Taxonomic value of the petiole anatomy in the genus Cinnamomum (Lauraceae) found in Sri Lanka

We assessed the petiole anatomy of 8 species of Sri Lankan Cinnamomum (C. capparu-coronde, C. citriodorum, C. dubium, C. litseaefolium, C. ovalifolium, C. rivulorum and C. sinharajaense and C. verum) belonging to the family Lauraceae using light microscopy in the petiole anatomy for identification and classification of species. This is the first report on comprehensive petiole anatomy in Cinnamomum species. The distinctive, important and key taxonomic characteristics of the petiole include the shape and outline of the petiole, the presence of winged extensions, surface grooves on upper surface, presence or absence of trichomes, structure of vascular bundle and stone cell characters (shape, structure, pits and fissure size). These identified petiole characters provide the additional information for the identification of Cinnamomum species. Almost all the characters studied had little difference within a species but vary among the species. However, shape of epidermal cells was relatively constant for all species. All polymorphic characters were used for Principal Component Analysis (PCA) and species were divided into three main clusters. The PCA revealed that acicular crystals, cluster of crystals, trichomes and trichome abundance contribute to the first component that account for 31.76% total variance. Shape of the petiole, upper surface wings and raphides are the major loading characters to the second component. Therefore, anatomical structures of the petiole are useful in the identification and may help for crop improvement, conservation, management and future usefulness of germplasm resources of Cinnamomum species. Keywords. Cinnamomum, Lauraceae, PCA, petiole anatomy, taxonomy