Mitigate Cd Toxicity Research Articles

Three species of rape responded to cadmium and melatonin alleviating Cd-toxicity in species-specific strategy

Cadmium (Cd) pollution has been a significant concern in heavy metal pollution, prompting plants to adopt various strategies to mitigate its damage. While the response of plants to Cd stress and the impact of exogenous melatonin has received considerable attention, there has been limited focus on the responses of closely related species to these factors. Consequently, our investigation aimed to explore the response of three different species of rape to Cd stress and examine the influence of exogenous melatonin in this scenario. The research findings revealed distinctive responses among the investigated rape species. B. campestris showed the resistance to Cd and exhibited lower Cd absorption and sustained its physiological activity under Cd stress. In contrast, B. juncea accumulated much Cd and increased the amount of anthocyanin to mitigate the Cd-damage. Furthermore, B. napus showed the tolerance to Cd and tended to accumulate Cd in vacuoles under Cd stress, thereby decreasing the Cd damage and leading to higher activity of antioxidant enzymes and photosynthesis. Moreover, the application of exogenous melatonin significantly elevated the melatonin level in plants and mitigated Cd toxicity by promoting the activity of antioxidant enzymes, reducing Cd absorption, enhancing the chelating capacity with Cd, decreasing Cd accumulation in organelles, and reducing its fluidity. Specifically, exogenous melatonin increased the FHAc content in B. campestris, elevated the phytochelatins (PCs) level in B. napus, and stimulated photosynthesis in B. juncea. In summary, the findings underscore the species-specific responses of the three species of rape to both Cd stress and exogenous melatonin, highlighting the potential for tailored mitigation strategies based on the unique characteristics of each species.

Red light mitigates Cd toxicity in Egeria densa by restricting Cd accumulation and modulating antioxidant defense system

Controlling light qualities have been acknowledged as an effective method to enhance the efficiency of phytoremediation, as light has a significant impact on plant growth. This study examined the effects of light qualities on cadmium (Cd) tolerance in aquatic plant Egeria densa using a combination of biochemical and transcriptomic approaches. The study revealed that E. densa exhibits higher resistance to Cd toxicity under red light (R) compared to blue light (B), as evidenced by a significant decrease in photosynthetic inhibition and damage to organelle ultrastructure. After Cd exposure, there was a significantly reduced Cd accumulation and enhanced levels of both glutathione reductase (GR) activity and glutathione (GSH), along with an increase in jasmonic acid (JA) in R-grown E. densa compared to B. Transcriptional analysis revealed that R caused an up-regulation of Cd transporter genes such as ABCG (G-type ATP-binding cassette transporter), ABCC (C-type ATP-binding cassette transporter), and CAX2 (Cation/H+ exchanger 2), while down-regulated the expression of HIPP26 (Heavy metal-associated isoprenylated plant protein 26), resulting in reduced Cd uptake and enhanced Cd exportation and sequestration into vacuoles. Moreover, the expression of genes involved in phytochromes and JA synthesis was up-regulated in Cd treated E. densa under R. In summary, the results suggest that R could limit Cd accumulation and improve antioxidant defense to mitigate Cd toxicity in E. densa, which might be attributed to the enhanced JA and phytochromes. This study provides a foundation for using light control methods with aquatic macrophytes to remediate heavy metal contamination in aquatic systems.

Insights into the alleviation of cadmium toxicity in rice by nano-zinc and Serendipita indica: Modulation of stress-responsive gene expression and antioxidant defense system activation

The adversities of cadmium (Cd) contamination are quite distinguished among other heavy metals (HMs), and so is the efficacy of zinc (Zn) nutrition in mitigating Cd toxicity. Rice (Oryza sativa) crop, known for its ability to absorb HMs, inadvertently facilitates the bioaccumulation of Cd, posing a significant risk to both the plant itself and to humans consuming its edible parts, and damaging the environment as well. The use of nanoparticles, such as nano-zinc oxide (nZnO), to improve the nutritional quality of crops and combat the harmful effects of HMs, have gained substantial attention among scientists and farmers. While previous studies have explored the individual effects of nZnO or Serendipita indica (referred to as S.i) on Cd toxicity, the synergistic action of these two agents has not been thoroughly investigated. Therefore, the gift of nature, i.e., S. indica, was incorporated alongside nZnO (50 mg L−1) against Cd stress (15 μM L−1) and their alliance manifested as phenotypic level modifications in two rice genotypes (Heizhan43; Hz43 and Yinni801; Yi801). Antioxidant activities were enhanced, specifically peroxidase (61.5 and 122.5% in Yi801 and Hz43 roots, respectively), leading to a significant decrease in oxidative burst; moreover, Cd translocation was reduced (85% for Yi801 and 65.5% for Hz43 compared to Cd alone treatment). Microstructural study showed a decrease in number of vacuoles and starch granules with ameliorative treatments. Overall, plants treated with nZnO displayed gene expression pattern (particularly of ZIP genes), different from the ones with alone or combined S.i and Cd. Inferentially, the integration of nZnO and S.i holds great promise as an effective strategy for alleviating Cd toxicity in rice plants. By immobilizing Cd ions in the soil and promoting their detoxification, this novel approach contributes to environmental restoration and ensures food safety worldwide.

The role of exogenous hydrogen sulfide in mitigating cadmium toxicity in plants: A comprehensive meta-analysis.

Reducing the accumulation of cadmium (Cd) and mitigating its toxicity are pivotal strategies for addressing Cd pollution's threats to agriculture and human health. Hydrogen sulfide (H2S) serves as a signaling molecule, playing a crucial role in plant stress defense mechanisms. Nevertheless, a comprehensive assessment of the impact of exogenous H2S on plant growth, antioxidant properties, and gene expression under Cd stress remains lacking. In this meta-analysis, we synthesized 575 observations from 27 articles, revealing that exogenous H2S significantly alleviates Cd-induced growth inhibition in plants. Specifically, it enhances root length (by 8.71%), plant height (by 15.67%), fresh weight (by 15.15%), dry weight (by 22.54%), and chlorophyll content (by 27.99%) under Cd stress conditions. H2S boosts antioxidant enzyme activity, particularly catalase (CAT), by 39.51%, thereby reducing Cd-induced reactive oxygen species (ROS) accumulation. Moreover, it impedes Cd translocation from roots to shoots, resulting in a substantial 40.19% reduction in stem Cd content. Additionally, H2S influences gene expression in pathways associated with antioxidant enzymes, metal transport, heavy metal tolerance, H2S biosynthesis, and energy metabolism. However, the efficacy of exogenous H2S in alleviating Cd toxicity varies depending on factors such as plant species, concentration of the H2S donor sodium hydrosulfide (NaHS), application method, and cultivation techniques. Notably, NaHS concentrations exceeding 200 μM may adversely affect plants. Overall, our study underscores the role of exogenous H2S in mitigating Cd toxicity and elucidates its mechanism, providing insights for utilizing H2S to combat Cd pollution in agriculture.

Effect of cadmium on polystyrene transport in parsley roots planted in a split-root system and assessment of the combined toxic effects

Micro and nanoplastics (MPs/NPs) coupled with heavy metals are prevalent in both aquatic and terrestrial ecosystems. Their ecological toxicity and combined adverse effects have obtained significant concern. Past studies primarily focused on how MPs/NPs influence the behavior of heavy metals. Yet, the possible effects of heavy metals on MP/NP transport and toxicity within co-contaminated systems are still not well-understood. In this study, we conducted split-root experiments to explore the transport and toxicity of polystyrene (PS) particles of varying sizes in parsley seedlings, both with and without the addition of cadmium (Cd). Both the PS-NPs (100 nm) and PS-MPs (300 nm) traveled from the PS-spiked roots (Roots-1) to the non-PS-spiked roots (Roots-2), with or without Cd, possibly because of phloem transport. Furthermore, the presence of Cd reduced the accumulation and movement of PS-NP/MP in the roots, likely due to the increased positive charge (Cd2+) on the PS surface. PS-NPs/MPs in both Roots-1 and Roots-2 were observed using transmission electron microscopy (TEM). When Cd was added to either Roots-1 (PS + Cd|H) or Roots-2 (PS|Cd), there was a minor reduction in the chlorophyll a and carotenoids content in leaves with PS|H. The adverse impacts of MPs|H on both indicators were influenced by the MP concentration. However, chlorophyll b significantly increased in the PS|H, PS + Cd|H, and PS|Cd treatments. Consequently, the chlorophyll a/b ratio declined, indicating inhibition of photosynthesis. The dehydrogenase content showed a minor change in Roots-1 and Roots-2 without Cd stress, whereas it significantly decreased on the Cd-spiked side and subsequently inhibited root growth. In contrast, the marked rise in glutathione (GSH) levels within Cd-spiked roots suggested, based on Gaussian analysis, that GSH and Cd chelation were instrumental in mitigating Cd toxicity. When Cd was introduced to both Roots-1 and Roots-2 simultaneously (PS + Cd|Cd), the aforementioned index showed a notable decline.

Alfalfa MsbHLH115 confers tolerance to cadmium stress through activating the iron deficiency response in Arabidopsis thaliana.

Cadmium (Cd) pollution severely affects plant growth and development, posing risks to human health throughout the food chain. Improved iron (Fe) nutrients could mitigate Cd toxicity in plants, but the regulatory network involving Cd and Fe interplay remains unresolved. Here, a transcription factor gene of alfalfa, MsbHLH115 was verified to respond to iron deficiency and Cd stress. Overexpression of MsbHLH115 enhanced tolerance to Cd stress, showing better growth and less ROS accumulation in Arabidopsis thaliana. Overexpression of MsbHLH115 significantly enhanced Fe and Zn accumulation and did not affect Cd, Mn, and Cu concentration in Arabidopsis. Further investigations revealed that MsbHLH115 up-regulated iron homeostasis regulation genes, ROS-related genes, and metal chelation and detoxification genes, contributing to attenuating Cd toxicity. Y1H, EMSA, and LUC assays confirmed the physical interaction between MsbHLH115 and E-box, which is present in the promoter regions of most of the above-mentioned iron homeostasis regulatory genes. The transient expression experiment showed that MsbHLH115 interacted with MsbHLH121pro. The results suggest that MsbHLH115 may directly regulate the iron-deficiency response system and indirectly regulate the metal detoxification response mechanism, thereby enhancing plant Cd tolerance. In summary, enhancing iron accumulation through transcription factor regulation holds promise for improving plant tolerance to Cd toxicity, and MsbHLH115 is a potential candidate for addressing Cd toxicity issues.

Transcriptome analysis reveals ABA involved in the detoxification mechanism of macroalga Gracilariopsis lemaneiformis to cadmium toxicity

IntroductionCadmium (Cd) is a significant threat environmental pollutant in the marine ecological environment offshore. The macroalga, Gracilariopsis lemaneiformis, of significant economic value, is widely cultivated along China’s coastline. Yet, little is known about the molecular mechanisms underlying Cd tolerance in macroalga.MethodsHere, we examined the transcriptome of G. lemaneiformis exposed to Cd to identify the responses to Cd stress.Results and discussionOur findings revealed that Cd led to the retardation of growth rate in G. lemaneiformis, accompanied by a notable reduction in the content of photosynthetic pigments and a decrease in the expression of genes associated with the photosynthetic system and nitrogen metabolism. When exposed to Cd, there was a rapid increase in Cd levels through the upregulation of genes encoding GlZIP6 and GlIRT1. Additionally, the expression of Cd efflux transporters, GlZIP1 and GlABCG22, and the ABCC7 transporter for compartmentation to the vacuole, was induced to mitigate Cd toxicity. Cd also activated crucial genes involved in the ABA biosynthesis and enhanced ABA content, thereby inducing ABA signaling pathway. Furthermore, exogenous ABA reduced the growth inhibition of G. lemaneiformis under Cd stress. Redox homeostasis was adjusted to adapt to Cd toxicity, with thioredoxin, glutaredoxin cycle and ascorbate-glutathione cycle identified as playing significant in maintaining reactive oxygen species homeostasis. Moreover, transcription factors such as several MYBs, signal transmission factors G protein and heat shock proteins (sHSPs, HSP 40, HSP 90, HSP101) were involved in the detoxification of Cd. Collectively, this study provided a comprehensive understanding of the molecular mechanisms underpinning the of responses of macroalga G. lemaneiformis to Cd exposure.

The maize WRKY transcription factor ZmWRKY64 confers cadmium tolerance in Arabidopsis and maize (Zea mays L.).

ZmWRKY64 positively regulates Arabidopsis and maize Cd stress through modulating Cd uptake, translocation, and ROS scavenging genes expression. Cadmium (Cd) is a highly toxic heavy metal with severe impacts on crops growth and development. The WRKY transcription factor is a significant regulator influencing plant stress response. Nevertheless, the function of the WRKY protein in maize Cd stress response remains unclear. Here, we identified a maize WRKY gene, ZmWRKY64, the expression of which was enhanced in maize roots and leaves under Cd stress. ZmWRKY64 was localized in the nucleus and displayed transcriptional activity in yeast. Heterologous expression of ZmWRKY64 in Arabidopsis diminished Cd accumulation in plants by negatively regulating the expression of AtIRT1, AtZIP1, AtHMA2, AtNRAMP3, and AtNRAMP4, which are involved in Cd uptake and transport, resulting in Cd stress tolerance. Knockdown of ZmWRKY64 in maize led to excessive Cd accumulation in leaf cells and in the cytosol of the root cells, resulting in a Cd hypersensitive phenotype. Further analysis confirmed that ZmWRKY64 positively regulated ZmABCC4, ZmHMA3, ZmNRAMP5, ZmPIN2, ZmABCG51, ZmABCB13/32, and ZmABCB10, which may influence Cd translocation and auxin transport, thus mitigating Cd toxicity in maize. Moreover, ZmWRKY64 could directly enhance the transcription of ZmSRG7, a reported key gene regulating reactive oxygen species homeostasis under abiotic stress. Our results indicate that ZmWRKY64 is important in maize Cd stress response. This work provides new insights into the WRKY transcription factor regulatory mechanism under a Cd-polluted environment and may lead to the genetic improvement of Cd tolerance in maize.

Kinetin-mediated reduction of cadmium accumulation in rice (Oryza sativa L.) via modulation of cell wall binding capacity in a NO-dependent manner

Cadmium (Cd) is a heavy metal that is toxic to both plant growth and human health. Kinetin, a precursor of cytokinin, plays crucial roles in the response of plants to abiotic stress. However, the mechanism underlying kinetin detoxification in Cd-induced stress remains poorly understood. In this study, we observed a significant increase in endogenous kinetin levels in both rice shoots and roots under Cd stress. Furthermore, the application of exogenous kinetin resulted in a reduction in hemicellulose content within cell walls, thereby reducing the cell wall's capacity to bind Cd and limit its entry into cells. In addition, exogenous kinetin downregulated the transcript levels of genes associated with Cd uptake and root-to-shoot translocation while simultaneously upregulating the transcript levels of genes involved in Cd efflux from cells and sequestration into vacuoles, consequently leading to reduced Cd accumulation in rice plants. Moreover, kinetin significantly decreased nitric oxide (NO) accumulation in response to Cd stress, potentially facilitating detoxification during Cd-induced stress through a NO-dependent mechanism. Overall, our findings suggest that kinetin enhances rice's tolerance to Cd by increasing the cell wall's ability to bind Cd and regulating gene expression related to Cd accumulation. These mechanisms may be NO-dependent and could potentially inform the development of new strategies for mitigating Cd toxicity in agricultural systems.

Effects of Silicon Application on Nitrogen Migration in Soil–Rice Systems under Cadmium Stress

Cadmium (Cd) contamination is a serious threat to plants and humans, which subsequently impairs sustainable agricultural production and ecosystem service. Silicon (Si) has been applied to mitigate Cd toxicity, but inevitably has direct and indirect impacts on nitrogen (N) behaviors in soil and plants. However, what role plants play in the N response to Si in soil–rice systems under Cd stress is not known. Therefore, the effects of Si on N migration through different pathways in the soil-rice system were systematically investigated in a rice-cultivation lysimeter experiment. The rice was planted in Cd-contaminated (5 mg kg−1) and uncontaminated soils with three levels of Si application (0, 100, and 200 kg SiO2 hm−2), and the contents of N and Cd in different forms in plants and soils were measured. The group without Cd and Si was set as CK. The study reported that Cd stress caused Cd accumulation in plants, inducing a decrease of 26.0~83.4% in plant dry weights and a decrease of 15.7~46.6% in N concentration compared with CK. Moreover, the leaching of N in soils was increased by Cd, in which the NO3−-N rather than the NH4+-N was leached out. These adverse effects on the plant growth and soil N loss were significantly alleviated by Si application in two ways: (1) the Cd availability in soils was reduced with the acid-extractable Cd (the Cd form with high mobility), decreasing from 1.07 to ~0 mg kg−1; (2) the Cd uptake and translocation in plants were restricted, with the Cd content decreasing by 59.1~96.4% and the translocation index decreasing from 17.7% to 2.2%. The combination of the two mechanisms consequently increased the N absorption of plants from 1.35 to 2.75~3.5 g. The results of the N mass balance calculation showed that, compared with soil N flux, plant-absorbed N contributed predominantly (43.9~55.6%) to the soil total N variation. Moreover, there is a significant trade-off between plant-absorbed N and soil N flux. The magnitude and direction of the soil N flux were greatly and negatively affected by plant-absorbed N during the flooding period. Hence, we conclude that Si application could reduce the leaching of N in soil–rice systems under Cd stress, mainly due to the promotion of the N absorption of plants rather than N immobilization in soils. This study provided new evidence that plants played a dominant role in N response to Si in soil-rice systems under Cd stress.

Screening of Cadmium-Resistant Microbes to Improve the Tolerance of Sorghum bicolor (L.) Moench Against Cadmium

To improve the cadmium (Cd) resistance and the remediation ability of Sorghum bicolor (L.) Moench, fourteen Cd-resistant bacteria were screened from cadmium-contaminated soil, together with two strains preserved in the laboratory. It was found that 3 strains (ZR451, ZR452, and ZJSH1) significantly promoted the growth of Cd-stressed S. bicolor in hydroponics and mitigated Cd toxicity to plants, and SR8, ZRK1, and ZR211 promoted sorghum growth lightly. Further studies indicated that strains SR8, ZR211, and ZJSH1 were Cd-resistant and acid-resistant strains. Strains ZR211and ZR121 significantly produced two hormones (SA and GA), ZJSH1 significantly produced IAA and SA, and strains SR8, ZR451 and ZR452 produced one hormone. Strains SR8, ZR451, ZR452, and ZJSH1 produced siderophores. In addition, strain ZJSH1fixed nitrogen and produced ACC deaminase, while ZR451 and ZJSH1 solubilized phosphorus Correlation analysis showed that the Cd resistance of the strains was significantly and positively correlated with their IAA and GA production. The screening of the three cadmium resistant strains ZJSH1 (Sphingomonas paucimobilis), ZR451 (Bacillus cereus) and ZR452 (Bacillus cereus) provided bacterial resources for the efficient remediation of Cd-contaminated soils by bacterial - S. bicolor combination.

Regulation of cadmium uptake in the hyperaccumulator Solanum nigrum is mediated by glutathione

Solanum nigrum is a common hyperaccumulator of the heavy metal cadmium (Cd). Our study aims to investigate the impact of glutathione regulation, specifically glutathione overproduction or reduction, on the growth of S. nigrum and its soil remediation potential. To achieve this, plants were subjected to treatments using a glutathione inhibitor (buthionine sulfoximine) and a glutathione promoter (L-2-oxothiazolidine-4-carboxylic acid [OTC]). We assessed plant height, root length and biomass to evaluate the influence of Cd and glutathione regulation on plant growth. Furthermore, we analyzed chlorophyll content. Cd and malondialdehyde (MDA) contents were measured to determine the effect of glutathione regulation on Cd accumulation and lipid peroxidation. Our findings revealed that glutathione overproduction significantly increased the biomass of S. nigrum, resulting in an approximately 12% increase. Additionally, it led to a ca. 10% rise in chlorophylls content. The application of exogenous OTC enhanced reduced glutathione (GSH) content, accompanied by enhanced Cd accumulation. GSH can be converted to oxidized glutathione, which aids in combatting and mitigating Cd toxicity. The MDA content in plants also increased. The overproduction of glutathione holds promise for enhancing heavy metal accumulation and tolerance in hyperaccumulator plants. It provides a theoretical basis for improving hyperaccumulator plants genetically.

Methyl jasmonate reduces cadmium toxicity by enhancing phenol and flavonoid metabolism and activating the antioxidant defense system in pigeon pea (Cajanus cajan)

Cadmium (Cd) is absorbed by plant roots from soil along with essential nutrients and affects plant growth and productivity. Methyl jasmonate (Me-JA) play important roles to mitigate Cd toxicity in plants. We have investigated the role of Me-JA to ameliorate Cd toxicity in Pigeon pea (Cajanus cajan). Plant root growth, biomass, cellular antioxidant defense system and expression of key regulatory genes in molecular and signaling process have been analyzed. Two Cajanus cajan varieties AL-882 and PAU-881 were grown at 25 °C, 16/8h light/dark conditions in three biological replicates at 5 mM Cd concentration, three concentration of Me-JA (0, 10 nM, 100 nM) and two concentrations in combination of Me-JA + Cd (10 nM Me-JA +5 mM Cd, 100 nM Me-JA +5 mM Cd). The seedlings were exposed to Cd stress consequently plants showed decrease in primary root growth (60.71%, in AL-882 and 8.33%, in PAU-881), shoot and root biomass and antioxidant enzymes activities. Me-JA treatment resulted in increased primary root growth (63.64%, in AL-882) and overall plant biomass. Oxidative stress generated due to Cd stress was counter balanced by Me-JA treatment. Me-JA reduced H2O2 free radicals formation and enhanced antioxidant enzyme activities and phenolic content in stressed seedlings. Me-JA treatment increased expression of CALM, IP3, CDPK2, MPKs (involved in calcium and kinase signaling pathways) and reduced expression of metal transporters (IRT1 and HMA3) genes. This reduction in metal transporters gene expression is a probable reason for low toxicity effect of Cd in root after Me-JA treatment which has potential implications in reducing the risk of Cd in the food chain.

The damage caused by Cd toxicity to photosynthesis, cellular ultrastructure, antioxidant metabolism, and gene expression in young cacao plants are mitigated by high Mn doses in soil.

Manganese (Mn) is one of the essential mineral micronutrients most demanded by cacao. Cadmium (Cd) is highly toxic to plants and other living beings. There are indications that Mn can interact with Cd and mitigate its toxicity. The objective of this study was to evaluate the action of Mn on the toxic effect of Cd in young plants of the CCN 51 cacao genotype, subjected to different doses of Mn, Cd, and Mn+Cd in soil, through physiological, biochemical, molecular, and micromorphological and ultrastructural changes. High soil Mn doses favored the maintenance and performance of adequate photosynthetic processes in cacao. However, high doses of Cd and Mn+Cd in soil promoted damage to photosynthesis, alterations in oxidative metabolism, and the uptake, transport, and accumulation of Cd in roots and leaves. In addition, high Cd concentrations in roots and leaf tissues caused irreversible damage to the cell ultrastructure, compromising cell function and leading to programmed cell death. However, there was a mitigation of Cd toxicity when cacao was grown in soils with low Cd doses and in the presence of Mn. Thus, damage to the root and leaf tissues of cacao caused by Cd uptake from contaminated soils can be attenuated or mitigated by the presence of high Mn doses in soil.

Mechanisms underlying the alleviated cadmium toxicity in marine diatoms adapted to ocean acidification

Anthropogenic activities have significantly increased the influx of carbon dioxide and metals into the marine environment. Combining ocean acidification (OA) and metal pollution may lead to unforeseen biological and ecological consequences. Several studies have shown that OA reduces cadmium (Cd) toxicity in marine diatoms. Although these studies have shed light on the physiological and transcriptomic responses of diatoms exposed to Cd, many aspects of the mechanisms underlying the reduced metal accumulation in diatoms remain unknown. This study aims to address this unresolved question by comparing Cd subcellular distribution, antioxidant enzyme activity, relative expression of metal transporters, surface potential, surface composition, and transmembrane potential in the diatom Phaeodactylum tricornutum grown under ambient and 1200 µatm pCO2 conditions. Our findings reveal that diatoms grown in acidified seawater exhibit higher surface potential and higher plasma membrane depolarization. These changes and the competing effects of increased H+ concentration result in a blunted response of P. tricornutum to the Cd challenge. Consequently, this study offers a new explanation for mitigating Cd toxicity by marine diatoms adapted to OA.

Alleviation of cadmium toxicity and fortification of zinc in wheat cultivars cultivated in Cd contaminated soil

To address food production challenges and combat heavy metal toxicity, an economically viable and sustainable approach is essential. Cadmium (Cd) contamination poses risks to crops and human health. Leveraging the structural similarity between zinc (Zn) and cadmium, we explored foliar Zn spray's potential to alleviate Cd toxicity and enhance wheat yield. Our field study near Peshawar, Pakistan, during the 2021–2022 winter, employed a split-plot design to investigate Zn's impact on wheat biofortification. Across three wheat varieties (JANBAZ-10, Pirsabak (PS)-2013, PS-2015), four foliar Zn levels (0 %, 0.5 %, 1.0 %, 1.5 % solution) were tested at various growth stages. Pirsabak-2015 exhibited optimal results, with a 1 % foliar Zn treatment producing the highest grain yield (3409 kg ha−1), biological yield (9022 kg ha−1), grains per spike (56), and 1000-grain weight (40.6 g). Application of 1 % biochar also significantly increased grain yield. Zn concentration peaked in grains and leaves with 1.5 % Zn solution, followed by 1.0 % Zn in the PS-2015 cultivar. Moreover, 1 % Zn application enhanced photosynthetic parameters and significantly reduced cadmium concentrations in leaves and grains. Notably, 1.0 % Zn led to improved stress tolerance as indicated by decreased electrolyte leakage and increased superoxide dismutase and peroxidase activities. Applying 1.0 % Zn solution as a foliar spray during different growth stages demonstrates the potential to enhance wheat yield, increase grain Zn content, and mitigate Cd toxicity in Cd-contaminated soil. Further research across diverse cereal crops and climates will help establish 1.0 % Zn foliar spray as an effective Cd stress mitigation strategy.

Effect of foliar application of nanoparticles on growth, physiology, and antioxidant enzyme activities of lettuce (Lactuca sativa L.) plants under cadmium toxicity.

Nanotechnology has attracted the interest of scientists due to its wide range of application specifically in agriculture. Nanoparticles (NPs) may act as a promising materials to alleviate cadmium (Cd) stress in plants. This study aims to assess the impact of multiple nanoparticles including nSiO2 (50mg L-1:100mg L-1), nTiO2 (20mg L-1:60mg L-1), nZnO (50mg L-1:100mg L-1), nFe3O4 (100mg L-1:200mg L-1), nCuO (50mg L-1:100mg L-1), and nCeO2 (50mg L-1:100mg L-1) in combination with CdCl2 (5µM) to mitigate Cd toxicity in lettuce through foliar application in hydroponic solution. Current findings indicate that foliar application of nSiL + Cd (50mg L-1), nZnL + Cd (50mg L-1), and nTiL + Cd (20mg L-1) is more effective in improving growth, biomass, root architecture, and elevated photosynthetic efficiency, which might be attributed to the increasing uptake of essential micronutrient (K, Mg, Ca, Fe, Zn) under Cd stress. Similarly, treatment with nanoparticles leads to reduced accumulation of ROS and MDA in lettuce, while enhancing the SOD, POD, CAT, and APX activities. The results showed that nanoparticles have high tolerance against Cd as depicted by the inhibition in Cd accumulation by 3.2-58% and 10-72% in roots as well as edible parts of lettuce, respectively. In addition, Cd alone reduces the morphological traits, antioxidant enzyme activity, and photosynthetic activity, while increasing the ROS, MDA, and Cd accumulation in lettuce. This comprehensive study suggests the role of nanoparticles in reducing Cd toxicity in lettuce, signifying their importance as stress mitigation agents. However, long-term pot, priming, and field trials are needed to identify the optimal nanoparticle for the lettuce under variable environmental conditions.

Anionic polyacrylamide alleviates cadmium inhibition on anaerobic digestion of waste activated sludge

The uncontrolled discharge of industrial wastewater leads to a significant cadmium (Cd) accumulation in waste activated sludge (WAS), posing a serious threat to the steady operation of the anaerobic digestion (AD) system in wastewater treatment plants (WWTPs). Therefore, developing a viable approach to cope with the adverse effects of high-concentration Cd on the AD system is urgently required. This study aims to investigate the potential of using anionic polyacrylamide (APAM), a commonly used agent in WWTPs, to mitigate the adverse effects of Cd in a toxic amount (i.e., 5.0 mg per g total suspended solids (TSS)) on AD of WAS. The results showed that the effectiveness of higher APAM on Cd toxicity alleviation was less than that of lower APAM at the studied level (i.e., the effectiveness order was 1.5 mg APAM per g TSS > 3.0 mg APAM per g TSS > 6.0 mg APAM per g TSS). The moderate supplement of APAM (i.e., 1.5 mg per g TSS) recovered the accumulative methane yield from 190.5 ± 3.6 to 228.9 ± 4.1 mL per g volatile solids by promoting solubilization, hydrolysis, and acidification processes related to methane production. The application of APAM also increased the abundance of key microbes in the AD system, especially Methanolinea among methanogens and Caldilineaceae among hydrolyzers. Furthermore, APAM facilitated the key enzyme activities involved in AD processes and reduced reactive oxygen species (induced by Cd) production via adsorption/enmeshment of Cd by APAM. These findings demonstrate the feasibility of using moderate APAM to mitigate Cd toxicity during AD, providing a promising solution for controlling Cd or other heavy metal toxicity in WWTPs.

Galactoglucomannan oligosaccharides mitigate cadmium toxicity in maize protoplasts by improving viability and cell wall regeneration

To avoid human health endangerment via the food chain, the investigation of Cd's effects on plant growth and development, and the discovery of various compounds that would mitigate the toxic effects of Cd, are essential. Galactoglucomannan oligosaccharides (GGMOs) are biologically active compounds, which improve the growth and development of plants. Therefore, the impact of GGMOs on the mitigation of Cd toxicity on maize (Zea mays L.) protoplasts was the main objective of this research. Here, protoplast viability, de novo cell wall regeneration on protoplasts' surface and Cd-uptake by protoplasts were studied. To study the influence of different treatments over time, the protoplasts were sampled on various days during the 14-day-long cultivation. The medium containing 2,4-dichlorophenoxyacetic acid, 6-benzylaminopurine, and GGMOs in a 10−9 M concentration with a pH of 3.8 was found to be optimal for protoplast cultivation. The toxic effect of Cd2+, which was evident already on the 2nd day of cultivation, resulted in decreased protoplast viability, the de novo cell wall regeneration, and in increased Cd-uptake. However, the application of GGMOs on Cd-stressed protoplasts increased cell wall regeneration. Fully or partly regenerated cell walls decreased the uptake of Cd2+ through the plasma membrane and improved protoplast viability. This is the first study that confirmed that biologically active oligosaccharides promote cell wall regeneration on the protoplast surface in both non-stress and Cd-stress conditions.

Foliar application of selenium nanoparticles alleviates cadmium toxicity in maize (Zea mays L.) seedlings: Evidence on antioxidant, gene expression, and metabolomics analysis

The molecular and metabolic mechanisms of foliar selenium (Se) nanoparticles (SeNPs) application in mitigating cadmium (Cd) toxicity in crops have not been well studied. Herein, hydroponically cultured maize seedlings were exposed to Cd (20 μM) and treated without and with foliar SeNPs application. Effects of SeNPs on Cd transporter genes and plant metabolism were also explored. Results showed that compared to control plants without Cd exposure, Cd exposure decreased shoot height (16.8 %), root length (17.7 %), and fresh weight of root (24.2 %), stem (28.8 %), and foliar-applied leaves (Se-leaves) (15.0 %) via oxidative damage. Compared to Cd exposure alone, foliar SeNPs application at 20 mg/L (0.25 mg/plant) significantly alleviated the Cd toxicity by promoting photosynthesis and antioxidant capacity and fixing Cd in cell wall. Meanwhile, the mineral concentration of Ca (26.0 %), Fe (55.4 %), Mg (27.0 %), Na (28.6 %), and Zn (10.1 %) in Se-leaves was improved via foliar SeNPs application at 20 mg/L. QRT-PCR analysis further revealed that down- and up-regulation of the expression of ZmHMA2 and ZmHMA3 gene in Se-leaves contributed to reduced translocation of Cd in plants and enhanced Cd sequestration in the vacuole, respectively. Metabolomic results further indicated that metabolic pathways including carbohydrate metabolism, membrane transport, translation, amino acid metabolism, and energy metabolism were significantly affected by foliar SeNPs application. In conclusion, foliar SeNPs application at 20 mg/L could be a prospective strategy to mitigate Cd toxicity in maize.