Physiological response of five shrubs to NaHCO3 stress in Qitai Highway

Songnen Plain is one of the world’s 3 largest Soda Saline-Alkali Soil and one of China’s 5 major saline-alkali soil. Saline-alkali soil as an environmental factor has restricted development of farming and animal husbandry. Qitai highway is located in Songnen Plain which has serious soda saline-alkaline hazard. Salt resistance plant selection is of great significance for the ecological restoration in this area. The main components of Soda Saline-Alkali Soil is NaHCO3 which has more extent of injury to plant more than other harm and easily form white alkali spot on the surface of the earth to restrict plants growth. The ecological environment destruction of Saline-Alkali Soil was great and difficult to recover, especially for highway slope with road construction. In the present paper, five shrubs including Amorpha fruticosa, Tamarix chinensis, Caragana microphylla, Hippophae rhamnoides and Hedysarum fruticosum var. mongolicum were selected as test material. After 7 days treatments with 4 different NaHCO3 stress (0, 0~0.5, 0.5~1.0 and 1.0~1.5 g·kg-1), different indices including shrub leaf plasma membrane permeability (RPP), chlorophyll (Chl) content, superoxide dismutase (SOD) activity, malondialdehyde (MDA) content, soluble sugar (SS) content and proline (Pro) content were measured to test shrubs resistant to NaHCO3 stress. With the NaHCO3 stress increased, all of 5 shrubs’ membrane permeability increased,the total Chl amount of C.microphylla first increased and then decreased, the other four shrubs’ chlorophyll content declined. With the stress extended, MDA, SS, SOD, Pro content of 5 shrubs increased except with Pro content of A.fruticosa. All of these variations indicated that the tested shrubs can induce physiological protection to resist the stress of NaHCO3. However, these 5 tested shrubs had different protected ability with following order: A.fruticosaH.fruticosum var.mongolicumT.chinensisH.rhamnoidesC.microphyll. A.fruticosa and H.fruticosum var. mongolicum were more suitable 0.5, 1 and 1.5 g·kg-1 saline concentration of highway slope, H. hamnoides was suitable 1 g·kg-1 saline concentration and T. hinensis was suitable for slope 1.5 g·kg-1 saline concentration under of highway slope.