Leaf epidermal characteristics of Asiatic Buddleja L. under scanning electron microscope: Insights into chromosomal and taxonomic significance

The leaf epidermis of all 23 species from Asian Buddleja was investigated with scanning electron microscopy (SEM). Characteristics of trichome type, stomatal shape, cuticular membrane on adaxial and abaxial epidermis, inner margin of outer stomatal ledge and ornamentation of outer stomatal ledge are presented in this study. Among the Buddleja species, some distinct epidermal patterns were observed. These can be used to characterize and identify different sections among the Asian Buddleja species, viz. Alternifoliae, Curviflorae and Rectiflorae. In general, stomatal length of Buddleja increases with ploidy level. This character can be used to distinguish diploids from polyploids without preparation of caryograms. Based on this correlation Buddleja microstachya, B. subcapitata and B. bhutanica are characterized to be diploids, as concluded from their stomatal dimensions. Leaf epidermis characters can also be used to differentiate species pairs that are easily confused with each other, viz., B. asiatica and B. bhutanica, B. albiflora and B. nivea, B. candida and B. fallowiana, B. delavayi and B. forrestii, B. japonica and B. lindleyana, B. officinalis and B. paniculata.