Effects of mixed chloride-sulphate salinity and temperature on the germination of Peganum harmala seeds

Peganum harmala (Nitrariaceae) is a perennial species widely distributed in the semi-arid regions of the Palearctic, where salinity and temperature are important environmental factors affecting seed germination and establishment. This study evaluated the ef­fects of mixed sodium chloride-sulphate salts on the seed germination and early seedling development of P. harmala under two temperature regimes (25 and 30°C). The results demonstrate that the effects of salinity on P. harmala germination and early devel­opment depend not only on salt concentration but also on ionic composition in the substrate and temperature. Sodium chloride-dominated treatments exhibited stronger inhibitory effects on the germination and seedling vigour parameters, particularly at 30°C. The mixed saline environments induced specific physiological effects associated with ion interactions, distinct from those observed under the pure sodium chloride and sodium sulphate treatments. The recovery experiments revealed that the inhibitory effects of chloride-sulphate salinity were largely reversible, indicating that saline stress caused temporary osmotic constraints. While sodium chloride mainly delayed P. harmala germination during salt exposure, sodium sulphate exhibited stronger inhibitory effects on seed­ling growth and vigour after stress removal at 25°C. However, the seeds recovering at 30°C showed higher germination percentages and recovery rates, as well as biomass-related vigour responses, suggesting the existence of increased metabolic recovery following stress removal. These findings contribute to the understanding of P. harmala seed recruitment under mixed saline conditions pres­ent in its native semi-arid habitats and provide insight into seed responses to combined salinity and temperature stresses which are expected to intensify under global warming.