Improved Marjoram ( Origanum majorana L.) Tolerance to Salinity with Seed Priming Using Titanium Dioxide (TiO 2 )

Seed priming improves seed germination, plant establishment and growth even under stressful conditions. We studied the effect of seed priming with bulk (2 µm particles) and nanoparticle (13 nm) TiO 2 on physiological characteristics, essential oil content and percentage and free radical scavenging activity in marjoram ( Origanum majorana L.) under varied salinity conditions. We designed a factorial experiment with two factors and three replications. The first factor included three nanoparticle TiO 2 concentrations (20, 40 and 80 mg L −1 ), three bulk TiO 2 concentrations (20, 40 and 80 mg L −1 ) as seed priming agents and controls. The second factor included the four salinity levels (0, 25, 50 and 75 mM NaCl solution). Results of this study indicated that seed priming with bulk and nanoparticle TiO 2 improved free radical scavenging activity and physiological characteristics. Under non-saline conditions, seed priming with 40 mg L −1 of bulk or nanoparticle TiO 2 increased free radical scavenging activity significantly. When seeds were primed with 80 mg L −1 of bulk or nanoparticle TiO 2 , free radical scavenging activity decreased significantly. Under saline conditions, seed priming with 20 and 40 mg L −1 of bulk and nanoparticle TiO 2 improved free radical scavenging activity and physiological characteristics of marjoram as compared to non-priming conditions. Our results indicated that seed priming with 20 and 40 mg L −1 of bulk and nanoparticle TiO 2 is a practical way to improve seedling growth characteristics of marjoram in saline conditions by improving free radical scavenging activity.