Purpose: This study aimed to evaluate the effects of seed priming on Madagascar periwinkle (Catharanthus roseus L.) seedlings under saline conditions, focusing on salicylic acid and potassium nitrate treatments. Research method: The research was conducted at Ferdowsi University of Mashhad in 2024. F1 Seeds of the \\\'Sunstorm Red\\\' were primed with salicylic acid (150, 250 and 350 mg/L) and potassium nitrate (50 and 100 mg/L) for 24 hours. A factorial experiment based on a completely randomized design with three replications assessed four salinity levels (0, 4, 6, and 8 dS/m) and two sowing methods: direct sowing in pots and indirect sowing via germination in petri dishes followed by transplantation. Traits such as relative water content, SPAD index, electrolyte leakage, were measured 65 days after sowing. Findings: Seed priming significantly reduced the negative effects of salinity. Potassium nitrate priming outperformed salicylic acid in enhancing relative water content, SPAD index, stem and root lengths, and biomass. Direct sowing showed better resistance to salinity compared to indirect sowing, particularly in improving stem length, root length, and SPAD index. Primed seeds exhibited higher germination rates and stronger seedlings with enhanced growth characteristics compared to untreated seeds. Research limitations: The study was limited to specific priming agents and salinity levels, suggesting further research to optimize potassium nitrate concentrations for improved seedling production. Originality/Value: This research recommends potassium nitrate priming for robust C. roseus seedling production in saline environments. The findings can guide growers in selecting cost-effective priming strategies to enhance plant resilience and productivity sustainably.

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