Effects of seed morphological traits on Carex schmidtii germination under gibberellin and saline-alkali interactions

Carex schmidtii, a typical wetland plant species in Northeast China, plays a crucial ecological role in maintaining wetland ecosystem stability, carbon sequestration capacity and biodiversity. However, its extreme low seed germination percentage severely restricts the large-scale application of seed-based wetland vegetation restoration and ecological restoration practices. To clarify the combined regulatory effects of environmental factors and seed morphological traits on seed germination, this study measured seed morphological traits of C. schmidtii (length, width, projected area, and weight) and conducted germination experiments across gibberellin solution gradients (0.05-0.20 g/L) and saline-alkali gradients (0-50 mmol/L). The results showed that saline-alkali stress significantly inhibited the germination rate and germination index of C. schmidtii seeds, while gibberellin treatment and its interaction with saline-alkali stress significantly affected the days to first germination. In the Spearman correlation analysis, among seed morphological traits, seed weight was the most influential factor, showing significant positive correlations with germination percentage, germination rate, germination index, germination potential and peak value, and a negative correlation with days to first germination. In contrast, seed length, width and projected area had no significant relationship with any germination parameter. Integrated regression analyses further indicated that, under the experimental conditions of this study, intrinsic seed morphological traits exerted stronger effects on the seed germination process than external environmental factors, with heavier seeds partially mitigating the inhibitory effects of saline-alkali stress. These results provide a scientific basis for the selection and pretreatment of C. schmidtii seeds based on morphological traits in wetland restoration practices.