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Iron (Fe) is one of the essential nutrients for plant growth which is involved in several physiological functions. Hence, there are intensive efforts to improve plant tolerance to Fe deficiency, by genotypic screening and by the use of adapted physiological tools. The intend of the current study was to explore the seed priming effect with salicylic acid (SA 0.25 mM) and hydrogen peroxide (H2O2 20 mM), either separately applied or combined, on plant growth, nutritional elements status (Fe and potassium K), root acidification and photosynthetic activity in two S. carnosa cultivars (Sidi Khlif and Kalbia) with different tolerance to such constraint. Under unprimed conditions, Fe deficiency decreased plant growth, chlorophyll concentration, in addition to Fe and K contents. Moreover, it affected the photosynthetic activity by inhibiting the net CO2 assimilation rate and increasing the transpiration rate of both cultivars, following a reduced water use efficiency. The changes above described were much less pronounced in Sidi Khlif than in Kalbia. The stomatal conductance increased in Fe-deficient leaves of both cultivars, suggesting that the photosynthesis impairment should be attributed to non-stomatal factors. Interestingly, priming seeds with both agents significantly improved the growth performance and the rhizosphere acidification of deficient S. carnosa plants. However, the D + SA + H2O2 treatment had the most beneficial effect on S. carnosa plant growth. The degree of this stimulation may vary depending on the cultivar, the tissue and the priming agent applied. This could be owing to the photosynthetic performance modulation, leading to more efficient nutrient uptake.

The current work aimed to investigate the effect of seed priming with different agents (CaCl2, KCl, and KNO3) on germination and seedling establishment in seeds of the barley species of both Hordeum vulgare (L. Manel) and Hordeum maritimum germinated with three salt concentrations (0, 100, and 200 mM NaCl). The results showed that under unprimed conditions, salt stress significantly reduced the final germination rate, the mean daily germination, and the seedling length and dry weight. It led to a decrease in the essential nutrient content (iron, calcium, magnesium, and potassium) against an increase in sodium level in both of the barley species. Moreover, this environmental constraint provoked a membrane injury caused by a considerable increase in electrolyte leakage and the malondialdehyde content (MDA). Data analysis proved that seed priming with CaCl2, KCl, and KNO3 was an effective method for alleviating barley seed germination caused by salt stress to varying degrees. Different priming treatments clearly stimulated germination parameters and the essential nutrient concentration, in addition to increasing the seedling growth rate. The application of seed priming reduced the accumulation of sodium ions and mitigated the oxidative stress of seeds caused by salt. This mitigation was traduced by the maintenance of low levels of MDA and electrolyte leakage. We conclude that the priming agents can be classed into three ranges based on their efficacy on the different parameters analyzed, CaCl2 was placed in the first range, followed closely by KNO3, while the least effective was KCl, which placed in the third range.

The aim of this work was to investigate the role of salicylic acid (SA) seed priming on plant growth, chlorophyll content, photosynthesis and ionic composition in two ecotypes of Medicago sativa (Gabes and Presmenti) when subjected to salinity (75 mM) and iron deficiency (1 μM) either separately or combined. Our results showed that under unprimed conditions, salinity and iron (Fe) deficiency reduced shoot and root growth, photosynthetic and transpiration rates, chlorophyll concentration, stomatal conductance and ionic uptake. The reduction in all of these parameters was additive in the combined treatment with salinity and low Fe supply. This reduction depended on the ecotype, the tissue and the stress applied. However, under saline conditions, the Gabes ecotype showed tolerance by maintaining tissue hydration, growth, photosynthetic assimilation, chlorophyll biosynthesis and nutrient uptake, compared to the control. While priming seeds with 100 μM SA had the best positive impact on all studied physiological parameters under different stresses, and especially under the combined treatment, a 500 μM concentration had no effect. We conclude that the effect of seed priming with SA is dose-dependent and may vary depending on ecotypes and stress.