Relationship between Mg, B and Mn status and tomato tolerance against Cd toxicity

Magnesium and manganese induced changes on chemical, nutritional, antioxidant and antimicrobial properties of the pansy and Viola edible flowers

Pansy and viola edible flowers were grown hydroponically with different levels of Mg and Mn. The nutritional composition was determined using standard methods. Free sugars, fatty acids, organic acids, tocopherols, and phenolic compounds were analyzed using various HPLC and GC devises. The extract's antimicrobial, antioxidant, cytotoxicity, and anti-inflammatory activity were assessed. The results indicated that Mg enrichment negatively affected plant growth and mineral accumulation but improved photosynthetic performance. The edible flowers contained significant amounts of protein, low levels of fat, and varying sugar contents, such as glucose and fructose. Various fatty acids and phenolic compounds were identified, with different concentrations depending on the treatment. The flowers exhibited antioxidant potential, antimicrobial activity, cytotoxic effects, and anti-inflammatory properties. The correlations between the investigated parameters not only expand knowledge on Mg and Mn interaction but also catalyze significant advancements in sustainable agriculture and food health, fostering a healthier and more conscious future.

Impacts of simulated atmospheric cadmium deposition on the physiological response and cadmium accumulation of Sedum plumbizincicola

Atmospheric cadmium (Cd) deposition contributes to the accumulation of Cd in the soil-plant system. Sedum plumbizincicola is a Cd and Zn hyperaccumulator commonly used for the phytoremediation of Cd-contaminated soil. However, studies on the effects of atmospheric Cd deposition on the accumulation of Cd and physiological response in S. plumbizincicola are still limited. A Cd solution spraying pot experiment was conducted with S. plumbizincicola at three atmospheric Cd deposition concentrations (4, 8, and 12 mg/L). Each Cd concentration levels was divided into two groups, non-mulching (foliar-root uptake) and mulching (foliar uptake). The soil type used in the experiment was reddish clayey soil collected from a farmland. The results showed that compared with the non-mulching control, the fresh weight of S. plumbizincicola in non-mulching with high atmospheric Cd deposition (12 mg/L) increased by 11.35%. Compared with those in the control group, the malondialdehyde (MDA) content in the non-mulching and mulching S. plumbizincicola groups increased by 0.88-11.06 nmol/L and 0.96-1.32 nmol/L, respectively. Compared with those in the non-Cd-treated control group, the shoot Cd content in the mulching group significantly increased by 11.09-180.51 mg/kg. Under high Cd depositions, the Cd in S. plumbizincicola mainly originated from the air and was stored in the shoots (39.7-158.5%). These findings highlight that the physiological response and Cd accumulation of S. plumbizincicola were mainly affected by high Cd deposition and suggest that atmospheric Cd could directly be absorbed by S. plumbizincicola. The effect of atmospheric deposition on S. plumbizincicola cannot be ignored.

Integrated Ca, Mg, Cu, and Zn supply upregulates leaf anatomy and metabolic adjustments in Eucalyptus seedlings

Adaptive responses to abiotic stresses such as soil acidity in Eucalyptus-the most widely planted broad-leaf forest genus globally-are poorly understood. This is particularly evident in physiological and anatomical disorders that inhibit plant development and wood quality. We aimed to explore how the supply of Ca and Mg through liming (lime), combined with Cu and Zn fertilization (CZF), influences physiological and anatomical responses during Eucalyptus grandis seedlings growth in tropical acid soil. Therefore, related parameters of leaf area and leaf anatomy, stomatal size, leaf gas exchange, antioxidant system, nutrient partitioning, and biomass allocation responses were monitored. Liming alone in Eucalyptus increased specific leaf area, stomatal density on the abaxial leaf surface, and Ca and Mg content. Also, Eucalyptus exposed only to CZF increased Cu and Zn content. Lime and CZF increased leaf blade and adaxial epidermal thickness, and improved the structural organization of the spongy mesophyll, promoting increased net CO2 assimilation, and stomatal conductance. Fertilization with Ca, Mg, Cu, and Zn positively affects plant nutrition, light utilization, photosynthetic rate, and antioxidant performance, improving growth. Our results indicate that lime and CZF induce adaptive responses in the physiological and anatomical adjustments of Eucalyptus plantation, thereby promoting biomass accumulation.

Cadmium tolerance in tomato: determination of organ-specific contribution by diallel analysis using reciprocal grafts

Given the increasing problems of water and soil contamination with cadmium (Cd), it is necessary to investigate the genetic and physiological mechanisms of tolerance to this metal in different crops, which can be used for the development of effective crop management strategies. This study aimed to assess the potential of grafting as a strategy to increase Cd tolerance and reduce absorption in tomato by evaluating the contribution of the root system and aerial parts for tolerance mechanisms. To this end, reciprocal grafting and diallel analyses were used to examine the combining ability of contrasting tomato genotypes under exposure to 0 and 35 µM CdCl2. Roots and above-ground parts were found to have specific mechanisms of Cd tolerance, absorption, and accumulation. Grafting of the USP15 genotype (scion) on USP16 (rootstock) provided the greatest synergism, increasing the tolerance index and reducing the translocation index and Cd accumulation in leaves. USP163 exhibited potential for breeding programs that target genotypes with high Cd tolerance. In tomato, both Cd tolerance and accumulation in aerial parts are genotype- and tissue-specific, controlled by a complex system of complementary mechanisms that need to be better understood to support the development of strategies to reduce Cd contamination in aerial parts.

Effects of exogenous calcium on cadmium accumulation in amaranth

Calcium oxalate (CaOx) crystals in plants act as a sink for excess Ca and play an essential role in detoxifying heavy metals (HMs). However, the mechanism and related influencing factors remain unclear. Amaranth (Amaranthus tricolor L.) is a common edible vegetable rich in CaOx and a potential Cd hyperaccumulation species. In this study, the hydroponic experiment was carried out to investigate the effect of exogenous Ca concentrations on Cd uptake by amaranth. The results showed that either insufficient or excess Ca supply inhibited amaranth growth, while the Cd bioconcentration factor (BCF) increased with Ca concentration. Meanwhile, the sequence extraction results demonstrated that Cd mainly accumulated as pectate and protein-bound species (NaCl extracted) in the root and stem, compared to pectate, protein, and phosphate-bound (acetic acid extractable) species in the leaf. Correlation analysis showed that the concentration of exogenous Ca was positively correlated with amaranth-produced CaOx crystals but negatively correlated with insoluble oxalate-bound Cd in the leaf. However, since the accumulated insoluble oxalate-bound Cd was relatively low, Cd detoxification via the CaOx pathway in amaranth is limited.

Neutral-to-positive cadmium effects on germination and seedling vigor, with and without seed priming

This review gathered and analyzed data about (i) the Cd-induced impacts on seed germination and seedling vigor, and (ii) the use of different priming agents to mitigate Cd-induced impacts on the early plant development. Critical evaluation of the obtained data revealed intriguing results. First, seeds of diverse species can endure exposures to Cd. Such endurance is exhibited as maintenance of or even improvement in the seed germination and vigor (up to 15% and 70%, respectively). Second, the main factors influencing seed tolerance to Cd toxicity are related to temporal variations in anatomical, physiological, and/or biochemical features. Third, Cd can trigger diverse transgenerational effects on plants by shaping seed endophytes, by modulating seed provisioning with resources and regulatory elements, and/or by altering seed (epi)genomics. Fourth, different chemical, biological and physical priming agents can mitigate Cd-induced impacts on seeds, sometimes enhancing their performance over the control (reference) values. Overall, this review shows that the impacts of Cd on seed germination and vigor encompass not only negative outcomes but also neutral and positive ones, depending upon the Cd dose, media properties, plant species and genotypes, plant developmental stage and organ, and management approaches. Increasing our understanding of plant tolerance mechanisms against the growing background Cd pollution is relevant to support breeding programs, agricultural practices, and health-environmental policies.

New insights into cadmium tolerance and accumulation in tomato: Dissecting root and shoot responses using cross-genotype grafting

Cadmium (Cd) is one of the most threatening soil and water contaminants in agricultural settings. In previous studies, we observed that Cd affects the metabolism and physiology of tomato (Solanum lycopersicum) plants even after short-term exposure. The objective of this research was to use cross-genotype grafting to distinguish between root- and shoot-mediated responses of tomato genotypes with contrasting Cd tolerance at the early stages of Cd exposure. This study provides the first report of organ-specific contributions in two tomato genotypes with contrasting Cd tolerance: Solanum lycopersicum cv. Calabash Rouge and Solanum lycopersicum cv. Pusa Ruby (which have been classified and further characterized as sensitive (S) and tolerant (T) to Cd, respectively). Scion S was grafted onto rootstock S (S/S) and rootstock T (S/T), and scion T was grafted onto rootstock T (T/T) and rootstock S (T/S). A 35 μM cadmium chloride (CdCl₂) treatment was used for stress induction in a hydroponic system. Both shoot and root contributions to Cd responses were observed, and they varied in a genotype- and/or organ-dependent manner for nutrient concentrations, oxidative stress parameters, antioxidant enzymes, and transporters gene expression. The findings overall provide evidence for the dominant role of the tolerant rootstock system in conferring reduced Cd uptake and accumulation. The lowest leaf Cd concentrations were observed in T/T (215.11 μg g^-1 DW) and S/T (235.61 μg g^-1 DW). Cadmium-induced decreases in leaf dry weight were observed only in T/S (-8.20%) and S/S (-13.89%), which also were the only graft combinations that showed decreases in chlorophyll content (-3.93% in T/S and -4.05% in S/S). Furthermore, the results show that reciprocal grafting is a fruitful approach for gaining insights into the organ-specific modulation of Cd tolerance and accumulation during the early stages of Cd exposure.

Influence of C14 alkane stress on antioxidant defense capacity, mineral nutrient element accumulation, and cadmium uptake of ryegrass

In order to explore the influence of C14 alkane on physiological stress responses, mineral nutrient elements uptake, cadmium (Cd) transfer, and uptake characteristics of Lolium perenne L. (ryegrass), a series of pot trials were conducted which included a moderate level of Cd (2.182 mg·kg-1) without (control) and with five levels of C14 alkane (V/m, 0.1%, 0.2%, 0.5%, 1%, 2%). Biomass and Cd content in the root and shoot, chlorophyll content, antioxidant enzymes activity, and mineral nutrient elements in the shoot of ryegrass were determined at the end of the experiment. The results indicated that Cd uptake significantly elevated at 0.1% C14 alkane treatment, then gradually decreased with the increase of C14 alkane concentration. Compared with the control, chlorophyll content was significantly suppressed and malondialdehyde (MDA) concentration obviously increased. Superoxide dismutase (SOD) activity and catalase (CAT) activity significantly increased to prevent the C14 alkane stress. With the increase of C14 alkane, the Mn concentration gradually increased; Mg and Fe significantly decreased. Correlation analysis showed that Mn was positively correlated with SOD (with the exception of 2% treatment) and CAT (p < 0.01), and negatively correlated with Cd uptake (p < 0.01). It implied that the increase of Mn induced by C14 alkane stress was an important reason for the decrease of Cd uptake.

A review on adsorptive separation of toxic metals from aquatic system using biochar produced from agro-waste

Water is a basic and significant asset for living beings. Water assets are progressively diminishing due to huge populace development, industrial activities, urbanization and rural exercises. Few heavy metals include zinc, copper, lead, nickel, cadmium and so forth can easily transfer into the water system either direct or indirect activities of electroplating, mining, tannery, painting, fertilizer industries and so forth. The different treatment techniques have been utilized to eliminate the heavy metals from aquatic system, which includes coagulation/flocculation, precipitation, membrane filtration, oxidation, flotation, ion exchange, photo catalysis and adsorption. The adsorption technique is a better option than other techniques because it can eliminate heavy metals even at lower metal ions concentration, simplicity and better regeneration behavior. Agricultural wastes are low-cost biosorbent and typically containing cellulose have the ability to absorb a variety of contaminants. It is important to note that almost all agro wastes are no longer used in their original form but are instead processed in a variety of techniques to improve the adsorption capacity of the substance. The wide range of adsorption capacities for agro waste materials were observed and almost more than 99% removal of toxic pollutants from aquatic systems were achieved using modified agro-waste materials. The present review aims at the water pollution due to heavy metals, as well as various heavy metal removal treatment procedures. The primary objectives of this research is to include an overview of adsorption and various agriculture based adsorbents and its comparison in heavy metal removal.

Physiological responses and health risks of edible amaranth under simultaneous stresses of lead from soils and atmosphere

Lead (Pb) is widely distributed in the environment that can impose potential risks to vegetables and humans. In this work, we conducted a pot experiment in Southern China to examine the physiological response and risk of edible amaranth (Amaranthus tricolor L.) under the simultaneous stresses of lead from soil and atmosphere. The results indicate that the lead content of amaranth substantially exceeded China's national standard when Pb concentration from soils and atmosphere was high, and comparing to teenagers and adults, children exposed a higher health risk after consuming the contaminated amaranth. Under the co-stress, the lead in roots of amaranth mainly came from the soil, but the Pb from atmospheric deposition can significantly affect the lead concentration in leaves. While lead from atmospheric deposition is found to promote the growth of amaranth, the stress of lead from the soils shows an inhibitory effect, as indicated by the increase in H₂O₂ content, the damage in cell membranes, and the limitation in chlorophyll synthesis. The antioxidant system in stems and leaves of amaranth can effectively alleviate the Pb toxicity. However, the stress of high lead concentration from soils can substantially suppress the antioxidant enzyme activity of roots. While it is found that heavy metals in soils can significantly affect the vegetables grown in a multi-source pollution environment, we also call for the attention on the potential health risk imposed by the lead from atmospheric deposition. This study provides an important reference for the prevention and control of crop contamination in multi-source pollution environments.

Unraveling the mechanisms controlling Cd accumulation and Cd-tolerance in Brachiaria decumbens and Panicum maximum under summer and winter weather conditions

We evaluated the mechanisms that control Cd accumulation and distribution, and the mechanisms that protect the photosynthetic apparatus of Brachiaria decumbens Stapf. cv. Basilisk and Panicum maximum Jacq. cv. Massai from Cd-induced oxidative stress, as well as the effects of simulated summer or winter conditions on these mechanisms. Both grasses were grown in unpolluted and Cd-polluted Oxisol (0.63 and 3.6 mg Cd kg^-1 soil, respectively) at summer and winter conditions. Grasses grown in the Cd-polluted Oxisol presented higher Cd concentration in their tissues in the winter conditions, but the shoot biomass production of both grasses was not affected by the experimental conditions. Cadmium was more accumulated in the root apoplast than the root symplast, contributing to increase the diameter and cell layers of the cambial region of both grasses. Roots of B. decumbens were more susceptible to disturbed nutrients uptake and nitrogen metabolism than roots of P. maximum. Both grasses translocated high amounts of Cd to their shoots resulting in oxidative stress. Oxidative stress in the leaves of both grasses was higher in summer than winter, but only in P. maximum superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities were increased. However, CO₂ assimilation was not affected due to the protection provided by reduced glutathione (GSH) and phytochelatins (PCs) that were more synthesized in shoots than roots. In summary, the root apoplast was not sufficiently effective to prevent Cd translocation from roots to shoot, but GSH and PCs provided good protection for the photosynthetic apparatus of both grasses.

Lonchocarpus cultratus, a Brazilian savanna tree, endures high soil Pb levels

Industrial revolution markedly increased the environmental contamination by different pollutants, which include the metal lead (Pb). The phytoremediation potential of native species from tropical regions is little known, especially for woody plants. The present study aimed to evaluate the performance of Lonchocarpus cultratus (Fabaceae), a tree species from the Brazilian savanna, grown in soil that was artificially contaminated with increasing Pb concentrations (control and 4 Pb treatments, 56, 120, 180, and 292 mg kg^-1) for 6 months. The biomass of L. cultratus was not depressed by exposure to Pb, despite the high accumulation of this metal (up to 7421.23 μg plant^-1), indicating a high plant tolerance to this trace metal. Lead was mainly accumulated in roots (from 67 to 99%), suggesting that the low root-to-shoot Pb translocation is a plant strategy to avoid Pb-induced damages in photosynthetic tissues. Accordingly, the content of chlorophylls a and b was maintained at similar levels between Pb-treated and control plants. Moreover, increments in leaf area were noticed in Pb-treated plants in comparison to the control plants (on average, 24.7%). In addition, root length was boosted in plants under Pb exposure (22.6-66.7%). In conclusion, L. cultratus is able to endure the exposure to high Pb concentrations in soil, being a potential plant species to be used for Pb phytostabilization in metal-contaminated soils in tropical regions.

Tolerance of tomato to cadmium-induced stress: analyzing cultivars with different fruit colors

The objective of the present study was to assess the response of tomato cultivars with different fruit colors to exposure to increasing Cd levels in the substrate by measuring the impacts of Cd on the oxidative stress indicators and physicochemical features of fruits, as well as plant development and yield components. A completely randomized experiment in a 3 × 3 factorial design [tomato cultivar (which produces purple, red, or white fruits) vs Cd level in the substrate (0, 3.6, or 12 mg kg^-1)] was performed. The cultivation of plants in substrate containing 3.6 mg kg^-1 Cd did not affect yield, but fruits exhibited nonpermissive Cd concentrations in both peel and mesocarp across all cultivars. By contrast, yield was decreased in plants with red and white fruits after their cultivation in substrate containing 12 mg kg^-1 Cd, while the productivity of plants with purple fruits was maintained under such conditions. The hydrogen peroxide content in the fruit mesocarp depended only on cultivar. However, an increased lipid peroxidation level was detected in the mesocarp of purple fruits at the highest Cd concentration. No parameters of fruit quality [i.e., diameter, length, °Brix, pH, titratable acidity, color (L*, a*, and b*), and concentrations of lycopene and β-carotene in mesocarp] were affected by long-term exposure to Cd at 12 mg kg^-1. In conclusion, the results of this study suggested that the potential Cd side effects on diverse tomato quality features can be buffered at the fruit level because these features were maintained at the usual values despite high Cd concentrations in tomato peel and pulp. Moreover, these buffering mechanisms are independent of lycopene and β-carotene concentrations in fruit peel, since the three tomato cultivars that were evaluated in the present study (white fruits, possessing no or negligible concentrations of these carotenoids, and red and purple tomato, possessing high lycopene and β-carotene concentrations) were able to sustain several fruit quality parameters after long-term exposure to high Cd concentrations in the substrate.

Cadmium accumulation and physiological response of Amaranthus tricolor L. under soil and atmospheric stresses

In this study, cadmium (Cd) solution spraying and Cd-contaminated soil pot experiments were conducted to investigate the influence of Cd from atmospheric deposition and soil on the growth, cumulative distribution, chemical morphology, physiological, and biochemical responses of Amaranthus tricolor L. The results indicated that Cd in plants mainly came from soil (92-98%) and was stored in the roots in large quantities while the portion from atmospheric deposition could also effectively increase Cd content in stems and leaves (2-3%). Cd was mainly stored in plant cell walls and would transfer to the soluble part under high-concentration soil stress Cd from atmospheric deposition alone promoted the growth of plants, but high Cd concentrations from soil had the negative influence. The contents of H₂O₂ and MDA in plants increased under soil and atmospheric Cd stress, indicating that the plant cells were damaged by oxidative stress. The content of antioxidant enzymes such as POD, CAT, SOD, and antioxidants like AsA and GSH increased under low-concentration Cd stress but decreased under elevated stress, suggesting that high Cd-contaminated soil poses severe toxicity on the antioxidant system of the plants. Hence, the accumulation and physiological response of plants under multi-source Cd contamination were mainly affected by high soil Cd concentrations. Though the effect of atmospheric deposition is relatively less, it cannot be ignored.

Rapid Hormetic Responses of Photosystem II Photochemistry of Clary Sage to Cadmium Exposure

Five-day exposure of clary sage (Salvia sclarea L.) to 100 μM cadmium (Cd) in hydroponics was sufficient to increase Cd concentrations significantly in roots and aboveground parts and affect negatively whole plant levels of calcium (Ca) and magnesium (Mg), since Cd competes for Ca channels, while reduced Mg concentrations are associated with increased Cd tolerance. Total zinc (Zn), copper (Cu), and iron (Fe) uptake increased but their translocation to the aboveground parts decreased. Despite the substantial levels of Cd in leaves, without any observed defects on chloroplast ultrastructure, an enhanced photosystem II (PSII) efficiency was observed, with a higher fraction of absorbed light energy to be directed to photochemistry (ΦPSΙΙ). The concomitant increase in the photoprotective mechanism of non-photochemical quenching of photosynthesis (NPQ) resulted in an important decrease in the dissipated non-regulated energy (ΦNO), modifying the homeostasis of reactive oxygen species (ROS), through a decreased singlet oxygen (1O2) formation. A basal ROS level was detected in control plant leaves for optimal growth, while a low increased level of ROS under 5 days Cd exposure seemed to be beneficial for triggering defense responses, and a high level of ROS out of the boundaries (8 days Cd exposure), was harmful to plants. Thus, when clary sage was exposed to Cd for a short period, tolerance mechanisms were triggered. However, exposure to a combination of Cd and high light or to Cd alone (8 days) resulted in an inhibition of PSII functionality, indicating Cd toxicity. Thus, the rapid activation of PSII functionality at short time exposure and the inhibition at longer duration suggests a hormetic response and describes these effects in terms of "adaptive response" and "toxicity", respectively.

Mechanism of Remediation of Cadmium-Contaminated Soil With Low-Energy Plant Snapdragon

In the process of remediation of contaminated soil, we should give full play to the role of low-energy plants and fully display the concept of modern energy-saving and environmental protection. Phytoremediation is an effective method to remediate cadmium-contaminated soil, and root exudates play an important part in this process. Here, the response of snapdragon in a pot-culture experiment under two concentrations of Cd (1.0 and 2.5 mg/kg) was evaluated. Snapdragon is a medicinal plant with low energy consumption, which has low requirements on environmental factors and strong resistance. The results showed that both Cd concentrations interfere with the uptake of B, P, Cu, Mn, Mo, and Zn by the soil. The results also showed that plant type and Cd stress can significantly change the concentrations and species of root exudates. The metabolic changes of root exudates revealed the active defense mechanism of plants to Cd stress: up-regulating of amino acids to sequester/exclude Cd, regulation of citric acid on chelation/complexation, and precipitation of cadmium ions. The application of snapdragon can effectively reduce energy consumption and gradually improve the utilization rate of vegetation, which promotes the degradation of cadmium pollutants in soil.

Hormesis in plants under Cd exposure: From toxic to beneficial element?

Tolerance level to cadmium (Cd) toxicity is generally associated with reductions of the internal Cd accumulation in living organisms. In plants, Cd exposure frequently triggers negative effects on their growth and productivity. However, an increased number of studies has reported the improved performance of some plant species (or their accessions/genotypes/varieties/cultivars/clones) to Cd exposure, despite Cd accumulation in their roots and shoots. These results indicate that plants have developed protective strategies to neutralize the side-effects from Cd toxicity or, more controversially, mechanisms that employ Cd as beneficial element. Here, we gathered information about Cd-induced hormetic effects on plants, and explored the potential mechanisms that allow them to have a better performance under Cd exposure. The promotion of plant development depends on both direct and indirect Cd-induced alterations in the metabolism of plants and their surround environment. In addition, the mechanisms behind the positive Cd-induced transgenerational effects were also discussed in the present paper.

New insights into cadmium stressful-conditions: Role of ethylene on selenium-mediated antioxidant enzymes

Cadmium (Cd) contamination has generated an environmental problem worldwide, leading to harmful effects on human health and damages to plant metabolism. Selenium (Se) is non essential for plants, however it can improve plant growth and reduce the adverse effects of abiotic stress. In addition, ethylene may interplay the positive effects of Se in plants. In order to investigate the role of ethylene in Se-modulation of antioxidant defence system in response to Cd-stress, we tested the hormonal mutant Epinastic (epi) with a subset of constitutive activation of the ethylene response and Micro-Tom (MT) plants. For this purpose, Se mineral uptake, Cd and Se concentrations, pigments, malondialdeyde (MDA) and hydrogen peroxide (H₂O₂) contents, ethylene production, glutathione (GSH) compound, and superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), glutathione reductase (GR) and glutathione peroxidase (GSH-Px) activities were analysed in MT and epi plants submitted to 0.5 mM CdCl₂ and 1 μM of selenate or selenite. MT plants treated with both Se forms increased growth in the presence or not of 0.5 mM CdCl₂, but not change epi growth. Both Se forms reduced Cd uptake in MT plants and cause reverse effect in epi plants. P, Mg, S, K and Zn uptake increased in epi plants with Se application, irrespective to Cd exposure. Chlorophylls and carotenoids contents decreased in both genotypes under Cd exposure, in contrast to what was observed in epi leaves in the presence of Se. When antioxidant enzymes activities were concerned, Se application increased Mn-SOD, Fe-SOD and APX activities. In the presence of Cd, MT and epi plants exhibited decreased SOD activity and increased CAT, APX and GR activities. MT and epi plants with Se supply exhibited increased APX and GR activities in the presence of Cd. Overall, these results suggest that ethylene may be involved in Se induced-defence responses, that triggers a positive response of the antioxidant system and improve growth under Cd stress. These results showed integrative roles of ethylene and Se in regulating the cell responses to stressful-conditions and, the cross-tolerance to stress could be used to manipulate ethylene regulated gene expression to induce heavy metal tolerance.

Cadmium toxicity and its relationship with disturbances in the cytoskeleton, cell cycle and chromosome stability

This study aimed to investigate the mode of action of cadmium (Cd) toxicity at cell level, especially at early stages of plant exposure. Tomato seedlings were cultivated in growth media containing from 0.1 to 70 µM CdCl₂ for 24 h. Mitotic index, chromosome abnormality, DNA integrity and organization of tubulin-based structures were assessed in root cells. As higher the Cd concentration in the growth media, higher was the DNA damage intensity and the occurrence of chromosomal abnormalities that included chromosome lost, bridges, stickiness, C-metaphase and polyploidy. The profile of chromosomal aberrations also varied with elevated Cd concentration, being observed increases in the frequency of chromosome stickiness. The mitotic index was reduced at the lowest Cd concentration, but such reduction was statistically similar to that detected at the highest concentration, suggesting that mitotic depression is a rapid outcome and, at same time, a Cd-induced effect that is limited at the first 24 h of direct root exposure to this metal. Under exposure to 20 µM CdCl₂, heterogenous distribution of the spindle fibers, formation of two spindle complexes in both of the cell poles, absence of centrosome center, polarization of the spindle fibers during cell division, and non-uniform tubulin deposition in microtubule and phragmoplast were noticed. The results indicate that the tubulin-dependent components of cytoskeleton are Cd targets, and the sensitivity of tubulin-based structures to Cd exposure depends on cell cycle phase. Moreover, DNA damage intensity and chromosomal abnormality profile can be employed as markers of Cd toxicity level.

Quantitative proteomic analysis of tomato genotypes with differential cadmium tolerance

This is a report on comprehensive characterization of cadmium (Cd)-exposed root proteomes in tomato using label-free quantitative proteomic approach. Two genotypes differing in Cd tolerance, Pusa Ruby (Cd-tolerant) and Calabash Rouge (Cd-sensitive), were exposed during 4 days to assess the Cd-induced effects on root proteome. The overall changes in both genotypes in terms of differentially accumulated proteins (DAPs) were mainly associated to cell wall, redox, and stress responses. The proteome of the sensitive genotype was more responsive to Cd excess, once it presented higher number of DAPs. Contrasting protein accumulation in cellular component was observed: Cd-sensitive enhanced intracellular components, while the Cd-tolerant increased proteins of extracellular and envelope regions. Protective and regulatory mechanisms were different between genotypes, once the tolerant showed alterations of various protein groups that lead to a more efficient system to cope with Cd challenge. These findings could shed some light on the molecular basis underlying the Cd stress response in tomato, providing fundamental insights for the development of Cd-safe cultivars. Graphical abstract.