Abstract: In this article, the photosynthetic types of 233 plant species in Northeastern China prairie area were indentified, and the relationships of their relative distribution with latitude, soil salt content and soil pHvalue were analyzed. Afurther study of physiological adaptation of several typical C₃ and C₄ grasses to saline-alkali environment was conducted. The result shows that among the identified 233 species, 144 species are C₃ plants, belonging to 94 genera of 28 families. and 89 species are C₄ plants, belonging to 55 genera of 17 famities. At high latitude districts, C₃ plants show a higher growth dominance. but al low latitude and saline-alkali districts, C₄ plants show a relatively dominant distribution, and especially in severely saline-alkali districts, C₄ plants become evidently dominant species. Tile difference of plant distribution depends on its adaptation mechanism to the saline-alkali environment: C₃ plants conduct a penetrative regulation through their accumulation of proline and other organic solutes, and C₄ plants do this through the accumulation of intra-vocuole ions. Compared with C₃ plants, C₄ plants show a better adapting capability to tile saline-alkali environment.

Key words: Regionalization of ions, Photosynthetic type, Ecological distribution, Adaptation mechanism to saline-alkali environment, Penetrative regulation, marine organism, high seas in North Pacific Ocean, radioactive nuclide, monitoring, Fukushima nuclear accident