Cadmium minimization in wheat: A critical review

Remediation of Cd contaminated paddy fields by intercropping of the high- and low- Cd-accumulating rice cultivars

Intercropping cadmium (Cd) hyperaccumulators with crops have been widely applied in the remediation of contaminated farmland soils. However, most studies were done on drylands since the majority of the hyperaccumulators are susceptible to the aquatic environment, making the remediation of Cd-contaminated paddy fields particularly difficult. Our study attempts to address the issue by intercropping the high-Cd-accumulating (henceforth, "high-Cd") rice cultivars with the low-Cd-accumulating (henceforth, "low-Cd") ones, and to study the Cd removal, uptake and translocation during the remediation process. The results indicated that intercropping mode with 20-cm row spacing (intercropping-20 treatment) performed better than the that with 30-cm row spacing (intercropping-30 treatment), while intercropping had stronger impact on late rice compared to early rice. In general, the physiological condition of rice was stable under the intercropping-20 treatment, suggesting the growth of rice was not impeded. For late rice, as the intercropping-20 treatment can significantly reduce soil pH and increase the diethylenetriaminepentaacetic acid extracted Cd (DTPA-extracted Cd) from the rhizosphere soil, Cd accumulated more in the tissues of the high-Cd rice cultivars (H2), and its dry biomass increased. As a result, a drastic improvement in the total Cd removal rate by 38.55 % was noticed. Therefore, the reduction of total Cd concentration in 0-20 cm profile caused by removal, thus it could provide safer soil environment for the growth of low Cd-rice cultivars (L2), leading to a significant drop in the root Cd concentration and safer production of L2. Interestingly, intercropping had no effect on the yield per plant of low-Cd rice cultivars. For early rice, intercropping-20 treatment exerted trivial effects to all aspects. The intercropping-30 treatment has poor representativeness of all indicators because of the large intercropping distance. Our results demonstrate that intercropping of the high-Cd and the low-Cd rice cultivars is a potential mode for Cd remediation in paddy fields.

Integrated physio-biochemical and transcriptomic analysis revealed mechanism underlying of Si-mediated alleviation to cadmium toxicity in wheat

Cadmium (Cd) contamination has resulted in serious reduction of crop yields. Silicon (Si), as a beneficial element, regulates plant growth to heavy metal toxicity mainly through reducing metal uptake and protecting plants from oxidative injury. However, the molecular mechanism underlying Si-mediated Cd toxicity in wheat has not been well understood. This study aimed to reveal the beneficial role of Si (1 mM) in alleviating Cd-induced toxicity in wheat (Triticum aestivum) seedlings. The results showed that exogenous supply of Si decreased Cd concentration by 67.45% (root) and 70.34% (shoot), and maintained ionic homeostasis through the function of important transporters, such as Lsi, ZIP, Nramp5 and HIPP. Si ameliorated Cd-induced photosynthetic performance inhibition through up-regulating photosynthesis-related genes and light harvesting-related genes. Si minimized Cd-induced oxidative stress by decreasing MDA contents by 46.62% (leaf) and 75.09% (root), and helped re-establish redox homeostasis by regulating antioxidant enzymes activities, AsA-GSH cycle and expression of relevant genes through signal transduction pathway. The results revealed molecular mechanism of Si-mediated wheat tolerance to Cd toxicity. Si fertilizer is suggested to be applied in Cd contaminated soil for food safety production as a beneficial and eco-friendly element.

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.

Agronomic and ionomics indicators of high-yield, mineral-dense, and low-Cd grains of wheat (Triticum aestivum L.) cultivars

The accumulation of toxic and essential nutrient elements in wheat grain influences wheat yield, grain nutritional quality, and human health. Here, we assessed the potential for breeding wheat cultivars to combine high yield with low cadmium and high iron and/or zinc concentrations in grains, and we screened appropriate cultivars. A pot experiment was conducted to explore differences in grain cadmium, iron, and zinc concentrations among 68 wheat cultivars, as well as their relationships with other nutrient elements and agronomic characters. The results showed 2.04-, 1.71-, and 1.64-fold differences in grain cadmium, iron, and zinc concentrations, respectively, among the 68 cultivars. Grain cadmium concentration was positively correlated with grain zinc, iron, magnesium, phosphorus, and manganese concentrations. Grain copper concentration was positively correlated with grain zinc and iron concentrations, but not with grain cadmium concentration. Therefore, copper has a potential role in regulating grain iron and zinc accumulation without influencing cadmium concentration in wheat grain. There were no significant relationships between grain cadmium concentration and four important wheat agronomic characters (i.e., grain yield, straw yield, thousand kernel weight, and plant height), indicating that the breeding of low-cadmium-accumulating cultivars with dwarfism and high yield characteristics is possible. On cluster analysis, four cultivars (Ningmai11, Xumai35, Baomai6, and Aikang58) exhibited low-cadmium and high-yield characteristics. Among them, Aikang58 contained moderate iron and zinc concentrations, while Ningmai11 had relatively high iron but low zinc concentrations in the grain. These results imply that it is feasible to breed high-yield dwarf wheat with low cadmium and moderate iron and zinc concentrations in the grain.

Soil heavy metal(loid) pollution and health risk assessment of farmlands developed on two different terrains on the Tibetan Plateau, China

The quality of farmland soils on the Tibetan Plateau is important because of the region's ecological vulnerability and their close link with local food security. Investigation on the pollution status of heavy metal (loid)s (HMs) in the farmlands of Lhasa and Nyingchi on the Tibetan Plateau, China revealed that Cu, As, Cd, Tl, and Pb were apparently enriched, with the soil parent materials being the primary sources of the soil HMs. Overall, the farmlands in Lhasa had higher contents of HMs compared to those in the farmlands of Nyingchi, which could be attributed to the fact that the former were mainly developed on river terraces while the latter were mainly developed on the alluvial fans in mountainous areas. As displayed the most apparent enrichment, with the average concentrations in the vegetable field soils and grain field soils of Lhasa being 2.5 and 2.2 times higher compared to those of Nyingchi. The soils of vegetable fields were more heavily polluted than those of grain fields, probably due to the more intensive input of agrochemicals, particularly the use of commercial organic fertilizers. The overall ecological risk of the HMs in the Tibetan farmlands was low, while Cd posed medium ecological risk. Results of health risk assessment show that ingestion of the vegetable field soils could pose elevated health risk, with children facing greater risk than adults. Among all the HMs targeted, Cd had relatively high bioavailability of up to 36.2% and 24.9% in the vegetable field soils of Lhasa and Nyingchi, respectively. Cd also showed the most significant ecological and human health risk. Thus, attention should be paid to minimize further anthropogenic input of Cd to the farmland soils on the Tibetan Plateau.

Physiological and proteomic analyses reveal the important role of arbuscular mycorrhizal fungi on enhancing photosynthesis in wheat under cadmium stress

Arbuscular mycorrhizal fungi (AMF) are important in the phytoremediation of cadmium (Cd). Improving photosynthesis under Cd stress helps to increase crop yields. However, the molecular regulatory mechanisms of AMF on photosynthetic processes in wheat (Triticum aestivum) under Cd stress remain unclear. This study utilized physiological and proteomic analyses to reveal the key processes and related genes of AMF that regulate photosynthesis under Cd stress. The results showed that AMF promoted the accumulation of Cd in the roots of wheat but significantly reduced the content of Cd in the shoots and grains. The photosynthetic rates, stomatal conductance, transpiration rates, chlorophyll content, and accumulation of carbohydrates under Cd stress were increased by AMF symbiosis. Proteomic analysis showed that AMF significantly induced the expression of two enzymes involved in the chlorophyll biosynthetic pathway (coproporphyrinogen oxidase and Mg-protoporphyrin IX chelatase), improved the expression of two proteins related to CO₂ assimilation (ribulose-1,5-bisphosphate carboxylase and malic enzyme), and increased the expression of S-adenosylmethionine synthase, which positively regulates abiotic stress. Therefore, AMF may regulate photosynthesis under Cd stress by promoting chlorophyll biosynthesis, carbon assimilation, and S-adenosylmethionine metabolism.

Effect of titanium dioxide nanoparticles and co-composted biochar on growth and Cd uptake by wheat plants: A field study

Cadmium (Cd) is a common toxic trace element found in agricultural soils which is due to anthropogenic activities. Cadmium posed a significant risk to humans all around the world due to its cancer-causing ability. The current study demonstrated the effects of soil-applied biochar (BC) and foliar-applied titanium dioxide nanoparticles (TiO₂ NPs) (at a rate of 0.5% and 75 mg/L respectively) alone or in combination on growth and Cd accumulation in wheat plants under field experiment. Soil applied BC and foliar TiO₂ NPs, as well as BC coupled with TiO₂ NPs, reduced Cd contents in grains by 32%, 47%, and 79%, than control respectively. The usage of NPs and BC boosted the plant height as well as chlorophyll contents by lowering oxidative injury and changing antioxidant enzyme activities than control plants. The combined use of NPs and BC prevented excess Cd accumulation in grains over the critical level (0.2 mg/kg) for cereals. The health risk index (HRI) due to Cd was reduced by 79% by co-composted BC + TiO₂ NPs treatment than control. Although, HRI was lower than one for all treatments but this may exceed the limit if grains obtained from such field consumed over long periods. In conclusion, TiO₂ NPs and BC amendments can be implemented in fields across the globe where excess Cd is present soils. Additional studies on the use of such approaches in more precise experimental settings are needed in order to address this environmental problem at larger scale.

Heavy metal distribution in wheat plant components following foliar Cd application

Atmospheric deposition of Cd, from anthropogenic activities, can be directly deposited onto and absorbed into wheat plants, yet, how foliar absorbed Cd is translocated in wheat plants is not well understood. A pot experiment investigated foliar Cd application on the accumulation and distribution of heavy metals in various wheat parts. Wheat was grown in a Cd/heavy metal contaminated soil, and from grain heading to the filling stage, 0, 10, 20, 30 and 40 mg kg^-1 Cd solution was sprayed repeatedly on leaves (grain heads were covered). Foliar Cd application had no effect on grain yield and Cd concentration (3.01-3.51 mg kg^-1 for all treatments), while increased flag leaf blade and sheath Cd concentrations by 1.06-2.77 and 0.00-0.66 times, respectively. Cadmium concentration in the center of the peduncle, from the 40 mg kg^-1 Cd solution treatment, was 1.41 times that of the control (10.3 vs 7.30 mg kg^-1). Foliar Cd application also increased Cd accumulation (concentration × mass) of the flag leaf blade and sheath. Rachis and grain Pb concentrations were reduced, while stem Pb concentration was increased by Cd application. Cadmium application negatively affected whole plant Ni accumulation and concentration of certain wheat parts; Ni absorption inhibition may have occurred in roots via the downward transport of Cd. Overall results implied that the predominant portion of foliar applied Cd was retained in leaves, while lesser portions migrated to peduncle or root and affected the absorption/distribution of other metals in wheat plants. These results are important for further discerning the mechanism of wheat grain Cd accumulation, especially when grain is raised in areas where atmospheric deposition of Cd (e.g., near smelting facilities) is an issue from an environmental and human health perspective.

Effects of α-Fe2O3 nanoparticles and biochar on plant growth and fruit quality of muskmelon under cadmium stress

Cadmium pollution in farmland has become a global environmental problem, threatening ecological security and human health. Biochar is effective in remediation of soil pollution. However, high concentrations of biochar can inhibit plant growth, and low concentrations of biochar have limited mitigation effect on cadmium toxicity. Therefore, the combination of low-concentration biochar and other amendments is a promising approach to alleviate cadmium toxicity in plants and improve the safety of edible parts. In this study, muskmelon was selected as the research object, and different concentrations of α-Fe₂O₃ nanoparticles were used alone or combined with biochar to explore the effects of different treatments on muskmelon plants in cadmium-contaminated soil. The results showed that the combined application of 250 mg/kg α-Fe₂O₃ nanoparticles and biochar had a good effect on the repair of cadmium toxicity in muskmelon plants. Compared with cadmium treatment, its application increased plant height by 32.53%, cadmium transport factor from root to stem decreased by 32.95%, chlorophyll content of muskmelon plants increased by 14.27%, and cadmium content in muskmelon flesh decreased by 18.83%. Moreover, after plant harvest, soil available cadmium content in 250 mg/kg α-Fe₂O₃ nanoparticles and biochar combined treatment decreased by 31.18% compared with cadmium treatment. The results of this study provide an effective reference for the composite application of different exogenous amendments and a feasible idea for soil heavy metal remediation and mitigation of cadmium pollution in farmland.

Manganese and copper additions differently reduced cadmium uptake and accumulation in dwarf Polish wheat (Triticum polonicum L.)

This study investigated the effects of manganese (Mn) and copper (Cu) on dwarf Polish wheat under cadmium (Cd) stress by evaluating plant growth, Cd uptake, translocation, accumulation, subcellular distribution, and chemical forms, and the expression of genes participating in cell wall synthesis, metal chelation, and metal transport. Compared with the control, Mn deficiency and Cu deficiency increased Cd uptake and accumulation in roots, and Cd levels in root cell wall and soluble fractions, but inhibited Cd translocation to shoots. Mn addition reduced Cd uptake and accumulation in roots, and Cd level in root soluble fraction. Cu addition did not affect Cd uptake and accumulation in roots, while it caused a decrease and an increase of Cd levels in root cell wall and soluble fractions, respectively. The main Cd chemical forms (water-soluble Cd, pectates and protein integrated Cd, and undissolved Cd phosphate) in roots were differently changed. Furthermore, all treatments distinctly regulated several core genes that control the main component of root cell walls. Several Cd absorber (COPT, HIPP, NRAMP, and IRT) and exporter genes (ABCB, ABCG, ZIP, CAX, OPT, and YSL) were differently regulated to mediate Cd uptake, translocation, and accumulation. Overall, Mn and Cu differently influenced Cd uptake and accumulation; Mn addition is an effective treatment for reducing Cd accumulation in wheat.

Prediction heavy metals accumulation risk in rice using machine learning and mapping pollution risk

Rapid and accurate prediction of metal bioaccumulation in crops are important for assessing metal environmental risks. We aimed to incorporate machine learning modeling methods to predict heavy metal contents in rice crops and identify influencing factors. We conducted a field study in Jiangsu province, China, collecting 2123 pairs of soil-rice samples in a uniform measurement and using 10 machine learning algorithms to predict the uptake of Cd, Hg, As, and Pb in rice grain. The Extremely Randomized Tree model exhibited the best performance for rice-Cd and rice-Hg (Cd: R² = 0.824; Hg: R² = 0.626), while the Random Forest model performed best for As and Pb (As: R² = 0.389; Pb: R² = 0.325). The feature importance analysis showed that soil-Cd and pH had the highest impact on rice-Cd risk, which is in line with previous studies; while temperature and soil organic carbon were more important to rice-Hg than soil-Hg. Then, based on another set of 1867 uniformly distributed paddy soil samples in Jiangsu province, the Cd and Hg risks of soil and rice were visualized using the established models. Mapping result revealed an inconsistent pattern of hotspot distribution between soil-Hg and rice-Hg, i.e., a higher rice-Hg risk in the northern area, while higher soil-Hg in south. Our findings highlight the importance of temperature on Hg bioaccumulation risk to crops, which has often been overlooked in previous risk assessment processes.

Effect of Organic Amendments on Cadmium Bioavailability in Soil and its Accumulation in Rice Grain

A pot trial was conducted during the boro (dry) season to evaluate the impact of six traditional organic amendments (OAs) on the growth of SL-8 rice variety in both agricultural and cadmium (Cd) stressed soil at 2% and 4% application rates. Traditional OAs used in the study were cow dung, mustard oil cake (MOC), rice husk, saw dust, tea leaf and vermi compost (VC). Except for cow dung all other OAs were found to remove 99% of Cd from the aqueous solution, while cow dung removed 95%. Rice grain grown in OA-added soil in all application rates contained less Cd than the control. A 2% application rate was found to be more effective in reducing both Cd bioavailability and Cd in grain. OA application in soil significantly influenced soil pH in all cases. Though both bioavailable Cd in soil and grain Cd were reduced by the OA addition, the Cd uptake tendency of SL-8 rice variety markedly increased because of Cd spiking in soil.

Combined effects of zinc oxide nanoparticles and melatonin on wheat growth, chlorophyll contents, cadmium (Cd) and zinc uptake under Cd stress

Zinc oxide nanoparticles (ZnONPs) and melatonin (MT) have been known to regulate heavy metal toxicities in plants in some studies, the effect of their combined use on cadmium (Cd) uptake by wheat (Triticum aestivum L.) and underlying mechanisms is largely unknown. Thus, plant growth, uptake and translocation of Cd mediated by soil applied ZnONPs and foliar applied MT were investigated in wheat grown in Cd polluted soil under ambient conditions. The results depicted that ZnONPs stimulated the growth, chlorophyll contents, and yield of wheat in a dose additive way and this effect was further increased with foliar application of MT. 100 mg/kg of ZnONPs alone enhanced the grain yield by 60.5 % and this increase was about 177.5 % under combined ZnONPs and 100 μM MT treatment. ZnONPs treatments decreased Cd concentration whereas increased zinc (Zn) concentrations in shoots, roots, husks and grains and the effect was further increased with exogenous MT combined with NPs in a dose-additive way. 50 and 100 mg/kg ZnONPs treatments alone decreased grain Cd by 6.5 %, and 20 % and increased the Zn concentration by 20.1 % and 24 % than control. 100 mg/kg ZnONPs +100 μM MT treatment decreased the grain Cd by 63.5 % and increased grain Zn by 51 % than control treatment. Total Cd uptake (tissues biomass × Cd concentration in respective tissues) in shoots, roots, husks and grains increased with ZnONPs alone or combined with MT than control whereas soil post-harvest bioavailable Cd concentration decreased with treatments than control. The Cd reduction in grains was due to increase in biomass and Zn concentration thereby decreasing bioavailable Cd in soil and its accumulation in plants. This study suggested that combined use of ZnONPs and MT may provide new approaches for minimizing Cd and biofortification of Zn in edible parts of plants.

Exploring the safe utilization strategy of calcareous agricultural land irrigated with wastewater for over 50 years

The trace element (TE) contamination of farmland caused by wastewater irrigation threatens food security and food safety. We selected a typical calcareous soil area in western China that has been irrigated with wastewater for >50 years to explore safe use strategies for flax farmland contaminated by cadmium (Cd) and arsenic (As). We found that Cd and As were mainly accumulated in flax roots rather than seeds. However, regardless of the type of TE and acceptor, direct ingestion of the flaxseed would seriously endanger human health (hazard quotient >1). According to the results of redundancy analysis and Pearson correlation analysis, the concentration of Cd and As in flaxseed depended on the concentration of soil total TE, Olsen phosphorus, dissolved organic carbon, soil organic matter, and active calcium carbonate (CaCO₃). This was largely because the pH and total CaCO₃ content in topsoil of flax farmland decreased by 1.05 units and 37 %, respectively, compared with their background levels before wastewater irrigation. Interestingly, after pressing, Cd and As in flaxseed transferred to flaxseed oil were 3.87-10.55 % and 17.21-30.48 %, respectively, which led to an acceptable risk of adults and children (hazard quotient <1) consuming flaxseed oil. Our results suggest that with the production of flaxseed oil as the goal, the long-term wastewater-irrigated calcareous land can be safely utilized while obtaining income.

Overexpression of GmWRKY172 enhances cadmium tolerance in plants and reduces cadmium accumulation in soybean seeds

INTRODUCTION

Cadmium (Cd) stress is a significant threat to soybean production, and enhancing Cd tolerance in soybean is the focus of this study. The WRKY transcription factor family is associated with abiotic stress response processes. In this study, we aimed to identify a Cd-responsive WRKY transcription factor GmWRKY172 from soybean and investigate its potential for enhancing Cd tolerance in soybean.

METHODS

The characterization of GmWRKY172 involved analyzing its expression pattern, subcellular localization, and transcriptional activity. To assess the impact of GmWRKY172, transgenic Arabidopsis and soybean plants were generated and examined for their tolerance to Cd and Cd content in shoots. Additionally, transgenic soybean plants were evaluated for Cd translocation and various physiological stress indicators. RNA sequencing was performed to identify the potential biological pathways regulated by GmWRKY172.

RESULTS

GmWRKY172 was significantly upregulated by Cd stress, highly expressed in leaves and flowers, and localized to the nucleus with transcriptional activity. Transgenic plants overexpressing GmWRKY172 showed enhanced Cd tolerance and reduced Cd content in shoots compared to WT. Lower Cd translocation from roots to shoots and seeds was also observed in transgenic soybean. Under Cd stress, transgenic soybean accumulated less malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) than WT plants, with higher flavonoid and lignin contents, and peroxidase (POD) activity. RNA sequencing analysis revealed that many stress-related pathways were regulated by GmWRKY172 in transgenic soybean, including flavonoid biosynthesis, cell wall synthesis, and peroxidase activity.

DISCUSSION

Our findings demonstrated that GmWRKY172 enhances Cd tolerance and reduces seed Cd accumulation in soybean by regulating multiple stress-related pathways, and could be a promising candidate for breeding Cd-tolerant and low Cd soybean varieties.

Foliar application of nanoceria attenuated cadmium stress in okra (Abelmoschus esculentus L.)

Foliar application of nanoparticles (NPs) as a means for ameliorating abiotic stress is increasingly employed in crop production. In this study, the potential of CeO₂-NPs as stress suppressants for cadmium (Cd)-stressed okra (Abelmoschus esculentus) plants was investigated, using two cycles of foliar application of CeO₂-NPs at 200, 400, and 600 mg/l. Compared to untreated stressed plants, Cd-stressed plants treated with CeO₂-NPs presented higher pigments (chlorophyll a and carotenoids). In contrast, foliar applications did not alter Cd root uptake and leaf bioaccumulation. Foliar CeO₂-NPs application modulated stress enzymes (APX, SOD, and GPx) in both roots and leaves of Cd-stressed plants, and led to decreases in Cd toxicity in plant's tissues. In addition, foliar application of CeO₂-NPs in Cd-stressed okra plants decreased fruit Cd contents, and improved fruit mineral elements and bioactive compounds. The infrared spectroscopic analysis of fruit tissues showed that foliar-applied CeO₂-NPs treatments did not induce chemical changes but induced conformational changes in fruit macromolecules. Additionally, CeO₂-NPs applications did not alter the eating quality indicator (Mg/K ratio) of okra fruits. Conclusively, the present study demonstrated that foliar application of CeO₂-NPs has the potential to ameliorate Cd toxicity in tissues and improve fruits of okra plants.

Fulvic acid mitigates cadmium toxicity-induced damage in cucumber seedlings through the coordinated interaction of antioxidant enzymes, organic acid, and amino acid

Fulvic acid (FA) can significantly alleviate cadmium (Cd) stress, but the specific metabolic response of FA to Cd toxicity is still not clarified. In the present study, we used untargeted metabolomic [gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS)] analysis to profile cucumber metabolism in response to Cd stress after spray application of FA. Our results showed that 331 differentially enriched metabolites (DEMs) were identified in leaf materials. These DEMs were enriched in 21 shared pathways in comparative groups of "Cd treatment vs. the control treatment" and "FA + Cd treatment vs. the Cd treatment." Specifically, treatment with FA significantly enhanced the organic acid content (citric acid, isocitric acid, 2-oxoglutaric acid, fumaric acid, and malic acid), which would contribute to provide sufficient substrates for the tricarboxylic acid (TCA) cycle and amino acid biosynthesis, thereby ensuring the normal production of energy and amino acid. At the same time, FA significantly increased the amino acid content (aspartate, citrulline, histidine, leucine, and phenylalanine). The accumulation of organic acid and amino acid can act as chelating agents for heavy metal ions and as scavengers of reactive oxygen species (ROS), thereby reducing intracellular oxidative damage. Furthermore, the application of FA improves antioxidant enzymes and accelerates ROS clearance. The improved contents of organic acid and amino acid, and the increased activity of antioxidant enzymes both played a central role in the reduction of malondialdehyde (MDA, 14.08%), hydrogen peroxide (H₂O₂, 61.70%) contents, and superoxide anion radical (O₂^-, 30.41%) production rate in plants under Cd stress. Taken together, the present study demonstrates the effects of FA on the antioxidant capacity and carbohydrate and amino acid metabolism of cucumber seedlings exposed to Cd stress, which provides comprehensive insights into the regulation of plants' response to Cd toxicity with FA was applied in cucumber.

A state-of-the-art review on cadmium uptake, toxicity, and tolerance in rice: From physiological response to remediation process

Cadmium (Cd), a major contaminant of concern, has been extensively reviewed and debated for its anthropogenic global shifts. Cadmium levels in rice grains raise wide food safety concerns. The aim of this review is therefore to capture the dynamics of Cd in paddy soil, translocation pathways of Cd from soil to consumption rice, and assess its bio-accessibility in human consumption. In crop plants, Cd reduces absorption of nutrients and water, triggers oxidative stress, and inhibits plant metabolism. Understanding the mechanisms and behaviour of Cd in paddy soil and rice allows to explain, predict and intervene in Cd transferability from soil to grains and human exposure. Factors affecting Cd movement in soil, and further to rice grain, are elucidated. Recently, physiological and molecular understanding of Cd transport in rice plants have been advanced. Morphological-biochemical characteristics and Cd transporters of plants in such a movement were also highlighted. Ecologically viable remediation approaches, including low input cost agronomic methods, phytoremediation and microbial bioremediation methods, are emerging.

Remediation effects and mechanisms of typical minerals combined with inorganic amendment on cadmium-contaminated soil: a field study in wheat

The remediation of cadmium (Cd)-contaminated soil has gained much attention recently because Cd in soil threatens human health through the food chain. Although tremendous progress has been made in the remediation of Cd-contaminated soil in rice acid soil system, the mechanism and effects of Cd-contaminated soil remediation under these amendments in wheat weak alkaline soil are still limited. In this study, the remediation effect and related mechanism of Cd in weakly alkaline soil were carried out using zeolite, diatomite, and sodium bentonite as the main remediation components, supplemented by calcium dihydrogen phosphate and fulvic acid. The results of field experiments showed that the concentration of Cd reduced by 27.3 ~ 31.2% in rhizosphere soil and 34.3 ~ 54.2% in non-rhizosphere soil, and the maximum reduction rate of Cd concentration in wheat grain was 25.5%. The main factors affecting the concentration of Cd in wheat grains include the change in exchangeable Cd, the absorption capacity of wheat root, and the inhibitory effect on Cd transport from stem to grain in this paper. In general, this work provides a new potential management feasible pathway to alleviate the Cd toxicity of weakly alkaline soil and wheat grain.

Source-specific risk assessment for cadmium in wheat and maize: Towards an enrichment model for China

Cadmium (Cd) pollution of agricultural soil is of public concern due to its high potential toxicity and mobility. This study aimed to reveal the risk of Cd accumulation in soil and wheat/maize systems, with a specific focus on the source-specific ecological risk, human health risk and Cd enrichment model. For this we investigated more than 6100 paired soil and grain samples with 216 datasets including soil Cd contents, soil pH and grain Cd contents of 85 sites from China. The results showed that mining activities, sewage irrigation, industrial activities and agricultural practices were the critical factors causing Cd accumulation in wheat and maize cultivated sites. Thereinto, mining activities contributed to a higher Cd accumulation risk in the southwest China and Middle Yellow River regions; sewage irrigation influenced the Cd accumulation in the North China Plain. In addition, the investigated sites were classified into different categories by comparing their soil and grain Cd contents with the Chinese soil screening values and food safety values, respectively. Cd enrichment models were developed to predict the Cd levels in wheat and maize grains. The results showed that the models exhibited a good performance for predicting the grain Cd contents among safe and warning sites of wheat (R² = 0.61 and 0.72, respectively); while the well-fitted model for maize was prone to the overestimated sites (R² = 0.77). This study will provide national viewpoints for the risk assessments and prediction of Cd accumulation in soil and wheat/maize systems.

Coupling Effects of Potassium Fertilization Rate and Application Time on Growth and Grain Yield of Wheat (Triticum aestivum L.) Plants Grown Under Cd-Contaminated Saline Soil

Potassium is an essential macronutrient, where its availability regulates numerous biochemical, phenological, and physiological responses in plants. Synchronizing potassium supply with plant demand is a key factor to enhance growth and grain production of wheat grown in cadmium-contaminated saline soils. Field experiments were conducted in El Fayoum province, Egypt, between latitudes 29° 02′ and 29° 35′ N and longitudes 30° 23′ and 31° 05′ E, during the cropping seasons of 2017–2018 and 2018–2019 to determine the influence of different applied potassium rates and times on nutrient uptake and wheat yield grown under Cd-contaminated saline soil (ECe = 8.53 dS m−1 and Cd = 18 mg kg−1 soil). Four K levels (K0, K40, K80, and K120 representing 0, 40, 80, and 120 kg ha−1) were applied at different application times [full dose (basal) at sowing (100% S), two equal split doses at sowing and flowering stage (50% S + 50% F), and full dose at flowering stage (100% F)]. The experimental treatments were arranged in a randomized split complete block design and replicated three times. The applied K rates, times, and their interaction induced significant differences in nutrient uptake and physiological responses which in turn improved the growth and yield of the wheat crop. Potassium addition with 120 kg ha−1 at two equal split doses (50% S + 50% F) resulted in the highest values of plant height (97 cm), Fv/Fm (0.83), PI (5.49), SPAD (58.63), MSI (34.57), seed yield (5.04 t ha−1), straw yield (9.04 t ha−1), and water productivity (0.99 kg m−3). Similarly, the uptake of N, P, K, Ca, Mg, Fe, Mn, and Zn was increased, while the uptake of Na and Cd decreased as the K supply increased under the split application. The addition of potassium by 120 kg ha−1 in two equal split doses at the sowing and flowering stage could be a valuable approach to improve yield and yield quality of wheat crop grown under cadmium-contaminated saline soils.

Magnetic sodium alginate grafted with waste carbonaceous material for diclofenac sodium removal: optimization of operational parameters and process mechanism

As their manufacturing and consumption have increased, pharmaceutical chemicals have increasingly been found in wastewater. It is necessary to look into more effective methods, including adsorption, because current therapies can't completely eliminate these micro contaminants. This investigation aims to assess the diclofenac sodium (DS) adsorption onto an Fe3O4@TAC@SA polymer in a static system. Through Box-Behnken design (BBD), system optimization was carried out, and the ideal conditions - adsorbent mass of 0.01 g and agitation speed of 200 rpm - were chosen. The adsorbent was created utilizing X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR), allowing us to gain a comprehensive understanding of its properties. The analysis of the adsorption process revealed that the external mass transference was the primary rate-controlling step, and the Pseudo-Second-Order model demonstrated the best correlation to kinetic experimental results. An endothermic, spontaneous adsorption process took place. The removal capacity was 858 mg g-1, which is a respectable result when compared to other adsorbents that have been utilized in the past to remove DS. Ion exchange, π-π interactions, electrostatic pore filling and hydrogen bonding all play a role in the adsorption of DS on the Fe3O4@TAC@SA polymer. After careful examination of the adsorbent towards a true sample, it was determined to be highly efficient after three regenerative cycles.

Exogenous hydrogen sulfide and methylglyoxal alleviate cadmium-induced oxidative stress in Salix matsudana Koidz by regulating glutathione metabolism

BACKGROUND

Cadmium (Cd) is a highly toxic element for plant growth. In plants, hydrogen sulfide (H₂S) and methylglyoxal (MG) have emerged as vital signaling molecules that regulate plant growth processes under Cd stress. However, the effects of sodium hydrosulfide (NaHS, a donor of H₂S) and MG on Cd uptake, physiological responses, and gene expression patterns of Salix to Cd toxicity have been poorly understood. Here, Salix matsudana Koidz. seedlings were planted in plastic pot with applications of MG (108 mg kg^- 1) and NaHS (50 mg kg^- 1) under Cd (150 mg kg^- 1) stress.

RESULTS

Cd treatment significantly increased the reactive oxygen species (ROS) levels and malondialdehyde (MDA) content, but decreased the growth parameters in S. matsudana. However, NaHS and MG supplementation significantly decreased Cd concentration, ROS levels, and MDA content, and finally enhanced the growth parameters. Cd stress accelerated the activities of antioxidative enzymes and the relative expression levels of stress-related genes, which were further improved by NaHS and MG supplementation. However, the activities of monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR) were sharply decreased under Cd stress. Conversely, NaHS and MG applications restored the MDHAR and DHAR activities compared with Cd-treated seedlings. Furthermore, Cd stress decreased the ratios of GSH/GSSG and AsA/DHA but considerably increased the H₂S and MG levels and glyoxalase I-II system in S. matsudana, while the applications of MG and NaHS restored the redox status of AsA and GSH and further improved glyoxalase II activity. In addition, compared with AsA, GSH showed a more sensitive response to exogenous applications of MG and NaHS and plays more important role in the detoxification of Cd.

CONCLUSIONS

The present study illustrated the crucial roles of H₂S and MG in reducing ROS-mediated oxidative damage to S. matsudana and revealed the vital role of GSH metabolism in regulating Cd-induced stress.

Cadmium phytoextraction efficiency of hyperaccumulator as affected by harvest stage in three continuous years

Phytoremediation which mainly using hyperaccumulator is a very popular and environmental-friendly clean method. Long term continuous test is very important due to its low remediation efficiency in a growth period. Cd hyperaccumulator Rorippa globosa (Turcz.) Thell. Was used to explore the effect of two remediation modes (harvests at flowering and maturity stages) on the continuous remediation efficiency in a 3-year experiment using pot experiment with real Cd contaminated soil. The results showed that the biomass in maturity-harvest treatments was 1.12 times of that in flowering-harvest treatments due to the short vegetation time. Shoot Cd concentrations in the flowering-harvest treatments were on average 15.4% lower compared to the maturity-harvest treatments either. However, the Cd phytoextraction efficiency (PE) in the flowering-harvest treatments was 13.8% higher compared to the harvests at the maturity stage due to the growth cycle of R. globosa harvested at the flowering was 34.5% of shorter compared to those in the maturity harvest treatments. After three consecutive years of R. globosa phytoextraction, the concentration of extractable Cd decreased on average by 28.7% and corresponding PEs lower either. It was suggested that cultivation modes of R. globosa and low-accumulation crop rotation, or three times flowering harvests of R. globosa per year seemed to be a good choice in practical solution.

Temporal Comparative Transcriptome Analysis on Wheat Response to Acute Cd Toxicity at the Seedling Stage

Cadmium (Cd) is a non-essential and toxic metal that accumulates in plant's tissues and diminishes plant growth and productivity. In the present study, differential root transcriptomic analysis was carried out to identify Cd stress-responsive gene networks and functional annotation under Cd stress in wheat seedlings. For this purpose, the Yannong 0428 wheat cultivar was incubated with 40 µm/L of CdCl₂·2.5H₂O for 6 h at three different seedling growth days. After the quality screening, using the Illumina Hiseq 2000 platform, more than 2482 million clean reads were retrieved. Following this, 84.8% to 89.3% of the clean reads at three time points under normal conditions and 86.5% to 89.1% of the reads from the Cd stress condition were mapped onto the wheat reference genome. In contrast, at three separate seedling growth days, the data analysis revealed a total of 6221 differentially expressed genes (DEGs), including 1543 (24.8%) up-regulated genes and 4678 (75.8%) down-regulated genes. In total, 120 DEGs were co-expressed throughout all the growth days, whereas 1096, 1088, and 2265 DEGs were found to be selectively up-/down-regulated at 7d, 14d, and 30d, respectively. However, the clustering of DEGs, through utilizing the Kyoto Encyclopedia of Genes and Genomes (KEGG), revealed that the DEGs in the metabolic category were frequently annotated for phenylpropanoid biosynthesis. In comparison, a considerable number of DEGs were linked to protein processing in the endoplasmic reticulum under the process of genetic information processing. Similarly, in categories in organismal systems and cellular processes, DEGs were found in plant hormone signal transduction pathways, and DEGs were identified in the plant-pathogen interaction pathway, respectively. However, DEGs in "endocytosis pathways" were enriched in environmental information processing. In addition, in-depth annotations of roughly specific heavy metal stress-response genes and pathways were also mined, and the expression patterns of eight DEGs were studied using quantitative real-time PCR. The results were congruent with the findings of RNA sequencing regarding transcript abundance in the studied wheat cultivar.

FeCl3 and Fe2(SO4)3 differentially reduce Cd uptake and accumulation in Polish wheat (Triticum polonicum L.) seedlings by exporting Cd from roots and limiting Cd binding in the root cell walls

Wheat grown in cadmium (Cd)-contaminated soils easily accumulates more Cd in edible parts than the Chinese safety limit (0.1 mg/kg). FeCl₃ and Fe₂(SO₄)₃ have been used to extract Cd from Cd-contaminated soils. Thus, we hypothesized that FeCl₃ and Fe₂(SO₄)₃, used as iron (Fe) fertilizers, can reduce Cd uptake and accumulation in wheat. Here, a hydroponic experiment was performed with three FeCl₃ and Fe₂(SO₄)₃ concentrations under 80 μM CdCl₂ stress on dwarf Polish wheat (Triticum polonicum L., 2n = 4x = 28, AABB) seedlings. Compared with Fe deficiency, FeCl₃ and Fe₂(SO₄)₃ additions competitively reduced Cd concentrations. The reductions were not associated with changes in dry weight and root morphological parameters. FeCl₃ and Fe₂(SO₄)₃ additions reduced Cd concentrations in the following order from smallest to largest reduction: 25 μM Fe₂(SO₄)₃ < 200 μM FeCl₃ < 50 μM FeCl₃ < 100 μM Fe₂(SO₄)₃. Investigation of subcellular distributions showed that the four Fe fertilizers differentially reduced Cd binding in the root cell walls and enhanced root sucrose and trehalose. Cd chemical form analysis revealed that Fe fertilizer addition also differentially reduced root F_E, F_W, and F_NaCl. Transcriptomic analysis revealed that addition of FeCl₃ and Fe₂(SO₄)₃ differentially up-regulated several genes that hydrolyze cell wall polysaccharides and metal transporter genes for Cd uptake (IRT1 and CAX19) and export (ZIP1, ABCG11, ABCG14, ABCG28, ABCG37, ABCG44, and ABCG48) reducing Cd uptake and accumulation. Our results demonstrated that FeCl₃ and Fe₂(SO₄)₃ can reduce Cd accumulation in wheat, and 50 μM FeCl₃ is the most effective treatment.

Differences in the response mechanism of cadmium uptake, transfer, and accumulation of different rice varieties after foliar silicon spraying under cadmium-stressed soil

Most studies have shown that foliar silicon (Si) spraying can reduce the risk of rice quality safety caused by cadmium (Cd) contamination. However, it has recently been found that different rice varieties have different responses to Si. Therefore, we selected six rice varieties (YHSM, YXY1179, YXYLS, JLK1377, MXZ2, and YLY900) to compare the differences in the effects of leaf spray on Cd accumulation among different varieties. According to the change in Cd content in brown rice after Si application, the six rice varieties were divided into two types: Si-inhibited varieties (JLY1377, MXZ2, LY900, and YXYLS) and Si-stimulated varieties (WY1179 and YHSM). For Si-inhibited varieties, the Cd content of rice was reduced by 13.5%-65.7% after Si application. At the same time, the Cd content of the root, stem, leaf, panicle, and glume decreased to different degrees, the Cd content of the cell wall component increased by 2.2%-37.6%, the extraction state of Cd with strong mobile activity (ethanol-extracted and deionized water-extracted) was changed to the extraction state of Cd with weak mobile activity (acetic acid-extracted and hydrochloric acid-extracted), and the upward transport coefficient of different parts was reduced. For Si-stimulated varieties, Si application increased the Cd content of rice by 15.7%-24.1%. At the same time, the cell soluble component Cd content significantly increased by 68.4%-252.4% and changed the weakly mobile extraction state Cd to the strong mobile extraction state, increasing the upward transport coefficient of different sites. In conclusion, different rice varieties have different responses to Si. Foliar Si spraying inhibits the upward migration of Cd of Si-inhibited varieties, thereby reducing the Cd content of rice, but it has the opposite effect on Si-stimulated varieties. This result reminds us that we need to consider the difference in the effect of varieties in the implementation of foliar Si spraying in remediation of Cd-contaminated paddy fields.

Sources, transfers and the fate of heavy metals in soil-wheat systems: The case of lead (Pb)/zinc (Zn) smelting region

Heavy metals (HMs) from smelters pose severe challenges to the environmental soil quality of surrounding farmlands, and threaten human health through the food chain. This study explored the environmental effects of smelting activities on farmland soil, and additionally assessed the enrichment, transfer and health risk of HMs in soil-wheat systems. Multiple characterization results were combined to demonstrate that HMs from smelter waste were transferred to the surrounding soil. It was determined that the enrichment of HMs in soil-wheat systems is mainly controlled by the total HM concentration and pH in soil. Furthermore, the priority pollutant in soil-wheat systems was found to be Cd, and Cd affected the transfer of Cu, Mn and Pb from soil to wheat roots. Interestingly, the -OH stretching, C-H stretching, N-H amide and C-O bending were involved in detoxifying HMs in wheat. The mean values of non-carcinogenic and carcinogenic risks by consuming wheat grain were 9.1, 1.4E-02 (adults) and 11.3, 3.3E-03 (children), respectively, indicating a noteworthy health risk. This study highlighted the critical issues arising from Pb/Zn smelting activities on agricultural soils. Notwithstanding, to ensure food security, the affected regions could opt to follow up on the type of crops grown.

Deciphering soil amendments and actinomycetes for remediation of cadmium (Cd) contaminated farmland

Soil heavy metal pollution is one of the most serious environmental problems in China, especially cadmium (Cd), which has the most extensive contaminated soil coverage. Therefore, more economical and efficient remediation methods and measures are needed to control soil Cd contamination. In this study, different amendments (biochar (B), organic fertilizer (F), lime (L)) and actinomycetes (A) inoculants were applied to Cd contaminated farmland to explore their effects on wheat growth. Compared with Control, all treatments except A treatment were able to significantly increase the underground parts dry mass of wheat, with the highest increase of 57.19 %. The results showed that the B treatment significantly increased the plant height of wheat by 3.45 %. All treatments increased wheat SOD activity and chlorophyll content and reduced the MDA, which contributes to wheat stress resistance under Cd contamination. F, L and AF treatments can significantly reduce the Cd content in wheat above- and underground parts by up to 56.39 %. Soil amendments can modify the physical and chemical properties of the soil, which in turn affects the absorption of Cd by wheat. Moreover, the addition of soil amendments significantly affects the composition and structure of the rhizospheric soil bacterial community at the wheat jointing stage. The application of organic fertilizer increases the richness and diversity of the bacterial community, while lime makes it significantly decreases it. T-test and microbiome co-occurrence networks show that actinomycetes could not only effectively colonize in local soil, but also effectively enhance the complexity and stability of the rhizosphere microbial community. Considering the practical impact of different treatments on wheat, soil microorganisms, economic benefits and restoration of soil Cd contamination, the application of organic fertilizer and actinomycetes in Cd contaminated soil is a more ideal remediation strategy. This conclusion can be further verified by studying larger repair regions and longer consecutive repair cycles to gain insight into the repair mechanism.

Trx CDSP32-overexpressing tobacco plants improves cadmium tolerance by modulating antioxidant mechanism

The effects of overexpression of the thioredoxin-like protein CDSP32 (Trx CDSP32) on reactive oxygen species (ROS) metabolism in tobacco leaves exposed to cadmium (Cd) were studied by combining physiological measures and proteomics technology. Thus, the number of differentially expressed proteins (DEPs) in plants overexpressing the Trx CDSP32 gene in tobacco (OE) was observed to be evidently lower than that in wild-type (WT) tobacco under Cd exposure, especially the number of down-regulated DEPs. Cd exposure induced disordered ROS metabolism in tobacco leaves. Although Cd exposure inhibited the activities of superoxide dismutase (SOD), catalase (CAT), and l-ascorbate peroxidase (APX) and the expression of proteins related to the thioredoxin-peroxiredoxin (Trx-Prx) pathway, the increase in the activities of peroxidase (POD), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), glutathione reductase (GR), glutathione peroxidase (GPX), and glutathione S-transferase (GST) and their protein expression levels played an important role in the physiological response to Cd exposure. Notably, Trx CDSP32 was observed to alleviate the decrease in the expression and activities of SOD and CAT caused by Cd exposure and enhance the function of POD. Trx CDSP32 was observed to increase the H₂O₂ scavenging capacity of the ascorbic acid-glutathione (AsA-GSH) cycle and Trx-Prx pathway under Cd exposure, and it can especially regulate 2-Cys peroxiredoxin (2-Cys Prx) protein expression and thioredoxin peroxidase (TPX) activity. Thus, overexpression of the Trx CDSP32 gene can alleviate the oxidative damage that occurs in tobacco leaves under Cd exposure by modulating antioxidant defense systems.

Effect of soil texture and zinc oxide nanoparticles on growth and accumulation of cadmium by wheat: a life cycle study

Cadmium (Cd) is getting worldwide attention due to its continuous accumulation in agricultural soils which is due to anthropogenic activities and finally Cd enters in food chain mainly through edible plants. Cadmium free food production on contaminated soils is great challenge which requires some innovative measures for crop production on such soils. The current study evaluated the efficiency of zinc oxide nanoparticles (ZnONPs) (0, 150 and 300 mg/kg) on the growth of wheat in texturally different soils including clay loam (CL), sandy clay loam (SCL), and sandy loam (SL) which were contaminated with were contaminated with 25 mg/kg of Cd before crop growth. Results depicted that doses of ZnONPs and soil textures significantly affected the biological yields, Zn and Cd uptake in wheat plants. The application of 300 mg/kg ZnONPs caused maximum increase in dry weights of shoot (66.6%), roots (58.5%), husk (137.8%) and grains (137.8%) in CL soil. The AB-DTPA extractable Zn was increased while Cd was decreased with doses of NPs depending upon soil textures. The maximum decrease in AB-DTPA extractable Cd was recorded in 300 mg/kg of ZnONPs treatment which was 58.7% in CL, 33.2% in SCL and 12.1% in SL soil as compared to respective controls. Minimum Cd concentrations in roots, shoots, husk and grain were found in 300 mg/kg ZnONPs amended CL soil which was 58%, 76.7%, 58%, and 82.6%, respectively. The minimum bioaccumulation factor (0.14), translocation index (2.46) and health risk index (0.05) was found in CL soil with the highest dose of NPs. The results concluded that use of ZnONPs significantly decreased Cd concentration while increased Zn concentrations in plants depending upon doses of NPs and soil textures.

Effects of application of rice husk biochar and limestone on cadmium accumulation in wheat under glasshouse and field conditions

Cadmium (Cd) has seriously threatened the safe production of food crops. Passivator amendments are commonly used to control the soil Cd availability. Yet, few studies are tested to explore the effect of the combination of various amendments. Here, we investigated the effects of different amendments (2% rice husk biochar, 2% limestone, and 1% rice husk biochar + 1% limestone) on the growth and Cd accumulation of wheat in pot and field experiments. The results showed that under the low soil Cd condition, the maximum increase of soil pH (1.83) was found in the limestone treatment compared to CK in pot experiment. Compared with the CK, the treatment of rice husk biochar decreased soil Cd availability and grain Cd content by about 25% and 31.2%, respectively. In contrast, under high soil Cd condition, the highest soil pH was observed in limestone, while the lowest soil Cd availability and grain Cd concentrations were found in rice husk biochar treatment. In the field experiment, the treatment of 1% rice husk biochar + 1% limestone caused a significant increase of soil pH by about 28.2%, whereas the treatment of 2% rice husk biochar reduced soil Cd availability and grain Cd content by about 38.9% and 38.5% compared to the CK. Therefore, rice husk biochar showed great potential to reduce Cd availability and ensure safe food production.

The Status and Research Progress of Cadmium Pollution in Rice- (Oryza sativa L.) and Wheat- (Triticum aestivum L.) Cropping Systems in China: A Critical Review

The accumulation of cadmium in rice (Oryza sativa L.) and wheat (Triticum aestivum L.) is a serious threat to the safe use of farmland and to the health of the human diet that has attracted extensive attention from researchers. In this review, a bibliometric analysis was performed using a VOS viewer (1.6.18, Netherlands) to investigate the status of cadmium contamination in rice and wheat growing systems, human health risks, mechanisms of Cd uptake and transport, and the corresponding research hotspots. It has a certain reference value for the prevention and control of cadmium pollution in rice and wheat planting systems in China and abroad. The results showed that the Cd content in rice and wheat planting systems in the Yangtze River Basin was significantly higher than that in other areas of China, and the Cd content in rice and wheat grains and the hazard quotient (HQ) in Hunan Province was the highest. The average Cd concentration exceeded the recommended limit by about 62% for rice and 81% for wheat. The main reasons for the high Cd pollution in rice and wheat growing areas in Hunan are mining activities, phosphate fertilizer application, sewage irrigation, and electronic equipment manufacturing. In this review, we demonstrate that cadmium toxicity reduces the uptake and transport of essential elements in rice and wheat. Cadmium stress seriously affected the growth and morphology of plant roots. In the shoots, Cd toxicity was manifested by a series of physiological injuries, such as decreased photosynthesis, soluble protein, sugar, and antioxidant enzyme activity. Cadmium that accumulates in the shoots is transferred to grains and then passes up the food chain to people and animals. Therefore, methods for reducing cadmium content in grains of rice and wheat are urgently needed, especially in Cd-contaminated soil. Current research on Cd pollution in rice and wheat planting systems focuses on the bioavailability of Cd, soil rhizosphere changes in wheat and rice, and the role of antioxidant enzyme systems in alleviating heavy metal stress in rice and wheat.

Rhizospheric microbiomics integrated with plant transcriptomics provides insight into the Cd response mechanisms of the newly identified Cd accumulator Dahlia pinnata

Phytoremediation that depends on excellent plant resources and effective enhancing measures is important for remediating heavy metal-contaminated soils. This study investigated the cadmium (Cd) tolerance and accumulation characteristics of Dahlia pinnata Cav. to evaluate its Cd phytoremediation potential. Testing in soils spiked with 5-45 mg kg^-1 Cd showed that D. pinnata has a strong Cd tolerance capacity and appreciable shoot Cd bioconcentration factors (0.80-1.32) and translocation factors (0.81-1.59), indicating that D. pinnata can be defined as a Cd accumulator. In the rhizosphere, Cd stress (45 mg kg^-1 Cd) did not change the soil physicochemical properties but influenced the bacterial community composition compared to control conditions. Notably, the increased abundance of the bacterial phylum Patescibacteria and the dominance of several Cd-tolerant plant growth-promoting rhizobacteria (e.g., Sphingomonas, Gemmatimonas, Bryobacter, Flavisolibacter, Nocardioides, and Bradyrhizobium) likely facilitated Cd tolerance and accumulation in D. pinnata. Comparative transcriptomic analysis showed that Cd significantly induced (P < 0.001) the expression of genes involved in lignin synthesis in D. pinnata roots and leaves, which are likely to fix Cd²⁺ to the cell wall and inhibit Cd entry into the cytoplasm. Moreover, Cd induced a sophisticated signal transduction network that initiated detoxification processes in roots as well as ethylene synthesis from methionine metabolism to regulate Cd responses in leaves. This study suggests that D. pinnata can be potentially used for phytoextraction and improves our understanding of Cd-response mechanisms in plants from rhizospheric and molecular perspectives.

Multi-Omics Uncover the Mechanism of Wheat under Heavy Metal Stress

Environmental pollution of heavy metals has received growing attention in recent years. Heavy metals such as cadmium, lead and mercury can cause physiological and morphological disturbances which adversely affect the growth and quality of crops. Wheat (Triticum aestivum L.) can accumulate high contents of heavy metals in its edible parts. Understanding wheat response to heavy metal stress and its management in decreasing heavy metal uptake and accumulation may help to improve its growth and grain quality. Very recently, emerging advances in heavy metal toxicity and phytoremediation methods to reduce heavy metal pollution have been made in wheat. Especially, the molecular mechanisms of wheat under heavy metal stress are increasingly being recognized. In this review, we focus on the recently described epigenomics, transcriptomics, proteomics, metabolomics, ionomics and multi-omics combination, as well as functional genes uncovering heavy metal stress in wheat. The findings in this review provide some insights into challenges and future recommendations for wheat under heavy metal stress.

Foliar application of three dithiocarbamates inhibits the absorption and accumulation of Cd in wheat

In cadmium (Cd) contaminated farmland soil, antagonism between elements can be used to control the absorption and accumulation of Cd in crops through the external application of zinc (Zn) and manganese (Mn). Dithiocarbamates (DTCs) are highly effective fungicides commonly used in farmlands, and DTCs are rich in Zn and Mn. We selected three representative DTCs (propineb, mancozeb, and zineb) for a field experiment in Henan province, China. The effects of DTC on Cd absorption and accumulation in wheat and the interaction of Zn, Mn, and Cd in wheat after spraying of DTC were studied using different application times at the heading stage. The results showed that after foliar spraying of DTCs according to pesticide application requirements, wheat yield was not affected. The Zn and Mn contents in grains increased, with the highest increases being 19.2% and 12.4%, respectively. Zn and Cd as well as Mn and Cd were antagonistic in wheat, and the transport of Cd from soil to root and from husk to grain was inhibited. The bioconcentration factor (grains/soil) decreased from 1.3 to 0.68 and the translocation factor (grains/husks) decreased from 0.76 to 0.35. The Cd content in grains decreased by 60.4%, 52.8%, and 25.6% with mancozeb, propineb, and zineb applications, respectively, and the Cd reduction effect of spraying DTCs twice was better than that of spraying DTCs once and thrice. The results show that DTCs application could reduce the Cd content in wheat grains and realize the dual effects of crop disease prevention and Cd reduction.

Multiomics reveals an essential role of long-distance translocation in regulating plant cadmium resistance and grain accumulation in allohexaploid wheat (Triticum aestivum)

Cadmium (Cd) is a highly toxic heavy metal that readily enters cereals, such as wheat, via the roots and is translocated to the shoots and grains, thereby posing high risks to human health. However, the vast and complex genome of allohexaploid wheat makes it challenging to understand Cd resistance and accumulation. In this study, a Cd-resistant cultivar of wheat, 'ZM1860', and a Cd-sensitive cultivar, 'ZM32', selected from a panel of 442 accessions, exhibited significantly different plant resistance and grain accumulation. We performed an integrated comparative analysis of the morpho-physiological traits, ionomic and phytohormone profiles, genomic variations, transcriptomic landscapes, and gene functionality in order to identify the mechanisms underlying these differences. Under Cd toxicity, 'ZM1860' outperformed 'ZM32', which showed more severe leaf chlorosis, poorer root architecture, higher accumulation of reactive oxygen species, and disordered phytohormone homeostasis. Ionomics showed that 'ZM32' had a higher root-to-shoot translocation coefficient of Cd and accumulated more Cd in the grains than 'ZM1860'. Whole-genome re-sequencing (WGS) and transcriptome sequencing identified numerous DNA variants and differentially expressed genes involved in abiotic stress responses and ion transport between the two genotypes. Combined ionomics, transcriptomics, and functional gene analysis identified the plasma membrane-localized heavy metal ATPase TaHMA2b-7A as a crucial Cd exporter regulating long-distance Cd translocation in wheat. WGS- and PCR-based analysis of sequence polymorphisms revealed a 25-bp InDel site in the promoter region of TaHMA2b-7A, and this was probably responsible for the differential expression. Our multiomics approach thus enabled the identification of a core transporter involved in long-distance Cd translocation in wheat, and it may provide an elite genetic resource for improving plant Cd resistance and reducing grain Cd accumulation in wheat and other cereal crops.

Growth, physiological, and temperature characteristics in chinese cabbage pakchoi as affected by Cd- stressed conditions and identifying its main controlling factors using PLS model

BACKGROUND

Although hormesis induced by heavy metals is a well-known phenomenon, the involved biological mechanisms are not fully understood. Cadmium (Cd) is a prevalent heavy metal in the environment. Exposure of Cd, via intake or consumption of Cd-contaminated air or food, poses a huge threat to human health. Chinese cabbage pakchoi (Brassica chinensis L.) is widely planted and consumed as a popular vegetable in China. Therefore, studying the response of Chinese cabbage pakchoi to Cd- stressed conditions is critical to assess whether cabbage can accumulate Cd and serve as an important Cd exposure pathway to human beings. In this study, we investigated the influence of Cd stress on growth, photosynthetic physiology, antioxidant enzyme activities, nutritional quality, anatomical structure, and canopy temperature in Chinese cabbage pakchoi. A partial least squares (PLS) model was used to quantify the relationship between physical and chemical indicators with Cd accumulation in cabbage, and identify the main controlling factors.

RESULTS

Results showed that Cd stress significantly inhibited cabbage's growth and development. When Cd stress was increased, the phenotypic indicators were significantly reduced. Meanwhile, Cd stress significantly enhanced the oxidative stress response of cabbage, such as the activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), and the content of malondialdehyde (MDA) in leaves. Such a change tended to increase fenestrated tissues' thickness but decrease the thickness of leaf and spongy tissues. Moreover, Cd stress significantly increased soluble sugar, protein, and vitamin C contents in leaves as well as the temperature in the plant canopy. The PLS model analysis showed that the studied phenotypic and physicochemical indicators had good relationships with Cd accumulation in roots, shoots, and the whole plant of cabbage, with high coefficient of determination (R²) values of 0.891, 0.811, and 0.845, and low relative percent deviation (RPD) values of 3.052, 2.317, and 2.557, respectively. Furthermore, through analyzing each parameter's variable importance for projection (VIP) value, the SOD activity was identified as a key factor for indicating Cd accumulation in cabbage. Meanwhile, the effects of CAT on Cd accumulation in cabbage and the canopy mean temperature were also high.

CONCLUSION

Cd stress has significant inhibitory effects and can cause damage cabbage's growth and development, and the SOD activity may serve as a key factor to indicate Cd uptake and accumulation in cabbage.

Physio-Biochemical and Transcriptomic Features of Arbuscular Mycorrhizal Fungi Relieving Cadmium Stress in Wheat

Arbuscular mycorrhizal fungi (AMF) can improve plant cadmium (Cd) tolerance, but the tolerance mechanism in wheat is not fully understood. This study aimed to examine the physiological properties and transcriptome changes in wheat inoculated with or without Glomus mosseae (GM) under Cd stress (0, 5, and 10 mg·kg^-1 CdCl₂) to understand its role in wheat Cd tolerance. The results showed that the Cd content in shoots decreased while the Cd accumulation in roots increased under AMF symbiosis compared to the non-inoculation group and that AMF significantly promoted the growth of wheat seedlings and reduced Cd-induced oxidative damage. This alleviative effect of AMF on wheat under Cd stress was mainly attributed to the fact that AMF accelerated the ascorbate-glutathione (AsA-GSH) cycle, promoted the production of GSH and metallothionein (MTs), improved the degradation of methylglyoxal (MG), and induced GRSP (glomalin-related soil protein) secretion. Furthermore, a comparative analysis of the transcriptomes of the symbiotic group and the non-symbiotic group revealed multiple differentially expressed genes (DEGs) in the 'metal ion transport', 'glutathione metabolism', 'cysteine and methionine metabolism', and 'plant hormone signal transduction' terms. The expression changes of these DEGs were basically consistent with the changes in physio-biochemical characteristics. Overall, AMF alleviated Cd stress in wheat mainly by promoting immobilization and sequestration of Cd, reducing ROS production and accelerating their scavenging, in which the rapid metabolism of GSH may play an important role.

Identification of arsenic-tolerant varieties and candidate genes of tolerance in spring wheat (Triticum aestivum L.)

Despite the growing concerns about arsenic toxicity, information on tolerance and responsible genetic factors in wheat remains elusive. To address that, the present study aimed to screen the wheat varieties against arsenic based on growth parameters, yield, grain accumulation, and associated genes. A total of 110 wheat varieties were grown in arsenic-contaminated regions to record physio-morphological traits. The wheat 90K Infinium iSelect SNP array was used for the genome-wide association model to identify genomic regions. Wheat varieties such as Punjab-81, AARI-11, and Daman showed arsenic concentrations >45 μg/kg in similar conditions as well as the impact on grain yield, chlorophyll, Thousand Kernel Weight, and plant height. Contrastingly, varieties like Kohistan-97, As-2002, Barani-70, and Pari-73 showed grain concentrations <5 μg/kg grown under highly contaminated conditions. Three significant loci associated with arsenic accumulation in grain were identified on chromosomes 6A (qASG1-6A) and 6B (qASG3-6B and qASG4-6B). Annotation at these loci identified 39 wheat genes among which several were important for growth and tolerance against stress. The candidate gene (TraesCS6B02G429400) responsible for Glutathione-S-transferase was identified in the present study and must be investigated further using a transcriptomic approach. The present study provided background information for breeding prospects to improve wheat yield and tolerance against arsenic.

Zinc Biofortification through Basal Zinc Supply Reduces Grain Cadmium in Mung Beans: Metal Partitioning and Health Risks Assessment

Grain zinc (Zn) biofortification with less cadmium (Cd) accumulation is of paramount importance from human health and environmental point of view. A pot experiment was carried out to determine the influence of Zn and Cd on their accumulations in Mung bean tissues (Vigna radiata) in two contrast soil types (Dermosol and Tenosol). The soil types with added Zn and Cd exerted a significant effect on translocation and accumulation of metals in different tissues. The accumulation of Zn and Cd was higher for Tenosol than that for Dermosol. At control, the concentration of Cd followed a pattern, e.g., root > stem > petiole > pod > leaflet > grain for both soils. A basal Zn supply (5 mg kg−1) increased the grain Zn concentration to a significant amount (up to 67%). It also reduced Cd accumulation in tissues, including grains (up to 34%). No non-carcinogenic effect was observed for either the children or the adults as the EDI and PTDI values were below the safety limit; however, the ILCR values exceeded the safety limit, indicating the possibility of some carcinogenic effects. Added Zn helped to reduce the carcinogenic and non-carcinogenic health risks on humans.

S-Methylmethionine Effectively Alleviates Stress in Szarvasi-1 Energy Grass by Reducing Root-to-Shoot Cadmium Translocation

S-methylmethionine (SMM) is a universal metabolite of higher plants derived from L-methionine that has an approved priming effect under different types of abiotic and biotic stresses. Szarvasi-1 energy grass (Elymus elongatus subsp. ponticus cv. Szarvasi-1) is a biomass plant increasingly applied in phytoremediation to stabilize or extract heavy metals. In this study, Szarvasi-1 was grown in a nutrient solution. As a priming agent, SMM was applied in 0.02, 0.05 and 0.1 mM concentrations prior to 0.01 mM Cd addition. The growth and physiological parameters, as well as the accumulation pattern of Cd and essential mineral nutrients, were investigated. Cd exposure decreased the root and shoot growth, chlorophyll concentration, stomatal conductance, photosystem II function and increased the carotenoid content. Except for stomatal conductance, SMM priming had a positive effect on these parameters compared to Cd treatment without priming. In addition, it decreased the translocation and accumulation of Cd. Cd treatment decreased K, Mg, Mn, Zn and P in the roots, and K, S, Cu and Zn in the shoots compared to the untreated control. SMM priming changed the pattern of nutrient uptake, of which Fe showed characteristic accumulation in the roots in response to increasing SMM concentrations. We have concluded that SMM priming exerts a positive effect on Cd-stressed Szarvasi-1 plants, which retained their physiological performance and growth. This ameliorative effect is suggested to be based on, at least partly, the lower root-to-shoot Cd translocation by the upregulated Fe uptake and transport.

Effects of Rhizobium leguminosarum Thy2 on the Growth and Tolerance to Cadmium Stress of Wheat Plants

Cadmium (Cd) stress is an obstacle for crop production, quality crops, and sustainable agriculture. An important role is played by the application of eco-friendly approaches to improve plant growth and stress tolerance. In the current study, a pre-sowing seed treatment with Rhizobium leguminosarum strains, isolated from the leguminous plants Phaseolus vulgaris (strain Pvu5), Vicia sylvatica (strain VSy12), Trifolium hybridium (strain Thy2), and T. pratense (strain TPr4), demonstrated different effects on wheat (Triticum aestivum L.) plant growth under normal conditions. Among all tested strains, Thy2 significantly increased seed germination, seedling length, fresh and dry biomass, and leaf chlorophyll (Chl) content. Further analysis showed that Thy2 was capable of producing indole-3-acetic acid and siderophores and fixing nitrogen. Under Cd stress, Thy2 reduced the negative effect of Cd on wheat growth and photosynthesis and had a protective effect on the antioxidant system. This was expressed in the additional accumulation of glutathione and proline and the activation of glutathione reductase. In addition, Thy2 led to a significant reduction in oxidative stress, which was evidenced by the data on the stabilization of the ascorbate content and the activity of ascorbate peroxidase. In addition, Thy2 markedly reduced Cd-induced membrane lipid peroxidation and electrolyte leakage in the plants. Thus, the findings demonstrated the ability of the R. leguminosarum strain Thy2, isolated from T. hybridium nodules, to exert a growth-promoting and anti-stress effect on wheat plants. These results suggest that the Thy2 strain may enhance wheat plant growth by mitigating Cd stress, particularly through improving photosynthesis and antioxidant capacity and reducing the severity of oxidative damage. This may provide a basic and biological approach to use the Thy2 strain as a promising, eco-friendly candidate to combat Cd stress in wheat production.

Sulfur reduces the root-to-shoot translocation of arsenic and cadmium by regulating their vacuolar sequestration in wheat (Triticum aestivum L.)

Accumulation of arsenic (As) and cadmium (Cd) in wheat grain is a serious threat to human health. Sulfur (S) can simultaneously decrease wheat grain As and Cd concentrations by decreasing their translocation in wheat; however, the mechanisms are unclear. We conducted hydroponic experiments to explore the mechanisms by which S modulates As and Cd translocation and their toxicity in wheat. Wheat seedlings were grown in deficient sulfate (2.5 µM) or sufficient sulfate (1.0 mM) nutrient solutions for 6 days and then exposed to zero (control), low As+Cd (1 µM As plus 0.5 µM Cd), or high As+Cd (50 µM As plus 30 µM Cd) for another 6 days. Compared with the control, plant growth was not affected by low As+Cd, but was significantly inhibited by high As+Cd. In the low As+Cd treatment, S supply had no significant effect on plant growth or root-to-shoot As and Cd translocation. In the high As+Cd treatment, sufficient S supply significantly alleviated As and Cd toxicity and their translocation by increasing phytochelatin (PC) synthesis and the subsequent vacuolar sequestration of As and Cd in roots, compared with deficient S supply. The use of _L-buthionine sulfoximine (a specific inhibitor of γ-glutamylcysteine synthetase) confirmed that the alleviation of As and Cd translocation and toxicity in wheat by S is mediated by increased PC production. Also, TaHMA3 gene expression in wheat root was not affected by the As+Cd and S treatments, but the expression of TaABCC1 was upregulated by the high As+Cd treatment and further increased by sufficient S supply and high As+Cd treatment. These results indicate that S-induced As and Cd subcellular changes affect As and Cd translocation mainly by regulating thiol metabolism and ABCC1 expression in wheat under As and Cd stress.

Combined Impact of Excess Zinc and Cadmium on Elemental Uptake, Leaf Anatomy and Pigments, Antioxidant Capacity, and Function of Photosynthetic Apparatus in Clary Sage (Salvia sclarea L.)

Clary sage (Salvia sclarea L.) is a medicinal plant that has the potential to be used for phytoextraction of zinc (Zn) and cadmium (Cd) from contaminated soils by accumulating these metals in its tissues. Additionally, it has been found to be more tolerant to excess Zn than to Cd stress alone; however, the interactive effects of the combined treatment with Zn and Cd on this medicinal herb, and the protective strategies of Zn to alleviate Cd toxicity have not yet been established in detail. In this study, clary sage plants grown hydroponically were simultaneously exposed to Zn (900 µM) and Cd (100 μM) for 8 days to obtain more detailed information about the plant responses and the role of excess Zn in mitigating Cd toxicity symptoms. The leaf anatomy, photosynthetic pigments, total phenolic and anthocyanin contents, antioxidant capacity (by DPPH and FRAP analyses), and the uptake and distribution of essential elements were investigated. The results showed that co-exposure to Zn and Cd leads to an increased leaf content of Fe and Mg compared to the control, and to increased leaf Ca, Mn, and Cu contents compared to plants treated with Cd only. This is most likely involved in the defense mechanisms of excess Zn against Cd toxicity to protect the chlorophyll content and the functions of both photosystems and the oxygen-evolving complex. The data also revealed that the leaves of clary sage plants subjected to the combined treatment have an increased antioxidant capacity attributed to the higher content of polyphenolic compounds. Furthermore, light microscopy indicated more alterations in the leaf morphology after Cd-only treatment than after the combined treatment. The present study shows that excess Zn could mitigate Cd toxicity in clary sage plants.

Response of cauliflower (Brassica oleracea L.) to nitric oxide application under cadmium stress

Soil contamination with cadmium (Cd) is a persistent threat to crop production worldwide. The present study examined the putative roles of nitric oxide (NO) in improving Cd-tolerance in cauliflower (Brassica oleracea L.). The present study was conducted using four different genotypes of B. oleracea named as FD-3, FD-4, FD-2 and Ceilo Blanco which were subjected to the Cd stress at various concentrations i.e., 0, 5, 10 and 20 µM with or without the application of NO i.e., 0.10 mM in the sand containing nutrient Hoagland's solution. Our results illustrated that the increasing levels of Cd in the sand, significantly (P < 0.05) decreased shoot length, root length, shoot fresh weight, root fresh weight, shoot dry weight, root dry weight, germination percentage, germination index, mean germination time, time to 50% germination, chlorophyll a, chlorophyll b, total chlorophyll and carotenoid contents in all genotypes of B. oleracea. The concentration of malondialdehyde (MDA) and Cd accumulation (roots and shoots) increased significantly (P < 0.05) under the increasing levels of Cd in all genotypes of B. oleracea while antioxidant (enzymatic or non-enzymatic) capacity and nutritional status of the plants was decreased with varying levels of Cd in the sand. From all studied genotypes of B. oleracea, Ceilo Blanco and FD-4 was found to be most sensitive species to the Cd stress under the same levels of the Cd in the medium while FD-2 and FD-3 showed more tolerance to the Cd stress compared to all other genotypes of B. oleracea. Although, toxic effect of Cd in the sand can overcome by the application of NO which not only increased plant growth and nutrients accumulation but also decreased the oxidative damage to the membranous bounded organelles and also Cd accumulation in various parts of the plants in all genotypes of B. oleracea. Hence, it was concluded that application of NO can overcome Cd toxicity in B. oleracea by maintaining the growth regulation and nutritional status of the plant and overcome oxidative damage induced by Cd toxicity in all genotypes of B. oleracea.

The regulatory role of abscisic acid on cadmium uptake, accumulation and translocation in plants

To date, Cd contamination of cropland and crops is receiving more and more attention around the world. As a plant hormone, abscisic acid (ABA) plays an important role in Cd stress response, but its effect on plant Cd uptake and translocation varies among plant species. In some species, such as Arabidopsis thaliana, Oryza sativa, Brassica chinensis, Populus euphratica, Lactuca sativa, and Solanum lycopersicum, ABA inhibits Cd uptake and translocation, while in other species, such as Solanum photeinocarpum and Boehmeria nivea, ABA severs the opposite effect. Interestingly, differences in the methods and concentrations of ABA addition also triggered the opposite result of Cd uptake and translocation in Sedum alfredii. The regulatory mechanism of ABA involved in Cd uptake and accumulation in plants is still not well-established. Therefore, we summarized the latest studies on the ABA synthesis pathway and comparatively analyzed the physiological and molecular mechanisms related to ABA uptake, translocation, and detoxification of Cd in plants at different ABA concentrations or among different species. We believe that the control of Cd uptake and accumulation in plant tissues can be achieved by the appropriate ABA application methods and concentrations in plants.

WRKY74 regulates cadmium tolerance through glutathione-dependent pathway in wheat

Cadmium (Cd) is a toxic heavy metal to plants and human health. Ascorbate (ASA)-glutathione (GSH) synthesis pathway plays key roles in Cd detoxification, while its molecular regulatory mechanism remains largely unknown, especially in wheat. Here, we found a WRKY transcription factor-TaWRKY74, and its function in wheat Cd stress is not clear in previous studies. The expression levels of TaWRKY74 were significantly induced by Cd stress. Compared to control, the activities of GST, GR, or APX were significantly increased by 1.55-, 1.43-, or 1.75-fold and 1.63-, 2.65-, or 2.30-fold in shoots and roots of transiently TaWRKY74-silenced wheat plants under Cd stress. Similarly, the contents of hydrogen peroxide (H₂O₂), malondialdehyde (MDA), GSH, or Cd were also significantly increased by 2.39- or 1.25-fold, 1.54- or 1.20-fold, and 1.34- or 5.94-fold in shoots or roots in transiently TaWRKY74-silenced wheat plants, while ASA content was decreased by 47.4 or 43.3% in shoots, 10.7 or 6.5% in roots in these silenced wheat plants, respectively. Moreover, the expression levels of GSH, GPX, GR, DHAR, MDHAR, and APX genes, which are involved in ASA-GSH synthesis, were separately induced by 2.42-, 2.16-, 3.28-, 2.08-, 1.92-, and 2.23-fold in shoots, or by 10.69-, 3.33-, 3.26-, 1.81-, 16.53-, and 3.57-fold in roots of the BSMV-VIGS-TaWRKY74-inoculated wheat plants, respectively. However, the expression levels of TaNramp1, TaNramp5, TaHMA2, TaHMA3, TaLCT1, and TaIRT1 metal transporters genes were decreased by 21.2-76.3% (56.6%, 59.2%, 76.3%, 53.6%, 35.8%, and 21.2%) in roots of the BSMV-VIGS-TaWRKY74-inoculated wheat plants. Taken together, our results suggested that TaWRKY74 alleviated Cd toxicity in wheat by affecting the expression of ASA-GSH synthesis genes and suppressing the expression of Cd transporter genes, and further affecting Cd uptake and translocation in wheat plants.