Comparative taxonomy and evolutionary significance of foliar epidermis in Jasminum L. (Oleaceae) based on light and scanning electron microscopy

Abstract

Jasminum L. is an important genus of the Oleaceae family with nearly 200 species cultivated or distributed wild in almost all parts of the world. A comparative taxonomy and evolutionary relationship on the basis of foliar epidermal quantitative and qualitative micro-morphological characters of nine species of the genus Jasminum were assessed using light microscopy (LM) and scanning electron microscopy (SEM) techniques. Foliar epidermal anatomical attributes like number and size of cells, stomata, stomata complex, granular and non-granular trichomes along with the abaxial to adaxial cell ratio and stomata index were assessed as distinguished characters of the Jasminum foliar epidermis. Results displayed irregular types of cells, anomocytic, cyclocytic, anisocytic and giant stomata, peltate glands and unicellular or uniseriate trichomes in Jasminum species. The presence of domatia at the vein axil, glabrous, hairy, or spiny leaf margin, midrib, anticlinal view of the cells, cuticular folds and striations appeared as valuable micro-morphological attributes in Jasminum. The cluster analysis based on micro-morphology divided Jasminum species into two major clusters. The first cluster (C1) displayed four white flowering Jasminum species from section Unifoliolata with shared characters like simple opposite leaves with spinose and cuticular striations. The second cluster (C2) showed five white and yellow flower-bearing Jasminum species having compound leaves with cuticular folds or striations and spinose at their leaf margins. Conclusively, micro-morphological attributes are crucial to characterize and infer evolutionary relationships and the direction of character evolution from yellow to white flowering Jasminum.