New nano-ferro-silicon biochar promotes plant growth and grain yield under arsenic stress in rice

Abstract

Arsenic (As) is a ubiquitous and toxic metalloid in nature, posing significant risks to living organisms. Developing sustainable strategies to mitigate As stress and reduce As accumulation in rice is critical for ensuring food safety in contaminated regions. Herein, we synthesized a new nano-ferro-silicon biochar (NNFB) composed of biochar, γ-Fe₂O₃, and SiO₂, which effectively adsorbed As from aqueous solutions and soil. NNFB alleviated As toxicity by promoting rice seeding and root growth at the seed germination and seeding stages. Under 40 μM As(III) treatment, application of 0.25% and 0.5% NNFB regulated the reactive oxygen species (ROS) balance by reducing H₂O₂ accumulation and enhancing peroxidase (POD) activity in leaves. Additionally, NNFB reduced As uptake by regulating the expression of As transport genes OsABCC1, OsLsi1, and OsLsi2 at the seeding stage. In pot experiments with 40 mg/kg As(III)-contaminated soil, NNFB application significantly improved aboveground biomass, tiller number, and effective tiller count. Notably, seed number per plant increased by 6.93- and 7.93-fold in 0.5% and 1% NNFB treatments compared to the control. These findings demonstrate that NNFB efficiently adsorbs As, mitigates As stress at multiple growth stages, and enhances rice productivity, offering a promising solution for As-contaminated agricultural systems.

Keywords: arsenic stress alleviation; grain yield; new nano-ferro-silicon biochar; plant growth promotion; rice.

Figure 1

The manufacturing process of new nano-ferro-silicon biochar (NNFB).

Figure 2

Characterization analysis of NNFB. (A) SEM analysis of NNFB. Parts (A1–A3) were obtained at 10K X, 80K X, and 100K X, respectively. (B, C) XRD and XPS analysis of NNFB, respectively.

Figure 3

Characterization analysis of NNFB after full adsorption in As(III). (A) SEM analysis of NNFB after full adsorption in As(III). (B) As3d analysis of NNFB (B1) and NNFB after full adsorption in As(III) (B2), respectively. (C) Fe₂P analysis of NNFB (C1) and NNFB after full adsorption in As(III) (C2), respectively.

Figure 4

Comparison of seedling growth after treatment with NNFB under arsenic stress at seed germination stage in rice. (A) Comparison of the root (A1) and bud length (A2) of rice after 7 days of germination under treatment with 0, 20, 40, and 60 μM As(III), respectively (n=8). Duncan’s test, p < 0.05. (B) Phenotypes of rice after 7 days of germination under treatment with 40 μM As(III) alone (CK) and the combination of 40 μM As(III) with either 0.15% NNFB, NNFB A, or NNFB B. Bar = 1 cm. (C) Comparison of the root (C1) and bud length (C2) of rice after 7 days of germination under treatment with 40 μM As(III) alone (CK) and the combination of 40 μM As(III) with either 0.15% NNFB, NNFB A, or NNFB B, respectively (n=14). Duncan’s test, p < 0.05.

Figure 5

Comparison of the growth of 21-day-old seedlings and the expression level of As transport genes in rice after treatment with NNFB under arsenic stress. (A) Comparison of the root (A1) and aboveground length (A2) of 21-day-old seedlings after treatment with 40 μM As(III) alone (CK) and the combination of 40 μM As(III) with 0.25% or 0.5% NNFB for 3 days (n=12). Duncan’s test, p < 0.05. (B) DAB staining of leaves from 21-day-old seedlings treated with 40 μM As(III) alone (CK) and the combination of 40 μM As(III) with 0.25% or 0.5% NNFB for 3 days. (B1) 40 μM As(III); (B2) 40 μM As(III) + 0.25% NNFB; (B3) 40 μM As(III) + 0.5% NNFB. Bar = 1 mm. (C) Comparison of POD enzyme activity in leaves of 21-day-old seedlings after 3 days treatment with 40 μM As(III) alone and the combination of 40 μM As(III) with 0.25% or 0.5% NNFB, respectively. (D) Comparison of total As content in rice seedlings after 3 days treatment with 40 μM As(III) alone and the combination of 40 μM As(III) with 0.25% or 0.5% NNFB, respectively. Duncan’s test, p < 0.05. (E) Comparison of the relative expression level of OsABCC1 (E1), OsLsi1 (E2), and OsLsi2 (E3) in roots of 21-day-old rice seedlings after different time points (3, 6, 9, and 12 h) under treatment with 40 μM As(III) alone and the combination of 40 μM As(III) with 0.25% or 0.5% NNFB, respectively.

Figure 6

Comparison of the growth and yield traits of rice plants grown in arsenic contaminated soil with or without addition of NNFB. (A) Comparison of the growth amount of root (A1) and aboveground (A2) of rice plants grown in soils treated with 40 mg/kg As(III) without or with 0.5% or 1% NNFB. (B) Comparison of tiller number (B1) and effective tiller number (B2) of rice plants grown in soils treated with 40 mg/kg As(III) without or with 0.5% or 1% NNFB. (C) Comparison of seed number per plant of rice plants grown in soils treated with 40 mg/kg As(III) without or with 0.5% or 1% NNFB.

Figure 7

Manufacturing and working model of NNFB. (A) Manufacturing model of NNFB. (B) Production of NNFB. (C) Magnification model of NNFB that adsorbs As(III). (D) The rice plant treated with NNFB under As stress. Yellow circles represent the As ionic. The As concentration, H₂O₂ content, and the expressions of OsABCC1, OsLsi1, and OsLsi2 were decreased, and the POD activity, growth amount of aboveground and root, effective tillering number, and seed number per plant were increased after NNFB treatment. The blue and red fonts mean decrease and increase, respectively.