Seed Priming with Gallic Acid and Hydrogen Peroxide as a Smart Approach to Mitigate Salt Stress in Faba Bean (Vicia faba L.) at the Germination Stage

Salinity is a widespread environmental stress that severely impedes plant growth and development from seed germination to harvest. Thus, the development of suitable management practices to minimize the deleterious effects of salt stress has become necessary. Among these methods, seed priming is considered as one of the potential physiological approaches to enhance seed germination in salt-affected soils. In the present research, we investigated the potentiality of gallic acid (1 mM) and hydrogen peroxide (2 mM) as priming agents to alleviate the salinity-inhibited germination of three faba bean cvs. (Najeh, Chourouk and Bachaar). The seeds were soaked in distilled water (hydropriming) or pretreated with gallic acid and hydrogen peroxide, individually and simultaneously, and then subjected to 150 mM NaCl-salinity. Our results revealed that mean germination time was significantly increased; whereas final germination percentage and germination index as well as dry weight and water content of the embryonic axes were considerably lowered by salt stress in the unprimed seeds of the three faba bean cvs. This decrease was associated with inhibited starch degradation and increased malondialdehyde contents. Our results also indicated that although all germination traits as well as starch metabolism were enhanced following gallic acid, hydrogen peroxide and hydropriming treatments to varying degrees, priming-mitigating effects were agent-dependent with regard to salt-induced oxidative damage, and osmoprotectant accumulation (proline and glycine betaine) as well as non-enzymatic (total polyphenols and flavonoids) and enzymatic (superoxide dismutase, catalase and guaiacol peroxide) antioxidant defense system. Contrarily to hydropriming treatment for which no obvious effects were observed, gallic acid and hydrogen peroxide priming significantly decreased the malondialdehyde content, increased proline and glycine betaine accumulation and enhanced the non-enzymatic as well as the enzymatic defense system to varying degrees for the three faba cvs. When compared to other treatments, simultaneous priming with gallic acid and hydrogen peroxide was more efficient in mitigating the adverse effects of salt stress on faba bean at the germination stage and may be, therefore, suggested as a potential strategy to overcome the salinity-mediated impairment of faba bean, particularly salt-sensitive genotypes, at the germination stage.