چكيده لاتين
The medicinal plant Withania coagulans (Stocks) Dunal is a member of the Solanaceae family and is native to arid and semi-arid regions of South Asia, including Iran. This valuable medicinal plant possesses numerous pharmacological properties due to its diverse phytochemical compounds, particularly withanolides. This study aimed to investigate the effect of different concentrations of putrescine on the physiological, biochemical, and enzymatic and non-enzymatic antioxidant system responses of W. coagulans under salinity stress in in vitro culture conditions. For this purpose, different putrescine treatments (0, 0.5, 1, and 2 mM) and two salinity levels (100 and 200 mM NaCl) were applied individually and in combination to the plantlets. The results showed that salinity stress alone significantly reduced growth indices, including fresh and dry weight, total chlorophyll content, carotenoids, and total protein, while increasing levels of reactive oxygen species, lipid peroxidation (MDA), hydrogen peroxide (H2O2), and sodium ion accumulation in plant tissues. The application of putrescine, especially at a concentration of 1 mM, led to significant improvements in growth indices, reduction of H₂O₂ and MDA, maintenance of ionic balance through increased K⁺/Na⁺ ratio, and strengthening of the antioxidant defense system. The activity of antioxidant enzymes, including superoxide dismutase, catalase, and ascorbate peroxidase, showed a significant increase in putrescine-treated plants under salinity stress compared to plants under salinity stress alone. Furthermore, the levels of total phenolic compounds, flavonoids, flavonols, anthocyanins, proline, glycine betaine, and total antioxidant capacity increased with different concentrations of putrescine under salinity stress conditions. Overall, the results demonstrate that putrescine plays an important role in enhancing the salinity tolerance of W. coagulans through regulating ionic balance, strengthening enzymatic and non-enzymatic defense systems, reducing oxidative stress, and increasing the biosynthesis of osmolytes and phenolic compounds. The findings of this research indicate that applying putrescine as a growth regulator at an appropriate concentration can be an effective strategy for improving growth and increasing resistance of this valuable medicinal plant under salinity stress.
