Abstract: Based on the data of the soil and tobacco leaf samples in the 565 site in Yunan Provice,the influence of the tobacco variety,soil and climate conditions on five leading chemical components of tobacco,including the total sugar,reducing sugar,total nitrogen,nicotine and protein content,were analyzed by using classification variance,correlation analysis and response analysis methods.The results showed that sunlight,air temperature and rainfall during field tobacco growing period were the main elements that affect tobacco chemical components;The temporal distribution and matching for sunshine duration,temperature and rainfall during field tobacco growing period in Yunnan influenced the contents of tobacco chemical components.More sunshine hours,lesser rainfall,higher average temperature and higher temperature differences between day and night in the prophase were propitious to accumulate sugar and to restrain the form of the nicotinamide and protein,while the sugar wastage and transfer decreased and the nitrogen content increased with lesser sunshine hours,more rainfall,lower average temperature and lower temperature differences between day and night in the metaphase and anaphase.The average temperature of each month during field tobacco growing period was negatively related to the sugar content of tobacco,but not significant to nicotine content.The content of total nitrogen and protein increased by the higher air temperature in July and August. The influence of soil conditions on chemical components of tobacco leaves was not significantly as meteorological factor.The differences of chemical components among four tobacco varieties were not remarkable.

Key words: Flue-cured tobacco, Flue-cured tobacco, Chemical components, Ecological factors, Yunnan