The Rubiaceae Lasianthus Species Microscopic Characteristics

Lasianthus Jack (Rubiaceae ) has more than 180 species. It occurs in Asia, Africa and America in the tropical and subtropical areas, and only one species in Australia. There are thirty-three species, four subspecies and three varieties in China. In this paper, we study the pollen morphology, leaf epidermal morphology, fruit and seed characters by light microscopy (LM), scanning electron microscopy (SEM) and stereomicroscope. The results are expected to elucidate the relationships of infra-generic sections and take taxonomical treatments in some difficult species. In addition, the relationships of Lasianthus and related genera are discussed.1.Pollen morphology19 Asian species of the genus Lasianthus and 5 species from other five related genera have been examined. Lasianthus is eurypalyous. The pollen grains are small to medium in size and spheroidal or subprolate in shape, and few are prolate. Pollen characters showed the remarkable diversity, such as aperture and exine ornamentation in particular. The apertures are usually (3)-4-(5) zonoaperturate, which are porate and pororate. The number of aperture varies from 3 to 5, and the majority of species are 3-4 zonoaperturate. Colporate pollen is unique. Exine is usually perforate, finely-reticulum or coarsely-reticulum. Pollen data appears to be morphologically distinct and worthy of recognition among species of Lasianthus, which may elucidate some clues for further studying the relationships of some species, infra-generic sections, as well as Lasianthus and related genera.2.Leaf epidermal morphology28 species of Lasianthus and related 4 genera with 6 species are investigated. It shows that the cells shape of upper leaf epidermal vary with irregular sinuolate, nearly elliptic and irregular polygonal. The lower leaf epidermal cells are usually irregularly sinuous or sinuate.