The Xylem Anatomy And Germination Of Geographical Substitute Caragana Species

Caragana is widely distributed in China,known for its strong adaptability.Although the Caragana have the same origin,in different habitats show different adaptability.Caragana can not only widely distributed in mild and humid regions,also grow in the dry barren areas.Caragana was selected for this study on the precipitation distribution of gradient different of the geographical substitute species.Morphological observation,comparison leaves,petioles and branch xylem anatomical structures,analysis of seed germination habitat suitability and the morphology of seed coat structure.Aims to study the adaptive evolution of Caragana and to investigate the drought relief system of plants.The results obtained area as followings:1.The species from humid and semi-humid areas with large single pinnate areas,higher plant height and less branched.The species from arid and semi-arid areas have smaller single pinnate areas,shorter plant height and more branched.2.The xylem of Caragana from humid and semi-humid areas have larger diameter and more tube.The species from arid and semi-arid areas,the xylem of Caragana have smaller diameter and ability to withstand external forces,namely(T/B)3 large.3.C.stipitata from humid areas have no germination.The species from semi-humid areas C.boisi and C.arborescens germination rate is low,respectively 23%and 40%,germination is slow.The species from arid and semi-arid regions germinate quickly.With variable temperature increases,the species from semi-humid areas remain unchanged or increase slightly;the species from arid and semi-arid areas germination rate has dropped significantly.4.All the seed germination rate decreased with decreasing water potential,the species from semi-humid areas C.boisi and C.arborescens have no longer seed germination with the-1.0MPa water potential.The species from semi-arid areas C.microphylla and C.intermedia also have germination with the water potential are-1.6MPa and-1.8MPa.The seed germination rate of C.korshinskii from arid areas,began to decline when the water potential of less than-0.8MPa,when the water potential-1.8MPa still germinate.5.The seed coat of C.stipitata and C.boisi have no water infiltration channel;the seed coat of C.arborescens is thinner than other species.C.microphylla,C.intermedia and C.korshinskii have many of water infiltration channels.