Abstract: A total of 1341 soil samples and 209 flue-cured tobacco leaf samples were collected from Hunan tobacco-growing areas, and their chlorine contents were determined. The soil water-soluble chlorine content in these areas ranged from 1.20 to 72.10 mg·kg^-1, and averaged （13.55±7.75）mg·kg^-1. 40.60% of the soil samples had a lower water-soluble chlorine content, with the lowest (8.88±8.04）mg·kg^-1 in western Hunan. The chlorine content of flue-cured tobacco leaves was from 0.15% to 0.49%, and averaged 0.31%±0.09 %. The chlorine content of different grades flue-cured tobacco leaves had a trend of X₂F>C₃F>B₂F, but the difference was not significant. After soil samples were grouped according to their water-soluble chlorine content, a significant difference was found in the chorine content of corresponding flue-cured tobacco leaves. There was a significant linear relationship between the chlorine content of flue-cured tobacco leaves and the water-soluble chlorine content of soil (R²=0.8106,P<0.01).

Key words: Arbuscular mycorrhiza, Poncirus trifoliata, Protective system, Drought tolerance, Functional mechanism