The responses of seed germination and seedling growth to alkali stress in alfalfa with different seed coat colors

Soil alkalization has a significant inhibitory effect on the successful colonization of plant seedlings. Thus, exploring the germination of seeds and growth of seedlings in alkaline environments is of great significance for agricultural production. In this study, alkaline salt sodium carbonate (Na₂CO₃) was used to simulate an alkaline environment and evaluate the effects of different alkali stress intensities 0 (CK), −0.1, −0.2, −0.3, −0.4, and −0.6 MPa on two coat colors (yellow and dark brown) of alfalfa seeds (Medicago sativa) on germination and seedling growth. The results showed that under the control conditions, the germination rate, potential, and index, and root system and seed vigor index of yellow seeds were 143.43%, 151.33%, 137.35%, 38.69%, and 103.39% higher than those of dark brown seeds, respectively. The germination ability of yellow seeds was enhanced under a low alkaline environment (−0.2 to −0.1 MPa), and the tolerance of yellow seeds to moderate alkali stress ( < −0.3 MPa) was better than that of dark brown seeds. However, the germination and growth of dark brown seeds were significantly inhibited under low alkali conditions (−0.2 to −0.1 MPa) and they could not survive in high alkali environments. Therefore, in actual production, selecting seeds with a higher proportion of yellow seeds is more conducive to the establishment of alfalfa grassland in areas with soil salinization.