For the purpose of evaluating the effect of chitosan on seed germination and some biochemical characteristics of the milk thistle herb in the conditions of salinity, an experiment was conducted as factorial in a completely randomized design (CRD) with three replications in the Laboratory of Seed Science and Technology of Shahed University, Tehran in 2015. Experimental factors comprised salinity levels (0, 4, 8 and 12 dS.m-1) and different levels of Chitosan (0, 0.25, 0.5, 0.75 and 1 percent). The results showed that salt stress reduced germination percentage, germination coefficient, germination speed, weight and length vigor index, radical, plumule and seedling length and total biomass and increased mean germination time. Seed priming with chitosan up to 0.5% concentration increased germination coefficient, weighted index vigor and plumule length. The highest amounts of total chlorophyll and total protein were obtained in seed priming with 0.5% chitosan levels in zero salinity level (control). By increasing salinity levels, the activity level of catalase and peroxidase increased, so that the highest level of the activity of these two enzymes was obtained in the salinity level of 12 dS.m-1 in pre-treatment with 0.5% Chitosan. The results showed that seed priming with chitosan of 0.5% could reduce harmful effects of salt stress on some traits of milk thistle seedlings and could even improve their growth.
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.
Objective: This study aimed to evaluate the effect of chitosan on germination indicators and the activity of antioxidant enzymes in safflower seedlings under salinity stress.
Method: The experiment was conducted using a factorial arrangement based on a completely randomized design with three replications at the University of Mohaghegh Ardabili in 2024. The experimental treatments included four salinity levels (0, 50, 100, and 150 mM NaCl) and four concentrations of chitosan (0, 0.2, 0.4, and 0.5% w/v), which were dissolved in 1% acetic acid.
Results: The results showed that salinity stress reduced the germination rate, radicle length, plumule length, seedling length, seedling fresh weight, and seedling dry weight. However, priming with different concentrations of chitosan, especially at 0.5%, improved these traits. The highest daily germination rate (0.114) was observed in the control group (distilled water priming) under 150 mM salinity. The activity of catalase and peroxidase enzymes in the control under 150 mM salinity increased by approximately 43% and 70%, respectively, compared to the 0.5% chitosan treatment under non-saline conditions. Similarly, the activity of superoxide dismutase enzyme in the 0.5% chitosan treatment under 150 mM salinity increased by about 67% compared to the control under non-saline conditions. Furthermore, the ascorbate peroxidase enzyme activity in seeds primed with 0.5% chitosan increased by 37% compared to the control (distilled water priming).
Conclusions: The results indicated that seed treatment with different concentrations of chitosan can mitigate the harmful effects of salinity on some traits of safflower seedlings and improve seedling growth. The best results were achieved when 0.5% chitosan was used under salinity conditions.
Highlights
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