Zinc oxide application alleviates arsenic-mediated oxidative stress via physio-biochemical mechanism in rice.

Arsenic (As) pollution in cultivated soils poses a significant risk to the sustainable growth of agriculture and jeopardizes food security. However, the mechanisms underlying how zinc (Zn) regulates the toxic effects induced by As in plants remain poorly understood. Hence, this study aimed to explore the potential of ZnO as an effective and environmentally friendly amendment to alleviate As toxicity in rice, thereby addressing the significant risk posed by As pollution in cultivated soils. Through a hydroponic experiment, the study assessed the mitigating effects of different ZnO dosages (Zn5, 5 mg L-1; Zn15, 15 mg L-1; Zn30, 30 mg L-1) on rice seedlings exposed to varying levels of As stress (As0, 0 µM L-1; As25, 25 µM L-1). The findings of the study demonstrate significant improvements in plant height and biomass (shoot and root), with a notable increase of 16-40% observed in the Zn15 treatment, and an even more substantial enhancement of 29-53% observed in the Zn30 treatment under As stress, compared to respective control treatment. Furthermore, in the Zn30 treatment, the shoot and root As contents substantially reduced by 47% and 63%, respectively, relative to the control treatment. The elevated Zn contents in shoots and roots enhanced antioxidant enzyme activities (POD, SOD, and CAT), and decreased MDA contents (13-25%) and H2O2 contents (11-27%), indicating the mitigation of oxidative stress. Moreover, the expression of antioxidant-related genes, OsSOD-Cu/Zn, OsCATA, OsCATB, and OsAPX1 was reduced when rice seedlings were exposed to As stress and significantly enhanced after Zn addition. Overall, the research suggests that ZnO application could effectively mitigate As uptake and toxicity in rice plants cultivated in As-contaminated soils, offering potential solutions for sustainable agriculture and food security.

Silicon nanoparticles alleviate cadmium toxicity in rice (Oryza sativa L.) by modulating the nutritional profile and triggering stress-responsive genetic mechanisms.

This study investigated the physiological and molecular responses of rice genotype '9311' to Cd stress and the mitigating effects of silicon oxide nanoparticles (SiO NPs). Cd exposure severely hindered plant growth, chlorophyll content, photosynthesis, and Cd accumulation. However, SiO NPs supplementation, particularly the SiONP100 treatment, significantly alleviated Cd-induced toxicity, mitigating the adverse effects on plant growth while maintaining chlorophyll content and photosynthetic attributes. The SiONP100 treatment also reduced Cd accumulation, indicating a preference for Si uptake in genotype 9311. Complex interactions among Cd, Si, Mg, Ca, and K were uncovered, with fluctuations in MDA and H2O2 contents. Distinct morphological changes in stomatal aperture and mesophyll cell structures were observed, including changes in starch granules, grana thylakoids, and osmophilic plastoglobuli. Moreover, following SiONP100 supplementation, genotype 9311 increased peroxidase, superoxide dismutase, and catalase activities by 56%, 44%, and 53% in shoots and 62%, 49%, and 65% in roots, respectively, indicating a robust defense mechanism against Cd stress. Notably, OsNramp5, OsHMA3, OsSOD-Cu/Zn, OsCATA, OsCATB, and OsAPX1 showed significant expression after SiO NPs treatment, suggesting potential Cd translocation within rice tissues. Overall, SiO NPs supplementation holds promise for enhancing Cd tolerance in rice plants while maintaining essential physiological functions.

Combined Effect of Nitrogen Fertilizer Application and High Temperature on Grain Quality Properties of Cooked Rice.

Ambient temperature and nitrogen (N) fertilizer are two of the most important factors that affect rice grain quality. However, less information has been available on the interactive effect of N fertilizer and ambient temperature on grain quality under stressful high temperature (HT). In this article, the effects of panicle N fertilizer, ambient temperature, and their interaction on starch composition, particle size distribution of starch granules, starch physicochemical properties, and storage protein accumulation in milled grains were investigated to clarify the potential role of panicle N fertilizer topdressing in regulating rice grain quality under stressful HT by using a two-factor experiment of three N levels in combination with two temperature regimes. Results showed that appropriate application of panicle N fertilizer could attenuate the adverse effect of HT during grain filling on milling quality and chalky occurrence to some extent, particularly for the effective alleviation of HT-induced decrease in milling quality. However, the topdressing of panicle N fertilizer tended to enhance starch gelatinization enthalpy (ΔH) and its setback viscosity in HT-ripening grains, with the simultaneous decrements in the number and surface area proportions of smaller starch granules under the higher N fertilizer in combination with HT exposure. The effects of higher nitrogen fertilizer and HT exposure on total protein content and gluten composition of grains were additively increased. Hence, the topdressing of panicle N fertilizer exacerbated HT-induced deterioration in cooking and eating quality, rather than alleviating the negative impact of HT exposure on the palatability of cooked rice.