The features of accumulation, chemical composition and properties of silica in panicles and other organs of rice Oryza sativa of a number of varieties of Far Eastern breeding at different stages of ontogenesis are investigated. The physicochemical parameters of ash samples obtained from rice panicles are studied: chemical composition, acid-base properties, specific surface area values, their dependence on the rice variety is shown. In the aboveground parts of plants selected in the flowering phase, the ash yield depends on the plant variety, the highest values are observed for the ultra-ripe Cascade variety, which is characterized by a short, thick and strong stem. During the period of full maturation of rice panicles, the ash content of fruit scales (husks) increases by 1.5–2 times. The highest content of silicon dioxide in the ash of the aboveground shoot of rice plants is observed in samples of fruit scales, both in the flowering phase (92.7-97.8%) and in the full ripeness phase (98.7%). By the method of X-ray phase analysis, it was found that the ash residues of straw in the flowering phase are in an amorphous–crystalline state, and in the full ripeness phase - mainly in an amorphous state. The maximum proportion of extractive substances was noted in the samples obtained from the leaf blade, which is determined by the phase of plant development, the assimilation function of the leaves and the transport function of the stems.