Background and Aims <p>Silicon (Si) plays a key role in enhancing stress tolerance in cereals, yet its functional significance in reproductive tissues remains poorly understood. In barley (<i>Hordeum vulgare</i> L.), Si accumulates at high concentrations in seed husks, protecting from excess transpiration and pathogen attack. Here, we investigate the genetic and physiological determinants of Si accumulation in barley seeds and its role in seedling development.</p> Methods <p>Seed Si concentrations were determined in 251 barley accessions, and a genome-wide association study (GWAS) was performed. Based on the most significant QTL identified, Si accumulation was investigated in the <i>nud1</i> mutant and its reference Golden Promise. Also, germination and Si uptake assays with whole and dehusked seeds were conducted.</p> Results <p>Seed Si concentrations varied widely among accessions, primarily determined by the presence of a husk. GWAS identified a major locus on chromosome 7H colocalizing with <i>Nudum1</i> (<i>Nud1</i>), which regulates husk adherence. Silicon supplementation assays showed that naked seeds lack Si accumulation while leaf Si levels remain unchanged. Germination assays with Golden Promise showed that seedlings from peeled seeds had weaker root growth and Si uptake than seeds with husks, whereas both traits restored when isolated husks were placed in contact with the growth medium to facilitate Si transfer.</p> Conclusion <p>Our findings establish the husk as a major Si reservoir in the seeds and show that, beyond acting as a mechanical barrier, husk-derived Si is readily plant-available and improves Si uptake and root development in seedlings.</p>