Physiological Mechanism of Aluminum Tolerance of Rice Root Border Cells and Root Tips Induced by Nano Silica Biomineralization Deposition

This study aimed to explore the physiological mechanism of silicon alleviating aluminum toxicity in plants, to study the effect of biomineralization structure constructed on rice root border cells and root tips on aluminum stress, so as to provide the theoretical and practical guidance for acid soil mineralization to alleviate aluminum toxicity of plants in southern China.

Employing rice (Oryza. Sativa L.) as the experimental materials, using root tips and root border cells as the research object, under 100 μmol·L^-1 aluminum stress treatment, polyethylenimine induced nano silica to form biomineralization structure on the surface of root tips and root border cells. Four treatments are administered: bare cells without aluminum stress (-Si-Al), bare cells with aluminum stress (-Si+Al), silica-coated cells without aluminum stress (+Si-Al), and silica-coated cells with aluminum stress (+Si+Al). The study examined the cell viability, levels of active oxygen species, and localization of active aluminum in root border cells, as well as the relative elongation of the root tips, levels of active oxygen species, callose content and localization of active aluminum in the root tips.

Under aluminum stress, compared with non biomineralization, polyethylenimine induced nano silica deposition on the cell wall of root border cells, so the survival rate of root border cells increased by 21.04%, the level of reactive oxygen species decreased by 87.65%, and the relative fluorescence value increased by 77.09% after Morin staining, and then effectively improved cell survival rate, reduced ROS production, and slowed down the programmed cell death; after polyethylenimine induced nano silica deposition in root tip, the relative growth rate of root tip increased by 26.95%, the level of reactive oxygen species decreased by 27.73%, the content of callose increased by 55.29%, and the relative fluorescence value increased by 55.45% after Morin staining, hematoxylin staining also showed that more Al³⁺ was deposited in the meristematic and transitional zones of root tip, and this indicated that the biomineralization deposition could adsorb more Al³⁺ on the surface of root tip, prevent Al³⁺ from entering the root tip to protect, and then alleviate the toxic effect of aluminum on root tip.

Polyethylenimine induced nano silica deposition on the cell wall endows rice root border cells and root tips with aluminum tolerance, and reduced aluminum accumulation in rice, thus ensuring food safety and human health.