Studies On The Ecological Adaptability Of The Genus Caragana On The Ordos Plateau

The Ordos Plateau, a relatively independent natural unit in the semiaridarea of China, is a multiplied-levels, typical and complicated ecotone. Eight species of the genus Caragana plants are growing in the typical steppe, desert steppe and steppe desert from the east to the west on the Ordos plateau. They are C. purdomii, C. opulens, C. intermedia, C. korshinskii, C. stenophylla, C. roborovskyi, C. tibetica and C. brachypoda. With large quantity, abundant species and wide distribution, Caragana plants play an important role on the Ordos Plateau where the shrub communities are the dominant life form. This thesis introduced the ecological adaptability of Caragana plants basing on the study of morphological characters, anatomical structures, physiological characters and genetic structure of the Caragana plants and the study of seasonal changes of physiological characters of the 5 species of genus Caragana transplanted to Huhhot Arboretum. The study results were as follows:1. Study results on morphological charactersThere was cuticle and wax on the leaf epidermis of the 8 species of the genus Caragana. Among them, the wax of C. purdomii was especially thick. The stomatal density of C. opulens, C. intermedia, C. korshinskii, C. stenophylla, C. roborovskyi, C. tibetica and C. brachypoda was comparatively low, and their stomas sunk below the epidermal cells. The sinking degree of the stomas of C. tibetica and C. roborovskyi was the deepest. The leaf epidermis of C. intermedia, C. korshinskii, C. tibetica and C. roborovskyi was covered with dense trichome. These micro morphological characters were of benefit to reduce water loss and reflex strong light, which were adaptive characteristics caused by the droughty environment on the Ordos Plateau.2. Study results on anatomical structuresThe mesophyll tissue of Caragana plants varied from bifacial leaf to transitional form to ring-palisade to total-palisade as the environment was getting drier from east to west The structure changing from typical mesomorphic to typical xeromorphic was an ecological adaptability to the transitive ecological environment of the Ordos Plateau where the vegetation zone was from eastern typical steppe and desert-steppe to western steppe-desert. The xeromorphic structures of the 8...