Influence of Amino Acids Mixture Application on Some Biochemical Aspects, Antioxidant Enzymes and Endogenous Polyamines of Vicia faba Plant Grown under Seawater Salinity Stress

Irrigation with diluted seawater can act as an alternate water resource and thus plays an important role in saving fresh water resources as well as promoting agriculture. Two pot experiments were conducted to elucidate the effect of foliar application with amino acid mixture (0, 500, 1000 and 1500 mg/L as AA0, AA1, AA2 and AA3, respectively) on faba bean plants irrigated with different seawater levels (0.23, 3.13 and 6.25 dS/m as S0, S1 and S2, respectively) regarding some physiological and biochemical aspects, lipid peroxidation, antioxidant enzymes and endogenous polyamines of faba bean (Vicia faba L.) plants. Irrigation of faba bean plants with different levels of seawater caused significant increases in osmotic solutes (total soluble sugars, free amino acids and proline), phenol content, lipid peroxidation, some antioxidant enzymes (IAA-oxidase, polyphenol oxidase; PPO, peroxidase; POX, super oxide dismutase; SOD, Catalase; CAT, ascorbate peroxidase; APX) and endogenous spermidine and spermine compared with control plants. At the same time, indole acetic acid (IAA), putrescine and total endogenous polyamine contents were decreased in response to different seawater levels. Under salt stress, foliar application with different concentrations stimulated the salt tolerance of faba bean plants via improving osmotic solutes (total soluble sugars, free amino acids and proline), phenolic content, IAA and endogenous polyamines, whereas lipid peroxidation and antioxidant enzymes (PPO, POX, SOD, CAT and APX) were significantly decreased. These results emphasize the potential of application of amino acids mixture in sustainable agriculture in arid and semiarid regions. In addition, it opens up new research lines aimed at obtaining maximum benefit from the amino acids under salinity or other osmotic stress conditions.