Salt tolerance during seed germination and early seedling stages of 12 halophytes

Abstract

Most studies on plant responses to salt stress have focused on one salt (e.g., NaCl). The aim of this study was to investigate the salt tolerance of halophytes with different seed masses to three different salts during germination and early seedling growth stages. Seeds of 12 halophytes were imbibed with five concentrations of NaCl, NaHCO3, or Na2SO4 solutions or with distilled water. Germination was recorded for 20 days. Un-germinated seeds were transferred to distilled water and recovery of germination was recorded for another 20 days. We measured the Na+ and K+ concentrations in the seedlings after the germination experiments. Most species showed higher germination percentages in NaCl than in NaHCO3 or Na2SO4 solutions. There were only significant differences in regressions of germination rates and salt concentrations for Anabasis salsa and Kalidium foliatum, between Na2SO4 solutions and the other salts. The Na+ concentration in the seedlings increased with increasing salt concentrations, while the K+ concentration was unchanged. Seed mass was significantly negatively correlated with the Na+/K+ ratio, and with decreasing germination percentage and decreasing germination rate at high salt concentrations. The halophytes showed species-specific responses to different salts. Some species were salt tolerators, while some were salt avoiders, as indicated by a high percentage recovery of germination in water after the alleviation of salinity. Seed mass was positively related to salt tolerance at high salinities.