Comparative study of the leaf anatomy of Dendrobium species (Orchidaceae) from South Kalimantan, Indonesia and its taxonomic significance

Dendrobium Sw. is a genus with high species diversity in the Orchidaceae family. One of the difficulties in identifying Dendrobium species is when the specimens bear no flowers or other fertile structures. The use of leaf anatomical characters for species identification is one of the possible solutions in dealing with sterile specimens. In this study, leaf anatomy was examined to assess its taxonomic significance in differentiating species and constructing phenetic relationships between sections within the genus Dendrobium. Sixteen specimens of Dendrobium from 14 species belonging to 9 sections were collected from South Kalimantan. Observations of leaf cross-sections resulted in 60 anatomical characters used for revealing taxonomic relationships between species using cluster analysis and principal component analysis. The result of the cluster analysis showed that the 14 species of Dendrobium were grouped into 3 clusters. The grouping patterns of species were corresponded to sectional classification.  The results of the principal component analysis indicated that the characters of the vascular bundles, hypodermis, epidermis and cuticle showed a major role in recognizing species from different sections. This study confirmed the role of leaf anatomy as taxonomic evidence for the identification of sterile specimens and for supporting classification at a sectional level in the genus Dendrobium.