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Effect of soil cadmium on growth, oxidative stress and antioxidant system in wheat seedlings (Triticum aestivum L.)
Abstract
Effects of different concentrations of soil cadmium (0-33mg kg(-1)) on growth, oxidative stress, and antioxidant response of wheat seedlings (Triticum aestivum L.) were investigated using pot experiments. A slight stimulatory effect on seedling growth was observed, especially at low Cd concentrations (less than 3.3mg kg(-1)). Results of the electron paramagnetic resonance (EPR) determination showed a decrease in unstable free radical level in the leaves, followed by a significant increase with increasing Cd concentrations. Malondialdehyde (MDA) contents were significantly enhanced by a high Cd concentration. Activity levels of some antioxidant enzymes in the leaves, including superoxide dismutase (SOD, EC1.12.1.1), catalase (CAT, EC1.11.1.6), guaiacol peroxidase (GPX, EC1.11.1.7), ascorbate peroxidase (APX, EC1.11.1.11) and glutathione reductase (GR, EC1.6.4.2), did not change much at low Cd concentrations (less than 3.3mg kg(-1)), but fluctuated drastically at high Cd concentrations. GSH contents and GSH/GSSG ratios decreased at low Cd concentrations, then increased at high Cd concentrations. Wheat seedlings might overcompensate at low Cd concentrations, resulting in a low oxidative stress and a positive effect on growth. Changes in biochemical parameters would occur before any visible symptom of toxicity appeared, and the endpoint based on these parameters might be more sensitive or indicative than morphological observations in revealing the eco-toxicity of Cd. Based on the results of this study, we propose that the toxic critical value of soil Cd in inducing oxidative stress to wheat seedlings is between 3.3mg kg(-1) and 10mg kg(-1).
... Antioxidant enzyme activity: Superoxide dismutase (SOD), Catalase (CAT), and peroxidase (POD), were determined by using the Lin et al., (2007) method. ...
... The method outlined by Lin et al., (2007) was followed for the determination of SOD enzyme activity. 100μL of enzyme extract, 200μLof methionine (22 M), 500μL of phosphate buffer (pH 5), 200μL of Triton X (0.1 M), 100μL of NBT (20 M) and 800μL of distilled water were exposed to UV light for 15 minutes in laminar air flow cabinet. ...
... The catalase enzyme activity was estimated by following the protocol of Lin et al., (2007). Enzyme extract (100 μL) was taken in a test tube and 100μL H2O2 (5.9 mM) added in it. ...
... It enters ecosystems as a result of fuel combustion, metallurgical production, improper disposal of batteries, mining, etc. (Khan et al. 2017). Even at low concentrations Cd has an extremely negative effect on plants disturbing many aspects of physiology by reducing growth, biomass, productivity, and changing composition of cell wall (Huybrechts et al. 2019;Lentini et al. 2018;Lin et al. 2007;Chen et al. 2008;Vatehová-Vivodová et al. 2018). The main mechanism of Cd toxicity is the excessive production of reactive oxygen species (ROS), which leads to imbalance in the cellular redox homeostasis (Huybrechts et al. 2019). ...
... When the balance between an organism's ROS and its antioxidant capacity is disrupted, oxidative stress occurs. Modifications in the activity of key enzymes responsible for counteracting induced by cadmium oxidative stress have been described by many researchers (Seifikalhor et al. 2020;Lin et al. 2007;Tiryakioglu et al. 2006;Çatav et al. 2020). ...
... The differences between the groups were determined using the Mann-Whitney U test (exact p-values are shown) enhanced in maize plants (Zea mays) exposed to 250 μM of Cd (Seifikalhor et al. 2020). In Lin et al. (2007), the effect of different (0-33 mg kg −1 ) Cd concentrations in soil on antioxidant response of wheat seedlings (Triticum aestivum L.) were studied and showed that activity levels of SOD, CAT, GP X , APX, and glutathione reductase (GR) did not change much at Cd concentrations of less than 3.3 mg kg −1 but changed significantly at higher Cd concentrations. The authors suggested that the induction of enzyme activity in group treated with 10 mg kg −1 Cd might indicate excessive accumulation of H 2 O 2 . ...
Cadmium leads to disturbance of plant growth, and the manifestation of toxicity can vary greatly in different genotypes within one species. In this work we studied the effect of Cd on growth, antioxidant enzyme activity, and phytohormonal status of four barley cultivars (cvs. Simfoniya, Mestnyj, Ca 220702, Malva). According to the earlier study on seedlings, these cultivars were contrast in tolerance to Cd: Simfoniya and Mestnyj are Cd-tolerant and Ca 220702 and Malva are Cd-sensitive. The results presented showed that barley plants accumulated more Cd in straw than in grain. Tolerant cultivars accumulated significantly less Cd in grain than sensitive ones. The leaf area appeared to be a growth parameter susceptible to Cd treatment. The significant differences in leaf area values depended on Cd contamination and were not associated with cultivars’ tolerance. Tolerance of cultivars was contingent on the activity of the antioxidant defense system. Indeed, activity of enzymes decreased in sensitive cultivars Ca 220702 and Malva under Cd stress. In contrast, in tolerant cultivars, increased activity of guaiacol peroxidase was revealed. The concentrations of abscisic acid and salicylic acid mostly increased as a result of Cd treatment, while the concentrations of auxins and trans-zeatin either decreased or did not change. The results obtained indicate that antioxidant enzymes and phytohormones play an important role in the response of barley plants to elevated concentrations of cadmium; however, these parameters are not able to explain the differentiation of barley cultivars in terms of tolerance to cadmium at the seedling stage. Therefore, barley intraspecific polymorphism for cadmium resistance is determined by the interplay of antioxidant enzymes, phytohormones, and other factors that require further elucidation.
... The stress causative agents (free radical components) were progressively decreased in the available soil Cd concentration by T. harzianum action (Table 4), indicating that no oxidative stress was imposed by the remaining concentrations of Cd in the soil (counted by about 14% reduction from non-inoculated control plant, Figure 3B) due to T. harzianum action that advocated by low MDA content and LOX activity that reflected on membrane stability and integrity evidenced by low electric leakage value. Similar findings were detected by Lin et al. (2007) and Maksymiec et al. (2007). Consequently, well-functional membranes with adequate integrity and tight controlled permeability can be maintained, thus efficiently reducing water loss and providing high turgidity and firmness and optimum water status for metabolic activities that are evidenced by values of WUE and RWC comparable with that of control (Table 2). ...
... The abatement of H 2 O 2 and • OH and stabilization of O ·− 2 production in the Cd stress plant inoculated with T. harzianum reflected that the Cd levels remained in the soil owing to T. harzianum action are in an acceptable extent that harmfully impact plants. This may also suggest that the stimulatory effects of low concentrations of Cd on the growth of sunflower plants may be joined with a limited degree of free radical accumulation and restricted oxidative stress (Lin et al., 2007). However, when organisms are subjected to low Cd concentrations, their intrinsic GSH might be rapidly consumed because of a high cellular prerequisite for SH compounds to resist stress by prompting PC synthesis (Yamazaki et al., 2018), which may explain the increasing PCs content in our study owing to T. harzianum action. ...
... This was efficiently achieved by soil supplementation with microbes. Similar results were registered for wheat seedlings by Lin et al. (2007). ...
Background
Cadmium (Cd) is a highly toxic heavy metal. Its emission is suspected to be further increased due to the dramatic application of ash to agricultural soils and newly reclaimed ones. Thereby, Cd stress encountered by plants will exacerbate. Acute and chronic exposure to Cd can upset plant growth and development and ultimately causes plant death. Microorganisms as agriculturally important biofertilizers have constantly been arising as eco-friendly practices owing to their ability to built-in durability and adaptability mechanisms of plants. However, applying microbes as a biofertilizer agent necessitates the elucidation of the different mechanisms of microbe protection and stabilization of plants against toxic elements in the soil. A greenhouse experiment was performed using Trichoderma harzianum and plant growth-promoting (PGP) bacteria (Azotobacter chroococcum and Bacillus subtilis) individually and integrally to differentiate their potentiality in underpinning various resilience mechanisms versus various Cd levels (0, 50, 100, and 150 mg/kg of soil). Microorganisms were analyzed for Cd tolerance and biosorption capacity, indoleacetic acid production, and phosphate and potassium solubilization in vitro. Plant growth parameters, water relations, physiological and biochemical analysis, stress markers and membrane damage traits, and nutritional composition were estimated.
Results
Unequivocal inversion from a state of downregulation to upregulation was distinct under microbial inoculations. Inoculating soil with T. harzianum and PGPB markedly enhanced the plant parameters under Cd stress (150 mg/kg) compared with control plants by 4.9% and 13.9%, 5.6% and 11.1%, 55.6% and 5.7%, and 9.1% and 4.6% for plant fresh weight, dry weight, net assimilation rate, and transpiration rate, respectively; by 2.3% and 34.9%, 26.3% and 69.0%, 26.3% and 232.4%, 135.3% and 446.2%, 500% and 95.6%, and 60% and 300% for some metabolites such as starch, amino acids, phenolics, flavonoids, anthocyanin, and proline, respectively; by 134.0% and 604.6% for antioxidants including reduced glutathione; and by 64.8% and 91.2%, 21.9% and 72.7%, and 76.7% and 166.7% for enzymes activity including ascorbate peroxidase, glutathione peroxidase, and phenylalanine ammonia-lyase, respectively. Whereas a hampering effect mediated by PGP bacterial inoculation was registered on levels of superoxide anion, hydroxyl radical, electrolyte leakage, and polyphenol oxidase activity, with a decrease of 0.53%, 14.12%, 2.70%, and 5.70%, respectively, under a highest Cd level (150 mg/kg) compared with control plants. The available soil and plant Cd concentrations were decreased by 11.5% and 47.5%, and 3.8% and 45.0% with T. harzianum and PGP bacterial inoculation, respectively, compared with non-inoculated Cd-stressed plants. Whereas, non-significant alternation in antioxidant capacity of sunflower mediated by T. harzianum action even with elevated soil Cd concentrations indicates stable oxidative status. The uptake of nutrients, viz., K, Ca, Mg, Fe, nitrate, and phosphorus, was interestingly increased (34.0, 4.4, 3.3, 9.2, 30.0, and 1.0 mg/g dry weight, respectively) owing to the synergic inoculation in the presence of 150 mg of Cd/kg.
Conclusions
However, strategies of microbe-induced resilience are largely exclusive and divergent. Biofertilizing potential of T. harzianum showed that, owing to its Cd biosorption capability, a resilience strategy was induced via reducing Cd bioavailability to be in the range that turned its effect from toxicity to essentiality posing well-known low-dose stimulation phenomena (hormetic effect), whereas using Azotobacter chroococcum and Bacillus subtilis, owing to their PGP traits, manifested a resilience strategy by neutralizing the potential side effects of Cd toxicity. The synergistic use of fungi and bacteria proved the highest efficiency in imparting sunflower adaptability under Cd stress.
... The production of oxidative stress and the substitution of critical cofactors of numerous enzymes, like Zn, Fe, and Mn, are two plausible causes for the development of these illnesses. Various researchers have associated oxidative stress with introduction to high heavy metal concentrations [40,41]. Heavy metals' influence on plants, according to [42][43][44], growth suppression, physical harm, and a decay in physical, biological, and plant function are all consequences. ...
... Furthermore, excessive copper levels in growing media harmed all 3 vegetable crops, causing chlorosis in new leaves, brown, stunted, coralloid roots, as well as plant development inhibition [48,49]. [40] find that under higher Cd concentrations, the content of protein of desolate carrot (Daucus carota) and common sunflower (Helianthus annuus) decreased. Increased Zn concentrations reduced the content of protein of algae and Rapeseed (Brassica napus), according to [50]. ...
... The reduce in content of protein has been linked to increased protease activity speeding up protein breakdown [51,52] or heavy metals interfering with nitrogen metabolism. Heavy metals, according to [53], may disrupt nitrogen metabolism, reducing protein synthesis in vegetables, and are also reason for a decrease in photosynthesis, which affects protein synthesis [40]. Cd could impair the absorption of Fe, potassium, Mn & calcium [54], and the toxicity amount had been observed to be higher in the case of specific heavy metals. ...
Vegetables are a prevalent nutrition for people all over the world because they are high in important nutrients, antioxidants, and metabolites that function as buffers for acidic compounds created during digestion. Vegetables, on the other hand, absorbed both vital and poisonous substances through the soil. Possible human health concerns, including as cancer and renal damage, have been linked to the consumption of heavy metal-contaminated vegetables (HMs). Heavy metals like Cr, Mn, Fe, Ni, Cu, Zn, Cd, Pb, and Hg were found in high concentrations in popular vegetables such as Amaranthus tricolour L., Chenopodium album L., Spinacia oleracea, Coriandrum sativum, Solanum lycopersicum, and Solanum melongena. The toxicity, fortification, health hazard, and heavy metals sources grown in soil are detailed in this review study.
... The plant possesses a specific ion absorption system, that is critical for biomass and yield. The BCF and the TF were reported to be less than one in all treatment combinations in the experiment, which indicated that spinach crops grown in the presence of Pb and PM did not perform as hyperaccumulators (Lin et al. 2007;Saha et al. 2017a). For the removal of trace metals from soil, plant spends energy. ...
... When PM was added to soil, it mineralized and produced many different kinds of low-molecular-weightorganic acids (Imran et al. 2021), that might have mediated reduction in heavy metal toxicity (Minhas et al. 2021). Various researchers reported similar types of findings in various crops: Khan et al. (1999) in spinach under hydroponic culture, Lin et al. (2007) in wheat, Dotaniya et al. (2019a, b, c) in spinach and Dotaniya et al. (2020) in Indian mustard. In the experiment, it was observed that enhancing doses of lead reduced the Pb removal capacity of spinach from 0.149 to 0.037 (Table 4). ...
Direct discharge of waste into water bodies and mining are two major sources of lead contamination in ecosystems. Water scarcity promoted the usage of industrial effluent-contaminated waters for crop production, mainly in peri-urban areas. These wastewaters may contain heavy metals and pollute crop ecosystems. These metals can reach the living cell via contaminated raw foodstuffs that grow under these conditions and cause various ill effects in metabolic activities. In this study, graded levels of pressmud (0, 2.5, 5, 10 g/kg) were applied on lead imposed soil with different contamination levels (0, 100, 150, 300 mg/kg) and metal dynamics was studied in spinach crop. Experimental results showed that the addition of pressmud upto 10 mg/kg had decreased different phytoremediation indices in spinach crop. Whereas, increasing Pb level enhanced the indices’ values, indicating accumulation of significant amount of Pb in spinach biomass. However, application of pressmud (upto 10 mg/kg) reduced the bioconcentration factor (BCF) from 0.182 to 0.136, transfer factor (TF) from 0.221 to 0.191, translocation efficiency 66.11–59.34%; whereas, Pb removal enhanced from 0.063 to 0.072 over control treatment. These findings suggest that application of pressmud declined Pb concentration, the BCF and the TF in test crop which lead to less chances of adverse effect in human. These information are very useful for effectively managing wastewater irrigated agricultural crop production systems.
... •to a certain extent, a finding that is in accordance with previous investigations in wheat seedlings (Lin et al. 2007;Chen et al. 2014). In contrast to Cd, Zn is a necessary metal prosthetic group of Cu/Zn-SOD, playing a key role in maintaining the function of SOD (Wang and Jin 2005). ...
... decrease of APX activity, this is similar to the results of Lin et al. (2007), soil Cd pollution significantly reduced APX activity in heat seedlings. Apart from oxidization through the APX pathway, AsA can also be oxidized via the AO pathway with O 2 participation, resulting in a loss of AsA without a reduction of H 2 O 2 (Zhang et al. 2020d). ...
We examined the effects of Cd and Zn exposure on the photosynthetic function and the tolerant mechanisms of ROS metabolism in tobacco leaves. The results showed that the photosynthesis inhibition caused by Cd exposure was due to the limitation of both stomatal and non-stomatal factors, while Zn exposure only showed a significant effect on the Gs of tobacco leaves. Cd increased the generation rate of O2•– and the content of H2O2, but Zn did not lead to the ROS burst. Cd enhanced the POD activity, but inhibited SOD and CAT activities. The activities of SOD and POD significantly increased under Zn exposure. Cd inhibited the activity and expression of APX. The up regulation of GPX, GR and GST expression and the increase of their activities also play a positive role in the adaptation to Cd. Although Zn inhibited the activities of APX and GPX, it had little effect on other enzyme activities and protein expression in AsA-GSH cycle. TPX and TrxR activities, Trx-Prx pathway-related proteins are very sensitive to Cd. However, only PrxQ and 2-Cys Prx BAS1, which are located in chloroplast, and Trx-HFC164 were significantly down-regulated in Trx-Prx pathway under Zn exposure.
... Heavy metals from soil can enter the human body through ingestion, inhalation, or skin (11). Soil ingestion is of special concern in terms of acute exposure in children (9,(12)(13)(14)(15)(16). Heavy metals from soil can cause oxidative stress and DNA damage (17)(18)(19)(20)(21)(22)(23) leading to multiple organ damage, cancer, developmental problems, and even death (24)(25)(26)(27). ...
... Even though the hazard indices for all three exposure scenarios and all three heavy metals were lower than 1, indicating exposure below risk thresholds, this estimation does not take into account other sources of exposure, such as food, water, and air (22,(60)(61)(62)(63). ...
The aim of this study was to assess the risk of human exposure to lead (Pb), cadmium (Cd), and mercury (Hg) through agricultural soil by considering both uncertainty and variability in key exposure parameters. For this reason we collected soil samples from 29 locations in the Tuzla Canton (Bosnia and Herzegovina) and measured their metal levels with inductively coupled plasma atomic emission or absorption spectrometry (ICP-AES and ICP-AAS, respectively). The levels of Pb ranged from 13.33 to 1692.33 mg/kg, of Cd from 0.05 to 3.67 mg/kg, and of Hg from 0.02 to 2.73 mg/kg. To estimate cancer and non-cancer risks we used deterministic and semi-probabilistic methods. Lead was found to involve higher health risk than the other two heavy metals. Its hazard index (HI) decreased between population groups (children>women>men) and exposure routes (ingestion>skin contact>inhalation). Our Monte Carlo simulations indicated that Pb HIs for both adult populations had a 0.6 % probability to exceed the threshold value of 1, while in children this probability was 14.2 %. Cd and Hg showed no probability to exceed the threshold in any scenario. Our simulation results raise concern about possible adverse health effects of heavy metals from soil, especially in children. It is very important to continue monitoring environmental pollution and assess human health risk, not only with respect to soil, but also with other important environmental compartments, such as air and water.
... In order to limit Cd-induced oxidative damage to membrane systems, cell organelles, and DNA, plants exhibit various physiological and transcriptional responses that avoid or alleviate the toxic effects of reactive oxygen species (ROS) (He et al., 2013;Redovniković́ et al., 2017). Various enzymatic and nonenzymatic antioxidants play key roles in scavenging ROS (He et al., 2013;Lin et al., 2007;Guo et al., 2015). For example, the ascorbate-glutathione (AsA-GSH) metabolism cycle including AsA, GSH and the related enzymes, complemented with other antioxidant enzymes is a significant antioxidant protection system against ROS . ...
... Herein, the activities of the SOD and CAT in leaves were both increased by the Cd treatment, indicated that antioxidant defense system may play important roles in the response and tolerance of A. auriculiformis to Cd toxicity. MDA and GSH are physiological indicators of the plant response to various abiotic stresses, and they reflect the production levels and detoxification of ROS (Shah et al., 2001;Lin et al., 2007). The significant increase in MDA in A. auriculiformis leaves in response to the Cd treatment indicated that Cd accumulation in leaves enhanced membrane lipid peroxidation (Fig. S1). ...
Cadmium (Cd) has toxic effects on plants. Nitrogen (N), an essential element, is critical for plant growth, development and stress response. However, their combined effects on woody plants, especially in N-fixing tree species is still poorly understood. Our previous study revealed that the fast-growing Acacia auriculiformis showed strong Cd tolerance but the underlying mechanisms was not clear, which constrained its use in mine land reclamation. Herein, we investigated the physiological and proteomic changes in A. auriculiformis leaves to reveal the mechanisms of Cd tolerance and toxicity without N fertilizer (treatment Cd) and with excess N fertilizer (treatment CdN). Results showed that Cd tolerance in A. auriculiformis was closely associated with the coordinated gas exchange and antioxidant defense reactions under Cd treatment alone. Exogenous excessive N, however, inhibited plant growth, increased Cd concentrations, and weaken photosynthetic performance, thus, aggregated the toxicity under Cd stress. Furthermore, the aggregated Cd toxicity was attributed to the depression in the abundance of proteins, as well as their corresponding genes, involved in photosynthesis, energy metabolism (oxidative phosphorylation, carbon metabolism, etc.), defense and stress response (antioxidants, flavonoids, etc.), plant hormone signal transduction (MAPK, STN, etc.), and ABC transporters. Collectively, this study unveils a previously unknown physiological and proteomic network that explains N diminishes Cd detoxification in A. auriculiformis. It may be counterproductive to apply N fertilizer to fast-growing, N-fixing trees planted for phytoremediation of Cd-contaminated soils.
... PC was not differ significantly between resistant and susceptible genotypes. PC and MDA were reported to increase under abiotic stresses such as heavy metals, salt, and alkaline-saline stresses (Mukherjee and Choudhuri 1983;Lin et al. 2007;Lamhamdi et al. 2013;El-Saadony et al. 2017;Hafez et al. 2020;Alamer and Fayez 2020). Moreover, previous studies reported that PC and MDA are important in improving stripe rust tolerance in wheat (Chen et al. 2015;Lone et al. 2016). ...
Wheat stripe rust and alkaline-saline soils are two major factors affecting wheat planting areas globally. Producing wheat genotypes that tolerate the combined effect of these two factors will enhance wheat production. A set of 16 wheat genotypes was evaluated for yield and stripe rust adult plant resistance under normal and alkaline-saline (AS) soils. The effects of single stripe rust stress (Yr) as well as combined Yr + AS stress were tested on yield and physiological parameters. Similar correlations were observed between each pair of yield traits, physiological traits, and stripe rust resistance under the tested environments. Misr 4 showed high performance under combined stress, as well as high stripe rust resistance. Combined Yr + AS stress had a significantly negative effect on yield compared to Yr stress alone. Increases in chlorophyll a, chlorophyll b, and and proline content (PC) improved wheat performance under combined stress conditions and enhanced stripe rust resistance. However, these factors did not play a role in improving wheat performance under single Yr stress. The tested traits could be used in selecting high-performance genotypes under single Yr and combined Yr + AS stresses, except for total chlorophyll and plant height. Understanding the role of increased wheat adaptation to combined Yr + AS stress will accelerate wheat breeding programs by producing genotypes that can confront the harmful effects of global climate change.
... In response to Cd stress, reactive oxygen species (ROS, such as singlet oxygen, hydroxyl radicals, hydrogen peroxide, and superoxide anion radicals) are produced in plant cells, damaging carbohydrates, DNA, and proteins and ultimately causing cell death (Lin et al., 2007;Rasool et al., 2013;Sachdev et al., 2021;Tran & Popova, 2013). Additionally, ROS contributes to the destruction of polyunsaturated lipids in cell membranes, causing malondialdehyde (MDA) to form, which can be used as a biomarker to evaluate the level of oxidative stress (Gill & Tuteja, 2010;Mishra et al., 2014;Shahabivand et al., 2016). ...
Due to environmental pollution, the risk of cadmium stress for crops is soaring, so researchers are exploring inexpensive solutions to enhance cultivated crops in contaminated soil. Using microorganisms to reduce cadmium risk has been one of the most effective strategies in recent decades. Serendipita indica (Piriformospora indica) is one of the best endophyte fungi that, in addition to reducing heavy metal stress for crops, can significantly reduce the threat of other abiotic stresses. As part of this research, cadmium in soil has been investigated, as well as its effects on plants' morphophysiological and biochemical characteristics. The present review has also attempted to identify the role of Serendipita indica in improving the growth and performance of crops, as well as its possible effect on reducing the risk of cadmium. The results showed that Serendipita indica enhance the growth and productivity of plants in contaminated environments by improving soil quality, reducing cadmium absorption, improving the activity of antioxidant enzymes and secondary metabolites, raising water and mineral absorption, and altering morphophysiological structures.
... The membrane integrity, catalase activity, and glycine betaine content exhibited the inverted U-shaped curves in wheat roots with seeds exposed to Cd from 5 to 1000 µM (Issaad et al. 2022). A slight stimulatory impact on wheat seedling growth was observed within low Cd concentrations (< 3.3 mg kg −1 ) in the soil (Lin et al. 2007). The endpoints of root and shoot length, chlorophyll content, and MDA content of wheat showed hormesis and paradoxical responses when wheat was exposed to several different pollutants including Cd, lead, copper, and manganese (Erofeeva 2014). ...
Cadmium is commonly recognized as toxic to plant growth, low-level Cd has promoting effects on growth performance, which is so-called hormesis. Although Cd toxicity in wheat has been widely investigated, knowledge of growth response to a broad range of Cd concentrations, especially extremely low concentrations, is still unknown. In this study, the morphological, physiological, and biochemical performance of wheat seedlings to a wide range of Cd concentrations (0–100 µΜ) were explored. Low Cd treatment (0.1–0.5 µM) improved wheat biomass and root development by enhancing the photosynthetic system and antioxidant system ability. Photosynthetic rate (Pn) was improved by 5.72% under lower Cd treatment (1 µΜ), but inhibited by 6.05–49.85% from 5 to 100 µΜ. Excessive Cd accumulation induced oxidative injury manifesting higher MDA content, resulting in lower photosynthetic efficiency, stunted growth, and reduction of biomass. Further, the contents of ascorbate, glutathione, non-protein thiols, and phytochelatins were improved under 5–100 µΜ Cd treatment. The ascorbate peroxidase activity in the leaf showed a hormetic dose–response characteristic. Correlation analysis and partial least squares (PLS) results indicated that antioxidant enzymes and metabolites were closely correlated with Cd tolerance and accumulation. The results of the element network, correlation analysis, and PLS showed a crucial role for exogenous Cd levels in K, Fe, Cu, and Mn uptake and accumulation. These results provided a deeper understanding of the hormetic effect of Cd in wheat, which would be beneficial for improving the quality of hazard and risk assessments.
... However, in excess, they become potentially toxic, inducing oxidative stress, toxicity, and surplus accumulation of reactive oxygen species (ROS) in plants [8]. This overproduction of ROS can result in DNA and RNA damage, enzyme inhibition, and protein oxidation in plant cells [9]. Lead (Pb) is one of the widespread non-biodegradable and toxic heavy metal elements in the environment [5,10,11]. ...
In recent years, the remediation of heavy metal-contaminated soils has attracted great attention worldwide. Previous research on the removal of toxic heavy metals from wastewater effluents through adsorption by typical solid wastes (e.g., fly ash and coal gangue) has mainly focused on the control of wastewater pollutants. In this study, a coal gangue (CG) by-product from Hancheng City was used as a raw material to prepare polymeric aluminum chloride-loaded coal gangue-based porous carbon (PAC-CGPC) by hydrothermal synthesis. This material was subsequently employed to assess its performance in mitigating Pb2+ in soils. In addition, the effects of the pore structure of the prepared material on the adsorption rates, adsorption mechanisms, and plant root uptakes of soil Pb2+ were investigated in this study. The raw CG and prepared PAC-CGPC materials exhibited specific surface areas of 1.8997 and 152.7892 m2/g, respectively. The results of adsorption kinetics and isotherms indicate that the adsorption of Pb2+ based on PAC-CGPC mainly follows a pseudo-second-order kinetic model, suggesting that chemisorption may be the dominant process. In addition, the adsorption isotherm results showed that the Freundlich model explained better the adsorption process of Pb2+, suggests that the adsorption sites of lead ions on APC-CGPC are not uniformly distributed and tend to be enriched in APC, and also shows the ion exchange between aluminum and lead ions. The thermodynamic model fitting results demonstrated the occurrence of spontaneous and exothermic PAC-CGPC-based adsorption of Pb2+, involving ion exchange and surface complexation. The effects of the PAC-CGPC addition on soybean plants were further explored through pot experiments. The results revealed substantial decreases in the Pb2+ contents in the soybean organs (roots, stems, and leaves) following the addition of the PAC-CGPC material at a dose of 3% compared with the control and raw CG groups. Furthermore, the addition of the PAC-CGPC material at a dose of 3% effectively reduced the bioavailable Pb2+ content in the soil by 82.11 and enhanced soybean growth by 15.3%. These findings demonstrated the inhibition effect of the PAC-CGPC material on the translocation of Pb2+ in the soybean seedlings. The modified CG adsorbent has highly pore structure and good hydrophilicity, making it prone to migration in unsaturated soils and, consequently, enhancing Pb2+ immobilization. This research provides theoretical support for the development of CG-based materials capable of immobilizing soil pollutants.
... This, in order to generate reducing power, which may play a role in redox mechanisms in plant cells (Chaffei et al. 2009;Lopez-Milan et al. 2009). It has been widely described that Cd exposure causes oxidative stress, and accordingly several enzymes and metabolites involved in defense mechanisms against oxidative stress elicited by Cd ( Dong et al. 2006;Lin et al. 2007). Data presented showed that in ammonium tomato leaves, PEPC and ICDH activities decreased under Cd conditions. ...
It was known that cadmium (Cd) toxicity evoked protective reactions that could induce cell death. But the question arises was the effect of nitrogen regime on Cd plant responses. To got more explications, we examined the effects of Cd in NH 4 +-fed tomato plants treated continuously or transitory by 25µM of CdSO 4. Reduction of glutamine synthetase (GS) activity by Cd disappeared progressively after transfer of Cd-stressed tomato to control medium. It has been shown that Cd enhanced activity and protein accumulation of cytosolic isoenzyme (GS1) and reduced those of chloroplastid isoenzyme (GS2). When Cd-treated tomato plants were transferred on control medium, GS1 protein level diminished. Whereas, GS2 protein level remained unchanged. Our data showed that Cd stimulated the seven isoenzymes activities of glutamate deshydrogenase (NADH-GDH). Cadmium reduced too, phosphoenolpyruvate carboxylase (PEPC) and isocitrate dehydrogenase (ICDH) activities. Thus, we suggested that CO 2 anaplerotic fixation into organic acids was secondary in leaves. Especially as photosynthetic rate (Amax) and photochemical quenching (qp) were stimulated and non-photochemical quenching was reduced (NPQ) by Cd in leaves of NH 4 +-fed tomato.
... This may be because the roots were the first organ that came into contact with Cd. Cd is mainly enriched in roots, with only a small fraction transferred to the ground, and the above-ground part of the plant is more sensitive to Cd, and even low concentrations of Cd will also cause damage to it, and to avoid this damage, plants will retain Cd in the roots through various mechanisms [61]. ...
Heavy metal (HM) contamination poses a serious threat to safe crop production and human health, and different maize inbred lines respond differently to cadmium (Cd) stress. However, the morphological and physiological characteristics of maize inbred lines seedlings are not clear under Cd stress. In this study, we analyzed the agronomic traits and physiological and biochemical indices of inbred maize seedlings under Cd stress in the seedling stage using the inbred lines Kui3, CML118, Mo17, B73, and B77 as the materials. These five inbred maizes were treated with five different concentrations of Cd (0, 1, 3, 5, and 7 mg L−1, respectively) were applied and the indices of the maize seedlings determined on day 15. The aboveground and belowground biomass of five maize inbred lines seedlings showed a decreasing trend under Cd stress. Leaf relative water content and SPAD values also decreased, but the overall decrease in relative water content was small, and the differences were not significant. Surprisingly, Cd stress affected the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), leading to enhanced mem-brane lipid peroxidation. The cadmium content varied greatly between varieties under Cd stress, but all of them had lower Cd content above ground than below ground, and the varieties with the highest and lowest transfer coefficients were Mo17 (0.33–0.83) and B73 (0.06–0.44), respectively. Kui3 had the greatest difference in soluble protein content under Cd stress, which showed a de-creasing trend, and the soluble sugar content was significantly decreased in general compared to that of CK. The soluble sugar content was higher than CK under Cd treatment, and the proline content of the maize seedlings of all of the inbred lines showed an increasing trend compared to CK. Overall, there were significant genotypic differences in the Cd stress response to Cd toxicity in the maize inbred lines seedlings, and, in general, this study helps us to understand the mechanism of maize inbred lines seedlings response to Cd stress. It provides a theoretical basis for the se-lection and breeding of varieties, and food safety.
... Analogously to what happens with the Cd, exposure to SeNPs at low doses could stimulate the antioxidant enzymes and enhance their activities. However, at high levels, the application of SeNPs may induce stress and disturb enzyme synthesis, as reported for Cd (Lin et al., 2007;Vögelli-Lange and Wagner, 1990). Other studies showed that the application of Se at low concentrations has beneficial effects on plants, stimulating seedling growth, participating in the antioxidant defense system, and increasing tolerance against abiotic stress (Andrade et al., 2018;Yao et al., 2010). ...
... The decline in foliar chlorophyll content restricted photosynthetic rates and caused growth reduction. Similar conclusions have been drawn by Azhar et al. (2019) and Rehman et al. (2023), where Cd-induced reductions in wheat and rice plant height were attributed to the potential denaturation of protein bonds, specifically H-S protein bonds, resulting in hindered plant growth (Lin et al., 2007). Furthermore, it has been observed that Cd negatively impacts the dry biomass of roots, shoots, and grain yield ( Fig. 1), primarily through physiological changes (Fig. 2) and the limited uptake of essential nutrients. ...
Cadmium (Cd) accumulates in the vegetative tissues of rice and wheat crops, posing a serious threat in the food chain. A long-term field experiment was conducted to investigate the effects of rice husk biochar (RHB), farm manure (FM), press mud (PrM), and poultry manure (PM) on the growth, yield, and economics of wheat and rice crops grown with sewage water. The results showed that RHB increased wheat plant height (27, 66, 70%), spike-length (33, 99, 56%), straw yield (21, 51, 49%), and grain yield (42, 63, 65%) in year-1, year-2, and year-3, than respective controls. For rice crop, RHB showed the maximum increase in plant height (64, 92, 96%), spike length (55, 95, 90%), straw yield (34, 53, 55%), and grain yield (46, 66, 69%) each year (2019–2021), compared to their respective controls. The Cd immobilization was increased by the application of RHB while other treatments followed FM > PrM > PM > control in each year of wheat and rice crops. For year-1, benefit-cost ratio remained maximum with the application of FM while for the 2nd and 3rd years in sequence, RHB proved more economical than other treatments and consistently produced wheat and rice with lower Cd concentration than FM, PrM, and PM in grains. This long-term experiment suggested that the application of organic amendments consistently increased biomass of rice and wheat and decreased the Cd concentration in tissues. The RHB remained more effective compared with FM, PrM, and PM in terms of yield, low Cd accumulation and economics of rice and wheat crops.
... However, in our study, we found that Cd pollution at a concentration of 1 mg kg − 1 did not induce a significant rise in MDA levels in the leaves of both species, regardless of soil type, indicating that both species can tolerant such a level of Cd pollution. Similarly, Lin et al. (2007) found that only when the Cd pollution exceeded 10 mg kg − 1 , there was an increase in cell membrane permeability and peroxidation extent in the leaves of Triticum aestivum, as indicated by MDA levels. Under alkaline purple soils, the significant increase in H 2 O 2 content in the leaves of both species may mainly act as a second messenger to activate gene expression of antioxidant enzymes and other metabolic pathways related to oxidative stress (Saxena et al., 2016). ...
... 1-2, Table S3, S4). The negative effects of Cd on wheat seedling have already been reported by our previous research [118,78] and other studies [39,49,79]. As a non-essential but beneficial element, Si is recognized its potential roles in protecting plant from adverse environment [64]. ...
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.
... Such a variable response to Cd stress among genotypes was also reported in a small number of maize genotypes and other crops. 32,33,34 Shoot dry weight, primary root depth, and total root length were often used as key traits for assessing genotype tolerance to stress due to the sensitivity to Cd toxicity. 17,19,35 However, the single-trait screening method could overlook other important traits and their interactions. ...
BACKGROUND
Cadmium (Cd) contamination in farmland is a serious environmental and safety issue affecting plant growth, crop productivity, and human health. This study aimed to investigate genotypic variation in root morphology and Cd accumulations under moderate Cd stress among diverse maize genotypes. Twenty maize genotypes with contrasting root systems were assessed for Cd tolerance 39 days after transplanting (V6, six‐leaf stage) under 20 μmol L⁻¹ CdCl2 using a semi‐hydroponic phenotyping platform in a glasshouse.
RESULTS
Cadmium stress significantly inhibited plant growth across all genotypes. Genotypic variation in response to Cd toxicity was apparent: shoot dry weight varied from 0.13 (genotype NS2020) to 0.35 g plant⁻¹ (Dongke301) with deductions up to 63% compared with non‐Cd treatment (CK). Root dry weight of 20 genotypes ranged from 0.06 (NS2020) to 0.18 g plant⁻¹ (Dongke301) with a deduction up to 56%. Root length ranged from 2.21 (NS590b) to 9.22 m (Dongke301) with a maximal decline of 76%. Cadmium‐treated genotypes generally had thicker roots and average diameter increased by 34% compared with CK. Genotypes had up to 3.25 and 3.50 times differences in shoot and root Cd concentrations, respectively. Principal component and cluster analyses assigned the 20 genotypes into Cd‐tolerant (five genotypes) and Cd‐sensitive (15 genotypes) groups.
CONCLUSIONS
Maize genotypes varied significantly in response to moderate Cd stress. Cadmium‐tolerant genotypes optimized root morphology and Cd accumulation and distribution. This study could assist in the selection and breeding of new cultivars with improved adaptation to Cd‐contaminated soil for food and feed or land remediation purposes. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
... However, phytoavailability and uptake of Cd in soil is influenced by many factors, including soil pH or the presence of other ions, and is also dependent on the particular plant species (Haider et al., 2021). Nevertheless, low Cd concentrations can have a stimulatory effect on plant growth as was previously demonstrated in many plants, including rice or wheat (Aina et al., 2007;Lin et al., 2007). ...
Hydroponic experiments were performed to examine the effect of prolonged sulfate limitation combined with cadmium (Cd) exposure in Arabidopsis thaliana and a potential Cd hyperaccumulator, Nicotiana tabacum. Low sulfate treatments (20 and 40 µM MgSO4) and Cd stress (4 µM CdCl2) showed adverse effects on morphology, photosynthetic and biochemical parameters and the nutritional status of both species. For example, Cd stress decreased NO3⁻ root content under 20 µM MgSO4 to approximately 50% compared with respective controls. Interestingly, changes in many measured parameters, such as chlorophyll and carotenoid contents, the concentrations of anions, nutrients and Cd, induced by low sulfate supply, Cd exposure or a combination of both factors, were species-specific. Our data showed opposing effects of Cd exposure on Ca, Fe, Mn, Cu and Zn levels in roots of the studied plants. In A. thaliana, levels of glutathione, phytochelatins and glucosinolates demonstrated their distinct involvement in response to sub-optimal growth conditions and Cd stress. In shoot, the levels of phytochelatins and glucosinolates in the organic sulfur fraction were not dependent on sulfate supply under Cd stress. Altogether, our data showed both common and species-specific features of the complex plant response to prolonged sulfate deprivation and/or Cd exposure.
... In the presence of stress, senescence occurs earlier. Stunted growth is the first observable response when plants such as tomato, wheat, maize and beans are stressed (Lin et al., 2007;Sobkowiak and Deckert, 2003;Sandalio et al., 2001;Adriano, 2001;Baccouch et al., 1998). Roots are the first structures damaged and affected by trace metal uptake in plants. ...
... The antioxidant enzyme system is an important resistance mechanism for plants to respond to various environmental stresses and plays an important role in the process of plants adapting to adversity (Lin et al. 2007). In Lanping County, Yunnan Province, where the soil is heavily polluted by heavy metals, maize is the main local food crop. ...
Pb, Cu, Cd, Zn content of soil in mining areas and abandoned land, flats of the Pijiang River and farmlands were investigated. On this basis of soil heavy metal pollution, the changes of antioxidant enzyme system in maize (Qiandan 88) under different Pb concentrations (0, 20, 40, 60, 80, 100, 150, 200, 500, 1000, 2000, 3000 mg/L) stress were studied. The results show that the content of Pb, Cu, Cd, and Zn in soil is the highest in mining areas and abandoned land, followed by flats of the Pijiang River > farmlands, and that the variation range of Pb, Cu, Cd in mining areas and abandoned land are 106.40–2564.72, 14.83–490.88, 22.57–712.77 mg/kg, respectively, which are higher than that of the other land use types. When maize is under stress of 20–500 mg/L Pb concentration, T-SOD activity of maize leaves increase with the increase of Pb concentration and the highest value is 50.21 U/mg prot, but under Pb concentration > 1000 mg/L stress, T-SOD activity of maize leaves decrease gradually. The activity of POD decreases with the increases of Pb concentration, and the lowest POD activity of leaves in maize with the value of 93.24 U/mg prot is appeared in Pb 1000 mg/L concentration treatment group. MDA content in leaves of maize increases with the increase of the Pb concentration and the highest value is 101.98 nmol/mg prot, then the content of MDA decreases gradually when the Pb concentration is more than 500 mg/L, which indicates that the membrane lipid peroxidation of maize leaves under high concentration of Pb stress is serious and leads to the cell damage.
... The positive effects of environmental stress on plant growth have been poorly discussed in the literature, and the mechanisms remain unknown [34]. Moreover, few studies have shown that high temperature and drought stress can trigger a series of physiobiochemical compensations in plants. ...
High temperatures and droughts following winter dormancy can negatively affect seedling growth and mortality. An open-field experiment was conducted to study the growth and mortality of Larix kaempferi seedlings in response to spring warming and drought treatments and to determine whether seedlings could regain their growth capability once the treatments were discontinued. In May 2020, 1-year-old seedlings were exposed to four treatments: control, warming-only, drought-only, and the combined warming and drought. Drought treatment reduced the seedling height and root collar diameter and increased the mortality rate. The combined warming and drought treatments had the highest mortality rates, followed by the drought, control, and warming treatments. However, after the cessation of the treatments, the combined warming and drought treatments increased seedling height, root collar diameter, and individual seedling biomass because the high mortality rate relaxed competition among seedlings. This suggests that the effects of low competition on the surviving seedlings may mitigate the negative effects of warming and drought on seedling growth. Our study demonstrates that despite the high mortality and decreased growth during the treatment period, seedlings subjected to combined high temperature and drought stress showed short-term high levels of growth compared to seedlings subjected to a single stress.
... Heavy metals are extremely poisonous and are extremely detrimental to soil and plants [1]. Zinc, Copper, and other contaminants such as Cadmium, Arsenic, Lead, Chromium, Nickel, and others are required by the human body for structural and essential activities in very minimal quantity, however, a higher concentration is extremely toxic [2][3][4][5]. Heavy metals are industrial waste products that end up as contaminants in the soil [6][7][8][9][10]. Agriculture is also a source of these contaminants. ...
Heavy metals in the environment can cause serious health problems to plants and animals. Plants absorb Pb from the soil as well as from the air. Experiments in the laboratory and in the pot-house conditions were carried out at the center for the environmental sciences, the University of Sindh, Jamshoro to see the effect of lead acetate Pb(C 2 H 3 O 2) 2 on the yield and yield attributes of wheat (Triticum aestivum L.). Experiments were conducted in a factorial design with three replicates. Six wheat varieties namely Abadgar, SKD-1, Anmol-91, Tj-83, Imdad, and Sonalika, were tested for lead acetate tolerance. Four treatment T1= Control (no lead application), T2= 30ppm Pb acetate, T3= 50ppm Pb acetate, and T4= 70ppm Pb acetate were designed. Results indicated that variety SKD-1 produced significantly higher shoot and root length at 30, 50, and 70ppm lead acetate stress than other varieties. An analysis of variance revealed that lead had a considerable impact on yield and yield-related characteristics except for SPAD chlorophyll, the genotype-treatment interaction was significant for all characteristics. The varieties Imdad and SKD-1 produced the highest grains spike-1 (39.6 and 37.0) and grain yields plant-1 (14.33 and 13.0gram) respectively, at the highest stress level and are declared as tolerant cultivars.
... Yang et al. (2007) observed a significantly positive correlation between an increase in H 2 O 2 and root elongation inhibition when soybean seedlings were treated with Cd, and excessive H 2 O 2 was removed by POD in soybean seedlings. Lin et al. (2007) reported that MDA content in wheat seedling leaves was significantly increased under Cd stress (10 mg kg − 1 ), and SOD and CAT activities did not change significantly at Cd concentration of 3.3 mg kg − 1 ; however a violent fluctuation in antioxidant enzyme activities was observed at high Cd concentration. Guo et al. (2019) showed that different wheat tolerance to Cd stress was due to differences between wheat cultivars, and the activity of SOD, POD and CAT, and MDA concentration in a Cd-tolerant cultivar (Bainong 160) was increased to alleviate oxidative damage; however, no significant changes were observed in Bainong 160 biomass compared to controls under Cd stress. ...
The purpose of the study was to compare differences in Cd²⁺ flux in the vicinity of root tips of 20 soybean cultivars under mild Cd stress conditions using non-invasive micro-test technology (NMT). The results indicated that Cd²⁺ influx to the root tips under mild Cd treatment was higher compared to controls. Cd²⁺ influx showed an obvious spatial distribution, with the highest Cd²⁺ influx measured 300 μm from the root tips, and a gradually decrease above and below this site. The cultivar Liaodou32 had a lower Cd uptake (3.40 pmol cm⁻² s⁻¹), while Liaodou23 had a relatively higher Cd uptake (66.37 pmol cm⁻² s⁻¹). Cluster analysis showed that the order of the average Cd²⁺ influx of the cultivars at a distance of 300 μm from the root tips was as follows: high-uptake cultivars (61.80 pmol cm⁻² s⁻¹)>medium-high-uptake cultivars (33.92 pmol cm⁻² s⁻¹)>medium-low-uptake cultivars (19.78 pmol cm⁻² s⁻¹)>low-uptake cultivars (4.84 pmol cm⁻² s⁻¹). We also analyzed physiological responses of different soybean cultivars to mild Cd stress. The results indicated that mild Cd stress could inhibit soluble protein production and root vigor among individual soybean cultivars. Moreover, stress increased SOD, CAT and POD activities and MDA content in root tissues. It should be noted that the physio-biochemical indicators of low-uptake cultivars did not change significantly after exposure to mild Cd stress compared to controls. Pearson's correlation analyses showed that all physio-biochemical indicators were significantly positively associated with influx, except of root SP and biomass. PCA analysis demonstrated that root vigor was a dominant factor causing the differences in Cd tolerance among different soybean seedling cultivars. NMT is of great significance for safe utilization of contaminated soil to distinguish the cultivars with different enrichment capacity for heavy metals from different crop cultivars.
... These results were in good agreement with those reported in previous studies (Saleh et al. 2020;Rizwan et al. 2016;Ci et al. 2010). This finding might be caused by excessive Cd, thereby reducing the total chlorophyll and net photosynthetic rate necessary for wheat growth and increasing the concentration of malondialdehyde in leaves (Adrees et al. 2020;Guo et al. 2019;Kaya et al. 2019;Lin et al. 2007). The low variation of Cd concentration in grains derived from these characteristics might be influenced by additional features such as the ability of roots to absorb Cd and/or translocation form of Cd among the root, stem, leaf, and grain. ...
The cadmium (Cd) and micronutrient contents in grains were used as screening indicators through a pot experiment, and the hierarchical cluster analysis was used to select wheat cultivars with low Cd and high micronutrient contents. The potential human health risks caused by wheat intake and the relationship between the Cd concentration in wheat grains and 12 agronomic traits were also investigated using the risk assessment model and logistic equation fitting, respectively. Yannong-23, Zhongmmai-175, and Luyuan-502, the main wheat cultivars promoted in the Huang-Huai-Hai region of China, were screened for low Cd accumulation and high micronutrient. Health risk assessment results demonstrated that children showed a high noncarcinogenic risk and that adults posed a high carcinogenic risk. The results of the agronomic trait analysis showed that low-Cd accumulation wheat cultivars had high spikelet number and fresh and dry weights of root, stem, and leaf (p < 0.05). Logistic curve fitting results showed that among all agronomic traits, the root dry weight was the most suitable factor with remarkable goodness of fit and showed a significant negative correlation. The Cd concentration in wheat grains could be predicted by the logistic curve equation obtained by fitting this trait. Results provided theoretical support for the safe use of slightly to moderately contaminated farmland, formulation of health risk management policies for different populations, and breeding of high-quality wheat.
... Similar findings were also demonstrated in M. sinensis var. giganteus (Arduini et al., 2004) and Triticum aestivum (Lin et al., 2007). Some investigations demonstrated Cd 2+ at a lower concentration can enhance photosynthesis and have a positive relationship with zinc, calcium, copper, and magnesium (Rivelli et al., 2014;Zhang et al., 2014). ...
The role of iron plaque in Miscanthus sac�chariforus seedling growth and cadmium ion (Cd2+) uptake, translocation, and tolerance was explored. The seedlings were cultivated for 10 d in half-strength Hoagland’s nutrient solution containing 0 mg L−1, 1.0 mg L−1, 5.0 mg L−1, 10.0 mg L−1, and 20.0 mg L−1 Cd2+ after iron plaque formation induced by 30 mg L−1 ferrous ion (Fe2+). Most of the Cd2+ were immobilized in the plant roots, and its concentration increased by 760.52–1872.01% in the non-induced and by 230.29-661.01% in the induced groups com�pared to the control. Compared with the non-induced
group, in the induced group, Cd2+ concentration in the roots decreased by 33.30–42.68%, and a simi�lar tendency was also observed in the shoots. Iron plaque formation could efectively contribute to Cd2+uptake and immobilization, and Cd2+ concentration
increased by 96.78–99.04% compared to the con�trol. This process accounted for the decreased Cd2+concentration in the roots, indicating the iron plaque functioned as a barrier against Cd2+ entering into the roots. When the seedlings were exposed to Cd2+ for 15 d, the translocation factor for Cd2+ in the induced group increased by 32.50–42.03% in comparison with that in the non-induced group, indicating the plaque
signifcantly facilitated Cd2+ translocation from roots to shoots. The iron plaque eliminated the negative efects of higher Cd2+ concentration on shoot biomass as observed in the induced group and could maintain the Cd2+ tolerance of the seedlings.
... Indeed, some studies show its induction by the metal treatment, while others reveal an inhibitory effect on the activity of the enzyme. Indeed, the induction of GR activity can be attributed to an increase in its substrate (GSSG: oxidized form of glutathione) (Lin et al. 2007). The results obtained are in line with the work carried out on Hibiscus cannabinus L. by Feng-tao et al. (2013) where he reported that the glutathione reductase activity (GR) was much larger than the control, ensuring that sufficient quantities of GSH were available to respond to the cadmium stress. ...
In this study, we investigated the efect of the homeopathic drug Zincum Metallicum (ZM) on zinc (Zn) toxicity in the plant
species Lepidium sativum L. We focused on growth parameters, Zn uptake and numerous biochemical parameters. Seedlings
were hydroponically subjected during 7 days to 0.05, 500, 1000, 1500 and 2000 µM Zn2+, in the absence or presence of 15ch
or 9ch ZM. In the absence of ZM, Zn induced negative efect on growth especially at the dose of 2 mM. Zn induced also
chlorosis, reduced total chlorophyll and/or carotenoid content and increased the level of malondialdehyde (MDA). Under
Zn toxicity (500, 1000 and 1500 µM), the superoxide dismutase (SOD), catalase (CAT), gaiacol peroxidase (GPX) and glutathione reductase (GR) activities were increased or not signifcantly afected, while at 2000 µM Zn afected the activity of
these enzymes. At the highest Zn level (2 mM), proline and total polyphenol and favonoid contents were markedly increased
in leaves and roots of L. sativum. Additionally, ZM supply considerably ameliorated the plant growth, photosynthetic pigment
contents and increased non-enzymatic antioxidant molecules and enzymatic activities against Zn-induced oxidative stress.
Our data suggest that homeopathic properties of ZM may be efciently involved in the restriction of Zn-induced oxidative
damages, by lowering Zn accumulation and translocation in the leaves and roots of Lepidium sativum L.
... Indeed, some studies show its induction by the metal treatment, while others reveal an inhibitory effect on the activity of the enzyme. Indeed, the induction of GR activity can be attributed to an increase in its substrate (GSSG: oxidized form of glutathione) (Lin et al. 2007). The results obtained are in line with the work carried out on Hibiscus cannabinus L. by Feng-tao et al. (2013) where he reported that the glutathione reductase activity (GR) was much larger than the control, ensuring that sufficient quantities of GSH were available to respond to the cadmium stress. ...
In this study, we investigated the effect of the homeopathic drug Zincum Metallicum (ZM) on zinc (Zn) toxicity in the plant species Lepidium sativum L. We focused on growth parameters, Zn uptake and numerous biochemical parameters. Seedlings were hydroponically subjected during 7 days to 0.05, 500, 1000, 1500 and 2000 µM Zn2+, in the absence or presence of 15ch or 9ch ZM. In the absence of ZM, Zn induced negative effect on growth especially at the dose of 2 mM. Zn induced also chlorosis, reduced total chlorophyll and/or carotenoid content and increased the level of malondialdehyde (MDA). Under Zn toxicity (500, 1000 and 1500 µM), the superoxide dismutase (SOD), catalase (CAT), gaiacol peroxidase (GPX) and glutathione reductase (GR) activities were increased or not significantly affected, while at 2000 µM Zn affected the activity of these enzymes. At the highest Zn level (2 mM), proline and total polyphenol and flavonoid contents were markedly increased in leaves and roots of L. sativum. Additionally, ZM supply considerably ameliorated the plant growth, photosynthetic pigment contents and increased non-enzymatic antioxidant molecules and enzymatic activities against Zn-induced oxidative stress. Our data suggest that homeopathic properties of ZM may be efficiently involved in the restriction of Zn-induced oxidative damages, by lowering Zn accumulation and translocation in the leaves and roots of Lepidium sativum L.
... In the presence of stress, senescence occurs earlier. Stunted growth is the first observable response when plants such as tomato, wheat, maize and beans are stressed (Lin et al., 2007;Sobkowiak and Deckert, 2003;Sandalio et al., 2001;Adriano, 2001;Baccouch et al., 1998). Roots are the first structures damaged and affected by trace metal uptake in plants. ...
Over the last few decades, the use of pesticides and discharge of industrial and domestic wastewater on water surfaces have increased. Especially, Copper (Cu) pollution in aquatic ecosystems could constitute a major health problem, not only for flora and fauna but also for humans. To cope with this challenge, environmental monitoring studies have sought to find Cu-specific biomarkers in terrestrial and aquatic flora and/or fauna. This review discusses the toxic effects caused by Cu on the growth and development of plants, with a special focus on aquatic plants. While copper is considered as an essential metal involved in vital mechanisms for plants, when in excess it becomes toxic and causes alterations on biomarkers: biochemical (oxidative stress, pigment content, phytochelatins, polyamines), physiological (photosynthesis, respiration, osmotic potential), and morphological. In addition, Cu has a detrimental effect on DNA and hormonal balance. An overview of Cu toxicity and detoxification in plants is provided, along with information regarding Cu bioaccumulation and transport. Awareness of the potential use of these reactions as specific biomarkers for copper contamination has indeed become essential.
... Comparable changes in the enzymatic activities under different concentrations of heavy metals specifically Cd toxicity have been reported earlier 67,68 . However, some of the studies are in deviation with our results reporting a decrease in SOD activity under the higher concentration of Cd level [69][70][71] . The deviation in results could ensue due to the difference in the time duration of Cd stress applied, the intensity of Cd, and specifically plant stage and cultivar. ...
Heavy metals contaminate the soil that alters the properties of soil and negatively affect plants growth. Using microorganism and plant can remove these pollutants from soil. The present investigation was designed to evaluate the induced effect of Bacillus pumilus on maize plant in Cadmium (Cd) contaminated soil. Three different concentrations of Cd (i.e. 0.25, 0.50 and 0.75 mg kg−1) were applied in soil under which maize plants were grown. The germination percentage, shoot length, leaf length, number of leaves, root length, fresh weight and nutrient uptake by maize plant were determined. The experiment was conducted by using complete randomized design (CRD) with three replicates. The result indicated that germination percentage, Shoot length, leaf length, root length, number of leaves, and plant fresh weight were reduced by 37, 39, 39, 32 and 59% respectively at 0.75 mg kg−1 of CdSO4 concentration but when maize seeds inoculated with Bacillus pumilus significantly increased the germination percentage, shoot length, leaf length, number of leaves, plant fresh weight at different concentrations of CdSO4. Moreover, the plant protein were significantly increased by 60% in T6 (0.25 mg kg−1 of CdSO4 + inoculated seed) and Peroxidase dismutase (POD) was also significantly higher by 346% in T6 (0.25 mg kg−1 of CdSO4 + inoculated seed), however, the Superoxide dismutase (SOD) was significantly higher in T5 (0.75 mg kg−1 of CdSO4 + uninoculated seed) and was 769% higher as compared to control. The Cd contents in Bacillus pumilus inoculated maize roots and shoots were decreased. The present investigations indicated that the inoculation of maize plant with Bacillus pumilus can help maize plants to withstand Cd stress but higher concentration of Cd can harm the plant. The Bacillus pumilus has good potential to remediate Cd from soil, and also have potential to reduce the phyto availability and toxicity of Cd.
In the modern era, pollution has become a major issue of concern worldwide. This might be due to the rapid advancement of industrialization, urbanization and agricultural practices. Indiscriminate disposal of heavy metals, especially cadmium and lead-loaded waste, presents a severe risk to human life and the ecosystem and seems to be a major issue of concern in the modern era. These pollutants finally settle in each and every phase of the earth contaminating the whole biosphere, atmosphere, lithosphere and hydrosphere. Phytoremediation is the method of utilization of plants for the treatment of contaminants from the environment or transformation of harmful into harmless forms. Phytoremediation proved to be the efficient, green approach, pollution-free, economical and ecofriendly alternative for the removal of hazardous heavy metals from polluted areas. Certain characteristics of plants which make them appropriate for the process of phytoremediation are fast growth, increased biological mass, hairy and high bioaccumulation coefficient and deep root system.
Environmental pollution is among most dangerous challenges for the wellbeing of organisms. Due to anthropological and agricultural practices, heavy metals are typically present in soil or are transferred into the environment. Cadmium-polluted soil emphasizes two key points: first, they affect the plant’s life cycle by reducing crop yields, and second, they are absorbed as well as accumulated in plant tissues and ultimately enter inside the food chain to harm animals as well as humans. The major goal of plant biotechnology studies is to know how plants deal with cadmium toxicity and the aim of plant breeders is to generate plants that can withstand cadmium exposure.
Mangrove Avicennia marina has the importantly potential for cadmium (Cd) pollution remediation in coastal wetlands. Unfortunately, the molecular mechanisms and transporter members for Cd uptake by the roots of A. marina are not well documented. In this study, photosynthetic and phenotypic analysis indicated that A. marina is particularly tolerant to Cd. The content and flux analysis indicated that Cd is mainly retained in the roots, with greater Cd influx in fine roots than that in coarse roots, and higher Cd influx in the root meristem zone as well. Using transcriptomic analysis, a total of 5238 differentially expressed genes were identified between the Cd treatment and control group. Moreover, we found that 54 genes were responsible for inorganic ion transport. Among these genes, AmHMA2, AmIRT1, and AmPCR2 were localized in the plasma membrane and AmZIP1 was localized in both plasma membrane and cytoplasm. All above gene encoding transporters showed significant Cd transport activities using function assay in yeast cells. In addition, the overexpression of AmZIP1 or AmPCR2 in Arabidopsis improved the Cd tolerance of transgenic plants. This is particularly significant as it provides insight into the molecular mechanism for Cd uptake by the roots of mangrove plants and a theoretical basis for coastal wetland phytoremediation.
To improve the remediation of heavy metal pollution by typical wetland vegetation and maintain the health of wetland ecosystems under the water-sediment regulation scheme (WSRS) application, we evaluated the potential ecological risk of heavy metals in surface sediment in the Yellow River estuary affected by the WSRS. The ranges of Cr, Cu, Zn, Cd, and Pb content in surface sediment were 52.44–100.80 mg·kg⁻¹ dry weight (DW), 16.38–21.19 mg·kg⁻¹ DW, 64.77–255.50 mg·kg⁻¹ DW, 0.12–0.24 mg·kg⁻¹ DW, and 5.40–8.63 mg·kg⁻¹ DW, respectively, and potential ecological risk coefficients showed that Cd was associated with moderate potential risk. We further examined effects of Cd in a greenhouse experiment to explore the influence of short-term Cd input and water logging condition changes induced by WSRS on the Cd absorption characteristics of Suaeda salsa (L.) Pall in the Yellow River estuary. The results showed that total biomass decreased but Cd content in tissue of S. salsa increased with increasing Cd input and the accumulation factor reached maximum values at 100 μg·L⁻¹ of Cd, indicating that S. salsa efficiently accumulated Cd. Water logging depth significantly affected S. salsa growth and Cd absorption with deeper water logging being detrimental to growth. The interaction effect of Cd input and water logging depth on Cd content and accumulation factor was significant. These results suggest that WSRS caused short-term heavy metal input and changes in water conditions affect wetland vegetation growth and heavy metal absorption in the downstream estuary.
Cadmium pollution is severe in cucumber, although grafting is an effective method to improve its stress tolerance. Pumpkin is the commonly-used grafting rootstock for cucumber, and the breeding of rootstock with cadmium tolerance plays a vital role in the safe production of cucumber. However, there are no reports on rootstocks specific for cadmium tolerance. In this study, the rootstock of a pumpkin cross combination and its parents were used for the study of cadmium stress. The results indicated that under the 24mg·L − 1 cadmium stress, the relative conductivity of cross combination decreased by 35.86%~36.31% compared with the parents. When the concentrations of cadmium stress were 8 mg·L − 1 and 16 mg·L − 1 , respectively, the peroxidase (POD) activity of cross combination was higher than those of the parents. The subcellular distribution of cadmium in the root systems of the cross and the 041 − 1 parent was in the cell wall first, followed by the cytoplasm and organelle, while that in the root system of 360-3 parent was in the cell wall first, followed by the organelle and cytoplasm. Under cadmium stress with the 24mg·L − 1 concentration, the transfer coefficient of cross was significantly lower than that of the parents. The cross initiated the activity of membrane protective enzyme POD under cadmium stress, relieved the damage to membrane, and reduced the toxicity of cadmium through the accumulation of cadmium in the cell wall that blocked its entrance to the cytoplasm. This study provides a theoretical foundation to breed cadmium-tolerant rootstocks for melon vegetables.
The present paper provides the first integrative assessment of the occurrence of nitric oxide (NO) induced hormetic effects in plant biology. Hormetic dose responses were commonly reported for NO donors on numerous plant species of agricultural and other commercial value. The NO donors were also shown to protect plants from a wide range of chemical (i.e., multiple toxic metals) and physical stressors (i.e., heat, drought) in preconditioning (aka priming) experimental protocols showing hormetic dose responses. Practical approaches for the use of NO donors to enhance plant growth using optimized dose response frameworks were also assessed. Considerable mechanistic findings indicate that NO donors have the capacity to enhance a broad range of adaptive responses, including highly integrated antioxidant activities. The integration of the hormesis concept with NO donors is likely to become a valuable practical general strategy to enhance plant productivity across a wide range of valuable plant species facing environmental pollution and climate changes.
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.
Cadmium (Cd) is a heavy metal, which will pollute the soil and affect the growth and development of plants. Grafting can alleviate the toxicity of heavy metals. Pumpkin (Cucurbita moschata Duch.) is the commonly-used grafting rootstock for melon plants, and the breeding of rootstock with cadmium tolerance plays a vital role in the safe production of melon plants. In this study, the rootstock pumpkin MB3, FB1 and their hybrid F1 ZF1 were used as experimental materials. The substrate culture was applied under conditions of cadmium (8, 16, and 24 mg/L), and the defense response of pumpkin rootstock to cadmium was studied, cadmium free stress was used as control. The experimental results indicated that under the cadmium stress, the growth of pumpkin seedlings was inhibited, but compared with the control, Cd promoted the plant height of ZF1. The determination of cadmium content in each part of pumpkin seedlings showed that the Cd accumulation ability of ZF1 roots was higher than that of parents, and the transfer coefficient to shoot was low, which reduced the concentration of Cd in leaves, improved the photosynthetic assimilation of leaves and Cd tolerance of pumpkin seedlings, and enhanced the activities of antioxidant enzymes (SOD, POD, CAT). Root activity and root scanner showed that ZF1 roots had the least damage under Cd stress compared with MB3 and FB1 parents. The distribution of cadmium concentration in root systems subcellular showed that under cadmium stress, ZF1 initiated the activity of membrane protective enzyme, relieved the damage to membrane, and reduced the toxicity of cadmium through the accumulation of cadmium in the cell wall that blocked its entrance to the cytoplasm. This study provides a theoretical foundation to breed cadmium-tolerant rootstocks for melon plants.
Boron (B) is an essential microelement for plant growth and has been shown to reduce cadmium (Cd) toxicity in wheat through modulating gene expression. However, there is not enough information about the effects of different applications of B fertilizer on the accumulation of Cd, particularly throughout the wheat growth period. This experiment employed two different B fertilization methods. The soil application method utilized 1.5 mg B kg⁻¹ soil (Cd+B) and foliar application utilized 0.1% (F0.1%), 0.3% (F0.3%), and 0.6% (F0.6%) B concentrations along with 4 mg kg⁻¹ Cd. The results showed that B application in the soil reduced Cd concentrations per plant by 43.9% at the seedling stage, 74.59% in the roots, and 52.11% in the shoots at the elongation stage. At the same time, Cd concentrations in the roots were higher by B application at the anthesis and maturity stages, suggesting that B retains more Cd in the roots. The gray correlation analysis showed that the gray relational coefficients followed the following order: F0.3% > F0.1% > Cd+B > F0.6%. According to quantitative real-time PCR analysis, the six Cd transporters were mostly expressed in the roots at the seedling stage and anthesis stage. In addition, the expression of TCONS1113, TRIAE1060, and TRIAE5370 showed a negative correlation relationship with Cd concentration at the seedling stage, both in roots and shoots. At the anthesis stage, the expression of TCONS1113 and TRIAE5370 in roots was higher in Cd-treated plants compared to B-treated plants, and a similar tendency was noted for the expression of TRIAE5770 and TRIAE1060 in shoots as well. These results suggest that B application could significantly inhibit Cd uptake and translocation by regulating the expression of Cd transporter genes, especially at the seedling stage and the elongation phase in wheat.
The magnetic field can alter the hydrogen-bond structure and polarity characteristics of water; therefore, we hypothesize that magnetized water can affect plant physiological functions, including metal detoxification and excretion. In this study, the amount of Cd excreted on the leaves of Festuca arundinacea was estimated using magnetized water and normal water irrigation patterns. Irrigation with magnetized water improved the shoot dry weight and Cd content in F. arundinacea by 13.6% and 52.8%, respectively, compared to the control. Magnetized water irrigation also increased antioxidant enzyme activities in plant leaves, thereby alleviating the oxidative damage. The concentration of ferritin was 0.91 folds higher than that of the control, increasing the Fe sequestration and detoxification capacity of F. arundinacea. The amount of Cd excreted was significantly higher under magnetized water irrigation, thereby increasing the annual Cd removal by 109.7% from soil by leaf washing compared with that of the control. In contrast, F. arundinacea irrigated with magnetized water excreted 38.1% less Fe owing to the increase in ferritin levels, compared with that of the control. This study suggests a novel pathway of Cd phytoremediation by rinsing excreted Cd from the leaf surface without harvesting and replanting F. arundinacea.
Cadmium (Cd) is a major environmental contaminant due to its widespread industrial use. Cd contamination of soil and water is rather classical but has emerged as a recent problem. Cd toxicity causes a range of damages to plants ranging from germination to yield suppression. Plant physiological functions, i.e., water interactions, essential mineral uptake, and photosynthesis, are also harmed by Cd. Plants have also shown metabolic changes because of Cd exposure either as direct impact on enzymes or other metabolites, or because of its propensity to produce reactive oxygen species, which can induce oxidative stress. In recent years, there has been increased interest in the potential of plants with ability to accumulate or stabilize Cd compounds for bioremediation of Cd pollution. Here, we critically review the chemistry of Cd and its dynamics in soil and the rhizosphere, toxic effects on plant growth, and yield formation. To conserve the environment and resources, chemical/biological remediation processes for Cd and their efficacy have been summarized in this review. Modulation of plant growth regulators such as cytokinins, ethylene, gibberellins, auxins, abscisic acid, polyamines, jasmonic acid, brassinosteroids, and nitric oxide has been highlighted. Development of plant genotypes with restricted Cd uptake and reduced accumulation in edible portions by conventional and marker-assisted breeding are also presented. In this regard, use of molecular techniques including identification of QTLs, CRISPR/Cas9, and functional genomics to enhance the adverse impacts of Cd in plants may be quite helpful. The review’s results should aid in the development of novel and suitable solutions for limiting Cd bioavailability and toxicity, as well as the long-term management of Cd-polluted soils, therefore reducing environmental and human health hazards.
Human activities such as unsustainable chemical based agriculture practices, industrialization, urbanization, improper waste disposal, etc. have resulted in the release of enormous quantities of toxicants, i.e. xenobiotic compounds such as agrochemicals which includes fertilizers, pesticides, industrial waste, agricultural waste, and domestic waste having metals, metalloids, etc. in different ecosystems causing various types of pollution in all the spheres of this planet. Both anthropogenic and natural pollutants affect diverse life forms including humans thereby causing various types of stress in them. Abiotic components of an ecosystem such as release of Heavy metals due to anthropogenic processes induce oxidative stress in different agricultural crops all over the globe. Fenugreek (Trigonella foenum-graecum L.) is a significant annual leguminous crop having both food as well as medicinal importance. Heavy metal such as Copper (Cu), Mercury (Hg), Arsenic (As), etc. induce oxidative stress in fenugreek adversely affecting growth parameters, i.e. reduction in seed germination, reduction in vegetative growth, adversely affecting photosynthetic machinery causing inhibition in induction of pigments such as chlorophyll and carotenoid. Cytotoxic affects such as reduction in cell division, mitosis, chromatin structure are also associated with heavy metal induced oxidative stress along with generation of reactive oxygen species (ROS) and induction of antioxidant enzymes, super oxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), etc. in response of heavy metal induced oxidative stress.
We aimed to investigate how sulfur (S) application prior to oilseed rape cultivation influences the uptake of cadmium (Cd) by rice grown in low- and high-Cd soils. A pot experiment involving four S levels (0, 30, 60, 120 mg S kg⁻¹) combined with two Cd rates (low and high—0.35 and 10.35 mg Cd kg⁻¹, respectively) was conducted. Soil pore water during rice growth and plant tissues at maturity were analyzed. The soil pore water results indicated that S application decreased Cd solubility under submergence due to the S-induced increase of soil pH and the enhancement of sulfide formation in soil micropores. When S was applied at rates of 30, 60 and 120 mg S kg⁻¹, brown rice Cd concentrations decreased by 18%, 18%, and 55% (p < 0.05) in the low-Cd soil but increased by 20%, 40%, and 40% in the high-Cd soil compared with those in the non-S treatment. The different effects of S on Cd accumulation in brown rice were related to Cd-induced oxidative stress in the rice plants. In low-Cd soils, a S-induced increase in phytochelatins in rice roots restricted and inhibited Cd translocation in brown rice. In high-Cd soils, the Cd-induced oxidative stress in rice plants weakened the protective effects of S, while highlighted the promotion of Cd uptake by S. Overall, S fertilizer is recommended for oilseed rape–rice rotations in low-Cd paddy fields. In high Cd-contaminated fields, oilseed rape–rice rotations are suitable for the simultaneous remediation by oilseed rape and production of rice without S fertilization.
The changes in membrane permeability (soluble leakage), lipid peroxidation, and activities of superoxide dismutase (SOD) and
catalase have been studied during in situ senescence of leaves of Nicotiana tabacum L., cv. Wisconsin 38. After full leaf expansion was reached there was a rapid, almost linear increase in the rate of 86Rb leakage from the preloaded leaf discs, with leaf age. Parallel with this increase in membrane permeability was a cumulative
increase in the level of lipid peroxidation. At the same leaf age there were changes in the activities of SOD and catalase.
SOD activity decreased on the basis of fresh weight but did not change when measured on the basis of protein content probably
due to relative stability of SOD during the senescence-associated general decline in protein content. Catalase activity first
increased parallel with the chlorophyll content of the leaf and then, after full leaf expansion, declined on the basis of
both fresh weight and protein content. These changes in membrane permeability, lipid peroxidation, and the enzyme activities
coincide in leaf age with the decline in protein and chlorophyll contents and in chlorophyll a: b ratio. When the senescence
of the bottom-most leaves was reversed by removing the stem from immediately above them, the senescence-associated changes
in protein and chlorophyll contents, lipid peroxidation, and the enzyme activities were also reversed. It is suggested that
leaf senescence may be a consequence of cumulative membrane deterioration due to increasing level of lipid peroxidation probably
controlled by, among other factors, the activities of SOD and catalase.
Cadmium is a toxic metal that produces disturbances in plant antioxidant defences giving rise to oxidative stress. The effect of this metal on H2O2 and O2·− production was studied in leaves from pea plants growth for 2 weeks with 50 µm Cd, by histochemistry with diaminobenzidine (DAB) and nitroblue tetrazolium (NBT), respectively. The subcellular localization of these reactive oxygen species (ROS) was studied by cytochemistry with CeCl3 and Mn/DAB staining for H2O2 and O2·−, respectively, followed by electron microscopy observation. In leaves from pea plants grown with 50 µm CdCl2 a rise of six times in the H2O2 content took place in comparison with control plants, and the accumulation of H2O2 was observed mainly in the plasma membrane of transfer, mesophyll and epidermal cells, as well as in the tonoplast of bundle sheath cells. In mesophyll cells a small accumulation of H2O2 was observed in mitochondria and peroxisomes. Experiments with inhibitors suggested that the main source of H2O2 could be a NADPH oxidase. The subcellular localization of O2·− production was demonstrated in the tonoplast of bundle sheath cells, and plasma membrane from mesophyll cells. The Cd-induced production of the ROS, H2O2 and O2·−, could be attributed to the phytotoxic effect of Cd, but lower levels of ROS could function as signal molecules in the induction of defence genes against Cd toxicity. Treatment of leaves from Cd-grown plants with different effectors and inhibitors showed that ROS production was regulated by different processes involving protein phosphatases, Ca2+ channels, and cGMP.
We studied how the relationship between cadmium (Cd) toxicity and oxidative stress influenced the growth, photosynthetic efficiency,
lipid peroxidation, and activity of ntioxidative enzymes in the roots and leaves of rice(Oryza sativa L Dongjin). Plants were exposed to Cd for 21 d. Both seedling growth and photosynthetic efficiency decreased gradually with
increasing cadmium concentrations. Lipid peroxidation increased slowly in both roots and leaves, causing oxidative stress.
However, each tissue type responded differently to Cd concentrations with regard to the induction/ inhibition of antioxidative
enzymes. The activity of Superoxide dismutase (SOD) increased in both roots and leaves. Ascorbate peroxidase (APX) activity
increased in leaves treated with up to 0.25 µM Cd, then decreased gradually at higher concentrations. In contrast, APX activity
in roots increased and remained constant between 0.25 and 25 µM Cd. Enhanced peroxidase (POD) activity was recorded for treatments
with up to 25/M Cd, gradually decreasing at higher concentrations in the leaves but remaining unchanged in the roots. Catalase (CAT) activity
increased in the roots, but decreased in the leaves, whereas the activity of glutathione reductase (GR) was enhanced in both
roots and leaves, where it remained elevated at higher Cd concentrations. These results suggest that rice seedlings tend to
cope with free radicals generated by Cd through coordinated, enhanced activities of the antioxidative enzymes involved in
detoxification.
Clonal, hydroponically grown poplar plants (Populus × canescens, a hybrid of Populus tremula × Populus alba) were exposed to Cd or H2O2 to find out whether Cd-induced injury was related to the disturbance of the cellular redox control in root tips. Cd exposure resulted in an inhibition of antioxidative enzymes (superoxide dismutase, EC 1.15.1.1; catalase, EC 1.11.1.6; ascorbate peroxidase, EC 1.11.1.11; monodehydroascorbate radical reductase, EC 1.1.5.4; glutathione reductase, EC 1.6.4.2) but had fewer effects on dehydroascorbate reductase (EC 1.8.5.1) activities. Glutathione concentrations decreased, whereas ascorbate remained unaffected by Cd. Five micromoles of Cd were subinjurious in short-term experiments and stimulated root growth. Fifty micromoles of Cd retarded shoot growth faster than root growth, caused a more severe loss in antioxidative capacity than 5 μM Cd and resulted in an accumulation of H2O2 in roots. Exposure to H2O2 had an effect on antioxidative enzymes similar to that found under the influence of Cd, but caused GSH accumulation, and loss of ascorbate. The present data indicate that both agents acted via the disturbance of the cellular redox control.
A method for measurement of both oxidized (GSSG) and reduced (GSH) glutathione has been developed, with use of o-phthalaldehyde (OPT) as a fluorescent reagent. The method takes advantage of the reaction of GSH with OPT at pH 8 and of GSSG with OPT at pH 12; GSH can be complexed to N-ethylmaleimide to prevent interference of GSH with measurement of GSSG. The method gave “recoveries” of 91 to 110% for both GSH and GSSG and was quite specific for glutathione; and none of the manipulations appeared to influence the amount of glutathione present in the tissue. Results for GSH levels agreed well with earlier reports but levels of GSSG estimated here were higher than earlier reported values. The reasons for the apparently higher levels of GSSG are discussed.
Uptake of cadmium into cultured cells and its effects on cell growth and DNA synthesis are measured over a range of Cd concentrations of seven orders of magnitude. Cd uptake is found to be proportional to the external Cd concentration and to incubation time over a very broad range of concentrations. At least 200 mmol cadmium per kg dry weight of cells can be accumulated in this way, leading to exhaustion of the major intracellular Cd binding sites before cell death.
On the other hand, very low cadmium concentrations down to 100 pM stimulate cell growth and DNA synthesis significantly. Stimulation is found in all three mammalian cell types examined: namely L6J1, a rat permanent myoblast cell line, LLC-PK1 porcine renal epithelial cells, and a primary rat chondrocyte culture. Cd acts as a cofactor with serum in L6J1 cultures, but is stimulatory only in serum-free cultures of chondrocytes. Stimulation occurs at Cd concentrations too low to result in a measurable induction of metallothionein. This might implicate the action of response amplifiers in the chain of events leading to Cd-stimulated DNA replication and cell growth.
Spin trapping has become a valuable tool for the study of free radicals in biology and medicine. The electron spin resonance hyperfine splitting constants of spin adducts of interest in this area are tabulated. The entries also contain a brief comment on the source of the radical trapped.
Measurements of the quantum efficiencies of photosynthetic electron transport through photosystem II (phiPSII) and CO2 assimilation (phiCO2) were made simultaneously on leaves of maize (Zea mays) crops in the United Kingdom during the early growing season, when chilling conditions were experienced. The activities of a range of enzymes involved with scavenging active O2 species and the levels of key antioxidants were also measured. When leaves were exposed to low temperatures during development, the ratio of phiPSII/phiCO2 was elevated, indicating the operation of an alternative sink to CO2 for photosynthetic reducing equivalents. The activities of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase, and superoxide dismutase and the levels of ascorbate and alpha-tocopherol were also elevated during chilling periods. This supports the hypothesis that the relative flux of photosynthetic reducing equivalents to O2 via the Mehler reaction is higher when leaves develop under chilling conditions. Lipoxygenase activity and lipid peroxidation were also increased during low temperatures, suggesting that lipoxygenase-mediated peroxidation of membrane lipids contributes to the oxidative damage occurring in chill-stressed leaves.
The relation between Cd and oxidative stress in BY2 cell cultures of tobacco was studied. In response to 5 mM Cd, a rapid generation of H2O2 has been detected in tobacco cell cultures by the oxidative quenching of the fluorescent reporter dye pyranine. This oxidative burst reached the maximum production of H2O2 after 10 min of treatment with Cd. This response could be considered as short term hypersensitive response previous to the oxidative stress caused by the metal at the cell plasma membrane. The observed antioxidant enzymatic response to the oxidative burst was preceded by an increased peroxidation of lipids with a significant increase in the activities of superoxide dismutase and ascorbate peroxidase. The results presented in this study point out to the plasma membrane as the primary target for the short term production of activated oxygen species in response to Cd in BY2 tobacco cells followed by a coordinated activation of the antioxidant enzymatic system.
Toxic metals (lead, cadmium, mercury and arsenic) are widely found in our environment. Humans are exposed to these metals from numerous sources, including contaminated air, water, soil and food. Recent studies indicate that transition metals act as catalysts in the oxidative reactions of biological macromolecules therefore the toxicities associated with these metals might be due to oxidative tissue damage. Redox-active metals, such as iron, copper and chromium, undergo redox cycling whereas redox-inactive metals, such as lead, cadmium, mercury and others deplete cells' major antioxidants, particularly thiol-containing antioxidants and enzymes. Either redox-active or redox-inactive metals may cause an increase in production of reactive oxygen species (ROS) such as hydroxyl radical (HO.), superoxide radical (O2.-) or hydrogen peroxide (H2O2). Enhanced generation of ROS can overwhelm cells' intrinsic antioxidant defenses, and result in a condition known as "oxidative stress". Cells under oxidative stress display various dysfunctions due to lesions caused by ROS to lipids, proteins and DNA. Consequently, it is suggested that metal-induced oxidative stress in cells can be partially responsible for the toxic effects of heavy metals. Several studies are underway to determine the effect of antioxidant supplementation following heavy metal exposure. Data suggest that antioxidants may play an important role in abating some hazards of heavy metals. In order to prove the importance of using antioxidants in heavy metal poisoning, pertinent biochemical mechanisms for metal-induced oxidative stress should be reviewed.
A protein determination method which involves the binding of Coomassie Brilliant Blue G-250 to protein is described. The binding of the dye to protein causes a shift in the absorption maximum of the dye from 465 to 595 nm, and it is the increase in absorption at 595 nm which is monitored. This assay is very reproducible and rapid with the dye binding process virtually complete in approximately 2 min with good color stability for 1 hr. There is little or no interference from cations such as sodium or potassium nor from carbohydrates such as sucrose. A small amount of color is developed in the presence of strongly alkaline buffering agents, but the assay may be run accurately by the use of proper buffer controls. The only components found to give excessive interfering color in the assay are relatively large amounts of detergents such as sodium dodecyl sulfate, Triton X-100, and commercial glassware detergents. Interference by small amounts of detergent may be eliminated by the use of proper controls.
Plants adapt to environmental stresses through specific genetic responses. The molecular mechanisms associated with signal transduction, leading to changes in gene expression early in the stress response, are largely unknown. It is clear, however, that gene expression associated with acclimatory responses is sensitive to the redox state of the cell. Of the many components which contribute to the redox balance of the cell, two factors have been shown to be crucial in mediating stress responses. Thiol/disulphide exchange reactions, particularly involving the glutathione pool and the generation of the oxidant H2O2, are central components of signal transduction in both environmental and biotic stresses. These molecules are multifunctional triggers, modulating metabolism and gene expression. Both are able to cross biological membranes and diffuse or be transported long distances from their sites of origin. Glutathione and H2O2 may act alone or in unison, in intracellular and systemic signalling systems, to achieve acclimation and tolerance to biotic and abiotic stresses.
Measurements of the quantum efficiencies of photosynthetic electron transport through photosystem II (φPSII) and CO2 assimilation (φCO2) were made simultaneously on leaves of maize (Zea mays) crops in the United Kingdom during the early growing season, when chilling conditions were experienced. The activities of a range of enzymes involved with scavenging active O2 species and the levels of key antioxidants were also measured. When leaves were exposed to low temperatures during development, the ratio of φPSII/φCO2 was elevated, indicating the operation of an alternative sink to CO2 for photosynthetic reducing equivalents. The activities of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase, and superoxide dismutase and the levels of ascorbate and α-tocopherol were also elevated during chilling periods. This supports the hypothesis that the relative flux of photosynthetic reducing equivalents to O2 via the Mehler reaction is higher when leaves develop under chilling conditions. Lipoxygenase activity and lipid peroxidation were also increased during low temperatures, suggesting that lipoxygenase-mediated peroxidation of membrane lipids contributes to the oxidative damage occurring in chill-stressed leaves.
The absolute requirement of oxygen for a potato tuber (cv. Pentland Crown) to display a resistant response toErwinia carotovora has been demonstrated in EPR measurements. These show that a relatively stable free radical is formed in inoculated hosts only after exposure to air. In an attempt to isolate and identify unstable free radical precursors, experiments have been conducted in which the chemical spin trap α-(4-pyridyl 1-oxide)-N-tert-butyl-nitrone (POBN) was incorporated into the tissue either at the time of inoculation or upon exposure to air. A single radical adduct was observed with spectral parameters that resemble those of a lipid-derived radical.
Of all the elements, the most important to consider in terms of food-chain contamination are arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb) and selenium (Se). Where soils are enriched in these elements, it is usually through the agricultural, industrial or urban activities of man, except for Se where high concentrations in soil are often derived from high-Se parent rock materials. The propensity for plants to accumulate and translocate these contaminants to edible and harvested parts depends largely on soil and climatic factors, plant genotype and agronomic management. Elevated As intake, especially of inorganic As, is most likely to arise from high-As drinking water than from ingestion of food. Cadmium and Se are of the greatest concern in terms of terrestrial food-chain contamination, with the former element receiving most attention. Worldwide, the probability of insufficient Se in the human diet exceeds that of toxicity, with deficiency usually associated with monotonous vegetarian diets in areas with Se-deficient soils. Excessive human intake of Cd is of concern as this element accumulates over a lifetime in the body, with impairment of kidney function being the main adverse effect. Cadmium inputs to soil in fertilizer, biosolids, soil amendments and atmospheric deposition often exceed outputs in crops and drainage waters, so that Cd concentrations in many agricultural soils are slowly increasing. However, evidence for increases in Cd concentrations in crops over time is contentious, as is the evidence for human health problems due to low-level Cd contamination of the food chain. Adverse health effects due to Cd intake have been manifest only in situations of gross soil contamination, with a predominantly rice-based diet, where soil–plant and plant–human transfer of Cd would have been enhanced. Human feeding studies have indicated that food Cd bioavailability is dependent on Fe nutrition, and animal studies have indicated that Zn, Ca, P and other elements and food constituents (e.g. fiber, phytate) affect Cd bioavailability. While plant breeding and agronomic management can minimize soil–plant transfer of Cd, and maximize concentrations of antagonists to Cd assimilation in humans, it remains important that inputs of this metal to soil be minimized.
Spin trapping has become a valuable tool for the study of free radicals in biology and medicine. The electron spin resonance hyperfine splitting constants of spin adducts of interest in this area are tabulated. The entries also contain a brief comment on the source of the radical trapped.
In chloroplasts, chlorophyll-photosensitized production of 1O2 is an unavoidable reaction. Chloroplast thylakoids univalently photoreduce molecular oxygen producing O2- through the autoxidation of an electron acceptor in photosystem I. In chloroplasts, O2- produced in thylakoids is disproportionated by superoxide dismutases (SOD) in the stroma, and the H2O2 thus produced is reduced to water by ascorbate peroxidase. Ascorbate is regenerated from its oxidation products, dehydroascorbate (DHA) and monodehydroascorbate, by photoreductants through the system shown diagrammatically in this chapter. Ascorbate peroxidase, DHA reductase, and nicotinamide adenine dinucleotide (NADH)-dependent monodehydroascorbate reductase are localized in the chloroplast stroma, as are the enzymes participating in the generation of glutathione (GSH) and NADH. The production of O2- is enhanced under conditions where the generation rate of photoreductant in thylakoids exceeds that required for CO2 reduction; low CO2 concentration and high light intensity. O2- is, however, produced even when CO2 is supplied to chloroplasts and the photoproduction of O2- appears to be indispensable for the prevention of overreduction of electron carriers in the cyclic electron transport pathway. Thus, the photorcduction of O2- is an inevitable reaction in chloroplasts. Scavenging of O2- and H2O2 is essential for chloroplasts to maintain their ability to fix CO2, because several enzymes in the CO2-reduction cycle are sensitive to active oxygen. Production of O2- and H2O2 and their scavenging system are discussed in this chapter.
Although the superoxide anion radical (O) has been implicated in the phytotoxicity of ozone, (O3), its role has been inferred from indirect evidence based on the activity of oxyradical scavenging systems in the leaf, particularly superoxide dismutase (SOD). Direct observations of radical signals obtained by electron paramagnetic resonance spectrometry (EPR) of intact, attached leaves of bluegrass (Poa pratensis L.) and ryegrass (Lolium perenne L.) and leaf pieces of radish (Raphanus sativus L.) during exposure to 240 μg m−3 O3 in air flowing through the spectrometer cavity have revealed the appearance of a signal with the characteristics of O. The exposures used were insufficient to cause any necrotic injury to the leaves. The appearance of the signal is light-dependent, suggesting that it originates in the chloroplast, and its appearance is reduced in leaves in which the apoplastic pool of ascorbic acid has been enriched by prior vacuum infiltration. In each species, the signal only appeared after about 1 h of exposure to O3, and then increased steadily over the next 4 h. The lability of the species responsible for the signal is such that it can no longer be reliably detected about 15 min after cessation of the exposure to O3. These observations are interpreted as indicating that apoplastic ascorbate initially reduces the production of O, probably by reducing the penetration of O3 into the cell, with any O produced being scavenged by the chloroplastic SOD-per-oxidase system, but its formation from O3 then begins to exceed the capacity of the scavenging systems to remove it.
Germinating seedlings of mung bean (Phaseolus vulgaris L. cv. K-16) were treated with different concentrations of cadmium acetate (10, 50 and 100 μM). Cd2+ lowered the chlorophyll and heme levels. The level of lipid peroxides were higher on day 3 than on day 6. However, Cd2+ treatment significantly enhanced the level of lipid peroxides. Similarly, a dose-dependent induction of lipoxygenase (EC 1.13.11.12) activity was observed with Cd2+ treatment. Further, the activities of antioxidant enzymes such as superoxide dismutase (EC 1.15.1.1) and catalase (EC 1.11.1.6) were decreased. Our results suggest that lipoxygenase-mediated accumulation of lipid peroxides on the one hand and inhibition of free radical scavenging enzymes like superoxide dismutase and catalase on the other caused a pronounced reduction in the chlorophyll and heme levels of the seedlings. The experiments conducted on the effect of Cd2+ on dark-grown seedlings did not conform with the result of light-grown seedlings. Though chlorophyll and heme levels decreased in a dose-dependent manner, no accumulation of lipid peroxides was observed, suggesting that the inhibition of chlorophyll synthesis by Cd2+ is achieved both by reaction with constituent biosynthetic enzymes as well as peroxide-mediated degradation.
Plants adapt to environmental stresses through specific genetic responses. The molecular mechanisms associated with signal transduction, leading to changes in gene expression early in the stress response, are largely unknown. It is clear, however, that gene expression associated with acclimatory responses is sensitive to the redox state of the cell. Of the many components which contribute to the redox balance of the cell, two factors have been shown to be crucial in mediating stress responses. Thiol/disulphide exchange reactions, particularly involving the glutathione pool and the generation of the oxidant H2O2, are central components of signal transduction in both environmental and biotic stresses. These molecules are multifunctional triggers, modulating metabolism and gene expression. Both are able to cross biological membranes and diffuse or be transported long distances from their sites of origin. Glutathione and H2O2 may act alone or in unison, in intracellular and systemic signalling systems, to achieve acclimation and tolerance to biotic and abiotic stresses.
Because glutathione (GSH) is an important antioxidant and metal chelator, this study was undertaken to determine whether the role of this tripeptide in cadmium tolerance of Rhizobium leguminosarum is linked to its antioxidant properties.Two strains expressing different degrees of tolerance to cadmium (Cd) stress were used and the influence of the addition of extracellular GSH to the growth media was determined. Oxidative stress indexes and reactive oxygen species (ROS) scavenging enzymes were evaluated, as well as changes in GSH and oxidized GSH (GSSG) levels.Results confirmed that CdCl2 imposes oxidative stress in R. leguminosarum, which was characterized by an increase in GSSG formation and an induction of the activities of superoxide dismutase (SOD), GSH peroxidase (GPX), GSH reductase (GR) and catalase (CAT). Addition of reduced GSH to the growth media had a protective effect, particularly in the sensitive strain.Our findings show that increased tolerance in R. leguminosarum is not related to a higher efficiency in the oxygen scavengers per se, but to ratios of intracellular reduced GSH. Furthermore, we demonstrated that the supply of GSH to the sensitive strain enhanced survival, concluding that GSH plays a crucial role in Cd tolerance in this species. However, this role consists in preventing the oxidative stress to the cell, rather than reducing its effects.
Rice plants accumulate high quantities of Cd and Ni when grown for 10 days in a medium containing these heavy metals. Accompanying Cd and Ni uptake, a decrease in shoot and root length was observed, though dry matter accumulation was not affected accordingly. Metal treatments also induced a decrease in K, Ca and Mg contents in the plants, particularly in the shoots, indicating that Cd and Ni interfered not only with nutrient uptake but also with nutrient distribution into the different plant parts. Addition of abscisic acid (ABA) or gibberellic acid (GA3) to the external solution could not overcome the depressing effects of the metals on nutrient acquisition, and even induced a further decrease of Ca content in Ni-treated plants. Both hormones also reduced, significantly, heavy metal incorporation into the plants. Additionally, hormonal applications affected the transport of Cd and Ni to the shoots, resulting in a higher percentage of the metals taken up remaining in the roots.
Plants of miscanthus were grown in nutrient solution supplied with 0, 0.25, 0.50, and 0.75 mg l−1 cadmium and were harvested after 1 and 3 months of treatment. With cadmium up to 0.50 mg l−1 biomass of secondary culms and roots was increased at both harvests, whereas biomass of the main culm and the rhizome was slightly increased at the first harvest and decreased at the second. With 0.75 mg l−1 Cd biomass of all plant parts except roots was decreased at both harvests. The biomass of the entire plant was always higher than in controls with 0.25 and 0.50 mg l−1 Cd and lower with 0.75 mg l−1 Cd. Relative growth rates (RGRs) showed that the two lower Cd levels stimulated growth only during the first growth period, whereas during the second they reduced growth of the main culm and the rhizome and did not affect that of secondary culms and roots. Root morphology changed with 0.75 mg l−1 Cd: length, surface, and volume drastically decreased, whereas dry weight was not affected and root average diameter increased. All Cd levels decreased specific dry weight increment (SDWI) but did not affect the (net uptake rates) NUR of nitrogen and the N-concentration of different plant parts. Roots showed the highest Cd-concentrations at both harvests and with all Cd levels, and leaves the lowest. The Cd-concentration of aerial plant parts was highest with 0.50 mg l−1 Cd and lowest with 0.75 mg l−1, whereas that of roots increased with Cd supply. Between the first and the second harvest the Cd-concentration of roots, rhizome, and main culm increased only with the highest Cd-level, whereas that of leaves and secondary culms with all levels. The Cd-NUR was linearly related to the concentration of the metal in the nutrient solution during the first month of application and was very low during the following two. Above summarized patterns suggest that cadmium flows passively into roots but the saturation of binding sites limits its uptake. The metal is slowly translocated to the shoot due to mechanisms that restrict internal Cd-transport. This regulation is partially disrupted with 0.75 mg l−1 Cd but translocation to aerial organs is still restricted probably due to reduced transpiration. In this research, the maximum Cd-content achieved by miscanthus was 3.8 mg per plant after a 3-month treatment with 0.75 mg l−1 Cd, but the maximum content of the shoot was 1 mg per plant and was obtained with 0.50 mg l−1 Cd.
A hydroponic experiment was carried out in a greenhouse to study genotypic differences in the effect of four Cd levels on lipid peroxidation and activities of antioxidant enzymes in barley plants during ontogenesis. A highly significant increase in malondialdehyde (MDA) content, and a stimulation of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities were recorded in plants subjected to 1 and 5 μM Cd. The effects increased with both Cd concentration in the medium and with time of exposure in 5 μM Cd treatments. There was a highly significant difference in the alternation of all these parameters but CAT activity among the four genotypes. Wumaoliuling, which was relatively sensitive to Cd toxicity in terms of growth, biomass and chlorophyll content both in the previous and present studies, accumulated much more MDA when exposed to 5 μM Cd than the three other relatively tolerant genotypes (Zhenong 1, ZAU 3 and Mimai 114). In contrast, the three tolerant genotypes maintained higher SOD and POD activities than Wumaoliuling over the whole duration of Cd exposure. The present investigation showed that Cd-stress induced a concentration- and genotype-dependent oxidative stress response in barley leaves, characterized by an accumulation of MDA and the alternation pattern of antioxidative enzymes, mainly SOD and POD may be attributed to the genotypic difference in Cd tolerance.
We have developed a Cd-resistant type (RT) from a Cd-sensitive wild-type (WT) of Arabidopsis thalaiana, and seedlings were grown on MS medium containing up to 500 μM of CdCl2 to study the relationship between Cd-induced phytoxicity and oxidative stress. Compared to WT, RT showed a higher level of survival, and lower hydrogen peroxide and lipid peroxidation levels expressed as thiobarbituric acid reacting substances (TBARS) production. These results indicate that RT seedlings experienced lower oxidative stress from Cd exposure. Furthermore, compared to WT, RT had significantly higher activities of superoxide dismutase (SOD and enzymes related to hydrogen peroxide removal such as guaiacol peroxidase (GPX), ascorbate peroxidase (APX) and glutathione reductase (GR). The differential between the responses of WT and RT seedlings to Cd suggests that Cd-induced phytotoxicity can be induced by hydrogen peroxide accumulation and subsequent oxidative stress. The results also imply that a lower hydrogen peroxide accumulation confers Cd-tolerance in seedlings.
In the present study, rice seedlings were exposed to a range of Cd concentrations (0.1 μM, 1 μM, 10 μM, 100 μM and 1 mM) for 15 days and a combination of different molecular approaches were used to evidence Cd effects and to assess the plants’ ability to counteract metal toxicity. At a macroscopical level, only the highest Cd concentration (1 mM) caused a complete plant growth inhibition, whereas the lowest concentrations seemed to stimulate growth. At genome level, the amplified fragment length polymorphism (AFLP) technique was applied to detect DNA sequence changes in root cells, showing that all the Cd concentrations induced significant DNA polymorphisms in a dose-dependent manner. Data also evidenced the absence of preferential mutation sites.Plant responses were analysed by measuring the levels of gluthatione (GSH) and phytochelatins (PCs), the thiol-peptides involved in heavy metal tolerance mechanisms. Results showed a progressive increase of GSH up to 10 μM of Cd treatment, whereas a significant induction only of PC3 was detected in roots of plants exposed to 100 μM of Cd. As suggested by the proteome analysis of root tissues, this last concentration strongly induced the expression of regulatory proteins and some metabolic enzymes. Furthermore, the treatment with 10 μM of Cd induced changes in metabolic enzymes, but it mainly activated defence mechanisms by the induction of transporters and proteins involved in the degradation of oxidatively modified proteins.
The toxic effects of cadmium on growth and development of living organisms are well documented. However, the molecular mechanisms responsible for the inhibition of plant growth by cadmium are still not completely understood. We determined the effects of cadmium concentrations in the range of 1–11 μM on the growth of Glycine max L. cv. Navico suspension-culture cells, as well as on the expression of two cell cycle genes: cyclin B1 and cyclin-dependent type A kinase (CDK-A). There was no detectable decrease in cell viability at any tested Cd2+ concentrations. The lower concentrations of Cd2+ (1–4 μM) stimulated cell culture growth; however, this did not correspond with increased expression of cell cycle genes. The inhibition of cell growth was observed at concentration of Cd2+ higher than 6 μM. Interestingly, it correlated well with the decreased cyclin B1 mRNA levels, but had no significant effect on the levels of CDK-A mRNA.
Pot experiments were conducted on 20 rice cultivars of different genotypes and origins by adding 100 mg/kg of cadmium (Cd) to soil. The aim was to investigate the effects of Cd on the dry matter accumulation and grain yield of different rice cultivars, the differences among rice cultivars and genotypes in Cd uptake and translocation, the interactions between Cd and five mineral nutrients Fe, Zn, Mn, Cu and Mg in response of the uptake and translocation in rice plant. The results showed that the effects of Cd on rice growth and development were variety dependent; some cultivars were strongly tolerant to soil Cd stress, while others were very sensitive. Differences existed among the cultivars for Cd uptake and distribution in rice plants, but the differences were not necessarily related to rice genotypes. Cd concentrations fell rapidly from roots to brown rice along rice plants, so the concentrations of Cd were very low in brown rice compared with other parts of rice plants. The effects of Cd on the concentrations of the mineral nutrients in the rice roots and leaves were mostly significant, however, the results varied with metal elements, rice plant organs and growing stages. Under soil Cd stress, the variations of the grain and straw yield of the cultivars were not correlated with the changes of any mineral nutrient in the rice plant. The regression analysis showed that, for their concentrations in roots and leaves, significant positive correlations between Cd and Fe, Cd and Zn, Cd and Cu existed, but no significant correlation between Cd and Mg, and the relationship between Cd and Mn varied with the organs of rice plant. These results suggested that rice cultivars differed greatly in growth and development responses to Cd and in absorption and translocation of Cd, Fe, Zn, Cu, Mn and Mg. The effects of Cd on the five mineral nutrients were not the main causes of the inhibition of Cd on rice growth and development. The interactions of Cd and Fe, Zn, Cu are synergetic in uptake and translocation from root to shoot by rice plants.
In Arabidopsis thaliana leaves, during the first hours of exposition to excess Cu or Cd, a considerable increase of hydrogen peroxide accumulation and superoxide radicals was observed. Imidazole—an inhibitor NADPH oxidase activity and propyl gallate, inhibitor synthesis of jasmonate, mostly decreased this effect. Increased superoxide radicals and hydrogen peroxide level was obtained after exogenous methyl jasmonate supply. Imidazole diminished the effect of methyl jasmonate on hydrogen peroxide burst. Excess Cd, in contrast to Cu, increased in the first hour of SOD activity, but this effect was suppressed by propyl gallate. The results indicated that the first effect of the investigated heavy metals stress was accumulation of superoxide radicals and hydrogen peroxide. That increase was mostly connected with the activity of NADPH oxidase, induction of jasmonate signaling pathways and partially, in the case of Cd, with superoxide dismutase activity increase.
Inhibition of root growth and modification of root morphology are the most sensitive responses of Lupinus luteus cv. Ventus L. to lead ions - Pb(NO3)2. Using electron paramagnetic resonance (EPR), we found that at the lead concentration of 150 mg.L–1, the level of free radicals remained at control level, whereas at the higher, sublethal concentration of 350 mg.L–1, they markedly increased. The EPR signal with the g-value at the maximum absorption of 2.0053 implied that the paramagnetic radical is derived from a quinone. The response of antioxidant enzymes, such as superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), peroxidase (POX, EC 1.11.1.7) and ascorbate peroxidase (APOX, EC 1.11.1.11), to exogenously applied lead ions was also examined. Enzyme activity was estimated as a function of time and concentration. Native polyacrylamide gel electrophoresis followed by specific staining revealed an increase in the activity of SOD, CAT, POX and APOX coinciding with the time of cultivation. A lead-dependent increase in activities of SOD and POX from root tip extracts was observed, whereas CAT and APOX activities decreased at the higher lead concentrations. These results suggest that at higher lead concentrations, the formation of both free radicals and reactive oxygen species is beyond the capacity of the an