Study on the Curing Characteristics of Flue-cured Tobacco Upper Leaves in Guizhou

In order to further optimize loose leaves bulk curing technology and make a clear curing characteristics of different flue-cured tobacco genotypes (Bina 1 and Guiyan 2),the changes of the water content, leaf morphology, electrical conductivity value, plastid pigments content, SPAD value and yellowing degree of upper tobacco leaves were studied during loose leaves bulk curing. The results showed that water content, leaf length and leaf width, leaf area, chlorophyll content and SPAD value gradually reduced, and conductivity value increased gradually while carotenoids content reduced first, then rose slightly of different flue-cured tobacco genotypes during loose leaves curing. At 38 ℃, Guiyan 2 had a higher water content than Bina 1;at the range of 48 ℃ to 54 ℃, both Bina 1 and Guiyan 2 had the biggest value of the decreasing amplitude of water content. Leaf length and leaf width changed greatly at the range of 42 ℃ to 48 ℃;compared with Bina 1,Guiyan 2 had a larger longitudinal shrinkage ratio,transverse shrinkage ratio and leaf area shrinkage ratio (P0.05),especially for leaf area shrinkage ratio(P0.05).Absolute conductivity and relative conductivity of Bina 1 had the biggest increasing amplitude at the range of 38 ℃ to 42 ℃ during curing while Guiyan 2 had the biggest increasing amplitude at the range of 48 ℃ to 54 ℃ during curing.However,relative conductivity of Guiyan 2 was significant higher than Bina 1 at 38 ℃(P0.05),and absolute conductivity and relative conductivity of Guiyan 2 were significant higher than Bina 1 at 54 ℃(P0.05).Chlorophyll content,carotenoids content and SPAD value of the Bina 1 and Guiyan 2 had the biggest decreasing amplitude at the range of fresh to 38 ℃ during curing.Bina 1 was yellowing faster than Guiyan 2 before 38 ℃,but then lower than it.Compared with Bina 1,Guiyan 2 had a better easy curing.And conductivity value,chlorophyll content and SPAD value all can be used as indexes for judging tobacco curing characteristics.