| Curing characteristics of tobacco leaves refers to the inherent tobacco leaves natures acquired in the agronomic process,which has a close relation with curing techniques and effects.Understanding of curing characteristics is the fundamental basis for developing appropriate curing methods and highlighting quality features of tobacco leaves.In order to investigate the curing characteristics of upper tobacco leaves of Xiangzhong tobacco growing areas,the dark chamber method and electric-heated flue-curing barn method were used for researches on yellowing and browning characteristics,dehydrating characteristics,chlorophyll degradation characteristics,polyphenol oxidase(PPO)activity and chemical compositions of the upper leaves.The main findings were as follows:(1)Curing characteristics of different cultivars of upper tobacco leaves: Upper leaves of different tobacco cultivars such as G80,K326 and Yunyan 87 in Xiangzhong tobacco areas exhibited different curing characteristics.Yunyan 87 showed better curing characteristics with good easy curing potential and good easy endurable curing potential;upper leaves of K326 showed medium curing characteristics with good easy curing potential but medium endurable curing potential;upper leaves of G80 showed medium curing characteristics with good easy curing characteristics but bad endurable curing potential.(2)Curing characteristics of upper tobacco leaves with different qualities: Different qualities of upper tobacco leaves of Yunyan 87(grown in Xiangzhong tobacco areas)had different curing characteristics.Normal and “fast-yellowing” tobacco leaves showed good curing characteristics with good easy curing potential and good easy endurable curing potential;“slow–yellowing” tobacco leaves showed medium curing characteristics with medium easy curing potential and good endurable curing potential;“premature senescence and pale” tobacco leaves showed medium curing characteristics with good easy curing potential and medium endurable curing potential.Normal and “fast-yellowing” tobacco leaves presented better curing characteristics than “slow–yellowing” and “premature senescence and pale” tobacco leaves.(3)Curing characteristics of upper tobacco leaves with different nitrogen application levels: The first till the third upper tobacco leaves and the fourth till the sixth upper leaves of Yunyan 87(grown in Xiangzhong tobacco areas)with different nitrogen applications(normal,high and low)showed different curing characteristics.In the same nitrogen application environment,the first till the third upper leaves and the fourth till the sixth upper leaves of Yunyan 87 showed no significant difference in curing characteristics.In the high nitrogen application condition,Yunyan 87 showed medium curing characteristics with good easy curing potential and medium endurable curing potential;in normal nitrogen application case,it showed good curing characteristics with good easy curing potential and good endurable curing potential;in low nitrogen application case,it showed medium curing characteristics with good easy curing potential and medium endurable curing potential.High or low nitrogen application would worsen curing characteristics of tobacco leaves.(4)Curing characteristics of upper tobacco leaves with different maturity in high nitrogen application environment: In high nitrogen application environment,upper tobacco leaves having different maturity in Xiangzhong tobacco areas had different curing characteristics.In terms of G80,upper leaves with high,moderate and low maturity all showed medium curing characteristics with good easy curing potential,but upper leaves with high maturity presented bad endurable curing potential;leaves with moderate maturity showed good curing characteristics with good endurable curing potential;and leaves with low maturity showed medium curing characteristics with medium endurable curing potential.While as for Yunyan 87,upper leaves with high maturity exhibited good easy curing potential and medium endurable curing potential;upper leaves with moderate maturity exhibited good easy curing potential and medium endurable curing potential;upper leaves with low maturity exhibited medium easy curing potential but bad endurable curing potential;the three kinds of leaves all showed medium curing characteristics,but leaves having high and moderate maturity were better than that having low maturity.(5)Curing characteristics of upper tobacco leaves of Yunyan 87 in different areas: Upper tobacco leaves of Yunyan 87 grown in Xiangzhong,Xiangnan and Xiangxi tobacco areas respectively presented different curing characteristics.Upper leaves of Yunyan 87 in Xiangzhong tobacco areas showed good curing characteristics with good easy curing potential and good endurable curing potential;Upper leaves of Yunyan87 in Xiangnan tobacco areas showed good curing characteristics with good easy curing potential and good endurable curing potential;Upper leaves of Yunyan87 in Xiangxi tobacco areas showed medium curing characteristics with good easy curing potential and medium endurable curing potential;Yunyan 87 grown in both Xiagnzhong and Xiangnan tobacco areas presented better curing characteristics than that in Xiangxi tobacco areas.(6)Curing characteristics of upper tobacco leaves of K326 in different areas: Upper tobacco leaves of K326 grown in Xiangzhong,Xiangnan tobacco areas respectively exhibited different curing characteristics.Upper leaves of K326 in Xiangzhong tobacco areas showed medium curing characteristics with good easy curing potential and medium endurable curing potential;Upper leaves of K326 in Xiangnan tobacco areas showed good curing characteristics with good easy curing potential and good endurable curing potential;K326 grown in Xiangnan tobacco areas presented significantly better endurable curing potential than that in Xiangzhong tobacco areas,and its curing characteristics in Xiangnan tobacco areas was also better than that in Xiangzhong tobacco areas. |
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