Chemotaxonomic significance of leaf wax n-alkanes in the Pinales (Coniferales)

Abstract

The chemotaxonomic significance of leaf wax n-alkanes was studied in 112 species and cultivars belonging to the Pinaceae, Cupressaceae, Podocarpaceae, Araucariaceae, Cephalotaxaceae, Sciadopityaceae and Taxaceae (Pinales). In general, n-alkanes ranged from 18 to 34 carbon numbers. In the Pinales, C 31 was the most abundant n-alkane (20.17%±1.68), followed by C 27 (2.84%±0.41), C 29 (2.59%±0.49) and C 25 (2.41%±0.22). In the Araucariaceae, n-alkane composition was characterized by low relative percentages of C 31 (5.23%±1.58), whereas the Cephalotaxaceae were characterized by high percentages of C 29 (31.95%±2.05) and C 27 (28.00%±1.00). The Cupressaceae had a mean composition of n-alkanes characterized by moderate percentages of C 31 (18.31%±2.32) and C 33 (5.36%±1.07), whereas in the Pinaceae, C 31 was the main n-alkane (25.40%±2.56). The Podocarpaceae were characterized by moderate percentages of C 29 (12.69%±9.16), C 31 (10.77%±2.70), C 27 (7.37%±5.83) and C 33 (6.59%± 5.71), whereas the Taxaceae had high percentages of C 31 (34.94%±7.85). Sciadopitys verticillata showed low percentages of all n-alkanes. Discriminant Analysis (DA) of the Araucariaceae, Cupressaceae and Pinaceae showed a good discrimination among subfamilies. Cluster Analysis (CA) and Principal Component Analysis (PCA) performed on species of the Pinales, showed a good separation among the families. The direct comparison of the present data with those obtained on species belonging to eleven angiosperm families provided further evidence of the chemotaxonomic significance of leaf wax n-alkanes.