The Morphological Comparison of Abaxial Epidermis of Leaf in Three Oryza Species

The genus Oryza includes more than 20 species, 3 of which differ particularly from the others. O. eichingeri is thought to distribute in both Asia and Africa disjunct, while the species O. officinalis and O. punctata have been confirmed to have both diploidy and tetraploidy. Abaxial epidermal characters of mature leaves in the 3 species were investigated under both light microscope (LM) and scanning electron microscope (SEM) to identify intraspecies micromorphological difference. Inconstant shape of the papillaes on the intercostal long cells within O. eichingeri was found. Except the nodular papillaes distributing on the leaf epidermis of Sri Lanka geographical race of the species, the elongate papillaes were also observed in Uganda race. Similarly, interspecies diversity existed in O. officinalis and O. punctata, especially among their different ploidies. In contrast to the granular shape papillaes around the stomata and less density of trichoma on costal zones in tetraploidies of O. officinalis, the triangle and overarching shape papillaes, and denser trachoma were observed in diploidies. Meanwhile, comparing with their tetraploid counterparts, the small papillaes on the intercostal long cells and low density of stoma were otherwise found in diploidies of O. punctata. These stable differences on abaxial epidermis of leaves could provide new evidences for recognition of the three species and identification of intraspecies taxa.