Morphological characteristics of wild Bromus inermis seeds from the northern slope of the Tianshan Mountains

The morphological characteristics of seeds reflect the genetic characteristics of species, and differential adaptation will occur under the influence of the external environment and internal conditions. Exploring the differences in morphological characteristics of Bromus inermis seeds in different regions is of significance in revealing the population renewal and environmental adaptability of this species. In this study, the seeds of wild B. inermis in nine areas on the northern slope of Tianshan Mountain were studied to elucidate the structure of seed appendages (lemma length, palea length, and awn length), seed length, seed width, seed thickness, 1000-seed weight, volume index, and coefficient of variation. The decoration of the seed coat was observed. The collection sites were Wenquan (T₁), Zhaosu (T₂) and Xinyuan counties (T₃) in the western section; Shawan (T₄), Hutubi (T₅), and Urumqi counties (T₆) in the middle section; and Jimusar (T₇), Qitai (T₈), and Balikun counties (T₉) in the eastern section. The objective was to explore the effects of habitat differences (mean annual temperature, mean annual precipitation, soil nutrients) on seed morphological characteristics. The results showed that: 1) There were significant differences in morphological characteristics of B. inermis seeds in different regions. In T₁, T₇, and T₈ regions, the seeds were not awned, and the seed epidermis was decorated with stripes, ridges, and reticulations. 2) The variation of morphological indices in the study area was 7.74%～44.17%, and the degree of variation was awn length > volume index > seed thickness > seed width > seed length > lemma length > palea length > 1000 seed weight. 3) The seed morphology index was positively correlated with the mean annual temperature and soil total phosphorus content; negatively correlated with the mean annual precipitation, soil total nitrogen and total potassium content; and was less affected by the soil electrical conductivity and pH value. 4) Cluster analysis divided the B. inermis seeds from nine regions into three groups. Group Ⅰ (T₁, T₄, T₅, T₇, T₈) was short in shape and small in volume. Group Ⅱ (T₂, T₃) was mid range in terms of shape and volume. Group Ⅲ (T₆, T₉) was long in shape and large in volume. Seed morphology showed certain adaptability to different habitats, but there was no obvious meridional geographical differentiation law.