Alleviates Cadmium Toxicity Research Articles

Sodium hydrosulfide alleviates cadmium toxicity by changing cadmium chemical forms and increasing the activities of antioxidant enzymes in salix

Cadmium (Cd) is a highly toxic element for plant. In order to reveal the effects of NaHS on Cd uptake, physiological and molecular responses of salix to Cd toxicity, NaHS-mediated hydroponics of salix under Cd stress was performed. The addition of NaHS reduces the salix biomass reduction caused by Cd poisoning. NaHS did not obviously reduce the total Cd level absorbed by salix, but significantly reduced the soluble Cd fractions and increased the insoluble Cd fractions in salix leaves and roots. NaHS reduced the distribution of Cd in organelles and vacuoles and increased the distribution of Cd in the cell wall of salix leaves and roots. NaHS promotes the level of antioxidant enzyme activities and gene expression of salix, and reduces the accumulation of MDA and H2O2 caused by Cd. NaHS increases the content of GSH and endogenous H2S in salix leaves and roots. The addition of NaHS can reduce the toxicity of Cd to salix without obviously reducing the Cd uptake by salix, thus improving the application of salix in phytoremediation to Cd.

Root iron plaque alleviates cadmium toxicity to rice (Oryza sativa) seedlings

Iron plaque (IP) on root surface can enhance the tolerance of plants to environmental stresses. However, it remains unclear the impact of Fe2+ on cadmium (Cd) toxicity to rice (Oryza sativa) seedlings. In this study, the effects of different Fe2+ and Cd2+ concentration combinations on rice growth were examined hydroponically. Results indicated that Fe2+ concentration up to 3.2 mM did not damage rice roots while induced IP formation obviously. Cd2+ of 10 μM repressed rice growth significantly, while the addition of 0.2 mM Fe2+ to 10 μM Cd2+ solution (Cd+Fe) did not damage rice roots, indicating that Fe2+ could ameliorate Cd toxicity to rice seedlings. Microstructure analysis showed Cd+Fe treatment induced the formation of IP with dense and intricate network structure, Cd adsorption on the root surface was reduced significantly. Cd concentration of rice roots and shoots and Cd translocation from roots to shoots with Fe+Cd treatment were reduced by 34.1%, 36.0% and 20.1%, respectively, in comparison to a single Cd treatment. Noteworthy, the removal of IP resulted in a larger loss of root biomass under Cd treatment. In addition, Cd+Fe treatment increased the activities of root superoxide dismutase and catalase by 105.5% and 177.4%, and decreased H2O2 and O2·- accumulation of rice roots by 56.9% and 35.9%, and recovered Cd-triggered electrolyte leakage obviously, when compared with a single Cd treatment. The results from this experiment indicated that the formed dense IP on rice roots decreased Cd absorption and reactive oxygen species accumulation, and Fe2+ supply alleviated Cd toxicity to rice seedlings.

Sulfur dioxide derivatives alleviate cadmium toxicity by enhancing antioxidant defence and reducing Cd2+ uptake and translocation in foxtail millet seedlings

Sulfur dioxide (SO2) was recently proposed as a novel bio-regulator in mammals. However, the possible advantageous effects of SO2 in plant adaptation to heavy metal-contaminated environments are largely unknown. In the present study, using Na2SO3/NaHSO3 derivatives as SO2 donors, we investigated the possible roles and regulation mechanisms of SO2 in alleviating Cd2+ toxicity in foxtail millet seedlings. Exogenous SO2 derivatives (0.5 mM) application significantly reduced the seedling growth inhibition caused by Cd2+ stress. Cd2+-induced oxidative damage was also alleviated by SO2 derivatives, which was supported by the decreased malondialdehyde (MDA) level in the leaves of seedlings pretreated with SO2 derivatives. These responses were related to the enhanced activities of representative antioxidant enzymes, including catalase and superoxide dismutase, as well as the up-regulation of ascorbate-glutathione cycle, which contributed to the scavenging of Cd2+-elicited O2•－ and H2O2 within the leaves of foxtail millet seedlings. Also, SO2 derivative application promoted sulfur assimilation and increased the content of glutathione and phytochelatins, which may help to enhance Cd2+ detoxification capacity in foxtail millet seedlings. Moreover, application of SO2 derivatives caused down-regulation of the transcript expression levels of several genes involved in Cd2+ uptake and translocation, such as NRAMP1, NRAMP6, IRT1, IRT2, HMA2, and HMA4, thus resulting in reduced Cd2+ accumulation in the shoots and roots of Cd2+-stressed seedlings. Collectively, these results suggest that exogenous SO2 derivative application can alleviate oxidative damage and restrict Cd2+ buildup, thereby reducing Cd2+-induced growth inhibition in foxtail millet seedlings upon Cd2+ exposure. This novel finding indicates that the usage of SO2 derivatives may be an effective approach for enhancing Cd2+ tolerance in foxtail millet and other crops.

Sulfide alleviates cadmium toxicity in Arabidopsis plants by altering the chemical form and the subcellular distribution of cadmium

Several sulfur compounds are thought to play important roles in the plant tolerance to cadmium (Cd), but the role of inorganic sulfide in Cd tolerance remains largely unknown. In this study, we found that Cd exposure increased the accumulation of soluble sulfide in Arabidopsis plants. When exogenous sulfide, in the form of NaHS, was foliarly applied, Cd-induced growth inhibition and oxidative stress were alleviated. In addition, although the foliar application of sulfide did not affect the total Cd levels, it significantly decreased the soluble Cd fractions in plants. Furthermore, foliar applications of sulfide decreased Cd distribution in the cytoplasm and organelles, but increased Cd retention in the cell wall, which is a less sensitive compartment. These results suggest that the Cd-induced accumulation of soluble sulfide alleviates Cd toxicity in plants by inactivating Cd and sequestering it into the cell wall.

Silicon alleviates cadmium toxicity in wheat seedlings (Triticum aestivum L.) by reducing cadmium ion uptake and enhancing antioxidative capacity.

Cadmium (Cd) is a toxic element that poses a great threat to human health, while silicon (Si) is a beneficial element and has been shown to have a mitigation effect on plants under Cd toxicity. However, the mechanisms underlying the role of Si in alleviating Cd toxicity are still poorly understood in wheat. Therefore, growth status, photosynthesis parameters, root morphology, antioxidant system, and Cd2+ uptake and flux under Cd toxicity were studied through hydroponic experiment, aiming to explore the mitigation of Si on Cd toxicity in wheat seedlings. The results showed that Si supply improved plant biomass as well as photosynthetic but had little effects on root morphology of seedlings under Cd stress. Si addition decreased Cd contents both in shoots and roots. In situ measurements of Cd2+ flux showed that Si significantly inhibited the net Cd2+ influx in roots of wheat. Si also mitigated the oxidative stress in wheat leaves by decreasing malondialdialdehyde (MDA) and hydrogen peroxide (H2O2) contents as well as by increasing superoxide dismutase (SOD) and guaiacol peroxidase (POD) activity. Overall, the results revealed that Si could alleviate Cd toxicity in wheat seedlings by improving plant growth and antioxidant capacity and by decreasing Cd uptake and lipid peroxidation.

Exogenous silicon alleviates cadmium toxicity in rice seedlings in relation to Cd distribution and ultrastructure changes

Silicon (Si) has inhibitory effects on cadmium (Cd) toxicity in rice, but the effects of Si-containing materials on the chemical properties of hydroponic media have been ignored. The increased pH value and introduction of excess cations when utilizing alkaline reagents may disguise the true function of the Si. Thus, the present study investigated Si-alleviated effect on Cd toxicity in rice seedlings by eliminating the aforementioned interferences. The hydroponic cultivation of rice seedlings was carried out to demonstrate the inhibiting effects of exogenous Si on Cd accumulation and distribution. The chlorophyll and carotenoid contents in leaf cells under Cd stress were also measured. Transmission electron microscopy was used to investigate ultrastructural changes in rice mesophyll cells, chloroplasts, and mitochondria under different Cd-stressed and Si-amended conditions. The alkalinity of the Si source was neutralized with nitric acid, and discrepancies in Na+ levels was eliminated by the addition of sodium nitrate to different treatments. Toxicity symptoms were observed in rice seedlings under Cd (5 mg L−1) treatment after 35 days, and the biomass, and chlorophyll and carotenoid contents, were lowered. The levels of these indices increased after adding 120 mg L−1 Si. The bioconcentration and translocation factor values indicated that Si reduced Cd accumulation in rice plants and also decreased the ratio of Cd translocation from roots to shoots, which effectively alleviated the Cd toxicity. The positive effects of Si were mainly reflected in the recovery of grana lamellae and membrane structures in chloroplasts, and restored membrane morphology and increased numbers of cristae in mitochondria. Exogenous Si reduced Cd uptake in rice seedlings, especially in shoots, and inhibited Cd transport into aboveground parts. In addition, Si restored the functions of chloroplasts owing to a decrease in lipid peroxidation. The application of Si indicated that Cd toxicity is alleviated partly because of the improvement in chloroplast biosynthesis and the diminution of Cd bioavailability.

The effects of exogenous salicylic acid on alleviating cadmium toxicity in Nymphaea tetragona Georgi

The effects of salicylic acid pretreatments on lipid peroxidation, photosynthetic pigments, the antioxidative system and cadmium (Cd) accumulation in waterlily under Cd stress were studied. A salicylic acid pretreatment lowered the concentrations of malondialdehyde and proline, but increased the contents of photosynthetic pigments, glutathione, non-protein thiol and phytochelatins. Salicylic acid pretreatments enhanced the activities of antioxidant enzymes, such as superoxide dismutase, peroxidase and ascorbate peroxidase. Furthermore, SA pretreatments also decreased the Cd concentrations in different plant organs. Thus, exogenous SA treatments could attenuate the toxic effects of Cd in Nymphaea tetragona.

Alleviation of cadmium toxicity in Lemna minor by exogenous salicylic acid

Cadmium (Cd) is a significant environmental pollutant in the aquatic environment. Salicylic acid (SA) is a ubiquitous phenolic compound. The goal of this study was to assess the morphological, physiological and biochemical changes in duckweed (L. minor) upon exposure to 10μM CdCl2, 10μM CdCl2 plus 50μM SA, or 50μM SA for 7 days. Reversing the effects of Cd, SA decreased Cd accumulation in plants, improved accumulation of minerals (Ca, Mg, Fe, B, Mo) absorption, increased endogenous SA concentration, and phenylalanine ammonialyase (PAL) activity. Chlorosis-associated symptoms, the reduction in chlorophyll content, and the overproduction of reactive oxygen species induced by Cd exposure were largely reversed by SA. SA significantly decreased the toxic effects of Cd on the activities of the superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, and glutathione reductase in the fronds of L. minor. Furthermore, SA reversed the detrimental effects of Cd on total ascorbate, glutathione, the ascorbic acid/oxidized dehydroascorbate and glutathione/glutathione disulphide ratios, lipid peroxidation, malondialdehyde concentration, lipoxygenase activity, and the accumulation of proline. SA induced the up-regulation of heat shock proteins (Hsp70) and attenuated the adverse effects of Cd on cell viability. These results suggest that SA confers tolerance to Cd stress in L. minor through different mechanisms.

Castasterone and Citric Acid Supplementation Alleviates Cadmium Toxicity by Modifying Antioxidants and Organic Acids in Brassica juncea

Brassinosteroids are known to manage various stresses including heavy metals in plants and castasterone is a bioactive form of brassinosteroids. Citric acid, a known metal chelator which is an intermediate of tricarboxylic cycle, is involved in various environmental adaptations. The present study was conducted to evaluate the synergistic role of citric acid and castasterone on various physiological and biochemical responses in Brassica juncea seedlings under cadmium stress. B. juncea seedlings were subjected to two levels of cadmium (0 and 0.6 mM) and citric acid (0 and 0.6 mM), and four levels of castasterone (0, 0.01, 1, and 100 nM). Exposure of cadmium induced phytotoxicity by elevating hydrogen peroxide (H2O2) and superoxide anion ( $${\text{O}}_{2}^{{. - }}$$ ) generation, decreasing photosynthetic pigment concentration, altering total carbohydrate content, and inducing stomatal closure. Seed priming with castasterone (at highest level) along with citric acid was most effective in ameliorating cadmium-induced toxicity which was manifested via reduced H2O2 and $${\text{O}}_{2}^{{. - }}$$ levels by 30.71 and 12.12%, respectively. The photosynthetic pigments, namely chlorophyll and carotenoid content, were improved by 47.17 and 34.06%, respectively, whereas total carbohydrates and polyphenolic contents were increased by 32.59 and 42.44%, respectively. Additionally, endogenous low-molecular weight organic acids were altered in response to cadmium toxicity, which were also increased with the castasterone and citric acid treatments. The results suggest that binary treatment of citric acid and castasterone may be more effective than individual treatments in alleviating cadmium-induced physiological damage through antioxidants and organic acids.

Exogenous GR24 Alleviates Cadmium Toxicity by Reducing Cadmium Uptake in Switchgrass (Panicum virgatum) Seedlings.

Strigolactones (SLs) are classified into plant hormones, playing a key role as a mediator of plant growth in response to several abiotic stresses, including drought and salinity. However, the role of SLs in cadmium (Cd)-induced stress to plants is still unknown. The physiological responses of switchgrass (Panicum virgatum) stressed in 10 μmol L−1 Cd to exogenous synthetic SLs analog, GR24 were studied in hydroponics. The Cd stress significantly caused the adverse effects on plant growth and root morphology, inhibited photosynthesis, but boosted lipid peroxidation of Switchgrass seedlings. After treatment of 1 μmol L−1 GR24, the above adverse effects caused by Cd stress were significantly alleviated, mainly reflects in improvement of shoot biomass, relative water content, root development, chlorophyll contents, activities of typical antioxidant enzymes, nutrient uptake. The reason for exogenous GR24 alleviating cadmium toxicity might be owing to that exogenous GR24 promoted the content of endogenous SLs, increased some essential element Fe (iron), Zn (zinc), Mn (manganese) and Cu (copper) uptake and reduced cadmium uptake, accumulation and partition in shoot of switchgrass seedlings.

Silica nanoparticles alleviate cadmium toxicity in rice cells: Mechanisms and size effects

Although it was recently determined that silicon can alleviate cadmium (Cd) toxicity in rice, the effects of silicon properties and the molecular mechanisms are still unclear. Here, the effect of silica nanoparticles (SiNPs) on Cd toxicity in rice was examined using cells cultured in suspension in the presence or absence of SiNPs (19 nm, 48 nm and 202 nm). The results showed that the presence of SiNPs substantially enhanced the proportion of live cells to 95.4%, 78.6% and 66.2%, respectively, suggesting that the extent of alleviation of Cd toxicity decreased gradually with size of SiNPs. The morphological results showed that dramatic damage and severe structural changes in the organelle integrity of cells occurred in the absence of SiNPs, whereas the cells exposed to the SiNPs remained nearly intact even in the presence of high concentrations of Cd. Furthermore, the SiNPs accumulated on the surface of the rice cells. Using inductively coupled plasma mass spectroscopy, Cd accumulated preferentially in plant cells with cell walls. In addition, noninvasive microtest technology showed that the average Cd2+ influx in those treated with SiNPs (19 nm, 48 nm and 202 nm) decreased by 15.7-, 11.1- and 4.6-fold, respectively. The gene expression of Cd uptake and transport (OsLCT1 and OsNramp5) was inhibited by SiNPs, but the gene expression of Cd transport into vacuole (OsHMA3) and Si uptake (OsLsi1) was enhanced by the SiNPs. These results indicate that the presence of SiNPs increased at least 1.87-fold the Si uptake capacity and inhibited the Cd uptake capacity, which together resulted in the alleviation of the toxicity of Cd in rice. This study provided a molecular-scale insight into the understanding of the SiNPs-induced alleviation of the toxicity of Cd in rice.

Alleviation of cadmium toxicity by potassium supplementation involves various physiological and biochemical features in Nicotiana tabacum L.

Potassium (K+) plays important roles in the development of plants and the response to various environmental stresses. However, the involvement of potassium in alleviating heavy metal stress in tobacco remains elusive. Greenhouse hydroponic experiments were conducted to evaluate the alleviating effects of K+ on tobacco subjected to cadmium (Cd) toxicity using four different K+ levels. Dose-dependent increases of plant biomass were found in both 0-μM Cd and 5-μM Cd treatments under different K+ levels, with the exception of the 1-mM KHCO3 (K3) treatment. The best mitigation effect was recorded with the 0.5-mM K+ (K2) treatment, which greatly alleviated Cd-induced growth inhibition, photosynthesis reduction, and oxidative stress. Compared with K0 treatment (no KHCO3 addition), K2 treatment significantly reduced Cd uptake and translocation after 5 and 10 days of Cd treatment. Moreover, the net photosynthetic rate, intracellular CO2 concentration, stomatal conductance, and transpiration rate as well as K+, zinc, manganese, copper, and iron concentrations in both shoots and roots after 10 days of Cd treatment significantly improved under the K2 treatment, and malondialdehyde accumulation in both shoots and roots was repressed, compared with K0 + Cd. Superoxide dismutase was found to play key roles in alleviating Cd-induced oxidative pressure in shoots of plants in K2 treatment under Cd treatment. Our findings advocate a positive role for K+ in reducing pollutant residues for safe production, especially in soils slightly or moderately polluted with Cd.

Effect of biochar on alleviation of cadmium toxicity in wheat (Triticum aestivum L.) grown on Cd-contaminated saline soil.

Soil degradation by salinity and accumulation of trace elements such as cadmium (Cd) in the soils are expected to become one of the most critical issues hindering sustainable production and feeding the increasing population. Biochar (BC) has been known to protect the plants against soil salinity and heavy metal stress. A soil culture study was performed to evaluate the effect of BC on wheat (Triticum aestivum L.) growth, biomass, and reducing Cd and sodium (Na) uptake grown in Cd-contaminated saline soil under ambient conditions. Soil salinity decreased the plant growth, biomass, grain yield, chlorophyll contents, and gas exchange parameters and caused oxidative stress in plants compared with Cd stress alone. Salt stress increased Cd and Na uptake and reduced the potassium (K) and zinc (Zn) uptake by plants. AB-DTPA-extractable Cd and soil electrical conductivity (ECe) increased under salt stress compared to the soil without NaCl stress. Biochar application improved the plant growth and reduced the Cd and Na uptake except in plants treated with higher BC and salt stress (5.0% BC+50mM NaCl). Biochar application reduced the oxidative stress in plants and modified the antioxidant enzyme activities, and reduced the bioavailable Cd under salt stress. The positive effects of BC under lower salt stress while the negative effects of BC under higher BC and salt levels indicated that BC doses should be used with great care in higher soil salinity levels simultaneously contaminated with Cd to avoid the negative effects of BC on growth and metal uptake.

Transcriptome Profiling Reveals the Important Role of Exogenous Nitrogen in Alleviating Cadmium Toxicity in Poplar Plants

Cadmium (Cd) is a non-essential metallic element with potentially deleterious effects on plants, animals, and human health. Many studies have indicated that nitrogen (N) application can effectively alleviate Cd toxicity in plants. However, the function of nitrogen in this process remains unclear. In this study, high-throughput RNA sequencing and comparative analysis were carried out on poplar (Populus cathayana Rehd) trees treated with only Cd or co-treated with N and Cd, and both treatments were compared against a negative control (no Cd or N) and plants treated with only N. The results showed that approximately 48045828, 46712688, 46681202, and 48076990 clean reads were obtained in the control, Cd, N + Cd, and N treatments. Gene ontology and pathway enrichment analysis (KEGG) indicated that differentially expressed genes (DEGs) could be classified primarily into 144 pathways, among which 19 were related to heavy metal transportation and cell detoxification. The up- and down-regulated DEGs were predominately involved in glutathione (GSH) synthesis, cysteine (Cys), glycine (Gly), brassinosteroid (BR), and salicylic acid (SA)-related pathways. Real-time quantitative PCR (RT-qPCR) revealed that the expression profiles of DEGs were consistent with the results from RNA sequencing analysis. Eight candidate genes encoding GSH, Cys, Gly, BR, and SA were associated with detoxification of Cd and were selected for further screening. A schematic model to explain the involvement of DEGs and N in the Cd-responsive regulatory network is proposed. This study represents the first comprehensive transcriptome-based characterization of N- and Cd-responsive DEGs in poplar. These results provide fundamental insight into the molecular mechanism of N assistance in Cd detoxification. In addition, the results of this study build a solid foundation for further genetic manipulation of Cd accumulation in plants and for the development of phytoremediation approaches to reclaim Cd-contaminated soils.

Exogenous malic acid alleviates cadmium toxicity in Miscanthus sacchariflorus through enhancing photosynthetic capacity and restraining ROS accumulation

Malic acid (MA) plays an important role in the regulation of plant growth, stomatal aperture, nutrition elements homeostasis and toxic metals tolerance. However, little is known about the effects of exogenous MA on physiological and biochemical responses to toxic metals in plants. To measure the alleviation roles of exogenous MA against cadmium (Cd), we determined the effects of MA on plant growth, net photosynthetic rate (Pn), reactive oxygen species (ROS) accumulation and the activities of anti-oxidant enzymes in the leaves of Miscanthus sacchariflorus (M. sacchariflorus) under Cd stress. The Cd exposure alone significantly inhibited plant growth and Pn, but increased the accumulation of ROS even though the anti-oxidant enzymes were markedly activated in the leaves of M. sacchariflorus. Treatment with MA significantly enhanced plant growth and decreased Cd accumulation accompanied by increasing Pn under Cd stress as compared to Cd stress alone, especially when treatment with high concentration of MA (200μM) was used. In addition, Cd and MA indicated synergistic effects by further increasing the activities and genes expression of partial anti-oxidant enzymes, thus resulting in higher glutathione accumulation and reduction of ROS production. The results showed that application of MA alleviated Cd-induced phytotoxicity and oxidant damage through the regulation of both enzymatic and non-enzymatic anti-oxidants under Cd stress in M. sacchariflorus.

Alleviation of cadmium toxicity in cucumber (Cucumis sativus) seedlings by the application of selenium

In the present study, the role of selenium in cadmium toxicity was investigated in cucumber seedlings by hydroponic experiments. The application of Se for cucumber exposed to Cd significantly reduced Cd accumulation in all tissues, elevated Cd-depressed chlorophyll content, and improved photosynthetic performance. External Se significantly reduced ·OH, H2O2 and malondialdehyde content. Exogenous Se balanced Cd-depressed elements (e.g., Se enhanced Cd-induced decreases in root Zn, leaf/stem/root Mn concentrations) and carbohydrate contents. External Se also significantly decreased the Cd-induced increases in Na+K+-, Ca2+Mg2+- and total ATPase activities, which recovered almost to control level. Results indicate that application of Se can alleviate Cd toxicity in cucumber seedlings by reducing Cd uptake and reactive oxygen species (ROS) accumulation, moreover protecting photosynthetic machinery from damaging, balancing elements and carbohydrate contents, and improving ATPase activities in cucumber.

Erratum to: Effect of taurine supplementation on hepatic metabolism and alleviation of cadmium toxicity and bioaccumulation in a marine teleost, red sea bream, Pagrus major.

This study was performed to unravel the mechanism of the beneficial action of taurine on marine teleost fish, red sea bream (Pagrus major), by analyzing the hepatic metabolism. Moreover, the ameliorative effects of the nutrient against cadmium toxicity and bioaccumulation were further evaluated. The fish were fed a diet containing 0 % (TAU0 %), 0.5 % (TAU0.5 %), or 5.0 % (TAU5.0 %) taurine for 40–55 days (d) and subjected to cadmium acute toxicity and bioaccumulation tests. Taurine deficiency in feed severely affected growth and the hepatic metabolic profiles of the fish, including a remarkable increase in myo-inositol, aspartate, and s-alanine in the TAU0 % group, which indicates a complementary physiological response to taurine deficiency. For the acute toxicity test, fish were fed the test diets for 55 d and were then exposed to different dose of cadmium ranging from 0 to 5.6 mg/L for 96 h. Fish fed taurine had a higher tolerance to cadmium than those not fed taurine. For the bioaccumulation test, fish were fed the test diets for 40 d and then were chronically exposed to 0.2 mg/L of cadmium for 28 d followed by depuration for 21 d. Cadmium concentrations in the liver and muscle of fish fed TAU5.0 % were significantly lower than those of fish fed TAU0 % for the first 7 d of exposure and the first 7 d of elimination. Our findings suggest a possible mechanism for the beneficial role played by taurine and that the inclusion of taurine in fish aquaculture feed may reduce cadmium contamination of fish intended for human consumption.

硅缓解植物镉毒害的生理生态机制

硅缓解植物镉毒害的生理生态机制

Methylglyoxal alleviates cadmium toxicity in wheat (Triticum aestivum L).

Methylglyoxal alleviates cadmium toxicity in wheat (Triticum aestivum L) by improving plant growth. For a long time, the reactive α, β-carbonyl ketoaldehyde methylglyoxal (CH3COCHO; MG) has been regarded as merely a toxic metabolite in plants, but, now, emerging as a signal molecule in plants. In this study, cadmium (Cd) stress decreased plant height, root length, fresh weight (FW), and dry weight (DW) in a concentration-dependent manner, indicating that Cd had toxic effects on the growth of wheat seedlings. The toxic effects of Cd were alleviated by exogenously applied MG in a dosage dependent fashion, and 700mM MG reached significant differences, but this alleviating effect was eliminated by the treatment with N-acetyl-L-cysteine (NAC, MG scavenger), suggesting that MG could mitigate Cd toxicity in wheat. This study reported for the first time that MG could alleviate Cd toxicity in wheat, uncovering a new possible physiological function for MG, and opening a novel line of research in plant stress biology.

Co-application of 6-ketone type brassinosteroid and metal chelator alleviates cadmium toxicity in B. juncea L.

Plant growth regulator-assisted phytoremediation has been assessed as a novel strategy to improve phytoremediation potential of plants. In the present work, potential of castasterone, a plant growth regulator, combined with citric acid was explored for phytoremediation of cadmium in Brassica juncea seedlings. The seedlings were raised under controlled laboratory conditions for 7days. Results revealed that 0.6mM cadmium exposure induced toxicity in the seedlings, which was reflected through root growth inhibition, accumulation of hydrogen peroxide and malondialdehyde, and loss of cell viability. Pre-sowing treatment of castasterone supplemented with citric acid enhanced cadmium accumulation in the roots (from 752μg/g DW to 1192μg/g DW) and shoots (from 88μg/g DW to 311μg/g DW) and also improved root length, shoot length, fresh weight, and dry weight of seedlings by 81, 17, 39, and 35%, respectively. The co-application reduced malondialdehyde accumulation by 39% and reduced oxidative stress by enhancing the activities of antioxidant enzymes (superoxide dismutase, guaiacol peroxidase, catalase, ascorbate peroxidase, dehydroascorbate, glutathione reductase, glutathione peroxidase, glutathione-S-transferase, polyphenol oxidase), maximum enhancement (82%) being in polyphenol oxidase. Similarly, the contents of water- and lipid-soluble antioxidants were found to increase by 31 and 4%, respectively. Confocal microscopy revealed enhanced content of NO. Results suggested that binary combination of castasterone and citric acid is helpful in improving cadmium accumulation and ameliorating metal toxicity in B. juncea seedlings.