The barley husk serves as a silicon source for seedling development

Background and Aims: Silicon (Si) plays a key role in enhancing stress tolerance in cereals, yet its functional significance in reproductive tissues remains poorly understood. In barley ( Hordeum vulgare 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. Methods: 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 nud1 mutantand its reference Golden Promise. Also, germination and Si uptake assays with whole and dehusked seeds were conducted. Results: 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 Nudum1 ( Nud1 ), which regulates husk adherence. Si supplementation assays showed that in the nud1 mutant, seeds lack Si accumulation while leaf Si levels remain unchanged. Germination assays with Golden Promise showed that seedlings from peeled seeds had reduced root growth and Si uptake, whereas both traits restored when isolated husks were in contact with the medium to facilitate Si transfer. Conclusion: 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.