Effects of mixed salt stress on the growth and physiological and biochemical characteristics of Elaeagnus angustifolia seedlings from different provenances

  Objective  The physiological responses of different provenances of Elaeagnus angustifolia to mixed salt stress were studied to provide basis for the selection of excellent salt tolerant germplasm and landscape application of Elaeagnus angustifolia.

  Method  Two-year-old Elaeagnus angustifolia seedlings from Yinchuan of Ningxia and Zhangye of Gansu of northwestern China were used as experimental materials. The mixed salt solution of 1∶1 (volume ratio) of NaCl and Na₂SO₄ was used to stress for 40 days, and the growth and physiological indexes of seedlings were observed.

  Result  With the increase of salt concentration and stress time, the leaf length, leaf width, shoot growth, ground diameter growth and chlorophyll content (Chl) of Elaeagnus angustifolia seedlings from two provenances decreased. The membrane permeability (MP), MDA content, proline content (Pro) and soluble sugar content (SS) of leaves showed an upward trend; the soluble protein content (SP) first increased, then decreased, and then increased; the activities of SOD and POD first increased and then decreased. With the increase of salt concentration, the net photosynthetic rate (P_n), stomatal conductance (G_s) and transpiration rate (T_r) of seedlings decreased, while the intercellular CO₂ concentration (C_i) increased. With the extension of stress time, the P_n of Elaeagnus angustifolia from two provenances decreased first, then increased and then decreased; stomatal conductance of leaves decreased first, then increased and then decreased; intercellular CO₂ concentration decreased first and then increased; transpiration rate of leaves showed a downward trend. The salt tolerance thresholds of Ningxia and Gansu provenances were 1.088% and 1.153%, respectively.

  Conclusion  Comprehensive analysis showed that the salt tolerance of Elaeagnus angustifolia seedlings in different provenances was different, and the salt tolerance of Elaeagnus angustifolia seedlings in Gansu provenance was stronger than that in Ningxia provenance. Chl, C_i, MDA, T_r, MP, Pro and other six indicators can be used as important indicators to evaluate the salt tolerance of Elaeagnus angustifolia. Leaf length, leaf width, shoot growth, ground diameter growth and other indicators can be used as auxiliary evaluation reference indicators. The results of this study are of great significance for the evaluation of salt tolerance and the introduction and cultivation of germplasm of Elaeagnus angustifolia, as well as the enrichment of plant landscape and improvement of ecological environment in saline-alkali area.