Variations of reproductive organs morphology of Stipa purpurea and relationship with climate on the Qinghai-Tibetan Plateau

As constructive species of alpine meadow and steppe, Stipa purpurea adapt to different climate conditions and is one of the most widely distributed plants on the Qinghai-Tibetan Plateau. Trypanophorous diaspora (including seeds and accessory organs) owned by S. purpurea is one of the most important factors for the plant to adapt to harsh environment. To illustrate the adaptive characteristics of this plant to the plateau environments, trypanophorous diasporas of 20 S. purpurea populations along a latitudinal gradient on the Qinghai-Tibetan Plateau were collected. Morphology characteristics of these diasporas from different populations were measured and their relationship with environmental conditions were also analysis in the present paper. The results showed that seed length, seed width, awn length and seed mass ranged from 0.692～1.255 cm, 0.392～0.713 mm, 2.394～8.736 cm and 0.678～1.560 mg, respectively. There were high values of coefficient of variability (CV) among populations in awn length and seed mass. Seed mass positively correlated with seed length and awn length. Seed length, seed width and awn length were positively correlated with each other. Seed length and seed mass increased significantly with equivalent latitude, but decreased with annual precipitation. Seed length displayed humpedshape relationships with mean annual air temperature. These 20 S. purpurea populations clustered into 3 groups according to these tested characteristics of trypanophorous diaspora, which consistent with geographic distributions of these populations.