaves > middle leaves > lower leaves. In terms of tobacco growing areas, δ13C value results of four tobacco growing areas showed as: Southwest planting area ≈ Huanghuai planting area > Yangtze River planting area > Southeast planting area. Moreover, the cluster analysis results showed that fragrant sweet tobacco and alcoholic sweet aroma tobacco were clustered clearly based on δ13C values of tobacco from different origins. However, the other four aroma types(burnt-sweet and burnt-fragrant type, mildly and honey sweet type, burnt-sweet and alcoholic sweet type and honey sweet type)cannot be clustered obviously as the independent variables.
Conclusion The stable carbon isotope composition of tobacco leaves has a negative correlation with longitude and a quadratic parabolic relationship with latitude. The stable carbon isotope composition of tobacco leaves at different leaf positions is different. The δ13C value can be used to effectively cluster the fragrant sweet and alcoholic sweet aroma tobacco.
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