Comprehensive evaluation of salt tolerance among four species of Chenopodiaceae at the germination stage

We investigated seed germination of four species of the subfamily Chenopodiaceae, including Kalidium foliatum, Kalidium caspicum, Halocnemum strobilaceum, andHalostachys caspica, under various salt stress conditions (NaCl concentration of 0, 100, 200, 300, 400, 500, 600 mmol·L⁻¹). The germination rate, germination potential, germination index, vigor index, and the length of radicle and plumule were measured to understand the salt tolerance threshold of the species. Further, a comprehensive evaluation of salt resistance by subordinate function method was conducted considering the technical reference for saline grassland improvement. The results showed that with the increasing salt concentration, the germination rate and potential, as well as germination and vigor indices of three of the four species, showed a decreasing trend. In contrast, the seed germination index, vigor index of H. caspica, and vigor index ofH. strobilaceum, initially showed an increasing trend and eventually a decreasing trend. The radicle and plumule lengths of the species except K. caspicum were higher than those of the control group under low salt stress (< 100 mmol·L⁻¹). At the germination stage, the salt tolerance threshold of H. caspica was the highest (307.44～836.00 mmol·L⁻¹), and that of K. caspicum was the lowest. The germination of germ seeds was completely inhibited under 300 mmol·L⁻¹ NaCl. Among the six indices, the thresholds of germination potential and vigor index were the lowest, whereas that of the germination percentage was the highest. According to the comprehensive analysis of membership function, the salt tolerance order of the four species was H. caspica > H. strobilaceum > K. foliatum > K. caspicum.