Plant Growth Promoters Alleviate Oxidative Damages and Improve the Growth of Milk Thistle (Silybum marianum L.) Under Salinity Stress

Silybum marianum (L.) Gaertn (Asteraceae) is a well-known medicinal plant enriched with antioxidative properties beneficial for liver-related diseases. The experiment was conducted to explore the effect of different PGPs as soil-supplied mode to modulate the growth-related attributes, gas exchange parameters, and antioxidative efficiency of different milk thistle ecotypes such as Faisalabad (FSD), Gujranwala (GUJ), Quetta (QTA), and Kallar Kahar (KK) under saline stresses conditions (NaCl 120 mM/irrigation water). After salinity development, ascorbic acid (AsA), thiourea (TU), and moringa leaf extract (MLE) were soil supplied with 500 µM, 250 µM, and 3% concentrations, respectively. Data conferring the growth parameters elucidate significant reduction in all growth parameters and pigment contents under salinity stress. The effect of PGPs effectively upregulates the activity of these enzymatic antioxidants and improved salt tolerance to saline field conditions with numerous additional stresses, and the order of improvement was AsA, followed by MLE and TU. The percent increase with AsA treatment was noted as GR (34.78), DHAR (1.73), MDHAR (11.83), soluble sugar (8.78), amino acid (7.47), and free proline 15.75, while percent decrease in H2O2 content was 20.56 as compared to control plants. QTA and FSD ecotypes were observed as salt-tolerant ecotypes compared to GUJ and KK.