Submitted to: Smithsonian Contributions to Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/1999
Publication Date: N/A
Citation: Interpretive Summary: Rice is one of the major food grains in the world. In order to maximize rice yields and thereby solve the problem of feeding the world, plant breeders are constantly striving to improve commercial varieties of rice by increasing yields and making the plants more resistant to plant diseases and insect attack. To accomplish this difficult task, commercial varieties must frequently be crossed with related wild type plants that provide the genes or genetic material which will lead to the introduction of new and improved varieties for agriculture. To help the plant breeders, scientists known as taxonomists collect and classify related plants and determine how closely they compare to the commercial varieties. This study uses a powerful microscopy, known as a scanning electron microscope, to observe the detailed features of flowers from 16 different collections of plants that are related to rice. The study describes the floral features of each of these plants and proposes a taxonomic classification that shows how these plant groups are related. This type of information is used by plant breeders for identifying plants having desirable genes that can be incorporated into new varieties of rice.
Technical Abstract: This investigation uses scanning electron microscopy to examine spikelet morphology in 16 species of Oryza, 1 species of Leersia and 1 species in each of the monotypic genera, Porteresia and Rhynchoryza. A detailed discussion of the spikelet epidermal features and their relationship to the pedicel and cupule is presented. The pedicel and cupule in species of Oryza are below the point of articulation of the spikelet, have similar epidermal features and are free from the vascular cylinder that proceeds upward into the spikelet. Therefore, we conclude that the pedicel cupules are not glumes but merely expanded apices of the pedicels. An original data set of 14 morphological characters was used to perform cladistic and phenetic analyses. Of these 14 characters, 6 describe the lemma, 3 describe the rachilla, 2 describe the glumes, 2 describe the articulation point and callus shape, and 1 describes the embryo. Our classification of Oryza consists of three subgenera: subg. Oryza, subg. Brachyantha comb. et sata. Nov., and subg. Schlechteria comb. et stat. nov. Within the subgenus Oryza, we recognize three sections: sect. Oryza (including series Oryza and ser. Latifoliae), sect. Ridleyanae, and sect. Padia.