Preliminary study on leaf epidermal micromorphological characteristics of 23 Chinese Paphiopedilum Pfitz. species

The leaves of 23 species of Paphiopedilum Pfitz. were observed by optical light microscopy. Principal component and cluster analyses were carried out on the measured values of 14 leaf epidermal micromorphological characters. Results showed that the leaf epidermis of the 23 plants had thicker cuticles. The upper epithelial cells were mostly polygonal and ovoid, with no stomatal distribution. The epidermal cells on some of the leaves had epidermal hairs, and the epidermal cells formed mastoid protrusions. A cell formed only one mastoid, and the surface of most species showed obvious or inconspicuous curvature uplift. Cell size and density varied greatly among different species; the stomata were widely distributed in the lower epidermis, which was composed of irregularly arranged guard cells, and the outer wall was thickened to varying degrees. Principal component analysis showed four principal components with an eigenvalue greater than one. Based on the clustering of the four principal components, the genus Paphiopedilum could be divided into two broad categories:Brachypetalum,Paphiopedilum, and Parvisepalum were clustered in Subgen. Brachypetalum. This study showed that the morphological characteristics of the leaf epidermis in the genus Paphiopedilum had certain stability and the epidermal cells in plant leaves demonstrated little variation in shape of the vertical wall. Due to environmental and climatic effects, stomatal organ size and stomatal density were distributed differently in different interspecific, thus showing interspecific diversity. Therefore, these micromorphological characteristics of the leaf epidermis could be used as a reference for classification.