Objective Water is an important factor limiting the growth and survival of plants in arid areas. The effects of precipitation changes on the desert Phytochemistry metrological characteristics, and the distribution of C, N, P and K elements in various plant organs are explored.

Method Based on the second-class of rare-endangered plants in China, Ammopiptanthus mongolicus, the only evergreen broad-leaved shrub in desert area, this paper analyzed the ecological stoichiometric characteristics of roots, stems and leaves of A. mongolicus under different precipitation gradients.

Results The results showed that the C content in the leaves was the most, followed by stems and roots, the nutrient contents of N、P and K in the leaves were also the most, followed by the roots and stems. The enrichment of the three nutrient elements N, P and K in the leaves could improve the photosynthetic rate of A. mongolicus and provide enough material support for plant growth and reproduction, reflecting the resource allocation pattern and plant growth strategy. Along the natural precipitation gradient, the roots, stems and leaves of A. mongolicus mainly showed a synergetic relationship. The content of N and P in each organ showed an upward trend with the increase of precipitation, while K showed a downward trend. A. mongolicus responded to the drought stress environment by increasing the content of K in each organ and reducing the content of N and P, indicating that there is an ecological strategy of simultaneous investment between the roots, stems and leaves of A. mongolicus. The ratio of N: P in each organ was relatively stable among different precipitation gradients. A. mongolicus counteracts the changes of element content with the environment by coordinating nutrient conservation strategies in a conservative way. The nutrient synergy between organs was much higher than that within organs. The N:P ratios of organs were all greater than 16, indicating that the growth of A. mongolicus was mainly limited by P.

Conclusion The stoichiometric characteristics of N, P, K in each organ have the same trend along the rainfall gradient, but show significant differences among different organs. The flexibility of stoichiometry is an important way to achieve plant self-regulation, which helps plants maintain their normal life activities under different environmental conditions.