Growth Enhancers to Mitigate Salinity Stress in Vicia faba

Abstract

ABSTRACTSoil salinity decreases growth, photosynthetic activity, and productivity and results in nutrient imbalance in plants. This study evaluated the efficacy of the foliar applied growth enhancer, Moringa oleifera Lam., leaf extract (MLE; 20 times diluted) and evaluated the efficacy of sulfate of potash as a source of potassium (SOP), 3%, in reducing salinity effects in faba bean (Vicia faba L.) plants. Salinity in the nutrient solution at 0.0 (control) and 135 mM from NaCl (S), equivalent to 13 dS·m−1, were used. Plants grown at 13 dS·m−1 had decreased chlorophyll (a+b), carotenoids, total protein contents, weight of 100 seed, enzyme activity of ribulose-1,5-bisphosphate-carboxylase/oxygenase (RuBPCase), photosynthetic activity (14CO2 fixation), and levels of N, P, and K in shoots and roots. Foliar application of MLE+S and SOP+S increased these compared to salt-stressed plants. Salt-stressed faba bean plants had increased proline content, Na+ and Cl− levels, and transpiration rate compared to control and plants treated with MLE+S and SOP+S. Foliar application of MLE+S and SOP+S decreased Na+ and Cl− levels and proline content below controls. Foliar applied MLE+S and SOP+S increased contents of N, P, and K in shoots and roots compared to salt-stressed and control plants. Foliar applied MLE and sulfate of potash ameliorated adverse effects of salinity by enhancing carboxylating enzyme activity of RuBPCase; total protein level; N, P, and K; photosynthetic activity (14CO2 assimilation); total yield; and plant secondary metabolites. Exogenously applied MLE provided more benefit against salinity stress than sulfate of potash. This first attempt to evaluate the potential of MLE and SOP as growth enhancers under salt-stressed Vicia faba indicated that exogenously applied MLE provided more benefit against salinity stress than sulfate of potash. More research is needed to investigate the cause of the responses. Further investigation is needed to quantify cytokinin content in MLE and SOP to determine the cause of enhanced responses.