Mitigation of salt stress in Phaseolus vulgaris L. by dopamine: Effects on growth, physiological parameters and antioxidant activity

Salinity, is one of the most important problems of the world's soils, has negative effects on germination and seedling growth, therefore reducing the yield of plants. This study investigated the effects of salt stress and dopamine (DA) treatments on plant growth, physiological parameters and nutritional elements of bean (Phaseolus vulgaris L.) through a pot experiment under greenhouse conditions. In this study, five different levels of DA: D-0 (0 μM), D-50 (50 μM), D-100 (100 μM), D-150 (150 μM), D-200 (200 μM) and three different doses of NaCl: S-0 (0 mM), S-50 (50 mM), S-100 (100 mM) were employed. The effects of salinity and DA on growth, physiological and biochemical properties of bean seedlings were statistically significant. Plant height, stem diameter, leaf area, shoot fresh weight (FW), shoot dry weight (DW), root FW and root DW of bean seedlings treated with 50 mM and 100 mM NaCl were lower than control (0 mM NaCl). However, exogenous DA treatments improved the growth parameters of bean seedlings in both 50-mM and 150-mM salt stress compared with control. 100 mM NaCl stress led to decrease in plant height (45.59%), stem diameter (14.33%), leaf area (62.81%), shoot FW (61.21%), shoot DW (46.70%), root FW (43.47%), root DW (45.33%) and CRV (49.44%) compared with control. Treatment with 100 μM exogenous DA at 100 mM NaCl increased plant FW by 129.30%, plant DW by 20.95%, root FW by 66.67%, root DW by 70.73% and CRV by 25.71%, compared with the control (0 mM NaCl). These findings suggest that DA may be used to decrease the effect of salt stress by inducing the systemic tolerance of plants. Thus, understanding the role of DA in salt tolerance introduces new possibilities to use this compound for agricultural purposes.