Candle-soot particles as a low-cost seed priming agent for enhanced germination and salinity tolerance in tomato

Salinity severely limits seed germination by inducing osmotic imbalance, ion toxicity, and oxidative stress, creating a need for affordable and effective priming strategies. This study evaluated candle-soot particles, carbonaceous particles collected from candle combustion, as a low-cost priming agent to improve tomato seed germination under salinity stress. Soot particles were synthesized using a flame-collection method, characterized, and applied as a priming treatment before germination under five salinity levels (0, 50, 100, 150, and 200 mM sodium chloride). Soot priming significantly improved germination percentage, seedling vigour, and stress tolerance across all salinity levels. Primed seedlings accumulated less Na + and Cl - , exhibited lower malondialdehyde and proline accumulation, and showed moderated catalase, peroxidase, polyphenol oxidase, and ascorbic acid oxidase activities, indicating reduced oxidative damage. These changes suggest that soot priming mitigated salinity stress by restricting excessive ion uptake and stabilizing cellular redox balance, thereby reducing oxidative injury during germination. Starch degradation and soluble sugar accumulation followed similar temporal trends in both primed and non-primed seeds under salinity stress. Overall, candle-soot particles acted as an effective, low-cost priming agent that mitigated salt stress by limiting ion uptake and stabilizing redox balance. These findings highlight soot-based priming as a promising approach for seed enhancement in salt-affected agricultural systems.