Effects of the application of nanoscale zero-valent iron on plants: Meta analysis, mechanism, and prospects

Improving wheat physio-biochemical attributes in ciprofloxacin-polluted saline soil using nZVI-modified biochar

The Ciprofloxacin (CIP) toxicity and salinity stress in agricultural soils cause risk to environmental and food safety. Consequently, it is essential to devise or use more effective techniques for mitigating salinity and ciprofloxacin-induced stress in soil. This study includes the nZVI-loaded biochar synthesis, integrating the unique characteristics of raw biochar with nZVI. The present study examined the impact of raw and nZVI-loaded biochar on soil quality and the mitigation of salinity stress and Ciprofloxacin toxicity in wheat plants. The results showed that the application of nZVI-loaded biochar treatments led to substantial enhancement in shoot biomass, root biomass, grain biomass, and spike biomass by 152.1, 54.3 %, 59.8 %, and 151 %, respectively compared to control treatment. The treatment with nZVI-loaded biochar significantly increased the rates of photosynthesis and transpiration, as well as the conductance of stomata. It also resulted in higher levels of intercellular CO2, photosynthetic pigments, and water use efficiency with increases of 49 %, 59 %, 57 %, 37 %, 40 %, and 95 %, respectively. The nZVI-loaded biochar significantly decreased electrolyte leakage, malondialdehyde (MDA), and hydrogen peroxide levels compared to the NaCl treatment alone. It also enhanced the activities of enzymatic antioxidants such as peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX), and ascorbate peroxidase (APX). The non-enzymatic antioxidants including total soluble sugars (TSS), flavonoids, total soluble proteins (TSP), phenolics, ascorbic acid, anthocyanin, proline, and glycine betaine significantly influenced by the nZVI-loaded biochar. The nZVI-loaded biochar effectively alleviates the stress of soils that are contaminated with hazardous amounts of Ciprofloxacin while improving the soil and plant health.

Unlocking the potential of carbon dots in agriculture using data-driven approaches

The utilization of carbon dots (CDs) in agriculture to enhance plant growth has gained significant attention, but the data remains fractionated. Systematically integrating existing data is needed to identify the factors driving the interactions between CDs and plants and strategically guide future research. Articles reporting on CDs and their effects on plants were searched based on inclusion and exclusion criteria, resulting in the collection of 71 articles comprising a total of 2564 data points. The meta-analysis reveals that the soil and foliar application of red-emitting bio-derived CDs at a low concentration (<10 ppm) leads to the most beneficial effects on plant growth. Random forest and gradient boosting algorithms revealed that the size and dose of CDs were important factors in predicting plant responses across multiple aspects (CDs properties, plant properties, environmental factors, and experimental conditions). Specifically, smaller sizes are more favorable to growth indicators (GI) below 6 nm, nutrient and quality (NuQ) at 3-6 nm, photosynthesis (PSN) below 7 nm, and antioxidant responses (AR) below 5 nm. Overall, our analysis of existing data suggests that CDs applications can significantly improve plant responses (GI, NuQ, PSN, and AR) by 10-39 %. To unlock the full potential of CDs, customized synthesis techniques should be employed to meet the specific requirements of different crops and climate condition. For example, we recommend the synthesis of small CDs (<7 nm) with emission peak values falling within the range of 405-475 and 610-670 nm to enhance plant growth. The global prediction of plant responses to CDs application in future scenarios have shown significant improvements ranging from 17 to 58 %, suggesting that CDs have widespread applicability. This novel understanding of the impact of CDs on plant response provides valuable insights for optimizing the application of these nanomaterials in agriculture.

Effects of remediation agents on rice and soil in toxic metal(loid)s contaminated paddy fields: A global meta-analysis

Toxic metal(loid)s contamination of paddy soil is a nonnegligible issue and threatens food safety considering that it is transmitted via the soil-plant system. Applying remediation agents could effectively inhibit the soil available toxic metal(loid)s and reduce their accumulation in rice. To comprehensively quantify how remediation agents impact the accumulation of Cd/Pb/As in rice, rice growth and yield, the accumulation of available Cd/Pb/As in paddy soil, and soil characteristics, 50 peer-reviewed publications were selected for meta-analysis. Overall, the application of remediation agents exhibited significant positive effects on rice plant length (ES = 0.05, CI = 0.01-0.08), yield (ES = 0.20, CI = 0.13-0.27), peroxidase (ES = 0.56, CI = 0.18-0.31), photosynthetic rate (ES = 0.47, CI = 0.34-0.61), and respiration rate (ES = 0.68, CI = 0.47-0.88). Among the different types of remediation agents, biochar was the most effective in controlling the accumulation of Cd/Pb/As in all portions of rice, and was also superior in inhibiting the accumulation of Pb in rice grains (ES = -0.59, 95 % CI = -1.04-0.13). This study offers an essential contribution for the remediation strategies of toxic metal(loid)s contaminated paddy fields.

The effects of iron-based nanomaterials (Fe NMs) on plants under stressful environments: Machine learning-assisted meta-analysis

Mitigating the adverse effects of stressful environments on crops and promoting plant recovery in contaminated sites are critical to agricultural development and environmental remediation. Iron-based nanomaterials (Fe NMs) can be used as environmentally friendly nano-fertilizer and as a means of ecological remediation. A meta-analysis was conducted on 58 independent studies from around the world to evaluate the effects of Fe NMs on plant development and antioxidant defense systems in stressful environments. The application of Fe NMs significantly enhanced plant biomass (mean = 25%, CI = 20%-30%), while promoting antioxidant enzyme activity (mean = 14%, CI = 10%-18%) and increasing antioxidant metabolite content (mean = 10%, CI = 6%-14%), reducing plant oxidative stress (mean = -15%, CI = -20%∼-10%), and alleviating the toxic effects of stressful environments. The observed response was dependent on a number of factors, which were ranked in terms of a Random Forest Importance Analysis. Plant species was the most significant factor, followed by Fe NM particle size, duration of application, dose level, and Fe NM type. The meta-analysis has demonstrated the potential of Fe NMs in achieving sustainable agriculture and the future development of phytoremediation.

Degradation of trichloroethylene by biochar supported nano zero-valent iron (BC-nZVI): The role of specific surface area and electrochemical properties

Direct electron transfer and the involvement of atomic hydrogen (H⁎) are considered the main mechanisms for reductive dechlorination promoted by nano zero-valent iron (nZVI) supported on highly conductive carbon. It is still unclear how precisely H⁎, the specific surface area, and the electrochemical characteristics contribute to biochar supported nano zero-valent iron (BC-nZVI) activity in chlorinated hydrocarbon contaminant removal. In this study, a range of BC-nZVIs were prepared by a liquid-phase reduction process, and the contributions of specific surface area and electrochemical performance to H⁎ generation and electron transfer have been assessed. The mechanism of trichloroethylene (TCE) dechlorination by BC-nZVIs has been evaluated in terms of removal efficiency and the ultimate degradation products. The results have demonstrated that BC-nZVIs exhibit a higher specific surface area and TCE degradation efficiency compared with the bare nZVI. Ethane, ethylene, and acetylene were the principal TCE degradation products. The elimination of TCE was not significantly affected by differences in BC-nZVI specific surface area, but electron transfer and sustained generation of H⁎ were dependent on the catalyst electrochemical characteristics. The electrochemical properties of biochar serve to lower the corrosion potential of nZVI, improving electronic transfer capability and reactivity and promoting direct electron transfer for the degradation of TCE. In addition, the enhanced electrochemical properties also facilitate the reaction of nZVI with water and can promote the sustained generation of H⁎. Generation of H⁎ played a key role in reductive dechlorination over BC-nZVIs, which was related to the properties of the biochar support. This study focuses on the role of H⁎ and electrochemical performance in TCE reductive dechlorination, and provides a theoretical foundation and experimental support for the practical application of BC-nZVIs.

Toxic effects and mechanisms of engineered nanoparticles and nanoplastics on lettuce (Lactuca sativa L.)

Engineered nanoparticles (ENPs) and nanoplastics (NPs) are typical nanoparticles in terrestrial environments. Till now, few studies have compared their toxicity and mechanism to plants. Here we investigated the effects of CuO, nZVI ENPs and polystyrene (PS) NPs on lettuce growth, metabolic functions, and microbial community structure. Results showed that low concentrations of nanoparticles decreased root biomass and promoted photosynthetic indicators, whereas increased reactive oxygen species (ROS) were detected in roots exposed to high concentrations of nanoparticles. High-dose CuO ENP exposure significantly raised the MDA content by 124.6 % compared to CK, causing the most severe membrane damage in the roots among the three types of nanoparticles. Although linoleic acid metabolism was down-regulated, the roots alleviated CuO stress by up-regulating galactose metabolism. Uptake of PS by roots similarly caused ROS production and activated the oxidative stress system by altering amino acid and vitamin metabolism. Faster microbial responses to nanoparticles were observed in the nZVI and PS networks. The root toxicity was indirectly mediated by ion release, NP uptake, or ROS generation, ultimately impacting root cell metabolism, rhizospheric microorganism and plant growth. These findings provide theoretical basis for assessing environmental impact of nanoparticles and their possible ecological risks.