1Department of Agronomy & Integrated Cropping Research Center, Eslamshahr Branch, Islamic Azad University, Eslamshahr, Iran.
2Department of Agronomy, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran.
Abstract
Investigating the effects of priming methods on seedling physiology under osmotic stress conditions is important to understand how priming enhances osmotic stress tolerance in safflower. The mechanisms by which priming achieves this at the physiological level, such as changes in osmoprotectants, antioxidants, and membrane damage, are not well understood. This research aims to fill these knowledge gaps and provide insights that can be used to optimize priming treatments and improve safflower productivity in drought-prone areas.. Seeds were treated with priming including distilled water, folic acid, glutathione, epibrassinolide and chitosan and then subjected to osmotic stresses including no osmotic stress, mild osmotic stress (4 bar) and severe osmotic stress (8 bar) for germination and seedling growth. Severe osmotic stress increased soluble leaf proteins, this increase was observed in all priming treatments except distilled water. Severe osmotic stress increased soluble leaf proteins by an average of 35% in folic acid, chitosan, and epibrassinolide treatments. Chitosan treatment exhibited 172% and 188% more proline under mild and severe stress, respectively, compared to the control. Folic acid treatment showed a 207% increase in catalase under severe stress. Epibrassinolide and glutathione treatments had 201% more superoxide dismutase (SOD) under non-stress conditions. Distilled water treatment had 48.6% more soluble sugars under non-stress, while glutathione and epibrassinolide treatments had 14.5% more under mild stress. Control treatment had the highest malondialdehyde (MDA) amounts under mild and severe stress. Chitosan treatment exhibited a 25% increase in seedling length under severe stress compared to the control. Under non-stress conditions, chitosan treatment had slightly lower seedling length compared to control, while glutathione and epibrassinolide treatments showed the highest lengths. Under mild stress, folic acid, chitosan, and epibrassinolide treatments were superior to control. Under severe stress, distilled water showed a 20% increase, while chitosan treatment showed a 25% increase in seedling length compared to control. Chitosan treatment improved safflower seedling growth under severe osmotic stress through mechanisms including increased osmoprotectant levels, enhanced antioxidant activity, and improved membrane integrity.
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