Integrative modelling of seed germination responses in three Stipa species under temperature, water and salt stress

Background Mitigating desertification requires understanding how temperature, water availability, and salinity regulate seed germination, a key process for plant establishment.Objective This study investigated the germination responses of three perennial Stipa grasses that dominate arid grasslands, with the aim of identifying their germination response under abiotic stresses.Methods Germination was tested under five constant temperatures (10–30°C) and varying intensities of water stress induced by poly(ethylene glycol) 6000 (0 to −1.2 MPa) and salinity stress induced by NaCl (0 to 0.2 M). Thermal time, hydrotime (θH), halotime and hydrothermal time (θHT) models were used to quantify germination parameters and species tolerance.Results The three Stipa displayed contrasting strategies. S. parviflora showed the most negative base water potential (ψb=−0.983 MPa) and the highest θH (491 MPa·day under NaCl) and θHT (1631−1721°C·MPa·day) values, indicating strong stress tolerance but slower germination. S. lagascae exhibited intermediate tolerance and wide thermal plasticity. S. tenacissima germinated rapidly under favourable conditions but was strongly inhibited by osmotic and saline stress.Conclusions These results highlight species-specific physiological thresholds governing germination under combined stresses and offer a predictive basis for selecting Stipa species and optimising seeding strategies for arid grassland restoration under climate change.