Species-specific modulation of nitro-oxidative stress and root growth in monocots by silica nanoparticle pretreatment under copper oxide nanoparticle stress

Abstract

Background: Abiotic stressors such as heavy metals and nanoparticles pose significant challenges to sustainable agriculture, with copper oxide nanoparticles (CuO NPs) known to inhibit root growth and induce oxidative stress in plants. While silica nanoparticles (SiO₂ NPs) have been shown to increase abiotic stress tolerance, their role in mitigating CuO NP-induced stress in crops, especially monocots, remains poorly understood. This study addresses this critical knowledge gap by investigating how SiO₂ NP pretreatment modulates CuO NP-induced stress responses, with a particular focus on root growth inhibition and nitro-oxidative stress pathways.

Results: Using an in vitro semihydroponic system, seeds were pretreated with varying concentrations of SiO₂ NPs (100-800 mg/L) before exposure to CuO NPs at levels known to inhibit root growth by 50%. SiO₂ NP pretreatment alleviated CuO NP-induced root growth inhibition in sorghum, wheat, and rye but intensified it in triticale. These responses are associated with species-specific alterations in reactive signaling molecules, including a reduction in nitric oxide levels and an increase in hydrogen sulfide in sorghum, a decrease in superoxide anion levels in rye, and elevated hydrogen peroxide levels in wheat. Protein tyrosine nitration, a marker of nitro-oxidative stress, was reduced in most cases, further indicating the stress-mitigating role of SiO₂ NPs. These signaling molecules were selected for their established roles in mediating oxidative and nitrosative stress responses under abiotic stress conditions.

Conclusions: SiO₂ NP pretreatment modulates CuO NP-induced stress responses through species-specific regulation of reactive oxygen and nitrogen species, demonstrating its potential as a tool for enhancing crop resilience. These findings advance the understanding of nanoparticle‒plant interactions and provide a foundation for future applications of nanotechnology in sustainable agriculture.

Clinical trial number: Not applicable.

Keywords: Copper oxide and silica nanoparticles; Monocotyledons; Nitro-oxidative stress response; Root growth inhibition; Species-specific response.

Fig. 1

Effects of CuO nanoparticle stress and SiO₂ nanoparticle pretreatment on the change in root length (A) and (lateral) root number (B) of sorghum, wheat, rye and triticale. The results are presented as the means ± standard errors (different letters indicate significant differences according to Duncan’s test; P ≤ 0.05; n.s., no significant change)

Fig. 2

Changes in the levels of superoxide anion (A) and hydrogen peroxide (B) in sorghum, wheat, rye and triticale root tips under CuO nanoparticle stress and SiO₂ nanoparticle pretreatment. The results are presented as the means ± standard errors (different letters indicate significant differences according to Duncan’s test; P ≤ 0.05; n.s., no significant change)

Fig. 3

Changes in the levels of nitric oxide (A) and peroxynitrite (B) in sorghum, wheat, rye and triticale root tips under CuO nanoparticle stress and SiO₂ nanoparticle pretreatment. The results are presented as the means ± standard errors (different letters indicate significant differences according to Duncan’s test; P ≤ 0.05; n.s., no significant change)

Fig. 4

Changes in the levels of hydrogen sulfide in sorghum, wheat, rye and triticale root tips under CuO nanoparticle stress and SiO₂ nanoparticle pretreatment. The results are presented as the means ± standard errors (different letters indicate significant differences according to Duncan’s test; P ≤ 0.05; n.s., no significant change)

Fig. 5

Changes in the callose content (A) and quercetin levels (B) in sorghum, wheat, rye and triticale root tips under CuO nanoparticle stress and SiO₂ nanoparticle pretreatment. The results are presented as the means ± standard errors (different letters indicate significant differences according to Duncan’s test; P ≤ 0.05; n.s., no significant change)

Fig. 6

Representative immunoblot showing protein tyrosine nitration in sorghum (A), wheat (B), rye (C) and triticale (D) roots under control conditions and after pretreatment with different amounts of SiO₂ NPs and CuO NP stress. The blue arrows indicate unchanged nitrated protein bands, the red arrows indicate new nitrated bands, the yellow arrows indicate increased nitrated protein bands, and the green arrows indicate decreased nitrated protein bands (NO-BSA: nitrated bovine serum albumin, used as a positive control)

Fig. 7

Effects of SiO₂ nanoparticle pretreatment of monocot seedlings on their subsequent CuO-induced stress responses. Different shades of green represent an increasing trend, different shades of red represent a decreasing trend, and n.c. represents no significant change