Abstract: In order to improve the proportion of high-quality tobacco leaves and the industrial availability of tobacco raw materials, Yunyan 87 was studied in Guangyuan tobacco-growing area of Sichuan Province, and two factors of planting density and number of leaves were used to design a randomized block experiment, aiming to clarify the effects of different planting density and the number of leaves on the yield and quality of flue-cured tobacco. The results showed that when the planting density of flue-cured tobacco was increased appropriately and the number of leaves was decreased, flue-cured tobacco could achieve normal growth and development, and compared with other treatments, flue-cured tobacco had significant advantages in leaf development; under medium and low density and medium and low number of leaves, the photosynthetic capacity of tobacco leaves was stronger; under M₂ density and L₂ leaves, flue-cured tobacco achieved better performance in average price, and the proportion of medium and high-grade tobacco, and the output value was the highest. In addition, the appropriate increase in density and decrease in the number of leaves left reduced the nicotine content of leaves after roasting, increased the content of reducing sugar, total sugar and sugar-base ratio, and the chemical composition was more coordinated, which had a significant advantage in tobacco quality evaluation. According to comprehensive analysis, the tobacco quality in Guangyuan tobacco growing area, Sichuan Province was better when the planting density was 18 750 plants/hm² and the number of leaves left was 16~18 leaves per plant.

Key words: planting density, number of leaves left, flue-cured tobacco, growth, photosynthetic characteristics, yield and quality