Auspicious Genus Floral Organogenesis And Embryo Research

Reineckia Kunth, one genus in the tribe Convallariae (family Convallariaceae), contains only one species:Reineckia carnea (Andr.) Kunth. It is a perennial herb endemic to China and Japan and often used as a traditional medicinal herb in southwest China. According to the date from morphology, anatomy, palynology, cytology, phytochemistry and molecular systematics, this study observed the floral organogenesis and embryology of Reineckia by SEM and light microscope. Combined related information on other Convallariae taxon, the relationships among those genera was discussed. The main conclusions listed as follows:The floral organ primordia of R. carnea initiated in a reversed unidirection type-from adaxial side to abaxial side. The positions of tepal and stamen primordia were opposite respectively, and three carple primordia initiated at the opposite sites to three stamen primordia. At the early stage, the growth of filaments was arrested, while tepal primordia were free. Till later young flowers reached 3.5-4.5mm in length, tepals became partly fused with filaments into a short tube. Carpel primordia rose up freely but fused in later development. The flowers on the tip of inflorescences were prone to vary in floral organ numbers. Considering the floral primodium morphology of R. carnea in early stages and floral organ number variation, tepals. and stamens should differentiate from common promordia. Characters of the floral organogenesis pattern and perianth tube formation time of Reineckia, Speirantha and Convallaria, revealed that Convallaria was more derived among them, and Speirantha was more primitive than Reineckia.The main embryological characters of R. carnea in mega-microsporogenesis, and development of female-male gametophytes are listed as follows:The anther was four sporangiate. The anther walls development conformed to the basic type. The tapetum, of which each cell contained two nuclei in the later stages, was of glandular type and single origin. Meiosis of the microspore mother cells was accompanied by successive cytokinesis, resulted in isobilateral and occasionally tetrahedral tetrads. Two-celled type mature pollen grains were reported. The ovary of R. carnea was trilocular with axile placentation. The ovule was bitegminous, crassinucellate and anatropous, with micropyle formed by the inner integument. The development of the embryo sac was of the Allium-type. After fertilization through the micropyle, the zygote turned into dormancy status without certain time phase. The polyembryony was recorded in R. carnea.The comparative embryology of Convallariae revealed that:Convallariae was a nature group and specific traits of monotypic genera in the tribe were isolated. This result re-confirmed the viewpoint that Reineckia was more derived than Speirantha; the relationship between Reineckia and Convallaria was closer than with other genera, and much further from the genus Aspidistra. The stasis phenomenon of gynoecium development occurred in floral organogenesis of Reineckia and the abortion of microspore and ovule may be the important causes of its low seed bearing ratio.