Foliar Application of Auxin or Cytokinin Can Confer Salinity Stress Tolerance in Vicia faba L.

Abstract

Soil salinity severely declines the availability of water and essential minerals to the plants, which hinders growth. The present study evaluates the potential roles of indole-3-acetic acid (IAA) and 6-benzyladenine (BA) for mitigating the adverse effects of soil-salinity in faba bean (Vicia faba L.). Plants were exposed to 150 mM NaCl stress and were sprayed with IAA (1.15 mM) or BA (0.9 mM). Our results revealed that foliar application of IAA or BA improved the growth traits of salinized faba bean due to the increased uptake of K+, Ca2+, and Mg2+ ions, accumulation of free amino acids, soluble sugars, and soluble proteins, and activity of superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase. The principal component analysis (PCA) and heatmap clustering indicated that salinity-exposed plants exhibited lower growth and biomass production, which correlated with higher accumulation of Na+ and malondialdehyde. Moreover, electrophoretic patterns of protein showed new bands in IAA- or BA-treated salt-stressed plants, indicating that IAA or BA treatment can reprogram the metabolic processes to confer salinity tolerance. We also found that IAA has a greater capacity to ameliorate the salt stress than BA, although there is no significant difference in yield between these treatments. Finally, these findings can be helpful for a better understanding of IAA- and BA-mediated salt tolerance mechanisms and increasing production of faba bean in saline soils.