Introduction Screening of halophytes is the key to biological improvement of saline-alkali soils. This study sought to determine the influence of low, moderate, and high combined saline-alkaline stress on the germination period of different halophytes and evaluate the salt-alkali tolerance of halophytes. Methods The paper-based culture method be used to determine the germination and growth indices of 9 halophytes under low, moderate, and high combined saline-alkaline stress. Results The study emphasizes (1) the germination strategies of the 9 annuals halophytes showed significant differentiation, falling into 2 categories: “rapid-type” and “slow-type”. Seeds of Suaeda corniculata , Halogeton arachnoideus (LZ), and Chenopodium quinoa belonged to “rapid-type”, completing germination within merely 1~3 days. (2) The combined saline-alkali stress exerted a typical “low-promotion and high-inhibition” effect. Under moderate stress (MS, salt content 0.55%, pH 8.90, EC 6.38 mS cm -1 ), the fresh weight of Salicornia europaea , Atriplex centralasiatica and Chenopodium glaucum was significantly higher than that of low stress (LS, salt content 0.27%, pH 8.03, EC 3.62 mS cm -1 ) and high stress (HS, salt content 0.73%, pH 9.63, EC 9.54 mS cm -1 ) treatments. Specifically, compared with the LS treatment, the fresh weights were increased by 18.73%, 9.87%, and 13.42% for the three species, respectively; compared with the HS treatment, the corresponding increases were 71.76%, 88.95%, and 127.46%, respectively. High stress preferentially inhibited radicle length, thereby affecting biomass. Taking Atriplex centralasiatica and Chenopodium quinoa as examples, the inhibition rate of radicle length (94.19%, 95.57%) was significantly higher than that of inhibition rate of germ length (40.54%, 32.48%). (3) Correlation analysis revealed a positive correlation between seed germination vigor and root development along with biomass accumulation. Seed germination performance in saline-alkali environments is determined by the plant’s genetic background, the external stress intensity, and their complex interaction. Conclusions Suaeda salsa demonstrated the strongest overall tolerance, while Suaeda corniculata , Salicornia europaea , and Halogeton arachnoideus are recommended for rehabilitating high, moderate, and low saline-alkali soils, respectively. This study elucidates halophyte germination strategies under combined saline-alkali stress, providing a theoretical basis toward effective species selection for saline-alkali land bioremediation.
Zhou et al. (Tue,) studied this question.