Taxonomic Study On Rhamnus In Shandong

Rhamnus belongs to Rhamnaceae.The scope and classificatiion of Rhamnus hasbeen in dispute. When investigated the forest germplasm resource of Shandongprovince, we collected more than260specimens of Rhamnus. In order to providesome scientific basis for taxonomical study of Rhamnus, we identified the specimens,observed the leaves epidermal micromorphology and seeds morphologycharacteristics, and also studied the molecular systematics of the genus based on ITSsequence.The leaf epidermis of Rhamnus was observed under both light microscope (LM)and scanning electron microscope (SEM). The leaf lower epidermis has stoma. Thepatterns of the leaf upper epidermis was divided into three types: corrugation stripes,corrugation scaly, stripes. The shapes of leaf lower epidermal cells were divided intothree kinds: sinuolate, wavy, straight or curved. And the patterns of the leaf lowerepidermis were divided into four kinds: the corrugation scaly, stoma have stripes onboth sides of the corrugation, nearly smooth have stripes, and corrugation stripes.There were three types of the inner margin of the outer stomatal ledge: smooth,lightwave, wave. By observing the patterns of the leaf epidermis, the inner margin ofthe outer stomatal ledge, we could distinguish the plants apart from each other.Micromorphological characteritics of leaf epidermis could provide some scientificbasis for taxonomical study of Rhamnus.We used the light anatomical microscope and scanning electron misrscope toobserve the seeds of Rhamnus. Using the light anatomical microscope, we found thatthe solid figures of seeds were divided into four kinds: ovoid, torque for round ovoid,obovoid, wide ovoid. The length of the groove has three kinds: less than1/2of theseed length, more than1/2seed length, and equal. Using the scanning electronmicroscopy (SEM), we found that the seeds patterns of each species were notidentical, and the patterns can be divided into four types: the surfaceof the seed moresmooth, the surface of the seed particle, seed surface is rough, the surface of the seeds with sag. By observing the solid figures of seeds, the length of the groove, and thesurface patterns, we could distinguish the species of Rhamnus. Therefore, themorphologiccal characteristics of seeds can be used as an important basis for theclassification of Rhamnus.In this study, we constructed the phylogenetic tree using ITS sequence. Theresults showed that the species of Rhamnus divided into two branches. Rhamnusdiamantiaca, Rhamnus davuricais and Rhamnus ussuriensis gathered together as aclade, and they separated respectively, which showed that the three species haveclosely relationship. Rhamnus arguta and Rhamnus yangtianshannensis gatheredtogether as a clade, which showed that they have closely relationship. Rhamnusarguta and Rhamnus yangtianshannensis seems similar in morphology, but theyseparated on the phylogenetic tree, so we concluded that Rhamnus yangtianshanensiscan be as a new species.According to the results of leaf epidermies, seeds and molecular, we coulddistinguish the species of Rhamnus. Rhamnus yangtianshanensisnensis, no materfrom the leaf epidermal micromophology, seed morphology or from molecular aspect,is different from other species, so Rhamnus yangtianshannensis can be as a newspecies.