Abstract: The seeds of 40 gramineous species were collected from the alpine meadow in eastern Qinghai-Tibet Plateau. Based on the data of 9 morphological characteristics of seeds, the relativity among the morphological characteristics of seeds with altitude, variance and seed weight was analyzed. The results showed that: ①The seeds traits of 40 gramineous species exhibited certain differentiations in 9 morphological characteristics and the variation of coefficient of ratio of length to high of seed was the highest, while the coefficient of variation of seed weight was the lowest, indicating that seed weight was more stable than the others among the characteristics studied. ②Correlation analyses suggested that there is significant linear correlation between the morphological variation of seeds and altitude, and there is significant linear correlation between seed length and seed weight. Variance considering three dimensions (length, breadth and high) of seeds have higher correlation to SL/SH.SL/SH instead of the variance considering three dimensions is more appropriate than the others to measure the seeds overall pattern of gramineous species; The altitude is an important factor affecting the seed size and its variation.

Key words: Gramineae, seed size, variation, the eastern Qinghai-Tibet Plateau