| The difference of total and reducing sugar concentrations(DARS)in cured tobacco leaves greatly affects the inductrial usability and quality of the leaves and their consuming flavor.DARS can be optimized by improving tobacco planting and leaf curing measures.These measures are believed to be an effective way toward optimizing DARS,bringing it to the desired value between 2.4 to 3.4 experimentally defined for high-quality cured leaves.In most tobacco leaves,however,DARS levels highly exceed the desired value,thus seriously reducing the leaf quality.To resolve this problem,the author carried out the DARS-optimization study.Different planting and curing measures(nitrogen fertilization amounts,transplanting,girdling,and harvest maturity,as well as yellowing time and degree in leaf curing process)were applied to Yunyan 87,a flue-cured tobacco cultivar that has been popularly planted in China.The subsequent effects on enzymatic activities of amylase and neutral invertase(NI)and concentrations of starch and sucrose in the cured leaves were analyzed with the attempt to demonstrate if these measures help optimizing the DARS level.(1)Among nitrogen fertilization amounts,compared with the conventional nitrogen application rate(7kg/667m~2),the total amylase and NI activities of 5kg/667m~2 treatment were significantly increased,the starch content was significantly decreased,the total sugar content increased by 3.02%and the reducing sugar content increased by 6.79%,the difference between the two sugars decreased by 24.11%and reached the high quality level;compared with delayed transplanting(May 20),transplanting on May 10 could increase the activities of total amylase and NI,decrease the content of starch,increase the content of total sugar by 10.12%,and increase the content of reducing sugar by 19.21%,the difference between two sugars was the most suitable and the effect was the best;compared with ungirdling treatment,the activities of total amylase and NI were significantly increased,the content of starch was significantly decreased,and the content of reducing sugar was increased by 8.95%,the difference between the two sugars was more appropriate and the effect was the best;among different harvest maturity treatments,compared with under mature and over mature treatments,the activities of total amylase and NI increased,starch content decreased significantly,reducing sugar content increased by 8.93%and%,and total sugar content increased by 7.66%and 10.80%,respectively,the difference between two sugars was appropriate and the effect was the best.(2)Among different yellowing degree treatment,the best sampling effect was at 100%yellowing degree,compared with 80%and 90%yellowing degree,the activity of total amylase and NI increased,the content of starch decreased,the content of total sugar increased by 10.75%and 3.32%,and the content of reducing sugar increased by 11.95%and 3.20%respectively,the sugar difference was reduced by 0.73%and 4.63%respectively,and the content of which was the most suitable and the effect was the best;among different yellowing temperature treatment,the best sampling effect was at the end of 42℃,compared with that at the end of 38℃and 40℃,the activity of total amylase and NI increased,starch content decreased significantly,total sugar content increased by 35.23%and 19.52%,reducing sugar content increased by 34.25%and20.24%,the difference between two sugars reached high-quality tobacco level;among different yellowing time treatments,prolonging the yellowing time could significantly promote the transformation of tobacco content,compared with fresh tobacco leaves,the activities of total amylase and NI of sampling at 36h were increased,the content of starch was significantly decreased,the content of total sugar was significantly increased by 1.41 times,the content of reducing sugar was significantly increased by 7.66 times,and the difference between two sugars was significantly reduced by 60.51%,and had the best effect. |
PDF Full Text Request