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Salinization and alkalization are worldwide problems of soil. To compare the effects of saline-alkaline stress on seedling growth between rice mutant and its wild type, we selected NaCl, Na2CO3 and NaHCO3 to simulate saline-alkaline stress, respectively, and selected two rice materials, ML04 is rice mutant and G19 is its wild type. Under saline-alkaline stress, the rice biomass sharply decreased, and the shoot fresh weight of ML04 was higher than that of G19. The saline-alkaline stress promoted the rice taking up Na+ but inhibited absorbing K+ in shoots. The Na+ and K+ contents under the alkaline stress were much more than those of under saline stress, and the Na+ content of ML04 was higher than that of G19 under alkaline stress treatments. The saline-alkaline stress reduced the root numbers (RN), total root length (TRL), root surface area (RSA), root volume (RV) and shoot length, but increased the Na+/K+ ratio and the root diameter (RD). And all these root indices of ML04 were higher than G19 under alkaline stress treatments. The high pH of alkaline salt stress might be an important reason for the severe damage to rice root system, which further limited the rice aboveground parts growth. In conclusion, the saline-alkaline stress inhibited the rice seedling growth, and most of the indices showed that the rice mutant (ML04) was much more tolerant to alkaline stress than its wild type (G19). [ABSTRACT FROM AUTHOR]