Study On The Morphology And Systematics Of Leguminosae In Northeastern China

The morphology and anatomical structure of leaf, fruit, seed and seedling of Leguminosae in Northeastern China were studied using paraffin section, GMA semi-section and SEM in this study. Additionally, ITS sequences were used to reconstruct IRLC phylogeny tree of Leguminosae in Northeastern China. The main results are as follows.1. Leaf:Leaf style of Leguminosae in Northeastern China is usually compound. Stipule shape is lanceolate, semi-sagittate, and the texture is herbaceous or scarious. Leaflet is ovate or oblong, usually with single celled non-glandular trichomes. T-shaped trichomes are found in Indigofera kirilowii and some species of Astragalus. Capitate glandular trichomes are found in some species of Tribe Phaseoleae, Tribe Vicieae, etc, and scaly trichomes occur in Glycyrrhiza. The anticlinal wall of epidermal cell is arched or sinuate, and the type of stomata is anomocytic, anisocytic or paracytic. Petiole transected outline is round, cordate, hastate or arched, with continuously arranged vascular tissue or three, five to more scattered larger vascular bundles. These characters, such as stipule texture, trichome type and main stomata type are usually consistent among species in a genus so that they can be served for the generic taxonomy.2. Fruit:Fruits are legumes, ovate, cylindrical or falcate, and faint yellow, brown to black. Pericarp is leathery or membranous which is divided into epicarp, mesocarp (with vascular bundle) and endocarp (with fiber or stone cell). Dehiscent pericarp is with a separation tissue at each suture. Sophora japonica and Psoralea corylifolia are with indehiscent colloid pericarp. Legume is single locular with one to several seeds. The legumes of Mimosa pudica and taxa of Hedysarum are segmented between seeds. The morphological differences of fruit shape, pericarp texture number of seed and fruit segmentation, etc, have some extent taxonomic values for generic classification.3. Seed:Suspensor and coleorhiza are present in the process of seed embryo formation of Mimosa pudica. Testa developed from outer integument. Mature testa is divided into palisade layer (with light line), hour-glass cell layer and mesophyll cell layer. The seed shape of most species is reniform, as well as ovate and spherical. The surface is smooth, with fracture line or pleurogram in some species. Hilum is at the side of seed, seldom on the top. The shape of hilum is punctiform, round, oval or linear. Endosperm is none or thin, scarcely thick. Most of radicle axes are bent, rarely straight. These characters are used as the dividing bases of the 3 subfamilies, tribes and genera.4. Seedling:During the seed germination of Mimosa pudica, the coleorhiza ruptures and then falls off. Radicle elongates to form a root system. Cotyledon is epigeal germination and epicotyl elongates. The external morphology of seedling is divided into two parts:root-hypocotyl-cotyledon and epicotyl. The cotyledon of M. pudica processes photosynthesis after extension, but the cotyledon of Sophora flavescens is hypogeal germination, so it only has nutrition storage function. According to cotyledon germination type, epicotyl elongate or not, type of first two leaves, etc, the seedlings of Leguminosae in Northeastern China are divided into 20 types. Seedling type is consistent in a genus, but more than one type occurs in Astragalus, Glycyrrhiza, and so on, which can be regarded as the intergeneric and interspecific classification bases.5. Systematics:The results based on the morphological and molecular analyses showed Tribe Galegeae and Tribe Hedysareae have an intimate relationship, and Tribe Trifolieae and Tribe Vicieae are closer. Astragalus is close to Oxytropis in Tribe Galegeae, but Caragana and Gueldenstaedtia are close to Hedysarum, and Glycyrrhiza is apart from the Tribe Galegeae. Tribe Trifolieae is a polyphyletic group, Medicago and Melilotus are intimate, and Trifolium is regarded as the basal group of remaining gerera of Tribe Trifolieae and Tribe Vicieae. Tribe Vicieae is a monophyletic group, the relationship between Pisum and Lathyrus is closer than Vicia.The morphological characters of Leguminosae in Northeastern China were systematically revealed in this study, which further improved the morphology of Leguminosae, confirmed the taxonomic values of these morphological characters in the systematics study of Leguminosae in Northeastern China, and provided the bases for classifying the groups of Leguminosae. Moreover, combining with the molecular methods, we discussed the systematics of Leguminosae in Northeastern China, which offered the evidences for study on the phylogeny of Leguminosae.