Phosphorus fertilization and mycorrhizal colonization change silver nanoparticle impacts on maize

Interaction of plants and metal nanoparticles: Exploring its molecular mechanisms for sustainable agriculture and crop improvement

Metal nanoparticles offer promising prospects in agriculture, enhancing plant growth and ensuring food security. Silver, gold, copper, and zinc nanoparticles possess unique properties making them attractive for plant applications. Understanding molecular interactions between metal nanoparticles and plants is crucial for unlocking their potential to boost crop productivity and sustainability. This review explores metal nanoparticles in agriculture, emphasizing the need to understand these interactions. By elucidating mechanisms, it highlights the potential for enhancing crop productivity, stress tolerance, and nutrient-use efficiency, contributing to sustainable agriculture and food security. Quantifying benefits and risks reveal significant advantages. Metal nanoparticles enhance crop productivity by 20% on average and reduce disease incidence by up to 50% when used as antimicrobial agents. They also reduce nutrient leaching by 30% and enhance soil carbon sequestration by 15%, but concerns about toxicity, adverse effects on non-target organisms, and nanoparticle accumulation in the food chain must be addressed. Metal nanoparticles influence cellular processes including sensing, signaling, transcription, translation, and post-translational modifications. They act as signaling molecules, activate stress-responsive genes, enhance defense mechanisms, and improve nutrient uptake. The review explores their catalytic role in nutrient management, disease control, precision agriculture, nano-fertilizers, and nano-remediation. A bibliometric analysis offers insights into the current research landscape, highlighting trends, gaps, and future directions. In conclusion, metal nanoparticles hold potential for revolutionizing agriculture, enhancing productivity, mitigating environmental stressors, and promoting sustainability. Addressing risks and gaps is crucial for their safe integration into agricultural practices.

Reveal molecular mechanism on the effects of silver nanoparticles on nitrogen transformation and related functional microorganisms in an agricultural soil

Silver nanoparticles (AgNPs) are widely present in aquatic and soil environment, raising significant concerns about their impacts on creatures in ecosystem. While the toxicity of AgNPs on microorganisms has been reported, their effects on biogeochemical processes and specific functional microorganisms remain relatively unexplored. In this study, a 28-day microcosmic experiment was conducted to investigate the dose-dependent effects of AgNPs (10 mg and 100 mg Ag kg-1 soil) on nitrogen transformation and functional microorganisms in agricultural soils. The molecular mechanisms were uncovered by examining change in functional microorganisms and metabolic pathways. To enable comparison, the toxicity of positive control with an equivalent Ag+ dose from CH3COOAg was also included. The results indicated that both AgNPs and CH3COOAg enhanced nitrogen fixation and nitrification, corresponding to increased relative abundances of associated functional genes. However, they inhibited denitrification via downregulating nirS, nirK, and nosZ genes as well as reducing nitrate and nitrite reductase activities. In contrast to high dose of AgNPs, low levels increased bacterial diversity. AgNPs and CH3COOAg altered the activities of associated metabolic pathways, resulting in the enrichment of specific taxa that demonstrated tolerance to Ag. At genus level, AgNPs increased the relative abundances of nitrogen-fixing Microvirga and Bacillus by 0.02 %-629.39 % and 14.44 %-30.10 %, respectively, compared with control group (CK). The abundances of denitrifying bacteria, such as Rhodoplanes, Pseudomonas, and Micromonospora, decreased by 19.03 % to 32.55 %, 24.73 % to 50.05 %, and 15.66 % to 76.06 %, respectively, compared to CK. CH3COOAg reduced bacterial network complexity, diminished the symbiosis mode compared to AgNPs. The prediction of genes involved in metabolic pathways related to membrane transporter and cell motility showed sensitive to AgNPs exposure in the soil. Further studies involving metabolomics are necessary to reveal the essential effects of AgNPs and CH3COOAg on biogeochemical cycle of elements in agricultural soil.

How does phosphorus influence Cd tolerance strategy in arbuscular mycorrhizal - Phragmites australis symbiotic system?

To clarify how phosphorus (P) influences arbuscular mycorrhizal fungi (AMF) interactions with host plants, we measured the effects of variation in environmental P levels and AMF colonization on photosynthesis, element absorption, ultrastructure, antioxidant capacity, and transcription mechanisms in Phragmites australis (P. australis) under cadmium (Cd) stress. AMF maintained photosynthetic stability, element balance, subcellular integrity and enhanced antioxidant capacity by upregulating antioxidant gene expression. Specifically, AMF overcame Cd-induced stomatal limitation, and mycorrhizal dependence peaked in the high Cd-moderate P treatment (156.08%). Antioxidants and compatible solutes responded to P-level changes: the primary driving forces of removing reactive oxygen species (ROS) and maintaining osmotic balance were superoxide dismutase, catalase, and sugars at limited P levels and total polyphenol, flavonoid, peroxidase, and proline at abundant P levels, we refer to this phenomenon as "functional link." AMF and phosphorus enhanced Cd tolerance in P. australis, but the regulation of AMF was P-dependent. Phosphorus prevented increases in total glutathione content and AMF-induced GSH/GSSG ratio (reduced to oxidized glutathione ratio) by inhibiting the expression of assimilatory sulfate reduction and glutathione reductase genes. The AMF-induced flavonoid synthesis pathway was regulated by P, and AMF activated Cd-tolerance mechanisms by inducing P-dependent signaling.

Effects of microplastics on cadmium accumulation by rice and arbuscular mycorrhizal fungal communities in cadmium-contaminated soil

Both microplastics (MPs) and cadmium (Cd) are common contaminants in soil-rice systems, but their combined effects remain unknown. Thereby, we explored the effects of three MPs, i.e., polyethylene terephthalate (PET), polylactic acid (PLA), and polyester (PES), on Cd accumulation in rice and the community diversity and structure of arbuscular mycorrhizal fungi (AMF) in soil spiked with or without Cd. Results showed that 2% PLA decreased shoot biomass (-28%), but PET had a weaker inhibitive effect. Overall, Cd alone did not significantly change shoot and root biomass and increased root biomass in combination with 0.2% PES. MPs generally increased soil Cd availability but decreased Cd accumulation in rice tissues. Both MPs and Cd improved the bioavailability and uptake of Fe and Mn in rice roots. MPs altered the diversity and community composition of AMF, depending on their type and dose and co-existing Cd. Overall, 2% PLA caused the most distinct changes in soil properties, plant growth and Cd accumulation, and AMF communities, but showed no synergistic interactions with Cd. In conclusion, MPs can mediate rice performance and Cd accumulation via altering soil properties, nutrient uptake, and root mycorrhizal communities, and biodegradable PLA MPs thought environment-friendly can exhibit higher phytotoxicity than conventional MPs.

Effects of Ag nanoparticles on plant growth, Ag bioaccumulation, and antioxidant enzyme activities in Phragmites australis as influenced by an arbuscular mycorrhizal fungus

Ag nanoparticles (AgNPs) are considered an emerging contaminant in recent years, and their harmful effects on plants pose new concerns, especially in coexistence with soil microorganisms. Arbuscular mycorrhizal fungi (AMF), as mutualistic fungi with most terrestrial plants, may contribute to alleviating nanotoxicity in plants. Herein, AgNP toxicity of different concentrations (1, 5, 10, 50, 100 mg/kg) on reed (Phragmites australis (Cav.) Trin. ex Steudel) as influenced by mycorrhizal inoculation with Funneliformis mosseae was investigated. The results revealed that concentration is the main factor influencing the AgNP phytotoxicity; AgNP dose had biphasic effects on AMF colonization, plant biomass, and antioxidant enzyme activities. Thereinto, different antioxidant enzymes had different tolerances to AgNP stress, and the turning point of their activities was respectively the following: POD-5 mg/kg < SOD-10 mg/kg < CAT-50 mg/kg. The growth configuration (root:shoot ratio) of Phragmites australis increased firstly and then decreased to cope with the increasing AgNP concentration. Additionally, the Ag accumulation and translocation of AgNP-exposed plants were relatively lower than that of equivalent Ag⁺-exposed plants. However, AMF inoculation improved plant antioxidant capability and biomass growth in response to AgNP-induced toxicity. Meanwhile, AMF effectively regulated the root:shoot ratio to accommodate AgNP stress. The linear model fittings and heat maps showed that the mycorrhizal plants exhibited a higher Ag accumulative rate and root partitioning (Ag organ distribution: root > stem > leaf) than the non-inoculated plants. Overall, our results demonstrated that AMF could diminish the negative effects induced by AgNPs and promote Ag immobilization in plant roots so as to alleviate AgNP-posed environmental risks.

The mechanism of arbuscular mycorrhizal enhancing cadmium uptake in Phragmites australis depends on the phosphorus concentration

Arbuscular mycorrhizal fungi (AMF) is a vital strategy to enhance the phytoremediation of cadmium (Cd) pollution. However, the function of AMF was influenced by phosphorus (P) concentration. To reveal the effect of AMF on the Cd accumulation of host plants under different P concentrations and how the AMF and P interact, this study comparatively analyzed the regulatory effects of AMF on the Cd response, extraction, and transportation processes of Phragmites australis (P. australis) under different P levels, and explored its physiological, biochemical and molecular biological mechanisms. The study showed that AMF could induce different growth allocation strategies in response to Cd stress. Moreover, AMF promoted plant Cd tolerance and detoxification by enhancing P uptake, Cd passivation, Cd retention in the cell wall, and functional group modulation. Under P starvation treatments, AMF promoted Cd uptake by inducing Cd to enter the iron pathway, increased the transport coefficient by 493.39%, and retained Cd in stems. However, these effects disappeared following the addition of P. Additionally, AMF up-regulated the expression of ZIP, ZIP, and NRAMP genes to promote cadmium uptake at low, medium, and high phosphorus levels, respectively. Thus, the Cd response mechanism of the AMF-P. australis symbiotic system was P dose-dependent.

Phytotoxicity response of sugar beet (Beta vulgaris L.) seedlings to herbicide fomesafen in soil

Fomesafen is the most widely used herbicide in the soybean field. However, there are urgent practical challenges with the long-term persistence of fomesafen in soil and its effects on the subsequent crops in agricultural production. Therefore, pot experiments were conducted to study the effects of fomesafen residues (0-0.05 mg kg^-1) on growth, photosynthetic characteristics, and the antioxidant defense system of sugar beet seedlings. The results showed that with the increase of fomesafen residues, the phytotoxicity index increased, while the plant height, leaf area, root length, root volume, and dry weight of sugar beet decreased. Photosynthetic pigment content, net photosynthetic rate (Pn), maximum photosynthetic efficiency (Fv/Fm), and actual photosynthetic efficiency (Y(II)) declined with a dose-dependent manner of fomesafen, but the intercellular CO₂ concentration (Ci) and non-photochemical quenching coefficient (NPQ) increased under fomesafen. On the other hand, the residues of fomesafen increased the content of malondialdehyde (MDA) and membrane permeability by aggravating oxidative stress and triggering the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and polyphenol oxidase (PPO). In addition, sugar beet seedlings were significantly sensitive to fomesafen as the concentration of fomesafen in the soil was up to 0.025 mg kg^-1. In conclusion, the present study showed that fomesafen residues in the soil could affect the morphophysiology and photosynthetic performance of sugar beet. This study is beneficial for understanding the effects of the herbicide fomesafen residues on non-target crops.

Phosphorus fertilization regimes and rates alter Cd extractability in rhizospheric soils and uptake in maize (Zea mays L.)

Understanding cadmium (Cd) extractability and transfer in soil-plant system is crucial for the evaluation of the remediation effect of Cd-contaminated soils. However, knowledge on the effects of different phosphorus (P) fertilizers on Cd uptake in plants, root morphology, and Cd extractability in rhizosphere soils remains very limited. In this study, a five-year field experiment was conducted to evaluate the impacts of four P fertilizers (i.e. calcium superphosphate, calcium magnesium phosphate, monopotassium phosphate, and compound fertilizer) on Cd uptake in maize (Zea mays L.), root morphology, and Cd extractability in rhizospheric acidic soils contaminated with Cd. The results showed that compared to the control, the contents of rhizospheric DTPA-Cd were respectively 18-40% and 8-29% lowered by the calcium magnesium phosphate and monopotassium phosphate, but 21-59% and 10-36% elevated by the calcium superphosphate and compound fertilizer. Similar effects of P fertilizers were observed on exchangeable Cd. Furthermore, the altered levels of the DTPA-Cd and exchangeable Cd in the rhizospheric soils were greater than those in the non-rhizospheric soils. Moreover, different P fertilization regimes altered the contents of Cd in maize tissues (roots, stems, leaves, and grains), and the alterations were closely related to the variation of DTPA-Cd and exchangeable Cd in the rhizospheric soils. Meanwhile, different P fertilization regimes enhanced root morphological parameters (root length, surface area, and volume), and the activities of urease and surcase. In general, the lowest concentrations of soil DTPA-Cd and Cd in maize tissues were found in the treatments with calcium magnesium phosphate. This study has demonstrated that the calcium magnesium phosphate can be used as a potential amendment agent for the acidic Cd-contaminated soils cultivated with maize.

Uptake, translocation, and transformation of silver nanoparticles in plants

This article reviews the plant uptake of silver nanoparticles (AgNPs) that occurred in soil systems and the in planta fate of Ag.

Recent advances in responses of arbuscular mycorrhizal fungi - Plant symbiosis to engineered nanoparticles

The application of engineered nanomaterials (ENMs) is increasing in all walks of life, inevitably resulting in a high risk of ENMs entering the natural environment. Recent studies have demonstrated that phytoaccumulation of ENMs in the environment may be detrimental to plants to varying degrees. However, plants primarily assimilate ENMs through the roots, which are inevitably affected by rhizomicroorganisms. In this review, we focus on a group of common rhizomicroorganisms-arbuscular mycorrhizal fungi (AMF). These fungi contribute to ENMs immobilization and inhibition of phytoaccumulation, improvement of host plant growth and activation of systematic protection in response to excess ENMs stress. In present review, we summarize the biological responses of plants to ENMs and the modulatory mechanisms of AMF on the immobilization of ENMs in substrate-plant interfaces, and indirectly regulatory mechanisms of AMF on the deleterious effects of ENMs on host plants. In addition, the information of feedback of ENMs on mycorrhizal symbiosis and the prospects of future research on the fate and mechanism of phyto-toxicity of ENMs mediated by AMF in the environment are also addressed. In view of above, synergistic reaction of plants and AMF may prove to be a cost-effective and eco-friendly technology to bio-control potential ENMs contamination on a sustainable basis.

Effect of Rhizophagus irregularis on Growth and Quality of Cannabis sativa Seedlings

Rhizophagus irregularis is an arbuscular mycorrhiza fungus that can enhance plant nutrition and reduce transplant shock on seedlings. The present study aims to evaluate the effects of this fungus on the quality of cannabis (Cannabis sativa L.) seedlings.A greenhouse float system experiment was conducted in a completely randomized design with three treatments. The treatments included the application of 40, 80 and 120 fungus spores per L of nutrient solution (AMF1, AMF2 and AMF3, respectively). The evaluation was performed based on the agronomic characteristics of the seedlings (root and stem length and weight, stem diameter), N and P content, survival rate, and the Dickson's quality index (DQI). Results indicated that root length and stem dry weight were significantly increased (by 34.14% and 21.4%, respectively) in the AMF3 treatment. The biomass of the seedlings' roots, the fresh weight and the N content were not affected by the AMF. On the contrary, survival rate, P content and DQI were significantly increased in AMF3 (by 5%, 24.3% and 12.4% respectively). Overall, our findings suggest that the application of high doses of Rhizophagus irregularis (AMF3) on float system-produced cannabis seedlings results in a considerable increment of their quality.

Advantage of Nanotechnology-Based Genome Editing System and Its Application in Crop Improvement

Agriculture is an important source of human food. However, current agricultural practices need modernizing and strengthening to fulfill the increasing food requirements of the growing worldwide population. Genome editing (GE) technology has been used to produce plants with improved yields and nutritional value as well as with higher resilience to herbicides, insects, and diseases. Several GE tools have been developed recently, including clustered regularly interspaced short palindromic repeats (CRISPR) with nucleases, a customizable and successful method. The main steps of the GE process involve introducing transgenes or CRISPR into plants via specific gene delivery systems. However, GE tools have certain limitations, including time-consuming and complicated protocols, potential tissue damage, DNA incorporation in the host genome, and low transformation efficiency. To overcome these issues, nanotechnology has emerged as a groundbreaking and modern technique. Nanoparticle-mediated gene delivery is superior to conventional biomolecular approaches because it enhances the transformation efficiency for both temporal (transient) and permanent (stable) genetic modifications in various plant species. However, with the discoveries of various advanced technologies, certain challenges in developing a short-term breeding strategy in plants remain. Thus, in this review, nanobased delivery systems and plant genetic engineering challenges are discussed in detail. Moreover, we have suggested an effective method to hasten crop improvement programs by combining current technologies, such as speed breeding and CRISPR/Cas, with nanotechnology. The overall aim of this review is to provide a detailed overview of nanotechnology-based CRISPR techniques for plant transformation and suggest applications for possible crop enhancement.