Visualization and quantification of cadmium accumulation, chelation and antioxidation during the process of vacuolar compartmentalization in the hyperaccumulator plant Solanum nigrum L

Hyperaccumulators store metals in the vacuoles of leaf cells. To investigate the role of vacuolar compartmentalization in Cd accumulation, chelation and induced antioxidation, we quantified the amounts of total cadmium (Cd), Cd²⁺, glutathione (GSH) and reactive oxygen species (ROS) in leaf cells of Solanum nigrum L. The results confirmed that vacuoles were, indeed, the main storage compartments for Cd. We then found that with increased Cd treatment concentration, the proportion of vacuolar Cd in protoplasts showed its ultimate storage capacity (82.24 %-83.40 %), and the Cd concentration stored in the protoplast maintained at a certain level (73.81-77.46 mg L^-1). Besides, studies on different forms of Cd showed that the chelation state was dominant in the protoplast. The large level appearance of Cd²⁺ outside the vacuole revealed the limitations of vacuolar Cd²⁺ sequestration. The relationships between the combined forms of Cd and GSH outside the vacuole (R² = 0.9906) showed GSH was mainly distributed to important compartments for chelation, not to vacuoles. We also demonstrated the presence of ROS-induced oxidative stress and detoxification mediated by the antioxidant GSH in vacuoles, suggesting that sequestration into vacuoles is an active process accompanied by chelation and antioxidant-mediated detoxification.

The potential of medicinal plant extracts in improving the phytoremediation capacity of Solanum nigrum L. for heavy metal contaminated soil

This study focused on the effects of eight medicinal plant extracts on Solanum nigrum L. potential to accumulate Cd and Pb from soil. These medicinal plants were common and relatively cheap. The eight 10% water extracts were made from the peel of Citrus reticulata Blanco (PCR), fruit of Phyllanthus emblica L. (FPE), root of Pueraria Lobata (Willd.) Ohwi (RPL), rhizome of Polygonatum sibiricum Red (RPS), root of Astragalus propinquus Schischkin (RAP), bud of Hemerocallis citrina Baroni (BHC), seed of Nelumbo nucifera Gaertn (SNN) and fruit of Prunus mume (Sieb.) Sieb.etZuce (FPM). The results showed that among all exposures, the treatment with FPE resulted in the significant increase (p < 0.05) of Cd and Pb concentration in shoots and roots of S. nigrum by 32.5% and 65.2% for Cd, and 38.7% and 39.6% for Pb. The biomasses of S. nigrum in all plant extract treatments were not significantly changed (p < 0.05) compared to the control (CK). The Cd and Pb extraction rates of S. nigrum in FPE treatment were increased respectively by 60.5% and 40.5% compared to CK. Though the treatment with EDTA significantly improved (p < 0.05) the concentration of Cd and Pb of S. nigrum, the Cd and Pb masses (ug plant^-1) of S. nigrum did not show any significant difference compared to the CK due to the significant decrease in the shoot (20.4%) and root (22.0%) biomasses. The chelative role of FPE might be relation with its higher polyphenolic compounds. However, not sure if the contents of polyphenolic compounds was the only differences between FPE and other additives. Thus, some unknown organic matters might also play active role. This study provided valuable information on improving the phytoremediation potential of hyperaccumulator.

Promotion of growth and phytoextraction of cadmium and lead in Solanum nigrum L. mediated by plant-growth-promoting rhizobacteria

Plant growth-promoting rhizobacteria (PGPR) are a specific category of microbes that improve plant growth and promote greater tolerance to metal stress through their interactions with plant roots. We evaluated the effects of phytoremediation combining the cadmium accumulator Solanum nigrum L. and two Cd- and Pb-resistant bacteria isolates. To understand the interaction between PGPR and their host plant, we conducted greenhouse experiments with inoculation treatments at Nanjing Agricultural University (Jiangsu Province, China), in June 2018. Two Cd- and Pb-resistant PGPR with various growth-promoting properties were isolated from heavy metal-contaminated soil. 16S rRNA analyses indicated that the two isolates were Bacillus genus, and they were named QX8 and QX13. Pot experiments demonstrated that inoculation may improve the rhizosphere soil environment and promote absorption of Fe and P by plants. Inoculation with QX8 and QX13 also enhanced the dry weight of shoots (1.36- and 1.7-fold, respectively) and roots (1.42- and 1.96-fold) of plants growing in Cd- and Pb-contaminated soil, and significantly increased total Cd (1.28-1.81 fold) and Pb (1.08-1.55 fold) content in aerial organs, compared to non-inoculated controls. We also detected increases of 23% and 22% in the acid phosphatase activity of rhizosphere soils inoculated with QX8 and QX13, respectively. However, we did not detect significant differences between inoculated and non-inoculated treatments in Cd and Pb concentrations in plants and available Cd and Pb content in rhizosphere soils. We demonstrated that PGPR-assisted phytoremediation is a promising technique for remediating heavy metal-contaminated soils, with the potential to enhance phytoremediation efficiency and improve soil quality.

Aqueous extracts from the selected hyperaccumulators used as soil additives significantly improve accumulation capacity of Solanum nigrum L. for Cd and Pb

The effects of soil treatment with aqueous extracts from three hyperaccumulators on Cd and Pb accumulation by Solanum nigrum L. were determined. The stem (S-RG) and leaf extracts (L-RG) of Rorippaglobosa (Turcz.) Thell., and stem extract (S-BP) of Bidens pilosa L. significantly enhanced Cd and Pb total accumulation capacity of S. nigrum compared to control (by 44 %, 47 %, and 29 % for Cd and by 28 %, 28 % and 21 % for Pb, respectively), while EDTA caused its 9 % and 15 % decrease due to the plant biomass reduction (by 33 %). The leaching experiments reflected affinity of additives to metal mobilization in soils. The concentrations of total organic acid in S-RG, L-RG and S-BP were the highest among studied extracts, which besides the beneficial effect on the soil environment (microbe number and enzyme activities), may be partial reasons of strong promotion of S. nigrum accumulation capacity for Cd and Pb. It was shown that hyperaccumulation properties of a plant are not a prerequisite of enhancing effect of the plant-based soil additive on the metal accumulation capacity of the target living hyperaccumultor. The plant-based chelators were found to be promising candidates for EDTA and other chemicals replacement in promoting efficient and environmentally safe phytoremediation.

The front-heavy and back-light nitrogen application mode to increase stem and leaf biomass significantly improved cadmium accumulation in Solanum nigrum L

Differently from the goal of fertilization in agricultural production to enhance the yield of seeds, the aim of present work focused on cadmium (Cd) phytoremediation is to increase the stem and leaf biomasses as much as possible due to they are the main organs of a hyperaccumulator extracting risk elements from soil. This experiment compared the effects of different nitrogen (N) application modes on Cd accumulation from soil by Solanum nigrum L. The results showed that stem and leaf biomasses of S. nigrum reached the maximum values with the N fertilizer application at Mode 4 (50 %: 40 %: 10 %, i.e. the front-heavy and back-light application of nitrogen fertilizer). In particular, application of N as (NH₄)₂SO₄ and CH₄N₂O produced the greatest increases in S. nigrum biomasses compared to the control (CK₂) with no N fertilizer. N concentration of S. nigrum and N fertilizer productivity under its different treatments were consistent with the above results. Similarly, Cd capacities were the highest in shoots of S. nigrum in Mode 4 either due to their Cd concentration without affected by N fertilizers. Thus, Mode 4 N application showed very important scientific merit for effective Cd phytoextraction in the real conditions.

Combined toxicity and detoxification of lead, cadmium and arsenic in Solanum nigrum L

A 3-factor-5-level central composite design was conducted to investigate the combined toxicity and detoxification mechanisms of lead (Pb), cadmium (Cd) and arsenic (As) in Solanum nigrum L. The three metal(loid)s exhibited low-dose stimulation and high-dose inhibition on plant length. Analyses of eleven oxidative stress and antioxidant parameters showed all Pb, Cd and As induced oxidative damages, and the co-exposure further enhanced their toxic effects. Pb, Cd and As were mainly accumulated in plant roots and poorly translocated to shoots, being beneficial for metal(loid) detoxification. The results of subcellular fractionation showed that Pb, Cd and As in plant leaves, stems and roots were mainly localized in the cell wall and soluble fractions. Most of Pb and As in soils occurred in residual fraction while Cd in exchangeable fraction. Although single Pb, Cd and As in all plant tissues existed predominantly in 1 M NaCl-soluble form, the d-H₂O and 80 % ethanol-soluble forms were increased under the binary or ternary combinations. This study will conduce to the potential use of S. nigrum L. in the phytostablization of soil co-contaminated with Pb, Cd and As.

Indole-3-acetic acid promotes cadmium (Cd) accumulation in a Cd hyperaccumulator and a non-hyperaccumulator by different physiological responses

To study the effects of indole-3-acetic acid (IAA) on cadmium (Cd) accumulation and the physiological responses of the Cd hyperaccumulator Solanum nigrum and non-hyperaccumulator Solanum melongena, a pot experiment was conducted in soil containing 2 mg kg^-1 Cd in which different concentrations of IAA (0, 10, 20, or 40 mg L^-1) were sprayed on plant leaves. The results showed that Cd accumulation in shoots of S. nigrum was significantly increased by 30% after the addition of 10 mg L^-1 IAA under 2 mg kg^-1 Cd stress compared to that in the control, but shoot Cd accumulation showed no significant change in S. melongena after this IAA treatment. Additionally, the growth and the proline content in the two species were significantly increased by 20 mg L^-1 IAA. The activities of peroxidase and catalase in leaves of S. nigrum and the activity of superoxide dismutase (SOD) in S. melongena were significantly increased and their malondialdehyde content was significantly decreased compared to those in the control. The root activity of S. nigrum was significantly improved after 10 and 20 mg L^-1 IAA treatments, but no significant difference was observed in S. melongena. The correlation analysis results showed that the Cd concentration in leaves of S. nigrum was significantly and positively correlated with the carotenoid and proline contents, and there was also a significant positive correlation between the Cd concentration and SOD activity in leaves of S. melongena. Therefore, S. nigrum is an ideal plant for the phytoextraction of Cd-contaminated soil assisted by IAA. IAA promotes Cd accumulation in plant shoots by enhancing the accumulation of carotenoids and proline in S. nigrum and maintaining a high leaf SOD activity in S. melongena.

Phytoremediation of multi-metal contaminated mine tailings with Solanum nigrum L. and biochar/attapulgite amendments

A greenhouse experiment was conducted to investigate an enhanced phytoremediation technique for multi-metal contaminated mine tailings by Solanum nigrum L. and using biochar/attapulgite as soil amendments. The 10% attapulgite (MA₂) and 10% biochar (MB₂) were recommended as the optimum chemical proportions for amendment materials. Plant length and fresh weight in the MA₂/MB₂-applied treatments were significantly higher than that in the non-amended treatment, indicating MA₂ and MB₂ amendments could alleviate metal phytotoxicity. Metal uptake in plant leaves was lower with MA₂ and MB₂ application than that in the non-amended treatment. However, metal uptake in plant roots was significantly increased with MA₂ and MB₂ application from the fifth month, suggesting that MA₂ and MB₂ had significant enhancement on metal stabilization. Temporal variation of metal translocation in soil-to-plant system showed that the function of MA₂ and MB₂ reached the plateau nearly in the seventh month. The removal rates of metals were higher after the application of MA₂ than MB₂, and by the following order: Cu (39.6%) > Zn (35.0%) > Cd (34.1%) > Hg (32.1%) > Pb (31.8%) > Mn (19.1%). The synergistic effect between S. nigrum L. and MA₂/MB₂ appeared to be particularly effective in terms of metal phytostabilization, and MA₂ was superior to MB_2.

Characteristics of cadmium accumulation and isotope fractionation in higher plants

Cadmium (Cd) pollution of the soil is an important global environmental issue owing to its great toxicity. The study of metal isotope fractionation is a novel technique that could be used to identify and quantify metal uptake and transport mechanisms in plant. In this study, cadmium tolerant Ricinus communis and hyperaccumulator Solanum nigrum have been cultured in different Cd concentration nutrient solutions. The Cd isotope values, metal elements concentrations in the organs (root, stem and leaf) in the two plant species have been measured during the growth periods (10d, 15d, 20d, 25d, and 30d). The results indicate that the organs of S. nigrum could be enriched with lighter Cd isotopes compared with R. communis. In addition, the Cd isotope fractionation become smaller when the plants were subjected to high Cd toxicity, which indicates that Cd isotope fractionation reflected the extent of Cd toxicity to plants. This study advances our current view of Cd translocation machination in plants.

Differential effects of acetophenone on shoots' and roots' metabolism of Solanum nigrum L. plants and implications in its phytoremediation

The wide ranges of uses for acetophenone make it more available and expected to accumulate in the biosphere, where consequently it can threat ecosystems. To remediate this problem, the use of Solanum nigrum L. plants for the clean-up of acetophenone-contaminated sites was explored. Also, plant root and shoot biometry and metabolism where assayed to better understand the effects of this organic compound and to pinpoint possible metabolic pathways to be targeted for future manipulations for increasing this plant species' remediation efficiency. Although undergoing through some stress, detected by increases in ROS and lipid peroxidation in both organs, plants were able to rapidly eliminate all acetophenone from the nutrient solution after 7 days of exposure, being this compound mainly detoxified at the root level. Additionally, acetophenone lead to a differential metabolic response in roots and shoots, where antioxidant mechanisms where differentially activated, while nitrogen assimilation was repressed in shoots and activated in roots. These results confirm that S. nigrum is a good phytoremediation tool for acetophenone and suggest that enhancing shoot GS activity may provide more nitrogen precursors for the synthesis of thiolated proteins and glutathione to increase tolerance to acetophenone in roots and shoots, respectively.

Host plant growth promotion and cadmium detoxification in Solanum nigrum, mediated by endophytic fungi

Current investigation conducted to evaluate the associated fungal endophyte interactions of a Cd hyper-accumulator Solanum nigrum Korean ecotype under varying concentrations of Cd. Two indole-3-acetic acid (IAA) producing fungal strains, RSF-4L and RSF-6L, isolated from the leaves of S. nigrum, were initially screened for Cd tolerance and accumulation potential. In terms of dry biomass production, the strain RSF-6L showed higher tolerance and accumulation capacity for Cd toxicity in comparison to RSF-4L. Therefore, RSF-6L was applied in vivo to S. nigrum and grown for six weeks under Cd concentrations of 0, 10, and 30mgKg^-1 of dry sand. The effect of fungal inoculation assessed by plant physiological responses, endogenous biochemical regulations, and Cd profile in different tissues. Significant increase were observed in plant growth attributes such as shoot length, root length, dry biomass, leaf area, and chlorophyll contents in inoculated RSF-6L plants in comparison to non-inoculated plants with or without Cd contamination. RSF-6L inoculation decreased uptake of Cd in roots and above ground parts, as evidenced by a low bio-concentration factor (BCF) and improved tolerance index (TI). However, Cd concentration in the leaves remained the same for inoculated and non-inoculated plants under Cd spiking. Fungal inoculation protected the host plants, as evidenced by low peroxidase (POD) and polyphenol peroxidase (PPO) activities and high catalase (CAT) activity. Application of appropriate fungal inoculation that can improve tolerance mechanisms of hyper-accumulators and reduce Cd uptake can be recommended for phyto-stabilisation/immobilisation of heavy metals in crop fields.

Cadmium accumulation is enhanced by ammonium compared to nitrate in two hyperaccumulators, without affecting speciation

Nitrogen fertilization could improve the efficiency of Cd phytoextraction in contaminated soil and thus shorten the remediation time. However, limited information is available on the effect of N form on Cd phytoextraction and associated mechanisms in plants. This study examined the effect of N form on Cd accumulation, translocation, and speciation in Carpobrotus rossii and Solanum nigrum Plants were grown in nutrient solution with 5-15 μM Cd in the presence of 1000 µM NH4 (+) or NO3 (-) Plant growth and Cd uptake were measured, and Cd speciation was analyzed using synchrotron-based X-ray absorption spectroscopy. Shoot Cd accumulation was 30% greater with NH4 (+) than NO3 (-) supply. Carpobrotus rossii accumulated three times more Cd than S. nigrum. However, Cd speciation in the plants was not influenced by N form, but it did vary with species and tissues. In C. rossii, up to 91% of Cd was bound to S-containing ligands in all tissues except the xylem sap where 87-95% were Cd-OH complexes. Furthermore, the proportion of Cd-S in shoots was substantially lower in S. nigrum (44-69%) than in C. rossii (60-91%). It is concluded that the application of NH4 (+) (instead of NO3 (-)) increased shoot Cd accumulation by increasing uptake and translocation, rather than changing Cd speciation, and is potentially an effective approach for increasing Cd phytoextraction.

Synthesis and herbicidal activity evaluation of novel α-amino phosphonate derivatives containing a uracil moiety

A series of novel α-amino phosphonate derivatives containing a uracil moiety 3a-3l were designed and synthesized by a Lewis acid (magnesium perchlorate) catalyzed the Kabachnik-Fields reaction. The bioassays {in vitro, in vivo [Glass House 1 (GH1) and Glass House 2 (GH2)]} showed that most of compounds 3 exhibited excellent and selective herbicidal activities; for example, in GH1 test, compounds 3b, 3d, 3f, 3h and 3j showed excellent and wide spectrum herbicidal activities at the dose of 1000 g/ha, and compounds 3b and 3j exhibited 100% inhibition activities against the four plants in both post- and pre-emergence treatments. Moreover, most of compounds 3 showed higher inhibition against Amaranthus retroflexus and Digitaria sanguinalis than Glyphosate did in pre-emergence treatment. In GH2 test, the four compounds (3b, 3d, 3h and 3j) exhibited 100% inhibition against Solanum nigrum, Amaranthus retroflexus and Ipomoea hederacea in post-emergence treatment and displayed 100% inhibition against Solanum nigrum, Amaranthus retroflexus in pre-emergence treatment at the rate of 250 g/ha, and compound 3b showed the best and broad spectrum herbicidal activities against the six test plants. However, the four compounds displayed weaker herbicidal activities against Lolium perenne and Echinochloa crus-galli than the other four plants at the rate of 250 g/ha in both pre- and post-emergence treatments. So, compounds 3 can be used as a lead compound for further structure optimization for developing potential selective herbicidal agent. Their preliminary structure-activity relationships were also investigated.

Potential of Gibberellic Acid 3 (GA3) for Enhancing the Phytoremediation Efficiency of Solanum nigrum L

A microcosm experiment with artificially contaminated soils was conducted in a greenhouse to evaluate the effect of gibberellic acid 3 (GA3) on phytoremediation efficiency of Solanum nigrum L. The GA3 was applied at three different concentrations (10, 100, 1000 mg L(-1)) to S. nigrum. Results indicated that GA3 can significantly (p < 0.05) increase the biomass of S. nigrum by 56 % at 1000 mg L(-1). Concurrently, GA3 application increased Cd concentrations in the shoot of S. nigrum by 16 %. The combined effects resulted in an increase in the amount of Cd extracted by a single plant by up to 124 %. Therefore, it is possible to use GA3 to promote the Cd phytoremediation efficiency of S. nigrum.

Determining soil enzyme activities for the assessment of fungi and citric acid-assisted phytoextraction under cadmium and lead contamination

Microorganism or chelate-assisted phytoextraction is an effective remediation tool for heavy metal polluted soil, but investigations into its impact on soil microbial activity are rarely reported. Consequently, cadmium (Cd)- and lead (Pb)-resistant fungi and citric acid (CA) were introduced to enhance phytoextraction by Solanum nigrum L. under varied Cd and Pb pollution levels in a greenhouse pot experiment. We then determined accumulation of Cd and Pb in S. nigrum and the soil enzyme activities of dehydrogenase, phosphatase, urease, catalase, sucrase, and amylase. Detrended canonical correspondence analysis (DCCA) was applied to assess the interactions between remediation strategies and soil enzyme activities. Results indicated that the addition of fungi, CA, or their combination enhanced the root biomass of S. nigrum, especially at the high-pollution level. The combined treatment of CA and fungi enhanced accumulation of Cd about 22-47 % and of Pb about 13-105 % in S. nigrum compared with the phytoextraction alone. However, S. nigrum was not shown to be a hyperaccumulator for Pb. Most enzyme activities were enhanced after remediation. The DCCA ordination graph showed increasing enzyme activity improvement by remediation in the order of phosphatase, amylase, catalase, dehydrogenase, and urease. Responses of soil enzyme activities were similar for both the addition of fungi and that of CA. In summary, results suggest that fungi and CA-assisted phytoextraction is a promising approach to restoring heavy metal polluted soil.

Targeting key metabolic points for an enhanced phytoremediation of wastewaters pre-treated by the photo-Fenton process using Solanum nigrum L

Several physiological, biochemical and molecular biology responses were analysed in Solanum nigrum L. plants exposed for 28 days to an effluent that resulted from the photo-Fenton treatment of a highly concentrated pesticide and systemic fungicide aqueous solution, containing metalaxyl as active compound (150mgL(-1)), in order to pinpoint metabolic steps for a future increase of these plants' capacity to deal with the chemical process by-products. Although plants suffered oxidative stress, as indicated by increased membrane damage and a negative effect on plant biomass, they absorbed the excess iron and acted on the resulting by-products present in the effluent after the photo-Fenton process. Nitrogen assimilation and metallothionein gene expression were down regulated, while glutathione biosynthesis increased. These results suggest an enhanced nitrogen assimilation and/or metallothionein accumulation as relevant key points for further plant improvement in order to increase the efficiency of this innovative strategy that considers integration of the photo-Fenton process (as chemical primary treatment) with S. nigrum L. plants (as biological remediation post-treatment) for heavily polluted wastewaters.

Chromium toxicity tolerance of Solanum nigrum L. and Parthenium hysterophorus L. plants with reference to ion pattern, antioxidation activity and root exudation

Chromium (Cr), being a highly toxic metal, adversely affects the mineral uptake and metabolic processes in plants when present in excess. The current study was aimed at investigating the Cr accumulation in various plant tissues and its relation to the antioxidation activity and root exudation. Plants were grown in soil spiked with different concentrations of Cr for three weeks in pots and analysed for different growth, antioxidants and ion attributes. Furthermore, plants treated with different concentrations of Cr in pots were shifted to rhizobox-like system for 48h and organic acids were monitored in the mucilage dissolved from the plant root surface, mirroring rhizospheric solution. The results revealed that the Cr application at 1mM increased the shoot fresh and dry weight and root dry weight of Solanum nigrum, whereas the opposite was observed for Parthenium hysterophorus when compared with lower levels of Cr (0.5mM) or control treatment. In both plant species, Cr and Cl concentrations were increased while Ca, Mg and K concentrations in root, shoot and root exudates were decreased with increasing levels of Cr. Higher levels of Cr treatments enhanced the activities of SOD, POD and proline content in leaves of S. nigrum, whereas lower levels of Cr treatment were found to have stimulatory effects in P. hysterophorus. P. hysterophorus exhibited highest exudation of organic acid contents. With increasing levels of Cr treatments, citric acid concentration in root exudates increased by 35% and 44% in S. nigrum, whereas 20% and 76% in P. hysterophorus. Cr toxicity was responsible for the shoot growth reduction of S. nigrum and P. hysterophorus, however, shoot growth response was different at different levels of applied Cr. Consequently, Cr stress negatively altered the plant physiology and biochemistry. However, the enhanced antioxidant production, Cl uptake and root exudation are the physiological and biochemical indicators for the plant adaptations in biotic systems polluted with Cr.

Phytoremediation potential of Solanum nigrum L. under different cultivation protocols

In this study, Solanum nigrum L. was used as a hyperaccumulator for remediation of cadmium contaminated soil, and 3 different cultivation protocols were investigated. The results showed that a double cropping treatment enhanced the phytoremediation efficiency significantly, since it increased the amount of Cd extracted in one growing season by a factor of 1.62 compared to single cropping. However, the labor cost for double cropping was twice that of single cropping. If the time consumed is considered as a cost of phytoremediation, the double cropping treatment might be considered as an effective and economic cultivation protocol by reducing the overall time required to reach the targeted soil quality.

Silicon attenuates cadmium toxicity in Solanum nigrum L. by reducing cadmium uptake and oxidative stress

Solanum nigrum L. is considered to be a potential plant for restoring Cd-contaminated soils. Si could enhance plants tolerance to heavy metal; however, the mechanism of Si-mediated alleviation of Cd toxicity in S. nigrum was not clear. Three-week-old S. nigrum seedlings were grown in Hoagland solution containing 0 or 100 μM Cd with or without 1 mM Si for 4 days. The results showed that the Cd concentration both in roots and shoots of Si-supplied plant was significantly reduced, especially in expanding and old leaves. The relative proportion of ethanol-extractable Cd, water-extractable Cd and NaCl-extractable Cd in roots was increased by adding Si, while the root-to-shoot Cd translocation was not decreased. Furthermore, in comparison with single Cd treatment, supplying Si could reduce H₂O₂ accumulation and cell death in roots, and the electrolyte leakage and H₂O₂ concentration in functional leaves. Moreover, the activity of superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), peroxidase (POD, EC 1.11.1.7) and ascorbate peroxidase (APX, EC 1.11.1.11) in functional leaves was markedly increased by Cd exposure, while the antioxidative enzyme activities in Cd plus Si treatment seedlings were significantly lower than that in Cd treatment alone, this decrease might be attributed to the reduction of Cd concentration and Cd-induced oxidative damages. These results demonstrate that Si-enhanced Cd tolerance in S. nigrum is mainly due to the decrease of Cd uptake in roots and Cd distribution in expanding and old leaves, as well as lowering oxidative stress induced by Cd in plants.

Physiological impacts of soil pollution and arsenic uptake in three plant species: Agrostis capillaris, Solanum nigrum and Vicia faba

In order to revegetate an industrial soil polluted by trace metals and metalloids (As, Pb, Cu, Cd, Sb), the impact of pollution on three plant species, Solanum nigrum and Agrostis capillaris, both native species in an industrial site, and Vicia faba, a plant model species, is studied. Following the study of soil pollution from the industrial wasteland of Auzon, it appears that the As is the principal pollutant. Particular attention is given to this metalloid, both in its content and its speciation in the soil that the level of its accumulation in plants. In V. faba and A. capillaris, the trace metals and metalloids inhibit the biomass production and involve a lipid peroxidation in the leaves. Furthermore, these pollutants cause a photosynthesis perturbation by stomatal limitations and a dysfunction of photosystem II. Whatever the plant, the As content is less than 0.1 percent of dry matter, the majority of As absorbed is stored in the roots which play the role of trap organ. In parallel, the culture of S. nigrum decreases significantly the exchangeable and weakly adsorbed fraction of As in rhizospheric soil. This study has highlighted the ability of tolerance to trace metals of S. nigrum and to a lesser extent A. capillaris. Our data indicate that V. faba is not tolerant to soil pollution and is not a metallophyte species.

Cd hyperaccumulative characteristics of Australia ecotype Solanum nigrum L. and its implication in screening hyperaccumulator

A pot culture experiment was used to determine the differences in uptake characteristics of a cadmium hyperaccumulator Solanum nigrum L. discovered in China, an ecotype from Melbourne, Australia and a non-hyperaccumulator Solanum melogena Australian ecotype was not significantly different to the China ecotype. In particular, Cd concentration in leaves and shoots of S. nigrum collected from Australia were 166.0 and 146.3 mg kg(-1) respectively when 20 mg kg(-1) Cd spiked, and were not significantly different to the ecotype imported from China which had 109.8 and 85.3 mg kg(-1) respectively, in the stems and leaves. In contrast, the tolerance of the eggplant to Cd was significantly less than the two S. nigrum ecotypes. Although some morphological properties of S. nigrum collected from Australia were different from that of the plants collected from China, Cd hyperaccumulator characteristics of two ecotypes were similar. The results suggested that the tolerance and uptake of Cd may be a constitutive trait of this species.

Comparative transcriptome analysis of cadmium responses in Solanum nigrum and Solanum torvum

• Solanum nigrum is a cadmium (Cd) accumulator, whereas Solanum torvum is a low Cd-accumulating plant. The molecular mechanisms that are responsible for differential cadmium (Cd) accumulation in the two Solanum species are poorly understood. • Here, grafting experiments confirmed that increased Cd loading into the root xylem was responsible for the differential Cd accumulation in the two Solanum species. An iron (Fe) supply assay indicated that low Fe accumulation in S. torvum leaves is related to its Cd sensitivity. • Transcriptome analyses revealed higher expression of the genes that encode several metal transporters as well as antioxidant-related genes, and several organic and amino acid biosynthesis/metabolism-related genes in Cd-treated S. nigrum. Our data also indicated that the different responsive mechanisms of the transporter genes to Fe deficiency might be responsible for differential uptake and redistribution of metals in the two Solanum species • These results form a basis upon which to further explore the molecular mechanisms of Cd accumulation and tolerance, and provide an insight into novel strategies that can be used for phytoremediation and food safety.

Comparative physiological responses of Solanum nigrum and Solanum torvum to cadmium stress

• Under cadmium (Cd) stress, Solanum nigrum accumulated threefold more Cd in its leaves and was tolerant to Cd, whereas its low Cd-accumulating relative, Solanum torvum, suffered reduced growth and marked oxidative damage. However, the physiological mechanisms that are responsible for differential Cd accumulation and tolerance between the two Solanum species are largely unknown. • Here, the involvement of antioxidative capacity and the accumulation of organic and amino acids in response to Cd stress in the two Solanum species were assessed. • Solanum nigrum contains higher antioxidative capacity than does S. torvum under Cd toxicity. Metabolomics analysis indicated that Cd treatment also markedly increased the production of several organic and amino acids in S. nigrum. Pretreatment with proline and histidine increased Cd accumulation; moreover, pretreatment with citric acid increased Cd accumulation in leaves but decreased Cd accumulation in roots, which indicates that its biosynthesis could be linked to Cd long-distance transport and accumulation in leaves. • Our data provide novel metabolite evidence regarding the enhancement of citric acid and amino acid biosynthesis in Cd-treated S. nigrum, support the role of these metabolites in improving Cd tolerance and accumulation, and may help to provide a better understanding of stress adaptation in other Solanum species.

Phytostabilization of nickel by the zinc and cadmium hyperaccumulator Solanum nigrum L. Are metallothioneins involved?

Some heavy metals (HM) are highly reactive and consequently can be toxic to living cells when present at high levels. Consequently, strategies for reducing HM toxicity in the environmental must be undertaken. This work focused on evaluating the Nickel (Ni) accumulation potential of the hyperaccumulator Solanum nigrum L., and the participation of metallothioneins (MT) in the plant Ni homeostasis. Metallothioneins (MT) are gene-encoded metal chelators that participate in the transport, sequestration and storage of metals. After different periods of exposure to different Ni concentrations, plant biometric and biochemical parameters were accessed to determine the effects caused by this pollutant. Semi-quantitative RT-PCR reactions were performed to investigate the specific accumulation of MT-related transcripts throughout the plant and in response to Ni exposure. The data obtained revealed that Ni induced toxicity symptoms and accumulated mostly in roots, where it caused membrane damage in the shock-treated plants, with a parallel increase of free proline content, suggesting that proline participates in protecting root cells from oxidative stress. The MT-specific mRNA accumulation analysis showed that MT2a- and MT2d-encoding genes are constitutively active, that Ni stimulated their transcript accumulation, and also that Ni induced the de novo accumulation of MT2c- and MT3-related transcripts in shoots, exerting no influence on MT1 mRNA accumulation. These results strongly suggest the involvement of MT2a, MT2c, MT2d and MT3 in S. nigrum Ni homeostasis and detoxification, this way contributing to the clarification of the roles the various types of MTs play in metal homeostasis and detoxification in plants.

Chemical-assisted phytoremediation of CD-PAHs contaminated soils using Solanum nigrum L

A well-characterized cadmium (Cd) hyperaccumulating plant Solanum nigrum was grown in Cd and polycyclic aromatic hydrocarbons (PAHs) co-contaminated soil that was repeatedly amended with chemicals, including EDTA, cysteine (CY), salicylic acid (Sa), and Tween 80 (TW80), to test individual and combined treatment effects on phytoremediation of Cd-PAHs contaminated soils. Plant growth was negatively affected by exogenous chemicals except for EDTA. S. nigrum could accumulate Cd in tissues without assistant chemicals, while there was no visible effect on the degradation of PAHs. Cysteine had significant effects on phytoextraction of Cd and the highest metal extraction ratio (1.27%) was observed in 0.9 mmol/kg CY treatment. Both salicylic acid and Tween 80 had stimulative effects on the degradation of PAHs and there was the maximal degradation rate (52.6%) of total PAHs while 0.9 mmol/kg Sa was applied. Furthermore, the combined treatment T(0.1EDTA+0.9CY+0.5TW80) and T(0.5EDTA+0.9CY+03Sa) could not only increase the accumulation of Cd in plant tissues, but also promote the degradation of PAHs. These results indicated that S. nigrum might be effective in phytoextracting Cd and enhancing the biodegradation of PAHs in the co-contaminated soils with assistant chemicals.

Cadmium-induced oxidative damage and protective effects of N-acetyl-L-cysteine against cadmium toxicity in Solanum nigrum L

The effects of cadmium (Cd) on the accumulation of hydrogen peroxide (H(2)O(2)) and antioxidant enzyme activities in roots of Solanum nigrum L. and the role of N-acetyl-l-cysteine (NAC) as a cysteine (Cys) donor against Cd toxicity were investigated. Cd at 50 and 200 microM significantly increased the contents of thiobarbituric acid-reactive substances (TBARS), the production of H(2)O(2) and superoxide anion (O(2)(-)), and the activities of catalase, guaiacol peroxidase, ascorbate peroxidase, glutathione peroxidase (GSH-Px), glutathione reductase, and superoxide dismutase. Experiments with diphenylene iodonium as an inhibitor of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and NaN(3) as an inhibitor of peroxidase showed that the major source of Cd-induced reactive oxygen species in the roots may include plasma membrane-bound NADPH oxidase and peroxidase. In addition, the effects of NAC on plant growth, antioxidant enzyme activity, and non-protein thiol content were analyzed. Under Cd stress, the addition of 500 microM NAC decreased the contents of TBARS and production of H(2)O(2) and O(2)(-), but increased levels of Cys and reduced glutathione (GSH), phytochelatins, and activity of GSH-Px in roots. These results suggest that NAC could protect plants from oxidative stress damage, and this protection seems to be performed via increased GSH biosynthesis. Furthermore, NAC treatment also increased the contents of protein thiols in S. nigrum roots. By using size-exclusion chromatography, we found involvement of NAC in the Cd tolerance mechanism through increased biosynthesis of Cd-binding proteins.

Salt affects plant Cd-stress responses by modulating growth and Cd accumulation

Cadmium contamination is a serious environmental problem for modern agriculture and human health. Salinity affects plant growth and development, and interactions between salt and cadmium have been reported. However, the molecular mechanisms of salinity-cadmium interactions are not fully understood. Here, we show that a low concentration of salt alleviates Cd-induced growth inhibition and increases Cd accumulation in Arabidopsis thaliana. Supplementation with low concentrations of salt reduced the reactive oxygen species level in Cd-stressed roots by increasing the contents of proline and glutathione and down-regulating the expression of RCD1, thereby protecting the plasma membrane integrity of roots under cadmium stress. Salt supplementation substantially reduces the Cd-induced elevation of IAA oxidase activity, thereby maintaining auxin levels in Cd-stressed plants, as indicated by DR5::GUS expression. Salt supply increased Cd absorption in roots and increased Cd accumulation in leaves, implying that salt enhances both Cd uptake in roots and the root-to-shoot translocation of Cd. The elevated Cd accumulation in plants in response to salt was found to be correlated with the elevated levels of phytochelatin the expression of heavy metal transporters AtHMA1-4, especially AtHMA4. Salt alleviated growth inhibition caused by Cd and increased Cd accumulation also was observed in Cd accumulator Solanum nigrum.

Isolation and characterization of hydroxyproline-rich glycopeptide signals in black nightshade leaves

A gene encoding a preprohydroxyproline-rich systemin, SnpreproHypSys, was identified from the leaves of black nightshade (Solanum nigrum), which is a member of a small gene family of at least three genes that have orthologs in tobacco (Nicotiana tabacum; NtpreproHypSys), tomato (Solanum lycopersicum; SlpreproHypSys), petunia (Petunia hybrida; PhpreproHypSys), potato (Solanum tuberosum; PhpreproHypSys), and sweet potato (Ipomoea batatas; IbpreproHypSys). SnpreproHypSys was induced by wounding and by treatment with methyl jasmonate. The encoded precursor protein contained a signal sequence and was posttranslationally modified to produce three hydroxyproline-rich glycopeptide signals (HypSys peptides). The three HypSys peptides isolated from nightshade leaf extracts were called SnHypSys I (19 amino acids with six pentoses), SnHypSys II (20 amino acids with six pentoses), and SnHypSys III (20 amino acids with either six or nine pentoses) by their sequential appearance in SnpreproHypSys. The three SnHypSys peptides were synthesized and tested for their abilities to alkalinize suspension culture medium, with synthetic SnHypSys I demonstrating the highest activity. Synthetic SnHypSys I was capable of inducing alkalinization in other Solanaceae cell types (or species), indicating that structural conformations within the peptides are recognized by the different cells/species to initiate signal transduction pathways, apparently through recognition by homologous receptor(s). To further demonstrate the biological relevance of the SnHypSys peptides, the early defense gene lipoxygenase D was shown to be induced by all three synthetic peptides when supplied to excised nightshade plants.

Protective effects of proline against cadmium toxicity in micropropagated hyperaccumulator, Solanum nigrum L

Solanum nigrum is a newly discovered Cd-hyperaccumulator. In the present study, the protective effects of proline against cadmium toxicity of callus and regenerated shoots of S. nigrum are investigated based on a high frequency in vitro shoot regeneration system. Proline pretreatment reduces the reactive oxygen species levels and protects the plasma membrane integrity of callus under cadmium stress, and therefore improves the cadmium tolerance in S. nigrum. Inductively coupled plasma mass spectroscopy analysis shows that exogenous proline increases the cadmium accumulation in callus and regenerated shoots of S. nigrum. Further analysis indicates that the improvement of cadmium tolerance caused by proline pretreatment is correlated with an increase of superoxide dismutase and catalase activity and intracellular total glutathione content. The interaction between proline and enzymic or non-enzymic antioxidants is discussed.

Effect of cadmium toxicity on nitrogen metabolism in leaves of Solanum nigrum L. as a newly found cadmium hyperaccumulator

Hyperaccumulators are ideal plant species used for phytoremediation of soils contaminated by heavy metals. A full understanding of metal tolerance mechanisms of hyperaccumulators will facilitate enhancing their phytoremediation efficiency. However, how Cd affects N metabolism and which role plays the response of N metabolism to Cd toxicity in the tolerance of hyperaccumulators are still unknown. To clarify these questions, this study investigated the effects of various soil Cd levels on the concentrations of N forms and the activity of key enzymes involved in N metabolism in leaves of the Cd hyperaccumulator, Solanum nigrum L. The results showed that its growth and all N metabolism indicators were normal at low Cd exposure (<or=12 mg kg(-1)). At 24 mg Cd kg(-1) soil, nitrate assimilation indicators (nitrate concentration and activity of nitrate reductase) were reduced significantly, whereas most ammonia assimilation indicators (ammonium concentration and activity of glutamine synthetase) remained normal. However, when exposed to a higher Cd level (48 mg kg(-1)), growth and most N metabolism indicators were reduced significantly. Therefore, N metabolism in leaves of S. nigrum could be tolerant of Cd toxicity to a certain extent (soil Cd concentration<or=12 mg kg(-1)), and this might be involved in the Cd-tolerance of this Cd-hyperaccumulator.

Effects of cadmium and arsenic on growth and metal accumulation of Cd-hyperaccumulator Solanum nigrum L

Remediation of heavy metal contaminated sites using hyperaccumulators presents a promising alternative to current environmental methodologies. In the pot-culture experiment, the effects of Cd, and Cd-As on the growth and its accumulation in the Cd-hyperaccumulator (Solanum nigrum L.) were determined. No reduction in plant height and shoot dry biomass was noted when the plants were grown at Cd concentration of <or= 25 mg/kg. The contents of Cd in the stems increased from 122 to 387 mg/kg with increasing Cd, with the Cd transfer factor and bioaccumulation factor being >1.0. The plant can be classified as a Cd-hyperaccumulator. Growing in the presence of 10 mg/kg Cd and 50 mg/kg As, the plant height and shoot dry matter yields did not decrease significantly (p>0.05) compared to that at 10 mg/kg Cd, however the stem Cd content increased by 28%. It was also observed that S. nigrum used exclusion strategy to reduce As uptake in the roots and restricted translocation into the shoots, resulting in As contents of the plant being root>leaf>stem>seed. The Cd accumulation capacity coupled with its relatively high As tolerance ability could make it useful for phytoremediation of sites co-contaminated by Cd and As.

EDDS and EDTA-enhanced zinc accumulation by Solanum nigrum inoculated with arbuscular mycorrhizal fungi grown in contaminated soil

The effect of two different chelating agents [EDTA and EDDS (S,S-ethylenediaminedissucinic acid)] on Zn tissue accumulation in Solanum nigrum L. grown in a naturally contaminated soil was assessed. Under those conditions, the response of the plant to the inoculation with two different isolates of arbuscular mycorrhizal fungi (AMF)--Glomus claroideum and Glomus intraradices--was also studied. Plants grown in the local contaminated soil (Zn levels of 433mg kg(-1)) accumulated up to 1191mg kg(-1) of Zn in the roots, 3747mg kg(-1) in the stems and 3409mg kg(-1) in the leaves. S. nigrum plants grown in the same soil spiked with extra Zn (Zn levels of 964mg kg(-1)) accumulated up to 4735, 8267 and 7948mg Zn kg(-1) in the leaves, stems and roots, respectively. The addition of EDTA promoted an increase in the concentration of Zn accumulated by S. nigrum of up to 231% in the leaves, 93% in the stems and 81% in the roots, while EDDS application enhanced the accumulation in leaves, stems and roots up to 140, 124 and 104%, respectively. In the stems, the presence of Zn was predominantly detected in the cortex collenchyma cells, the starch sheath and the internal phloem and xylem parenchyma, and the addition of chelating agents did not seem to have an effect on the localisation of accumulation sites. The devise of a chelate-enhanced phytoextraction strategy, using chelating agents and AMF, is discussed.

Monitoring the efficacy and metabolism of phenylcarbamates in sugar beet and black nightshade by chlorophyll fluorescence parameters

Desmedipham, phenmedipham and a 50% mixture of the two decreased the maximum quantum efficiency of photosystem II (F(v)/F(m)) and the relative changes at the J step (F(vj)) immediately after spraying in both sugar beet and black nightshade grown in the greenhouse. Sugar beet recovered more rapidly from phenmedipham and the mixture than from desmedipham. Desmedipham and the mixture irreversibly affected F(v)/F(m) and F(vj) in black nightshade at much lower doses than in sugar beet. Black nightshade recovered from phenmedipham injury at the highest dose in the first experiment (120 g AI ha(-1)) but not in the second experiment (500 g AI ha(-1)). The dry matter dose-response relationships and the energy pipeline presentation confirmed the same trend. There was a relatively good correlation between F(vj) taken 1 day after spraying and dry matter taken 2 or 3 weeks after spraying. The differential speed of herbicide metabolism between weed and crop plays an important role in herbicide selectivity and can be studied by using appropriate chlorophyll a fluorescence parameters.

On the mechanism of action and selectivity of the corn herbicide topramezone: a new inhibitor of 4-hydroxyphenylpyruvate dioxygenase

Topramezone is a new, highly selective herbicide of pyrazole structure for the post-emergence control of broadleaf and grass weeds in corn. The biokinetic properties and mode of action of topramezone were investigated in plants of Setaria faberi Herrm, Sorghum bicolor (L.) Moench, Solanum nigrum L. and the crop species corn (Zea mays L.). Within 2-5 days after treatment, topramezone caused strong photobleaching effects on the shoot, followed by plant death of sensitive weeds. The selectivity of topramezone between corn and the weed species has been quantified as above 1000-fold. By virtue of the plant symptoms and the reversal of the effects in Lemna paucicostata L. by adding homogentisate, it was hypothesized that topramezone blocks the formation of homogentisate, possibly through inhibition of 4-hydroxyphenylpyruvate dioxygenase (4-HPPD). Indeed, topramezone strongly inhibited 4-HPPD activity in vitro, with I(50) values of 15 and 23 nM for the enzyme isolated from S. faberi and recombinant enzyme of Arabidopsis thaliana L. respectively. The enzyme activity from corn was approximately 10 times less sensitive. After root and foliar application of [(14)C]topramezone, equivalent to field rates of 75 g ha(-1), the herbicide was rapidly absorbed and systemically translocated in the plant. Only marginal differences between leaf uptake and translocation of topramezone by the weeds and corn were found. Metabolism of foliar-applied [(14)C]topramezone was far more rapid in corn than in the weeds. A more rapid metabolism combined with a lower sensitivity of the 4-HPPD target enzyme contributes to the tolerance of corn to topramezone.

Zinc accumulation in Solanum nigrum is enhanced by different arbuscular mycorrhizal fungi

Solanum nigrum was found to proliferate in sediments with high levels of metal pollution. The effect of Zn on plant growth and tissue metal accumulation was assessed. The response of the plant to the inoculation with four different isolates of arbuscular mycorrhizal fungi (AMF) (Glomus sp. BEG140, Glomus claroideum, Glomus mosseae and Glomus intraradices) was studied. While the isolates of AMF did not have a significant (P<0.05) influence on mycorrhizal colonisation, increasing Zn concentration to high levels (500 and 1000 mgkg(-1)) induced significant (P<0.05) decrease of the AMF colonisation. In general, the presence of AMF did not affect the growth and biomass of S. nigrum individuals. However, the level of metal in the matrix affected S. nigrum growth; plants grown at 100 mgkg(-1) had significantly (P<0.05) lower leaf, stem, root and total biomass than control ones and plants growing at 500 and 1000 mgkg(-1) had the significantly (P<0.05) lowest biomass. Plants inoculated with the AMF G. claroideum and G. intraradices presented significantly (P<0.05) higher Zn accumulation in all plant tissues. In general, the stem tissues had the higher Zn content while the leaves registered the lowest values, which indicate a high translocation of the metal. AMF inoculation had no significant (P<0.05) influence on the metal translocation within the plant. This study suggests that inoculation with the AMF G. claroideum or G. intraradices, can enhance the Zn accumulation in the tissues of S. nigrum, not affecting the plant translocation capacities.

Influence of the acetolactate synthase inhibitor metsulfuron-methyl on the operation, regulation and organisation of photosynthesis in Solanum nigrum

The influence of the acetolactate synthase inhibitor metsulfuron-methyl on the operation of the photosynthetic apparatus was examined on 4-weeks-old climate chamber-grown Solanum nigrum plant. To have an indication on the relative performance of the photosynthetic apparatus of ALS-treated plants, the level of carbon dioxide (CO(2)) fixation, the relative quantum efficiency of photosystem I (Phi(PSI)) or photosystem II (Phi(PSII)) electron transport and leaf chlorophyll content were assessed for both control and treated plants at 2, 4 and 7 days after application of the herbicide. Results indicated a progressive inhibition of the level of CO(2) fixation, the relative quantum efficiency of photosystem I (Phi(PSI)) and II (Phi(PSII)) electron transport and the leaf chlorophyll content already 2 days after application of the herbicide. The linear relationship between the photosystem I and II was unaltered by herbicidal treatment and was sustained under conditions where large changes in pigment composition of the leaves occurred. It appears that the stress-induced loss of leaf chlorophyll is not a catastrophic process but rather is the consequence of a well-organised breakdown of components. Under photorespiratory and non-photorespiratory conditions, the relationship between the index of electron transport flow through photosystem I and II and the rate of CO(2) fixation is altered so that electron transport becomes less efficient at driving CO(2) fixation.

The upstream oxylipin profile of Arabidopsis thaliana: a tool to scan for oxidative stresses

Various physiological imbalances lead to reactive oxygen species (ROS) overproduction and/or increases in lipoxygenase (LOX) activities, both events ending in lipid peroxidation of polyunsaturated fatty acids (PUFAs). Besides the quantification of such a process, the development of tools is necessary in order to allow the identification of the primary cause of its development and localization. A biochemical method assessing 9 LOX, 13 LOX and ROS-mediated peroxidation of membrane-bound and free PUFAs has been improved. The assay is based on the analysis of hydroxy fatty acids derived from PUFA hydroperoxides by both the straight and chiral phase high-performance liquid chromatography. Besides the upstream products of peroxidation of the 18:2 and 18:3 PUFAs, products coming from the 16:3 were characterized and their steady-state level quantified. Moreover, the observation that the relative amounts of the ROS-mediated peroxidation isomers of 18:3 were constant in leaves allowed us to circumvent the chiral analyses for the discrimination and quantification of 9 LOX, 13 LOX and ROS-mediated processes in routine experiments. The methodology has been successfully applied to decipher lipid peroxidation in Arabidopsis leaves submitted to biotic and abiotic stresses. We provide evidence of the relative timing of enzymatic and non-enzymatic lipid peroxidation processes. The 13 LOX pathway is activated early whatever the nature of the stress, leading to the peroxidation of chloroplast lipids. Under cadmium stress, the 9 LOX pathway added to the 13 LOX one. ROS-mediated peroxidation was mainly driven by light and always appeared as a late process.