Micromorphological characteristics of Gentianaceae seeds in Shergyla Mountain area of Tibet and their systematic and taxonomic significance

Scanning electron microscopy and stereoscope were used to observe the seed micromorphology of 20 species from six genera of the Gentianaceae family in the Shergyla Mountain area of Tibet. Results showed that the seeds of these 20 plants were black, yellow, dark brown, tan, taupe, and reddish brown and seed shape was divided into long ovoid, ovoid, elliptical, oblong, and nearly spherical. Skin ornamentation could be divided into mesh, striped, scorpion, and chew types, with the textured type further subdivided into six subtypes. According to the micromorphological characteristics of seeds, we investigated the evolutionary trends, taxonomic significance, and classification identification of genus Gentianaceae, and found that Swertia L. and Gentiana (Tourn.) L. showed a relatively high degree of evolution. Based on the micromorphological characteristics of the seeds, we identified a close relationship among Lomatogonium A. Br., Halenia Borkh., and Gentianella Moench. The characteristics of seed skin ornamentation of the genus Gentianaceae were relatively consistent with the classification system. This study shows that seed micromorphology is of significance in plant taxonomic studies and can be used as a reference trait for the study of plant system division, identification, and evolution.