Effect of Different Harvesting Maturity on Physiological Characteristics and Quality of Wrapper after Drying

In order to explore the appearance, physiological characteristics, and quality of dried fresh tobacco leaves with different harvesting maturity treatments, the main tomato varieties Dexue 1 and Chuanxue 1 in Sichuan Province were selected as experimental subjects. Five different harvesting maturity treatments were conducted to investigate agronomic traits and SPAD of tobacco leaves in each treatment field. Key enzymes involved in carbon and nitrogen metabolism, degree of substance accumulation, pigment content, aging related indicators, and quality indicators of tobacco leaves after drying were measured for each treatment. PCA-X was use to analyze the relationship between physiological indicators and tobacco quality. The results showed that the stem leaf angle of the two varieties increased with maturity, while SPAD decreased with maturity. The activities of nitrate reductase and amylase in tobacco leaves, as well as the total carbon content, showed a trend of first increasing and then decreasing with the increase of maturity. The accumulation of malondialdehyde gradually increased, while proline exhibited a V-shaped curve. M₂ tobacco leaves of two varieties, after being air dried, have suitable oil thickness and tensile strength, and have a relatively coordinated chemical composition, meeting the characteristics of high-quality wrapper. The PCA-X analysis results showed that nitrate reductase, amylase, total nitrogen, potassium, petroleum ether extract, and potassium-chloride ratio were positively correlated with tobacco quality, while nitrogen-alkali ratio, sugar-alkali ratio, and chlorophyll b were negatively correlated with tobacco quality. In summary, the tobacco leaves harvested at M₂（59 days after transplanting Dexue 1 and 70 days after transplanting Chuanxue 1） had better quality after air drying.