A comparative study of silicon uptake, accumulation and understanding its role in salt stress mitigation in millets

Abstract

Food security faces mounting challenges because of population growth, economic stagnation, and climate change over the past decade. Millets outperform wheat and rice under marginal growth conditions and offer superior nutritional value. Although silicon (Si) is not traditionally considered essential for plant growth, increasing evidence suggests that it provides substantial benefits, particularly under stress. This study investigates the ability of millet crops to accumulate and transport Si and the role of exogenous Si application in mitigating salt stress in seven millet crops. Among these, pearl millet exhibited the highest Si transport and accumulation, with a maximum of 1.69 ± 0.10 % Si in leaves 1.41 times higher than the control. Agronomic traits such as plant height, leaf number, length, width, inflorescence size, and biomass improved significantly with Si supplementation, particularly in barnyard millet. Spectrophotometric assays revealed that Si accumulated predominantly in vegetative parts, including roots, stems, and leaves, rather than husks and seeds. FE-SEM analysis further confirmed an increased number of Si bodies on leaf and stem surfaces across all millets. Si supplementation exerted a protective effect against NaCl-induced salt stress. Salt stress reduced germination rates, seedling growth, and membrane integrity while increasing osmolyte and H₂O₂ accumulation. However, Si application under these conditions improved germination rates, seedling growth, pigment content, and antioxidant enzyme activity while reducing membrane damage, osmolyte, and H₂O₂ accumulation. These findings suggest that Si supplementation can significantly enhance millet growth, stress tolerance, and productivity under saline conditions, supporting its potential use as a fertilizer to improve agricultural resilience.

Keywords: Abiotic stress tolerance; Agronomic traits; Millet crops; Salt stress mitigation; Si accumulation and transport; Silicon supplementation.