A silicon particle-based courier promotes melatonin-mediated seed tolerance to nickel toxicity in rice

Rapid industrialization significantly contributes to environmental pollution, which has severe effects on plant growth and development. Various biomolecules are employed to combat stress in plants, but were limited by low efficiency and high loss. Nanoparticles (NPs) emerge as efficient and useful tools to cope with such problems, and amongst them, silicon nanoparticles have been proved to work well in ameliorating tolerance to abiotic stress, while they were also confronted with low loading efficiency. Here, we developed porous silicon (pSi) as a vehicle for the delivery of melatonin (MT), an antioxidant to scavenge reactive oxygen species, into the pre-germinated rice seeds, and subsequently evaluated the germination performance and seed tolerance under nickel (Ni) stress. Seed priming with pSi-MT improved the Ni-stressed germination rate by 3.72 and 1.45 fold as compared to the ones primed with water and MT, respectively, and was restored to 94.97% of the control, whose positive impacts were associated with the enhanced management capacity of pSi to load MT, which poses effects on the restriction of Ni absorption and stimulation of the antioxidant system, thereby maintaining the redox homeostasis to promote the reserve mobilization, nutrient uptake, and phytohormone synthesis. Collectively, the study proves the suitability of pSi delivery tools to carry molecules for agricultural applications.