Fig. 4

Analysis of H₂O₂, phenolics and lignin after Si treatment. a The H₂O₂ content per gram of roots was measured using an UV spectrophotometer at 390 nm. The bars represent the mean ± SE of four replicates, each containing a pool of six roots. Different letters indicate significant differences (Duncan’s multiple range test with P ≤ 0.05). b Quantitative RT-PCR analysis of OsRbohB gene related to H₂O₂production. c The lignin content in the cell wall residue (CWR) of rice roots was determined at 280 nm using the AcBr assay. d Quantitative RT-PCR analysis of OsC4H and OsCAD6 genes in the phenylpropanoid pathway. Relative transcript levels of OsC4H and OsCAD6were analyzed at 6, 24 and 72 h post-inoculation and normalized to three internal reference genes, OsEXP, OsEif5C and OsEXPnarsai. Data are shown as relative transcript levels in comparison with the control roots (expression level set at 1). The bars represent the mean expression levels±SE from two independent biological replicates and three technical replicates, each containing a pool of 6 plants. Asterisks indicate significant differential expression (Duncan’s multiple range test with P ≤ 0.05). e Total soluble phenolics content in roots of dried weight(DW) was measured using an UV spectrophotometer at 725 nm. Measurements were conducted at 24, 48 h post-inoculation after silicon amendment (Si + Mg) or water treatment (Mg). The bars represent the mean ± SE of the lignin content of 6 plants. Different letters indicate significant differences. f Effect of L-2-aminooxy-3-phenylpropionic acid (AOPP, an inhibitor of phenylpropanoid biosynthesis) on nematode infection. AOPP (100 μM) was applied to 2-week-old rice roots with or without 0.04% silicon 1 day before inoculation. Nematodes in the roots were counted at 14 days post-inoculation. The bars represent the means of the data from two independent biological replicates, each containing six plants. Different letters indicate significant differences (Duncan’s multiple range test with P ≤ 0.05)