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

<div><p>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 (<i>Oryza sativa</i> 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.</p></div

Correlation analysis of the vigour index of germinated rice seeds.

<p>Correlation analysis of the vigour index of germinated rice seeds.</p

Effects of La (at a LaCl₃ concentration of 0, 20, 100 or 300 mg/L) and acid rain (at pH value of 3.5, 4.5 or 5.5) on phytolith content (a), PhytLa content (b), the PhytLa content in seeds (c) and the PhytLa content/phytolith content ratio (d).

<p>Error bars are standard deviations (n = 4); different letters indicate significant differences between different treatments at P = 0.05 based on the least significant difference (LSD) test.</p

Correlations among PhytLa content, phytolith content and the PhytLa content in seeds.

<p>a PhytLa content vs. phytolith content; b phytolith content vs. the PhytLa content in seeds; c PhytLa content vs. the PhytLa content in seeds. n = 48.</p

The pie chart of the quantitative proportion of different phytolith morphologies.

<p>The total number of phytolith morphotypes is 7,488.</p

Effects of La (at LaCl₃ concentrations of 0, 20, 100 and 300 mg/L) and acid rain (at a pH of 3.5, 4.5 or 5.5) on the seed vigor index of rice germinated seeds [GI (a), RL (b), FW (c) and DW (d)].

<p>Error bars are standard deviations (n = 4). Different letters indicate significant differences between different treatments at P = 0.05 based on the least significant difference (LSD) test.</p

Effects of La (at a LaCl₃ concentration of 0, 20, 100 or 300 mg/L) and acid rain (at a pH of 3.5, 4.5 or 5.5) on dumbbell (a) and tube (b) in germinated rice seeds.

<p>Error bars are standard deviations (n = 4); different letters indicate significant differences between different treatments at P = 0.05 based on the least significant difference (LSD) test.</p

Formulas for the calculation of indicators of seed germination.

<p>Formulas for the calculation of indicators of seed germination.</p

Effects of different pH levels on phytolith morphology (here, the LaCl₃ concentration was 0 mg/L).

<p>The pH values from top to bottom are 5.5, 4.5 and 3.5, and the phytolith morphotypes from left to right are dumbbells, tubes, crenates, elongate smooths and elongate echinates.</p