Extended abstract Introduction: Due to the high sensitivity of seeds to damage caused by diseases or environmental stresses, germination is considered an important stage in the plant life cycle: Germination, its uniformity and emergence decline during storage due to seed vigor deterioration. Moisture stress is one of the important environmental factors affecting germination, especially during improper storage. Seed priming with gibberellic acid improves seedling characteristics in different plants under different environmental conditions. Therefore, this research aims to investigate the effect of gibberellic acid and seed deterioration on germination indices and antioxidant enzymes of safflower seeds (Carthamus tinctorius L.) under water stress conditions. Materials and Methods: In order to investigate the effect of gibberellic acid on germination indicators and changes in antioxidant enzymes of aged safflower seeds under osmotic stress conditions, a factorial experiment was conducted in the form of a completely randomized design with four replications. The first factor includes three osmotic stress levels: zero (control), -0.4, and -0.8 MPa, the second factor includes nine aging levels (zero, 1, 2, 3, 4, 5, 6, 7, and 8 days of aging). at a temperature of 41 degrees Celsius) and the third factor included seed priming treatment at three control levels (non-priming), zero (hydro-priming), and priming with 50 mg/l gibberellic acid. A 3-parametric sigmoid model was used to show the changes in germination indices at different levels of seed deterioration.
Results: The effect of osmotic stress, seed deterioration, and seed priming on the measured indices such as germination percentage, germination rate, seedling dry weight, normal seedling percentage, seedling length, seed germ, catalase, and ascorbate peroxidase, as well as seed protein were significant so that the measured indicators decreased with increasing seed deterioration and moisture stress. The results showed that the highest measured germination indices were obtained from seed treatment with 50 mg/l gibberellic acid under normal osmosis and non-deterioration conditions. Also, seed priming with gibberellic acid treatment caused an increase in catalase, ascorbate peroxidase, and protein activity compared to non-primed seeds under deterioration and non-deterioration conditions.
Conclusion: Results showed that the most suitable prime level used was gibberellic acid 50 mg/l, which had acceptable results under both stress conditions and normal conditions and deterioration and non-deterioration in comparison with other treatments. Therefore, the use of gibberellic acid hormone can help to improve germination indices as a result of changes in biochemical activities.
Highlights: 1. The effect of accelerated aging and priming on safflower seed germination under moisture stress conditions was investigated. 2.The effect of priming on catalase and peroxidase activity of aged safflower seeds was investigated.