Salicylic acid and iron-oxide nanoparticles improved the growth and productivity of ajowan under salt stress

Two factorial experiments with randomized complete block design in three replicates were conducted in a greenhouse at the University of Tabriz to investigate the individual and combined effects of SA and Fe2O3-NPs spray (1 mM and 3 mM, respectively) on cations contents, root and shoot growth, seed filling and yield parameters of salt-stressed ajowan plants (0, 4, 8 and 12 dS m-1 NaCl; as non-saline and low, moderate and high salinities, respectively). Salt stress enhanced Na+ contents and reduced K+ and Ca2+ contents, and K+/Na+ and Ca2+/Na+ ratios, leading to a reduction in root and shoot growth, particularly under high salinity. Reduction in plant growth parameters under salt stress had a negative impact on yield components and seed yield of ajowan. These deleterious impacts of salinity on plants were largely overcome by foliar treatments, particularly by SA + Fe2O3-NPs. The improvement of seed yield by these treatments was highly correlated with enhanced root and shoot growth, seeds per plant, and 1000-seed weight, especially under moderate and high salinities. Thus, the simultaneous application of SA and Fe2O3-NPs was the best foliar treatment for enhancing the growth and productivity of ajowan plants under normal and saline conditions.