Table 3.
The contents of chemical substances and polyphenols in tobacco leaves inside and outside the greenhouse at different curing stages
| Treatment | Sampling temperature (°C) | Continuous flue-curing time (h) | Conventional chemical compositions (%) | Polyphenols (mg g− 1) | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Total sugar | Reducing sugar | Total nitrogen | Nicotine | Potassium oxide | Water soluble chloride | Starch | Protein | Sugar–nicotine ratio | Nitrogen–nicotine ratio | Neochlorogenic acid | Chlorogenic acid | Caffeic acid | Scopoletin | Rutin | Kaempferol | |||
| Inside the greenhouse | Fresh tobacco leaves | – | 9.36Ac | 5.20Ab | 1.81Ac | 2.33Aa | 1.93Ab | 0.12Ab | 33.00Aa | 8.46Aa | 4.35Aa | 0.82Aab | 1.56Ac | 7.25Bc | 0.12Aab | 0.12Aab | 9.69Ab | 0.11Ab |
| 38 | 23.5 | 30.07Aa | 16.00Ba | 2.26Aab | 3.44Aa | 2.75Aab | 0.24Aa | 4.20Bb | 7.10Ab | 9.23Ba | 0.67Aab | 3.31Aab | 16.04Ba | 0.19Aa | 0.09Ab | 12.38Aab | 0.32Aa | |
| 42 | 16.5 | 18.79Bbc | 11.53Bab | 2.63Aa | 3.18Aa | 3.57Aa | 0.14Aab | 1.40Ab | 7.84Aab | 6.04Ba | 0.83Aab | 2.71Ab | 7.44Ac | 0.05Ab | 0.20Aa | 8.42Ab | 0.31Aa | |
| 48 | 15 | 21.65Bab | 11.98Bab | 2.39Aab | 2.80Aa | 2.98Aa | 0.18Aab | 2.44Ab | 7.70Aab | 7.84Ba | 0.85Aab | 3.60Aab | 12.35Aabc | 0.23Aa | 0.10Ab | 11.52Aab | 0.15Ab | |
| 54 | 22.5 | 20.48Bab | 10.18Bab | 2.19Abc | 3.35Aa | 3.44Aa | 0.14Aab | 1.03Ab | 7.26Aab | 6.58Ba | 0.66Ab | 4.01Aa | 14.62Aab | 0.21Aa | 0.16Aab | 14.06Aa | 0.16Ab | |
| Initially flue-cured tobacco leaves | – | 21.32Aab | 12.64Bab | 2.32Aab | 2.75Aa | 3.12Aa | 0.19Aab | 1.27Ab | 7.45Aab | 7.63Aa | 0.87Aa | 3.43Aab | 10.42Abc | 0.23Aa | 0.10Ab | 9.59Bb | 0.15Ab | |
| Outside the greenhouse | Fresh tobacco leaves | – | 7.60Ab | 3.79Ab | 1.53Ab | 2.12Aa | 1.43Aa | 0.06Aa | 39.94Aa | 6.87Ba | 3.61Ab | 0.73Aa | 1.30Ab | 14.15Abc | 0.21Aab | 0.13Aab | 11.1Aa | 0.10Ab |
| 38 | 23.5 | 36.95Aa | 25.06Aa | 1.44Bb | 1.89Ba | 2.12Aa | 0.14Aa | 13.25Ab | 5.41Bb | 20.74Aa | 0.78Aa | 2.18Bab | 23.20Aa | 0.25Aa | 0.06Ab | 14.18Aa | 0.19Ba | |
| 42 | 16.5 | 36.07Aa | 27.56Aa | 1.71Bab | 2.24Aa | 1.70Ba | 0.06Aa | 8.72Abc | 6.08Bab | 16.74Aa | 0.78Aa | 1.29Bb | 9.75Ac | 0.10Ab | 0.18Aa | 10.62Aa | 0.20Ba | |
| 48 | 15 | 33.2Aa | 23.02Aa | 1.99Ba | 2.86Aa | 1.76Ba | 0.07Ba | 7.41Abc | 6.56Aab | 14.07Aa | 0.79Aa | 3.07Aa | 16.73Ab | 0.25Aa | 0.12Aab | 13.28Aa | 0.08Ab | |
| 54 | 22.5 | 36.31Aa | 23.23Aa | 1.64Bab | 2.12Ba | 1.73Ba | 0.09Aa | 5.40Ac | 5.67Bab | 17.55Aa | 0.78Aa | 2.82Ba | 18.60Aab | 0.19Aab | 0.06Bb | 12.92Aa | 0.10Ab | |
| Initially flue-cured tobacco leaves | – | 30.88Aa | 24.42Aa | 2.00Aa | 2.58Aa | 2.07Ba | 0.06Ba | 8.48Abc | 6.82Aa | 12.11Aab | 0.79Aa | 2.62Aa | 15.69Ab | 0.29Aa | 0.11Aab | 14.37Aa | 0.08Ab | |
Different capital letters indicate that there were significant differences among different treatments at the same sampling temperature point. Different lowercase letters indicate that there were significant differences among different sampling temperature at the same treatments (P < 0.05). The values were the mean of three biological replicates