Comparative leaf anatomy of native and cultivated Pinus (Pinaceae) in Korea: implication for the subgeneric classification

Comprehensive comparative anatomy of Pinus leaves was carried out. Some anatomical features were found to be quite useful and supported the classification of genus to subgenus and section level. The number of needles per fascicle, number of vascular bundles, position of resin ducts, shape of leaf in cross section, and distribution of stomata on the leaf surface showed remarkable variation between different species and facilitated the classification of Pinus into minor groups: subgenus, section, and subsection. The members of subgenus Pinus had two vascular bundles whereas members of subgenus Strobus had only one vascular bundle. The position of resin ducts was more consistent in subgenus Strobus than in subgenus Pinus. Interestingly, the species of subsection Strobus included in this study lacked stomata on the abaxial surface. The results indicate that the number of needles per fascicle and needle size are inversely related, and more importantly that a greater numbers of needles per fascicle lead to a more angular shape.