Effects of lanthanum and acid rain stress on the bio-sequestration of lanthanum in phytoliths in germinated rice seeds

REEs in the environment can be absorbed by plants and sequestered by plant phytoliths. Acid rain can directly or indirectly affect plant physiological functions. Currently, the effects of REEs and acid rain on phytolith-REEs complex in plants are not yet fully understood. In this study, a high-silicon accumulation crop, rice (Oryza sativa L.), was selected as a representative of plants, and orthogonal experiments were conducted under various levels of lanthanum [La(III)] and pH. The results showed that various La(III) concentrations could significantly improve the efficiency and sequestration of phytolith La(III) in germinated rice seeds. A pH of 4.5 promoted phytolith La(III) sequestration, while a pH of 3.5 inhibited sequestration. Compared with the single treatment with La(III), the combination of La(III) and acid rain inhibited the efficiency and sequestration of phytolith La(III). Correlation analysis showed that the efficiency of phytolith La(III) sequestration had no correlation with the production of phytolith but was closely correlated with the sequestration of phytolith La(III) and the physiological changes of germinated rice seeds. Phytolith morphology was an important factor affecting phytolith La(III) sequestration in germinated rice seeds, and the effect of tubes on sequestration was more significant than that of dumbbells. This study demonstrated that the formation of the phytolith and La(III) complex could be affected by exogenous La(III) and acid rain in germinated rice seeds.