Micro-morphological study of Evolvulus spp. (Convolvulaceae): the old world medicinal plants

Several medicinal properties have been reported for plants in the genus Evolvulus, such as a brain tonic and antifungal from Evolvulus alsinoides, and a sedative and an anthelmintic from Evolvulus nummularius. Therefore, the correct identification of the source plants is critically important. The aim of this research was to investigate the micromorphology of two Evolvulus taxa used for herbal medicines compared with one worldwide ornamental species by using peeling, paraffin embedding, acetolysis, and SEM methods in order to support species identification.

Our findings indicate that all taxa share several common features, such as a single layer of epidermis on both sides of leaf surfaces, sinuous anticlinal epidermal cell walls, anomocytic, paracytic or laterocytic stomata, and capitate glandular trichomes. Y-shaped hairs were found in two species but not in E. nummularius. Similarly, isobilateral mesophyll occurs in both E. alsinoides and Evolvulus glomeratus, but a dorsiventral mesophyll is present in E. nummularius. Stems consist of a single layer of epidermis, one to four chlorenchyma layers, one to seven layers of cortical cells and a bicollateral bundle with pith in the center. The seed coat epidermal cell shapes were irregular or polygonal with raised and undulated anticlinal boundaries, and folded or flattened to concave periclinal walls. Pollens of all taxa are monads, spheroidally shaped with 28-47 µm diameter, and 15-pantocolpate apertures type with microechinate ornamentation.

An identification key to species is constructed based on leaf anatomy and seed coat characters. This data can be used in other subjects such as pharmaceutical botany, organic chemistry, taxonomy and horticulture, in terms of species identification.