Geochemical fractions and phytoavailability of Zinc in a contaminated calcareous soil affected by biotic and abiotic amendments

Comparison of soil addition, foliar spraying, seed soaking, and seed dressing of selenium and silicon nanoparticles effects on cadmium reduction in wheat (Triticum turgidum L.)

Wheat cadmium (Cd) contamination is a critical food security issue worldwide, and selenium (Se) and silicon (Si) are widely reported to reduce Cd accumulation in cereal crops. However, few studies have compared the most effective pathway to reduce Cd accumulation in crops using Se nanoparticles (nano-Se), Si nanoparticles (nano-Si), and their mixtures. Here, we investigated the concentrations of Cd in wheat using four application modes: soil addition, foliar spraying, seed soaking, and seed dressing combined with three different materials. The concentration of Cd in wheat grains can be significantly reduced by 31.30-62.99% and 36.96-51.04% through four applications of nano-Se and soil application and seed soaking of nano-Si, respectively. However, all treatments involving mixtures of nano-Si and nano-Se did not show a reduction in Cd concentration. The applications of both nano-Se and nano-Si can enhance antioxidant enzyme systems and regulate Cd-related gene expression to safeguard wheat tissues from Cd stress. Downregulation of the influx transporter from soil to root (TaNramp5) and from root to shoot (TaLCT1), along with the upregulation of the efflux transporter from cytoplasm to vacuole (TaHMA3), contributed to the nano-Si/nano-Se dependent Cd transport and reduced Cd accumulation in wheat grains. Overall, the application of nano-Se instead of nano-Si, and soil addition rather than foliar spraying, seed soaking, and seed dressing, can be efficiently utilized to reduce grain Cd accumulation from Cd-contaminated soils.

An assessment of nanotechnology-based interventions for cleaning up toxic heavy metal/metalloid-contaminated agroecosystems: Potentials and issues

Heavy metals (HMs) are among the most dangerous environmental variables for a variety of life forms, including crops. Accumulation of HMs in consumables and their subsequent transmission to the food web are serious concerns for scientific communities and policy makers. The function of essential plant cellular macromolecules is substantially hampered by HMs, which eventually have a detrimental effect on agricultural yield. Among these HMs, three were considered, i.e., arsenic, cadmium, and chromium, in this review, from agro-ecosystem perspective. Compared with conventional plant growth regulators, the use of nanoparticles (NPs) is a relatively recent, successful, and promising method among the many methods employed to address or alleviate the toxicity of HMs. The ability of NPs to reduce HM mobility in soil, reduce HM availability, enhance the ability of the apoplastic barrier to prevent HM translocation inside the plant, strengthen the plant's antioxidant system by significantly enhancing the activities of many enzymatic and nonenzymatic antioxidants, and increase the generation of specialized metabolites together support the effectiveness of NPs as stress relievers. In this review article, to assess the efficacy of various NP types in ameliorating HM toxicity in plants, we adopted a 'fusion approach', in which a machine learning-based analysis was used to systematically highlight current research trends based on which an extensive literature survey is planned. A holistic assessment of HMs and NMs was subsequently carried out to highlight the future course of action(s).

Morpho-physiological and biochemical response of wheat to various treatments of silicon nano-particles under drought stress conditions

Silicon nanoparticles (Si-NPs) have shown their potential for use in farming under water-deficient conditions. Thus, the experiment was accomplished to explore the impacts of seed priming of Si-NPs on wheat (Triticum aestivum L.) growth and yield under different drought levels. The plants were grown in pots under natural ecological environmental conditions and were harvested on 25th of April, 2020. The results revealed that seed priming of Si-NPs (0, 300, 600, and 900 mg/L) suggestively improved, the spike length, grains per spike, 1000 grains weight, plant height, grain yield, and biological yield by 12-42%, 14-54%, 5-49%, 5-41%, 17-62%, and 21-64%, respectively, relative to the control. The Si-NPs improved the leaf gas trade ascribes and chlorophyll a and b concentrations, though decreased the oxidative pressure in leaves which was demonstrated by the diminished electrolyte leakage and upgrade in superoxide dismutase and peroxidase activities in leaf under Si-NPs remedies over the control. The outcomes proposed that Si-NPs could improve the yield of wheat under a dry spell. In this manner, the utilization of Si-NPs by seed priming technique is a practical methodology for controlling the drought stress in wheat. These findings will provide the basis for future research and helpful to improve the food security under drought and heat related challenges.

A review of the influence of nanoparticles on the physiological and biochemical attributes of plants with a focus on the absorption and translocation of toxic trace elements

Trace elements (TEs) from various natural and anthropogenic activities contaminate the agricultural water and soil environments. The use of nanoparticles (NPs) as nano-fertilizers or nano-pesticides is gaining popularity worldwide. The NPs-mediated fertilizers encourage the balanced availability of essential nutrients to plants compared to traditional fertilizers, especially in the presence of excessive amounts of TEs. Moreover, NPs could reduce and/or restrict the bioavailability of TEs to plants due to their high sorption ability. In this review, we summarize the potential influence of NPs on plant physiological attributes, mineral absorption, and TEs sorption, accumulation, and translocation. It also unveils the NPs-mediated TE scavenging-mechanisms at plant and soil interface. NPs immobilized TEs in soil solution effectively by altering the speciation of TEs and modifying the physiological, biochemical, and biological properties of soil. In plants, NPs inhibit the transfer of TEs from roots to shoots by inducing structural modifications, altering gene transcription, and strengthening antioxidant defense mechanisms. On the other hand, the mechanisms underpinning NPs-mediated TEs absorption and cytotoxicity mitigation differ depending on the NPs type, distribution strategy, duration of NP exposure, and plants (e.g., types, varieties, and growth rate). The review highlights that NPs may bring new possibilities for resolving the issue of TE cytotoxicity in crops, which may also assist in reducing the threats to the human dietary system. Although the potential ability of NPs in decontaminating soils is just beginning to be understood, further research is needed to uncover the sub-cellular-based mechanisms of NPs-induced TE scavenging in soils and absorption in plants.

Vermicomposting of sewage sludge with organic bulking materials to improve its properties

Adverse properties of sewage sludge such as high concentration of toxic metals and the presence of pathogens have limited its use in agriculture. In this study, the effect of vermicomposting on some important chemical properties of sewage sludge was investigated as a factorial arrangement based on a completely randomized design with three replications. The studied factors were bulking agents in three concentrations (0, 5, and 10% v/v), earthworm (Eisenia fetida) in 2 different concentrations (0 and 50 adult earthworms/6 kg sewage sludge), and retention times in three levels (30, 60, and 90 days). Sewage sludge was obtained from the lagoons of Ghahdarijan refinery in Isfahan province in Iran. The results showed that vermicomposting significantly (p < 1%) reduced the number of coliforms and concentrations of Ni, Cr, and Pb and increased the organic carbon percent and N of the sewage sludge. When comparing different treatments, vermicomposting of sewage sludge with rice husk 10% v/v during retention times of 60 and 90 days were superior treatments in reducing the concentrations of Ni, Cr, and Pb and reducing the number of coliforms. Furthermore, the highest %OC was measured in the rice husk 10% + earthworm in the retention time of 90 days which was about 41% more than the control treatment. In general, it is concluded that vermicomposting significantly reduced the adverse properties of sewage sludge for using in agriculture as an organic fertilizer.

Silicon-based additive on heavy metal remediation in soils: Toxicological effects, remediation techniques, and perspectives

Chemical fertilizer is gaining increasing attention and has been the center of much research which indicating complex beneficial and harmful effects. Chemical fertilizer might cause some environmental hazards to the biosphere, especially in the agricultural ecosystem. The application of silicon (Si) fertilizer in agriculture has been proved to be able to create good economic and environmental benefits. Si is the second most abundant earth crust element. Si fertilizer improves soil quality and alleviates biotic and abiotic crop stress. It is of great significance to understand the function of Si fertilizer in agricultural utilization and environmental remediation. This paper reviews the Si-based fertilizer in farmland use and summarizes prior research relevant with characterization, soil quality improvement, and pollution remediation effects. Its use in agriculture enhances plant silicon uptake, mediates plant salt and drought stress and remediates heavy metals such as Al, As, Cd, Cu, Zn and Cr. This article also summarizes the detoxification mechanism of silicon and its effects on plant physiological activity such as photosynthesis and transpiration. Fertilizer materials and crop fertilizer management were also considered. Foliar spraying is an effective method to improve crop growth and yield and reduce biotic or abiotic stress. Silicon nanoparticle material provides potential with great potential and prospects. More investigation and research are prospected to better understand how silicon impacts the environment and whether it is a beneficial additive.

Effects of nanoparticles on trace element uptake and toxicity in plants: A review

Agricultural soils are receiving higher inputs of trace elements (TEs) from anthropogenic activities. Application of nanoparticles (NPs) in agriculture as nano-pesticides and nano-fertilizers has gained rapid momentum worldwide. The NPs-based fertilizers can facilitate controlled-release of nutrients which may be absorbed by plants more efficiently than conventional fertilizers. Due to their large surface area with high sorption capacity, NPs can be used to reduce excess TEs uptake by plants. The present review summarizes the effects of NPs on plant growth, photosynthesis, mineral nutrients uptake and TEs concentrations. It also highlights the possible mechanisms underlying NPs-mediated reduction of TEs toxicity at the soil and plant interphase. Nanoparticles are effective in immobilization of TEs in soil through alteration of their speciation and improving soil physical, chemical, and biological properties. At the plant level, NPs reduce TEs translocation from roots to shoots by promoting structural alterations, modifying gene expression, and improving antioxidant defense systems. However, the mechanisms underlying NPs-mediated TEs uptake and toxicity reduction vary with NPs type, mode of application, time of NPs exposure, and plant conditions (e.g., species, cultivars, and growth rate). The review emphasizes that NPs may provide new perspectives to resolve the problem of TEs toxicity in crop plants which may also reduce the food security risks. However, the potential of NPs in metal-contaminated soils is only just starting to be realized, and additional studies are required to explore the mechanisms of NPs-mediated TEs immobilization in soil and uptake by plants. Such future knowledge gap has been highlighted and discussed.

Effects of plant growth-promoting bacteria on EDTA-assisted phytostabilization of heavy metals in a contaminated calcareous soil

The objective of this research was to determine the combined effects of ethylenediaminetetraacetic acid (EDTA) and plant growth-promoting rhizobacteria (PGPR) on the phytostabilization of Cd, Pb, and Zn by corn and chemical fractionation of these elements in soil. Three heavy metal-resistant bacteria (P18, P15, and P19) were selected. All strains, belonging to the fluorescent pseudomonads, exhibited plant growth-promoting properties, including phosphorus solubilization and production of siderophore, indole acetic acid, and 1-aminocyclopropane-1-carboxylic acid deaminase. Applying EDTA individually or in combination with bacterial strains (P18 and P15) significantly increased shoot biomass. The highest dry shoot biomass was recorded in the combined treatment of EDTA and P15-inoculated pots. Application of EDTA in PGPR-inoculated pots increased concentrations of heavy metals in corn shoots and roots compared to the control. The highest concentration of Zn in corn root and shoot was observed in P15 + EDTA treatment, which were 2.0-fold and 1.3-fold higher than those in the untreated soil. Results of chemical speciation showed that the co-application of EDTA and fluorescent pseudomonads strains increased the bioavailability of Zn, Pb, and Cd by their redistribution from less soluble fractions to water-soluble forms. It was concluded that bacterial inoculation could improve the efficiency of EDTA in phytostabilization of heavy metals from multi-metal contaminated soils.

Effects of silicon nanoparticles on growth and physiology of wheat in cadmium contaminated soil under different soil moisture levels

Soil degradation with different stress conditions like accumulation of cadmium (Cd) contents in soil and drought stress has become one of the most dangerous issues that obstruct the sustainable agriculture production. Silicon nanoparticles (Si NPs) play beneficial roles in combating various biotic and abiotic stresses but their role under combined metal and drought stress is not studied. A pot study was designed to determine the effect of Si NPs on wheat (Triticum aestivum L.) growth and uptake of Cd grown in Cd contaminated soil with different water levels under ambient conditions. Four different levels of Si NPs (0, 25, 50, and 100 mg/kg) were applied in the soil before 1 week of wheat sowing and two water levels (70% and 35% soil water-holding capacity) were introduced after 50 days of seed sowing for the remaining growth period. The lowest biomass, yield, and photosynthesis were observed in the control plants while oxidative stress and the highest Cd concentrations in shoots, roots, and grains were observed in the control plants, and the drought stress further enhanced this effect on the plants. The Si NPs treatments improved the plant growth indicators and photosynthesis, and reduced the Cd concentrations in wheat tissues, especially in grains either without or with drought stress. The Si NPs reduced the oxidative stress in leaves as was indicated by the reduced production of hydrogen peroxide, electrolyte leakage, and malondialdehyde contents, and increase in superoxide dismutase and peroxidase activities. The improvement in wheat growth and a reduction in oxidative stress and Cd concentration in tissues were dependent on the levels of Si NPs and the effect was the highest with the highest level of NPs used.

Silicon nanoparticles enhanced the growth and reduced the cadmium accumulation in grains of wheat (Triticum aestivum L.)

The application of silicon (Si) under heavy metal stress is well known, but the use of Si nanoparticles (NPs) under metal stress in not well documented. Thus, the experiments were performed to investigate the impacts of soil and foliar applied Si NPs on wheat (Triticum aestivum L.) growth and cadmium (Cd) accumulation in grains under Cd toxicity. The plants were grown under natural environmental conditions and were harvested after physiological maturity (124 days after sowing). The results demonstrated that Si NPs significantly improved, relative to the control, the dry biomass of shoots, roots, spikes and grains by 24-69%, 14-59%, 34-87%, and 31-96% in foliar spray and by 10-51%, 11-49%, 25-69%, and 27-74% in soil applied Si NPs, respectively. The Si NPs enhanced the leaf gas exchange attributes and chlorophyll a and b concentrations, whereas diminished the oxidative stress in leaves which was indicated by the reduced electrolyte leakage and enhancement in superoxide dismutase and peroxidase activities in leaf under Si NPs treatments over the control. When compared with the control, the foliar spray of Si NPs reduced the Cd contents in shoots, roots, and grains by 16-58%, 19-64%, and 20-82%, respectively, whereas soil applied Si NPs reduced the Cd concentrations in shoots, roots, and grains by 11-53%, 10-59%, and 22-83%, respectively. In comparison with the control, Si concentrations significantly (p ≤ 0.05) increased in the shoots and roots in both foliar and soil supplementation of Si NPs. Our results suggested that Si NPs could improve the yield of wheat and more importantly, reduce the Cd concentrations in the grains. Thus, the use of Si NPs might be a feasible approach in controlling Cd entry into the human body via crops.

Seed priming with silicon nanoparticles improved the biomass and yield while reduced the oxidative stress and cadmium concentration in wheat grains

Cadmium (Cd) is among the non-essential elements for the growth of crops while silicon (Si) is a beneficial element for plant growth. There is little evidence regarding the use of silicon nanoparticles (Si NPs) on the reduction of Cd accumulation in crops especially wheat. The present study determined the impact of seed priming with Si NPs on Cd-induced responses in wheat in terms of growth, yield, photosynthesis, oxidative stress, and Si and Cd accumulation in wheat. Seed priming was done by different levels of Si NPs (0, 300, 600, 900, 1200 mg/L) for 24 h by providing continuous aeration. Afterwards, seeds were sown in soil contaminated with Cd. The results depicted that Si NPs positively affected the wheat growth and chlorophyll contents over the control. The Si NPs diminished the oxidative stress and positively affected the antioxidant enzyme activity. The Si NPs decreased the Cd concentrations in wheat, especially in grains, and increased the Si concentrations in plants. The Si NPs reduced the Cd contents by 10-52% in shoot, by 11-60% in roots, and by 12-75% in grains as compared with respective controls. The study suggested that the use of Si NPs may be a tool for reducing the Cd toxicity in wheat and declining its concentration in grains. Thus, Si NPs application by seed priming method might be helpful in increasing plants biomass and yield while reducing the oxidative stress and Cd uptake in wheat grains.

Draft Genome Sequence of Pseudomonas sp. Strain MWU13-2860, Isolated from a Wild Cranberry Bog in Truro, Massachusetts

Pseudomonas sp. strain MWU13-2860 was isolated from the rhizosphere of wild cranberry plants and is not closely related to Pseudomonas spp.

Pseudomonas sp. strain MWU13-2860 was isolated from the rhizosphere of wild cranberry plants and is not closely related to Pseudomonas spp. frequently isolated from soil. Its genome is 7.2 Mbp, with 61.24% G+C content, and contains homologs that may encode the carbohydrate-degrading enzymes xylanase, laccase, cellulase, alginate lyase, amylase, and chitinase.

Using nanoparticles from water treatment residuals to reduce the mobility and phytoavailability of Cd and Pb in biosolid-amended soils

Heavy metal pollution in soils amended with biosolids has been a serious problem worldwide for clean food production. Laboratory and greenhouse experiments were performed to assess the impact of water treatment residual nanoparticles (nWTRs), at different application rates (0.1, 0.2 and 0.3%), on immobilization and phytoavailability of Cd and Pb to canola (Brassica napus L.) plants in soils amended with biosolids spiked with three different rates of Cd or Pb. Application of nWTRs significantly increased the residual fractions of Cd and Pb in metal-spiked biosolid-amended soil and thereby increased the immobilization of Cd and Pb in the amended soil. The greatest immobilization of Cd and Pb was exhibited at an application rate of 0.3% nWTRs. In addition, the application of nanoparticles to the biosolid-amended soil significantly increased canola grain yield and significantly decreased Cd and Pb phytoavailability due to immobilization of Cd and Pb in the contaminated soil. The results demonstrate, for the first time, the capability of nanoscale WTRs in stabilizing heavy metals in contaminated soils and restoring degraded agricultural land.