Seed priming with silicon nanoparticles and nitric oxide optimizes barley growth in zinc-deficient condition: A crucial role of optimum level of endogenous nitric oxide.

Zinc (Zn) deficiency significantly impacts plant growth and productivity in agriculture. Seed priming is a promising strategy to enhance plant tolerance to nutrient deficiencies. This study examines the effects of priming barley (Hordeum vulgare L.) seeds with silicon nanoparticles (SiNPs), nitric oxide (NO), and their combination on germination and growth under Zn-deficient conditions. Primed seedlings showed superior growth, and improved photosynthetic efficiency, antioxidant enzyme activities, the ascorbate-glutathione cycle function, nutrient-related gene expression, and sucrose metabolism compared to the un-primed seedlings. Among the priming methods, the combination of SiNPs and NO had the most significant positive effect on barley growth under Zn deficiency. Priming of seeds with SiNPs was more effective against Zn deficiency than external SiNPs application at the seedling stage. Exogenous SiNPs added to already SiNPs-primed seedlings further improved growth under Zn deficiency. Contrary to this, NO addition to NO-primed seedlings inhibited growth due to excessive endogenous NO accumulation. Co-application of SiNPs and NO to SiNPs+NO- primed seedlings led to severe growth retardation due to build-up of endogenous NO production. These findings highlight seed priming's potential, especially with SiNPs, to address nutrient deficiencies in agriculture and the complex interactions of endogenous NO in priming-mediated regulation of Zn deficiency in barley.