Abstract: In this paper four populations of Stipa krylovii in Inner Mongolia steppe, collected from Xinhot, West Xilinhot, East Xilinhot, Bayanwula, respectively, were used for the study of their morphological variations. (1)The variation of some morphological characters was greater than that of other characters within the same population. (2)Among all populations some of the reproductive traits varied much more than others, and in the vegetative traits, dry matter weight per reproductive shoot had greater variation than height of vegetative shoot.(3) Most reproductive traits, including the number of florets per panicle, seeds per panicle, spikelets per panicle, height of reproductive shoot, dry matter weight per panicle, dry matter weight per reproductive shoot, seed weight per panicle and the ratio of seed weight/ reproductive shoot weight varied in a similar pattern, and their values increased with their habitats worsening. This suggested that S. krylovii could increase the allocation of the photosynthetic assimilate to sexual reproduction so as to respond to the adverse habitat. (4) The principal component analysis revealed that ten morphological traits were mainly responsible for the variations among populations. The ten traits included the length of panicle, ratio of the dry matter weight between seeds and reproductive shoot, the number of spikelets per panicle, the number of seeds per panicle, height of the reproductive shoot, height of vegetative shoot, weight of 1 000 seeds, length of awn apex, length of callus and length of the second segment of awn. The variation of these traits might have resulted from adaptability of S. krylovii to different habitats.

Key words: Stipa krylovii Roshev., morphological variation, principal component analysis