Silicon (Si) Alleviates Iron Deficiency Effects in Sea Barley (Hordeum marinum) by Enhancing Iron Accumulation and Photosystem Activities

Purpose: Silicon (Si) is a ubiquitous element and the second most abundant after oxygen in the Earth’s crust. Although silicon is not yet listed among the essential nutrients for higher plant growth, its beneficial impact on improving crop development and yield, especially under stressful environments such as iron deficiency, was well documented. Iron deficiency is a major concern for crop production mainly observed in calcareous soils all over the world. The objective of this study was to investigate the effects of silicon on sea barley (Hordeum marinum ssp. marinum) under iron deficiency. Methods: Twenty-six-day-old plants of H. marinum were exposed to three treatments, sufficient iron treatment (50 µM Fe), iron-deficient treatment (0.1 µM Fe), and iron-deficient treatment (0.1 µM Fe) combined with silicon application (0.5 mM NaSiO). Results: Our results showed that iron deficiency negatively affects almost all measured parameters. However, these depressive effects were significantly mitigated under silicon treatment. Indeed, silicon addition alleviated stress effect on the morphological aspect of plants and enhanced their growth (between + 93 % and + 283 %), water status (between + 57 % and + 58 %), photosynthetic pigment concentrations (between + 129 % and + 200 %), photosynthetic gas exchange (between + 73 % and + 129 %), and both Photosystem I (PSI) and Photosystem II (PSII) functions. However, a greater beneficial effect of silicon was observed on PSI, by comparison with PSII. This was concomitant with a significant increase of iron quantities in both roots and shoots by 153 % and 236 %, respectively. Conclusions: Based on our findings, silicon is able to mitigate the adverse effects of iron deficiency, probably by enhancing iron remobilization. Therefore, silicon application seems to be an effective and successful solution to cope with iron deficiency.