Seed priming techniques have been used to increase germination, improve germination uniformity and seedling establishment under stressed conditions. Seed priming was used in rye mountain (Secale montanum) to increase seed germination and tolerance on stress exposure (Cold stress). Rye seeds were treated with water (Hydro priming) and polyetelyn glycol 6000 (Osmo priming). The effect of priming was assessed on germination characteristics under cold stress (at 3°C) for 7 days. Analyze of variance for hydro priming showed that temperature × time of priming interaction was significantly (P < 0.01) for all traits under cold stress and for osmo priming showed that Concentration of PEG × Temperature × Time of priming interaction was significantly (P < 0.01) for all traits under cold stress except seedling dry weight (SDW). For hydro priming the highest germination percentage (GP) was attained from hydro priming at 15±1°C for 16 h (70%), whereas the highest normal seedling percentage (NSP) (22.5%), germination index (GI) (8.57), seedling vigor index (SVI) (38.9) and seedling length (SL) (1.7 cm) were in the hydro priming at 10±1°C for 16 h. For osmo priming the highest germination percentage (GP) (80 and 80.5%), normal seedling percentage (NSP) (48 and 45%), seedling vigor index (SVI) (101.26 and 85.25) and seedling length (SL) (2.11 and 1.89 cm) observed in the osmo priming with concentrations of -9 and -15 bar PEG at 15±1°C for 24 h.
Seed priming is one of the methods that can be taken to counteract the adverse effects of abiotic stress, also Seed priming treatments have been used to reduce the damage of aging and invigorate their performance in many crops. Objective of this study was to evaluation the effect of gibberellin on germination characteristics and antioxidant enzymes of safflower seeds after aging. Experimental design was a factorial one with complete randomized design with three replications. The first factor was priming by gibberellin (0 and 50 ppm) and non-primed seeds (control) and the secondary factor was combinations of four levels of aging (0, 1, 3 and 5 days of aging, at 43°C). The results showed that the priming and aging effects on germination percentage, germination index, normal seedling percentage, seedling length, vigor index, catalase and ascorbate peroxidase were significant, but on mean time to germination not significant. Results showed that, the highest germination characteristics such as; germination percentage, germination index, normal seedling percentage, seedling length, vigor index, catalase and ascorbate peroxidase were attained from priming by gibberellins, under non aged conditions. Also, our results indicated that seed aging is related to decrease of enzymes activity and may contribute to low seed germination efficiency, also priming increases enzyme activity and increases enzyme activity with priming treatment may contribute to improve germination characteristics. The general decreases in enzyme activity in the seed lowers the respiratory capacity, which in turn lowers both the energy (ATP) and assimilates supply of the germinating seed.
Seed priming with gibberellin (GA) enhances seed germination performance; but the quality of primed seeds in aging condition often reduces more than non-primed seeds. An experiment was conducted to evaluate the effect(s) of heat shock treatments on germination characteristics and enzyme activity of primed mountain rye (Secale montanum) seeds with gibberellin under accelerated aging. Heat shock treatments, can substantially decrease the speed of quality reduction of mountain rye (Secale montanum) primed seeds. In primed seeds with gibberellin, which has non-aged, the highest germination percentage (GP) and normal seedling percentage (NSP) was attained from heat shock treatment at 35°C for 3 h, also after 3 days aging, it was attained from heat shock treatment at 35°C for 3 h. After 3 days of aging the highest germination index (GI) was attained from unprimed seeds, but no significant difference with heat shock treatment at 35°C for 3 h. The minimum means time germination (MTG) was in heat shock treatment at 30°C for 3 h in non-aged seeds. After 3 days of aging, heat shock treatment reduce MTG as compared to the primed seeds. Heat shock treatment at 35°C for 3 h increased seed vigor index (SVI) as compared to the unprimed and primed seed in non-aged seeds and after 3 days aging. Seedling length (SL) increases with heat shock treatment at 30°C for 4 h in non-aged seeds as compared to the primed and unprimed seeds, but after 3 days of aging heat shock treatment except at 35°C for 3 h and 40°C for 4 h reduced SL as compared to the primed and unprimed seeds. Also, heat shock treatments increase some antioxidant enzymes [Catalase (CAT), Ascorbat peroxidase (APX)].