Abstract: To explore the role of SSR1 gene encoding a functionally unknown mitochondrial protein of Arabidopsis thaliana in plant growth and stress response, ssr1-2 and its suppressor mutants EMS143 and EMS145 were used to track the growth of their roots and aboveground parts, as well as their proline sensitivity and iron homeostasis, and the effects of ssr1-2 short root phenotype on aboveground growth of seedlings were analyzed by micrografting. The results showed that the primary root length of ssr1-2 was shorter and the root architecture was similar to the fibrous root system. The growth of their shoots was also retarded, but appeared considerably later than the short-root phenotype. The results of micrografting revealed that the roots of ssr1-2could restrict the growth of the wild-type shoots and, and conversely, the shoot of ssr1-2 could also affect the growth of the wild-type roots, but the former had a bigger effect. ssr1-2 showed a hypersensitive phenotype to proline in seed germination, root length and leaf chlorophyll content. In addition, ssr1-2 appeared insensitive to Fe nutrition, that was, the stimulating effect of Fe salt on seedling growth was significantly less than that of wildtype WS, indicating a significant decrease in its ability to utilize Fe. The results suggested that SSR1 might be involved in the regulation of A. thaliana root growth by affecting the utilization of iron nutrient, implying that the impairment of the mitochondrial iron utilization machinery might contribute significantly to the enhanced inhibitory effect of proline on plant growth and development.