Abstract: It is important for cigarette industry to get flue-cured tobacco leaves with accordant quality between agronomic characters and chemical components. Agronomic characters, however, are often inconsistent with chemical components, and this problem brings the difficulty of blending and decreases the benefits of cigarette industry. The purpose of this paper was to study the correlation between agronomic characters and chemical components and to provide theory basis for tobacco grading. By applying methods of descriptive statistics, ANOVA, multiple comparisons and degree distribution, 166 leaf samples of different positions including three grades of B₂F, C₃F, and X₂F from K326, a flue-cured tobacco cultivar widely planted in main tobacco areas in southern China, were selected as materials to study the relationship between chemical components and leaf length. The results indicated that there existed extensive variation among samples for chemical components and leaf length. The differences were not significant for chlorine content and ratio of potassium to chlorine (K₂O/Cl-), and were significant for leaf length, nicotine content, ratio of total nitrogen to nicotine (TN/nicotine) and ratio of reducing sugar to nicotine (RS/nicotine) among positions of flue-cured tobacco leaves. For total nitrogen and reducing sugar (RS) contents, cutters and lower leaf did not show significant difference, but both had significant difference with these in upper leaf. Similarly, for potassium (K₂O) content, these were non-significant difference in cutters and upper leaf, but significant difference in lower leaf. In the given range, the contents of nicotine, TN and K₂O increased with the increase of leaf length of upper leaf; however, TN/nicotine decreased with the increase of leaf length of upper leaf. The nicotine, RS, K₂O contents, and K₂O/ Cl- content increased with the increase of leaf length of cutters; Cl- content and T N/nicotine decreased with the increase of leaf length of cutters. The RS content, RS/nicotine, and K₂O/ Cl- increased with the increase of leaf length of lower leaf; nicotine, TN and Cl- content decreased with the increase of leaf length of lower leaf. More than 63.0 cm was a sensitive leaf length for nicotine, TN contents and RS/nicotine of upper leaf and K₂O and Cl- content of lower leaf.

Key words: Tobacco (Nicotiana tabacum L.) leaf, Stalk positions, Chemical components, Leaf length, Relationship analysis