Comparative petiole anatomy in the tribe Sorbarieae (Rosaceae) and its taxonomic implications
15 January 2018
Song, Jun-Ho; Hong , Suk-PyoWe conducted a comparative petiole anatomical study of 16 taxa (Adenostoma, 2 spp.; Chamaebatiaria, 1 sp.; Sorbaria, 6 spp., 3 vars., and 1 forma; and Spiraeanthus, 1 sp.) and the related genus Lyonothamnus(1 sp. and 1 ssp.). Distal, medial, and proximal regions were transversely sectioned using conventional embedding and staining methods. The main anatomical characteristics were as follows: cuticles, crystals, trichomes, and pericyclic fiber patterns. Three types of vascular nodal patterns were recognized: Type 1, simple-trace nodal pattern with slightly curved or U-shaped vascular bundle (Chamaebatiaria, Lyonothamnus, and Spiraeanthus); type 2, multiple-traces nodal pattern with free vascular bundles (Adenostoma); and type 3, bundles fuse to form a siphonostele nodal pattern (Sorbaria). Some petiolar anatomical characteristics (e.g., cuticles, crystals, trichomes, vascular nodal pattern, and pericyclic fiber patterns) provide useful information for taxonomic studies within the Sorbarieae. On the basis of these characteristics, a dichotomous key for identification at the generic/specific level within this tribe is provided. We also report a structural change in the vascular bundles from the stem-leaf transitional zone to the leaf medial zone.