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Aluminum (Al) is highly toxic to plants, since it causes stress and inhibits plant growth. Silicon (Si) is known to mitigate the stress caused by Al in several plant species. Thus, the current study aims to investigate the soothing effects of Si on morphophysiological and photosynthetic variables, and the attributes associated with oxidative stress in Schinus terebinthifolius plants exposed to Al. Treatments have followed a completely randomized design, with three repetitions based on the following Al/Si combinations (in mM): Treatment 1: 0 Al + 0 Si; Treatment 2: 0 Al + 2.5 Si; Treatment 3: 1.85 Al + 0 Si; Treatment 4: 1.85 Al + 2.5 Si; Treatment 5: 3.71 Al + 0 Si; Treatment 6: 3.71 Al + 2.5 Si. Each sampling unit consisted of a tray with 15 plants, totaling forty-five per treatment. Shoot and root morphological variables, photosynthetic variables, photosynthetic pigments, hydrogen peroxide concentration, lipid peroxidation (MDA), guaiacol peroxidase (POD) and superoxide dismutase (SOD) enzymes, and non-enzymatic antioxidant such as Ascorbic acid (AsA) and non-protein thiol (NPSH) concentration were assessed. Root growth inhibition followed by changes in root morphological variables have negatively affected root and shoot biomass production in plants only subjected to Al. However, adding 2.5 mM Si to the treatment has mitigated the toxic effects caused by 1.85 mM of aluminum on S. terebinthifolius plants.

Background: The kinetic parameters of peach rootstock are a major factor contributing to its nitrogen (N) uptake efficiency, which directly affects the yield and quality parameters. However, the impact of grafting on N kinetic parameters is not sufficiently known as rootstocks are grafted with other scion cultivars before being transplanted to the field. The objective of this study was therefore to evaluate whether the grafting of 'Okinawa' rootstock with the scion cultivar 'Chimarrita' can alter the kinetic parameters related to N uptake., Results: The plants were acclimatized in Hoagland solution for 21 days and, sequentially, were tested to assess the depletion of the internal reserves at 15 and 30 days in CaSO4 solution. Morphological and physiological parameters were evaluated, and kinetic parameters were calculated. The depletion period for to reach the minimum concentration (C min ) of NO 3 - and NH 4 + in the plant was 62 h and 56 h, respectively. The optimal time for internal reserve depletion for 'Okinawa' rootstock with and without the 'Chimarrita' scion was 30 days., Conclusion: 'Okinawa' rootstock grafted with 'Chimarrita' scion cultivar was more efficient in NO 3 - and NH 4 + uptake. © 2022 Society of Chemical Industry., (© 2022 Society of Chemical Industry.)

Orchards and vineyards account for significant copper (Cu) accumulation in the soil due to frequent Cu fungicide applications to control leaf diseases. Although grass species are distributed in these areas likely because of their physiological mechanisms to combat Cu toxicity-related stress, the aim of the present study is to identify grass species presenting biochemical-physiological responses that feature adaptive Cu toxicity tolerance mechanisms. Three grass species native to the Pampa and Atlantic Forest biomes (Paspalum notatum, P. plicatulum, and P. urvillei) and an exotic species (Cynodon dactylon) were tested. Plants were cultivated in pots filled with 4 kg of typic Hapludalf soil, under two Cu availability, control, and toxicity conditions (80 mg Cu kg soil -1 ). Photosynthetic parameters, relative growth rate, root dry matter, shoot dry matter, the activity of stress-fighting enzymes (superoxide dismutase and guaiacol peroxidase), root biometry, soluble organic carbon, soil pH, and electrical conductivity were evaluated. P. notatum and P. urvillei have physiological characteristics that allow high translocation factor and Cu accumulation in the root and shoot, and it allows their use in phytoremediation processes due to (1) greater activity of stress-fighting enzymes such as POD in the shoot; (2) to larger diameter roots, which allow greater Cu complexation in them - they are lesser sensitive to stress caused by Cu than the other species; and (3) greater soluble organic carbon exudation in the rhizosphere than species P. plicatulum and C. dactylon, which can complex Cu 2+ and reduce the presence of forms toxic to plants., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The objectives were (a) to evaluate whether grasses native to the Pampa biome, Axonopus affinis Chase, Paspalum notatum Flüggé and Paspalum plicatulum Michx, and the invasive grass Cynodon dactylon (L.). Pers have the potential to phytoremediate soil contaminated with Cu (0, 35 and 70 mg Cu kg -1 ); (b) assess whether the growth of these species is compromised by the excess of Cu available in the soil; and (c) determine the impact of excess Cu on the physiological responses of the studied species. C. dactylon presented the best performance in soil contaminated with 35 mg of Cu kg -1 . In C. dactylon, the concentrations of chlorophyll b and carotenoids increased, as did the photosynthetic rate and plant growth. Phytotoxic effects of Cu in soil contaminated with 70 mg of Cu kg -1 were more severe on A. affinis and led to plant death. The other species presented reduced photosynthetic and growth rates, as well as increased activity of antioxidant enzymes such as superoxide dismutase and guaiacol peroxidase. This very same Cu level has decreased photosynthetic pigment concentrations in P. notatum and P. plicatulum. On the other hand, it did not change chlorophyll a and b concentrations in C. dactylon and increased carotenoid concentrations in it. High values recorded for Cu bioaccumulation-in-grass-root factor, mainly in P. plicatulum, have indicated that the investigated plants are potential phytostabilizers. High C. dactylon biomass production-in comparison to other species-compensates for the relatively low metal concentration in its tissues by increasing metal extraction from the soil. This makes C. dactylon more efficient in the phytoremediation process than other species., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

High soil copper (Cu) concentrations in vineyards can cause phytotoxicity to grapevine rootstocks. In order to mitigate toxicity, the use of grapevine rootstock genetic variation and the application of amendments are possible strategies. The aim of this study is to assess the tolerance of grapevine rootstocks to Cu excess and whether phosphorus (P) and calcium (Ca) can reduce phytotoxicity caused by Cu. Grapevine rootstock seedlings were produced from selected stakes: Paulsen 1103 (Vitis berlandieri × Vitis rupestris); SO4 (Vitis berlandieri × Vitis riparia); IAC 572 ((Vitis Riparia × Vitis rupestris) × Vitis caribaea); and Isabel (Vitis labrusca). Seedlings were grown in nutrition solution added with the following treatments: 0.3 µM Cu (control); 60 µM Cu; 60 µM Cu and 62 mg L -1 P; 60 µM Cu and 400 mg L -1 Ca. High Cu concentration caused phytotoxicity in all rootstocks, impairing their growth and decreasing nutrient concentration and photosynthetic activity. P and Ca addition had positive effect on the photosynthetic activity of all rootstocks, although it was not enough to revert growth to levels comparable with controls. Overall, based on the results, the application of P and Ca was not efficient in mitigating Cu phytotoxicity in grapevine plants grown in solution. Isabel was the most sensitive rootstock to Cu phytotoxicity, whereas Paulsen 1103 and SO4 presented more tolerance and can be used, together with other management strategies, in contaminated vineyard areas. Therefore, careful genotype rootstock selection for use in high Cu soils is important, while Ca and P are not efficient mitigators of Cu toxicity., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Nanoparticles (NPs) have been progressively applied in the last decades, which may impact the environment. Synthesis of pigments, growing, and nutrient element uptake by plants can also be affected by NPs. The influence of lanthanum oxide nanoparticles (La 2 O 3 NPs) on growth, pigment synthesis, and nutrient element uptake by Pfaffia glomerata (Spreng.) Pedersen, a medicinal plant native in South America, was evaluated in the present study. P. glomerata plantlets were cultivated for 28 days in the absence (control) and presence of 100, 200, and 400 mg L -1 of La 2 O 3 NPs or bulk-La 2 O 3 (b-La 2 O 3 ) at the same cultivation conditions. Root development, aerial part growth, and pigment concentration in plants were affected by b-La 2 O 3 and La 2 O 3 NPs, mainly by La 2 O 3 NPs. In spite of alteration of nutrient element concentration observed for the 100 and 200 mg L -1 of La 2 O 3 NPs or b-La 2 O 3 treatments, Ca, Cu, Fe, K, La, Mg, Mn, Mo, P, S, and Zn determination in stems and leaves revealed drastically and similar decrease of these elements in plants cultivated in the presence of 400 mg L -1 of La 2 O 3 NPs or b-La 2 O 3 . Element distribution (mapping) determined by using laser ablation inductively coupled plasma mass spectrometry in leaves of plants submitted to treatment with 400 mg L -1 of b-La 2 O 3 or La 2 O 3 NPs showed differences in the distribution of elements, indicating distinct effects of b-La 2 O 3 and La 2 O 3 NPs on P. glomerata. As such, this study demonstrated that La 2 O 3 NPs may impact plant growth. However, more investigations are necessary for better understanding of the effect of La 2 O 3 on plants, including a broader range of concentration., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Copper (Cu) can be toxic to vegetables when it is absorbed and accumulated at large concentrations, a fact that increases the risk of excessive addition of this metal to the human food chain. The aims of the current study are (1) to determine the Cu concentrations that have critical toxic effects on beet and cabbage plants, and the potential of these plants to enter the human food chain, as well as (2) to assess the physiological and biochemical responses of representatives of these vegetables grown in nutrient solution presenting increasing Cu concentrations. Beet and cabbage plants were grown for 75 days in pots filled with sand added with nutrient solution presenting six Cu concentrations: 0.00, 0.52, 1.02, 1.52, 2.02 and 2.52 mg Cu L -1 . Dry matter yield and Cu accumulation in different plant organs were evaluated. Photosynthetic pigment contents, lipid peroxidation levels (TBARs), superoxide dismutase (SOD) and peroxidase (POD) activity and hydrogen peroxide (H 2 O 2 ) concentrations in leaves were evaluated. Critical Cu concentrations that led to toxicity in plant organs such as beetroot and cabbage head, which are often found in human diets, corresponded to 1.43 mg Cu L -1 and 1.59 mg Cu L -1 , respectively. High Cu concentrations in the nutrient solution have increased Cu concentrations and accumulation in plant tissues. This outcome justified the increased POD and SOD enzyme activity in the leaves of beet and cabbage plants, respectively, and was the cause of reduced plant growth in both crops. Cabbage plants presented higher tolerance to increased Cu levels in the growing environment than beet plants. However, it is necessary being careful at the time to consume both vegetables, when they are grown in Cu-enriched environments., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

When soybean is grown in soils with high heavy metal concentrations, it may introduce those contaminants into the human food chain, posing risks to human health. This study evaluated the effect of tilling the soil with high Cu, Zn, and Mn levels on soybean physiology and metal accumulation in seeds. Disturbed and undisturbed soil samples were collected in two different sites: a vineyard with high heavy metal concentration and a grassland area, containing natural vegetation. Two soybean cultivars were sown and grown in the greenhouse. Photosynthetic parameters and biochemical analysis of oxidative stress were performed. Cu, Zn, and Mn in leaves and seeds, dry mass, and weight of seeds were evaluated. Soil structure had a high influence on plant growth and physiology, while soil site had a high impact on heavy metal accumulation in leaves and seeds. Soybean plants that grown in vineyard soils with high heavy metal concentrations, accumulated 50% more Zn in leaves and seeds, 70% more Cu in leaves, and 90% more Cu in seeds, than those plants grown in grassland soils. Besides, Zn concentration in seeds was higher than the permissible limit. Moreover, the disturbance of both vineyard soil and grassland soil was not good for plant growth and physiology, which have increased TBARS and H 2 O 2 concentration in plants, transpiration rate, metal concentration in leaves and seeds. Soil disturbance may have caused organic matter oxidation and changes in the composition and quantity of soil microorganisms and it affects the availability of other nutrients in the soil., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Copper (Cu) is an essential element for plants, especially in photosynthesis, as it is required for plastocyanin function in electron transfer reactions at thylakoid membranes. In Arabidopsis thaliana, Cu deficiency leads to the Cu economy response, in which plants prioritize Cu usage by plastocyanin in detriment of non-essential cupric proteins. In rice (Oryza sativa), however, this response has not been characterized. Rice OsHMA5 is a Cu xylem-loading transporter involved in Cu translocation from roots to shoots, as suggested by the analysis of oshma5 mutant plants. Aiming to understand how rice plants respond to Cu deficiency and how decreased Cu translocation to shoots can affect this response, we characterized the physiological and molecular responses of WT and oshma5 plants under control and Cu deficiency treatments. We found evidence that shoots of oshma5 plants are more prone to Cu deficiency compared to shoots of WT plants, as demonstrated by decreased chlorophyll and Cu concentrations, and electron transport rate. Gene expression analysis revealed that Cu high-affinity transporters OsCOPT1 and OsCOPT5, along with a set of miRNAs and three Cu/Zn superoxide dismutases are responsive to Cu deficiency in both WT and oshma5 plants, suggesting their involvement in the Cu economy response. However, Fe superoxide dismutase was not up-regulated in rice, indicating a difference compared to the A. thaliana Cu economy model. Therefore, we provide evidence for a partially conserved Cu economy response in rice, in comparison to A. thaliana., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

Grass species native to South American can have mechanisms to tolerate copper (Cu) excess, which improves their use to phytoremediate Cu-contaminated soils . The aims of the present study are to assess the tolerance of grass species native to South American grasslands to copper-contaminated soils, as well as their adaptive responses under high Cu-stressed condition and to identify native grass species presenting the highest potential to be used for phytoremediation purposes. Soil samples were air-dried and their acidity, phosphorus and potassium levels were corrected, and the samples were incubated. Three Cu levels were used in the experiment: natural (Dose 0), with added of 40 mg kg -1 of Cu and with added of 80 mg kg -1 of Cu. Three Axonopus affinis , Paspalum notatum and Paspalum plicatulum seedlings were transferred to 5-L pots filled with soil in August and grown for 121 days. Soil solution was collected during cultivation with the aid of Rhizon lysimeters. Main concentrations of cations and anions, dissolved organic carbon and pH in the soil solution were analyzed and the ionic speciation was carried out. Cu toxicity impaired the growth of grass species native to South America, since Cu excess led to both changes in root morphology and nutritional unbalance. Among all assessed native species, Paspalum plicatulum was the one presenting the greatest potential to phytostabilize in Cu-contaminated soils, since it mainly accumulates Cu absorbed in the roots; therefore, its intercropping with grapevines is can be beneficial in Cu-contaminated soils.

Zinc (Zn) is a micronutrient, but its excessive concentration can impair plant growth and development. Fertilizers, liming materials, pesticides and fungicides containing Zn have contributed to increase its concentration in agricultural soils. The aim of the present study is to evaluate the effect of Zn excess on the non-enzymatic (anthocyanin and β-ecdysone) and enzymatic (superoxide dismutase-SOD and guaiacol peroxidase-GPX) antioxidant system of two P. glomerata accessions (JB and GD) grown in hydroponic system and soil, under short- and long-term exposure times. Three Zn levels (2, 100 and 200 μM) and two short-term exposure times (7 and 14 d) were tested in the hydroponic experiment. Three Zn levels (2, 100 and 200 mg kg -1 ) and two long-term exposure times (34 and 74 d) were tested in the soil experiment. The effects of Zn excess on P. glomerata accessions depended on the growth system and exposure time. Zinc excess in both tested growth systems resulted in significant change in the tissue oxidative process (MDA concentration) in both accessions, as well as broadened the antioxidant system response, which was based on antioxidant enzymes (SOD and GPX) and secondary metabolites (anthocyanins and β-ecdysone). The highest anthocyanin concentration was observed in accession JB, which was grown in hydroponics, but tissue anthocyanin concentration increased in both accessions, regardless of growth medium and exposure time. The β-ecdysone concentration in the roots increased in both accessions, but accession GD was more responsive to Zn excess. There was significant physiological variation in P.glomerata accessions in response to Zn excess., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier Ltd.)

Rice is a daily staple for half of the world's population. However, rice grains are poor in micronutrients such as Fe and Zn, the two most commonly deficient minerals in the human diet. In plants, Fe and Zn must be absorbed from the soil, distributed and stored, so that their concentrations are maintained at sufficient but non-toxic levels. The understanding of mechanisms of Fe and Zn homeostasis in plants has the potential to benefit agriculture, improving the use of micronutrients by plants, as well as to indicate approaches that aim at biofortification of the grains. ZIP transporters are commonly associated with Zn uptake, but there are few reports about their physiological relevance in planta . Here we describe a Tos17 loss-of-function line for the Zn plasma membrane transporter OsZIP7 ( oszip7 ). We showed that the absence of functional OsZIP7 leads to deregulated Zn partitioning, increasing Zn accumulation in roots but decreasing in shoots and seeds. We also demonstrated that, upon Zn deficiency, oszip7 plants slightly increase their photosynthetic performance, suggesting that these plants might be primed for Zn deficiency which makes them more tolerant. On the other hand, we found that Zn excess is more deleterious to oszip7 plants compared to wild type, which may be linked to secondary effects in concentrations of other elements such as Fe. Our data suggest that OsZIP7 is important for Zn homeostasis under physiological Zn concentrations, and that Fe homeostasis might be affected due to loss of function of OsZIP7., (© Prof. H.S. Srivastava Foundation for Science and Society 2020.)

Successive applications of copper fungicides on vines have resulted in increased copper content in vineyard soils over the years. This high copper content has affected the growth of young vines in eradicated vineyards. Thus, the cultivation of annual species for a few years is an alternative to copper phytostabilization, because it would be a good way to decrease copper availability to plants. The aim of this study was to evaluate the physiological responses of different soybean cultivars to copper concentration increase. Four different soybean cultivars were grown under three copper concentrations: 0.5, 20 and 40 μM in nutrient solution. The main outcomes of this study were: i) Cultivar M 6410 IPRO recorded the highest photosynthetic rate when plants were exposed to 40 μM of copper in the nutrient solution; ii) plants in cultivar M 6410 IPRO accumulated large copper concentrations in their roots although did not decrease the root dry mass, possibly due to the higher superoxide dismutase activity; iii) cultivar DM 5958 RSF IPRO recorded drastically reduced photosynthetic rate and dry mass production due to copper excess. We conclude that each cultivar responded differently to the excess of copper, but none of them showed tolerance to it.

Phytoremediation is an alternative for remediating soil contamination by copper, and its efficiency has been shown to increase when arbuscular mycorrhizal fungi (AMF) and earthworms are separately inoculated into the soil. This study evaluated the isolated and combined effects of inoculating earthworms and arbuscular mycorrhizal fungi into a sandy soil on copper phytoremediation by Canavalia ensiformis. The plants were grown in a greenhouse in soil contaminated with 100 mg Cu kg -1 with and without being inoculated with the arbuscular mycorrhizal fungus Rhizoglomus clarum and the earthworm Eisenia andrei. The availabilities of solid-phase Cu and other nutrients in the soil solution and plant growth were evaluated along with Cu phytotoxicity based on photochemical efficiency and oxidative stress enzyme activity. Accumulation of Cu and other nutrients in the shoots and roots; mycorrhizal colonization, nodulation, and reproduction; and Cu accumulation in the earthworm tissues were also evaluated. The copper caused photosynthetic and biochemical damage that reduced the shoot dry weight by 44% and the root dry weight by 29%. However, the arbuscular mycorrhizal fungus alleviated the Cu toxicity to the plant and increased the shoot dry weight by 81% in the contaminated soil. The earthworms increased the Cu uptake and translocation to the shoot by 31%. The combined presence of the arbuscular mycorrhizal fungus and earthworms in the contaminated soil increased the growth and Cu content of the aerial plant tissues, yielding a 200% increase in Cu accumulation (metal content × biomass) in the C. ensiformis shoots. Combined inoculation with earthworms and arbuscular mycorrhizal fungi increased copper phytoextraction by Canavalia ensiformis in a sandy soil., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The production and use of nanoparticles (NPs) in different fields increased in the last years. However, some NPs have toxicological properties, making these materials potential emerging pollutants. Therefore, it is important to investigate the uptake, transformation, translocation, and deposition of NPs in plants. In this work, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and micro X-ray fluorescence (μ-XRF) were used to investigate the uptake and translocation of La 2 O 3 NPs to stem and leaves of Pfaffia glomerata (Spreng.) Pedersen after in vitro cultivation of plants in the presence of 400 mg L -1 of La 2 O 3 NPs. By using LA-ICP-MS and μ-XRF, image of the spatial distribution of La in the leaves was obtained, where higher concentration of La was observed in the main veins. Differences in the signal profile of La in leaves of plants cultivated in the presence of bulk La 2 O 3 (b-La 2 O 3 ) and La 2 O 3 NPs were observed. Sharp peaks of La indicated that NPs were transported to the stems and leaves of plants treated with La 2 O 3 NPs. Both LA-ICP-MS and μ-XRF techniques have shown to be useful for detecting NPs in plants, but LA-ICP-MS is more sensitive than μ-XRF and allowed better detection and visualization of La distribution in the whole leaf.

Foliar fungicide application in grapevines increases the content of heavy metals such as copper (Cu) in vineyard soils, which may reach phytotoxic levels. The application of soil amendments such as limestone and vermicompost may reduce Cu availability and phytotoxicity. The study aimed to assess growth, physiological status and changes in root morphology in young grapevines grown for 12 months in Cu-contaminated soil with and without the application of soil amendments. Samples of a Typic Hapludalf soil were collected in a vineyard with more than 30 years of cultivation. The following treatments were used: 1) control (without amendment), 2) application of organic vermicompost (86.7 g kg -1 ) and 3) application of limestone (3 Mg ha -1 ). Grapevines (Paulsen 1103 rootstock) were transplanted and grown for 12 months in PVC soil columns. We assessed parameters of growth, photosynthesis and root morphology. Grapevines grown in soil treated with limestone showed increased growth, dry matter yield and photosynthetic efficiency. The highest Cu concentrations in root tissue were found in grapevines grown in control soil. The application of vermicompost in this study did not alleviate Cu toxicity. Grapevines grown in soil treated with vermicompost showed high manganese (Mn) concentration in shoots before the winter pruning, reflecting the high Mn concentrations in soil solution that caused Mn phytotoxicity, resulting in plant death after the winter pruning. The vermicompost used in this study is not suitable for agronomic use. The use of limestone was an effective strategy to reduce Cu availability and phytotoxicity., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Soil contamination with copper (Cu)-based agrochemicals used in vineyards for pest control is a growing problem. In this context, the application of soil amendment to limit Cu toxicity, especially for young plants after the replanting of vineyards, has been a concern for winemakers. Therefore, the aim of this study was to evaluate how different amendments can contribute to the decrease in Cu availability in areas vocated to viticulture. Furthermore, the aim was to evaluate to the effect of Cu on the biochemical and physiological changes in the development of the young vine plants, both at the shoot and the root level. Vine plants were grown in a greenhouse using a Typic Hapludalf soil characterized by 87.5 mg of Cu kg -1 (control). Three different amendments were applied to the soil: limestone (3 Mg ha -1 ), calcium silicate (3 Mg ha -1 ) and vermicompost (30 g of C kg -1 ). The amendment with vermicompost and calcium silicate caused a significant alkalization of the soil solution. Moreover, specifically for the treatment with vermicompost, the levels of Cu 2+ in the soil solution were consistently diminished with a clear benefit for plants (+89% biomass accumulation at the shoot level). In addition, this soil amendment led to a higher photosynthetic rate, lower superoxide dismutase (SOD, EC 1.15.1.1) and guaiacol peroxidase (POD, EC 1.11.1.7) activity and a higher percentage of fine roots with diameter between 0 < L ≥ 0.2 mm (particularly active in water and nutrient acquisition). In conclusion, results showed that vermicompost effectively reduced Cu phytotoxicityin young vines grown in soils with high Cu contents. Furthermore, this amendment might be an asset in enhancing the availability of other important micronutrients such as iron., (Copyright © 2018. Published by Elsevier Masson SAS.)

The phytoremediation of copper (Cu)-contaminated sandy soils can be influenced by the addition of vermicompost to the soil and the mycorrhization of plants. The objective of this study was to evaluate the effects of inoculation with the mycorrhizal fungus Rhizophagus clarus and the addition of different doses of bovine manure vermicompost on the phytoremediation of a sandy soil with a high Cu content using Canavalia ensiformis. Soil contaminated with 100 mg kg -1 Cu received five doses of vermicompost and was cultivated with C. ensiformis, with and without inoculation with mycorrhizal fungus, and the Cu and nutrients in the soil and soil solution were evaluated. The concentrations of Cu and other nutrients and the biomass and Cu phytotoxicity in the plants were quantified by gauging the photochemical efficiency, concentration of photosynthetic pigments and activity of oxidative stress enzymes. The vermicompost increased the soil pH and nutrient concentrations and reduced the Cu content of the solution. When the vermicompost was applied at a dose equivalent to 80 mg phosphorus (P) kg -1 , the phytoextraction efficiency was higher, but the phytostabilization efficiency was higher for vermicompost doses of 10 and 20 mg P kg -1 . The presence of mycorrhizal fungi increased Cu phytostabilization, especially at vermicompost doses of 10 and 20 mg P kg -1 . The use of vermicompost at low doses and inoculation with mycorrhizal fungi increase the phytostabilization potential of C. ensiformis in sandy soil contaminated by Cu.

Different growth rates of grasses from South American natural grasslands are adaptations to soils of low fertility. Grasses with fast growth rate are species with an accumulation of nutrients in soluble forms, with a high metabolic rate. This work aimed to study whether grasses with different growth rates have different phosphorus (P) uptake and efficiency of P use with high and low P availability in soil, as well as whether phosphatase activity is related to the species growth rate and variations in P biochemical forms in the tissues. Three native grasses (Axonopus affinis, Paspalum notatum, and Andropogon lateralis) were grown in pots with soil. Along plant growth, biomass production and its structural components were measured, as well as leaf acid phosphatase activity and leaf P chemical fractions. At 40 days of growth, leaf acid phosphatase activity declined by about 20-30% with an increase of P availability in soil for A. affinis and P. notatum, respectively. Under both soil P levels, P. notatum showed the highest plant total biomass, leaf dry weight and highest P use efficiency. A. affinis presented the higher P uptake efficiency and soluble organic P concentration in the leaf tissues. A. lateralis showed P-Lipid concentration 1.6 and 1.3 times higher than A. affinis and P. notatum, respectively. In conclusion, acid phosphatase activity in grass of higher growth rate is related to higher remobilization of P due to higher demand, as in A. affinis, and higher growth rates are associated with higher P uptake efficiency.

Arbuscular mycorrhizal fungi (AMF) improve plant ability to uptake P and tolerate heavy metals. This study aimed to evaluate the effect of available P and the inoculation of Rhizophagus clarus in a Cu-contaminated soil (i) on the activity of acid phosphatases (soil and plant), the presence of glomalin, and (ii) in the biochemical and physiological status of Mucuna cinereum. A Typic Hapludalf soil artificially contaminated by adding 60 mg kg -1 Cu was used in a 3 × 2 factorial design with three replicates. Treatments consisted of three P levels: 0, 40, and 100 mg kg -1 P. Each P treatment level was inoculated (+AMF)/non-inoculated (-AMF) with 200 spores of R. clarus per pot, and plants grown for 45 days. The addition of at least 40 mg kg -1 P and the inoculation of plants with R. clarus proved to be efficient to reduce Cu phytotoxicity and increase dry matter yield. Mycorrhization and phosphate fertilization reduced the activity of enzymes regulating oxidative stress (SOD and POD), and altered the chlorophyll a fluorescence parameters, due to the lower stress caused by available Cu. These results suggest a synergism between the application of P and the inoculation with R. clarus, favoring the growth of M. cinereum in a Cu-contaminated soil. This study shows that AMF inoculation represents an interesting alternative to P fertilization to improve plant development when exposed to excess Cu., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

A hydroponic experiment was carried out to investigate the effect of phosphorus (P) nutrition on arsenic (As) uptake and translocation within the seedlings of rice cultivars. The experiment occurred in three stages: I 5 days of acclimatization (nutritive solution); II 10 days under P (0.0 and 0.09 mM) and As (0.0 and 100 mM) treatments; III 5 days under recovery. The As exposure had significant effect reducing dry weights of shoots or roots, resulted in elevated concentrations of As in shoot tissues. BR-IRGA 409 showed the highest susceptibility to As in biomass production and root system parameters regardless the P level. This cultivar showed contrasting responses of As translocation to shoot tissue dependent on P levels, with the highest As concentration under low P and lowest under normal P levels. P nutrition was most striking on plants recovery for all cultivars under As exposure. Clearer separation of cultivars for phosphorus use efficiency (PUE) occurred at lower shoot P contents, that was, at higher levels of P deficiency stress. IRGA 424 showed higher PUE as compared to the others cultivars. Our results go some way to understanding the role of P nutrition in controlling the effects of As in rice shoots.

Vineyard sandy acid soils from South Brazil have experienced heavy metal contamination due to replacement of copper (Cu)-based by zinc (Zn)-based products to control foliar diseases. Thus, we evaluate physiological and nutritional status of black oat (Avena strigosa Schreb.), a common interrow crop in vineyards from this region. Soil was collected in a natural field from Santana do Livramento, in Rio Grande do Sul, the southernmost state of Brazil. Black oat was cultivated for 30 days in a greenhouse with application of 0, 30, and 60 mg Cu kg(-1) combined with 0, 15, 30, 60, 120, and 180 mg Zn kg(-1). After the trial period, dry matter accumulation of roots and shoots, Cu and Zn contents in roots and shoots, chlorophyll a fluorescence, photosynthetic pigments and catalase (CAT, EC 1.11.1.6) and peroxidase (POD, EC 1.11.1.7) activity were determined. Cu and Zn toxicity was evidenced by the decrease in plant growth of black oat as well as by the decrease of photochemical efficiency associated with the decrease in photosynthetic pigment content, especially with the highest doses of Cu and Zn. Furthermore, the activity of antioxidant enzymes (CAT and POD) was increased in intermediate doses of Zn, indicating the activation of the antioxidant system, but the stress condition in treatments with high levels of Cu and Zn was not reversed., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

The occurrence of high levels of Cu in vineyard soils is often the result of intensive use of fungicides for the preventive control of foliar diseases and can cause toxicity to plants. Nowadays many grape growers in Southern Brazil have replaced Cu-based with Zn-based products. The aim of the study was to evaluate whether the increase in Zn concentration in a soil with high Cu contents can interfere with the dynamics of these elements, and if this increase in Zn may cause toxicity to maize (Zea mays L.). Soil samples were collected in two areas, one in a vineyard with more than 30 years of cultivation and high concentration of Cu and the other on a natural grassland area adjacent to the vineyard. Different doses of Cu and Zn were added to the soil, and the adsorption isotherms were built following the Langmuir's model. In a second experiment, the vineyard soil was spiked with different Zn concentrations (0, 30, 60, 90, 180, and 270mg Zn kg(-1)) in 3kg pots where maize was grown in a greenhouse for 35 days. When Cu and Zn were added together, there was a reduction in the quantities adsorbed, especially for Zn. Zn addition decreased the total plant dry matter and specific leaf mass. Furthermore, with the increase in the activity of catalase, an activation of the antioxidant system was observed. However, the system was not sufficiently effective to reverse the stress levels imposed on soil, especially in plants grown in the highest doses of Zn. At doses higher than 90Znmgkg(-1) in the Cu-contaminated vineyard soil, maize plants were no longer able to activate the protection mechanism and suffered from metal stress, resulting in suppressed dry matter yields due to impaired functioning of the photosynthetic apparatus and changes in the enzymatic activity of plants. Replacement of Cu- by Zn-based fungicides to avoid Cu toxicity has resulted in soil vineyards contaminated with these metals and damaging of plant photosynthetic apparatus and enzyme activity., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Soils used for the cultivation of grapes generally have a long history of copper (Cu) based fungicide applications. As a result, these soils can accumulate Cu at levels that are capable of causing toxicity in plants that co-inhabit the vineyards. The aim of the present study was to evaluate growth parameters and oxidative stress in black oat plants grown in vineyard soils contaminated with high levels of Cu. Soil samples were collected from the Serra Gaúcha and Campanha Gaúcha regions, which are the main wine producing regions in the state of Rio Grande do Sul, in southern Brazil. Experiments were conducted in a greenhouse in 2009, with soils containing Cu concentrations from 2.2 to 328.7 mg kg(-1). Evaluated parameters included plant root and shoot dry matter, Cu concentration in the plant's tissues, and enzymatic and non-enzymatic biochemical parameters related to oxidative stress in the shoots of plants harvested 15 and 40 days after emergence. The Cu absorbed by plants predominantly accumulated in the roots, with little to no translocation to the shoots. Even so, oat plants showed symptoms of toxicity when grown in soils containing high Cu concentrations. The enzymatic and non-enzymatic antioxidant systems of oat plants were unable to reverse the imposed oxidative stress conditions., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)

Grapevines grown on acid soils with low fertility in southern Brazil are treated with intense foliar applications of copper (Cu) fungicides, resulting in an increased level of Cu in the soil and increased toxicity. The present study evaluated the accumulation and bioavailability of Cu, and soils with varying levels of Cu from the main producing regions of southern Brazil were collected. The forms of Cu present in the soil were assessed using chemical extractants; additionally, oat cultivation was performed, reflecting the use of the plant as an indicator of Cu bioavailability. Cu accumulated in the topsoil, mainly in bioavailable forms, and there was also an increase of Cu up to a depth of 0.4 m. Cu was primarily found in the mineral fraction, with apparent saturation of the soil organic matter functional groups. Inceptisol and Alfisol soils with a long history of cupric fungicide application were found to have levels of Cu toxic to oat plants. Furthermore, accumulated copper in Alfisol soil from the Campanha Gaúcha region of the state of Rio Grande do Sul had higher bioavailability compared to Cu accumulated in Inceptisol soil from the Serra Gaúcha region. In addition, the copper concentration in roots was found to serve as an indicator of Cu bioavailability in soil, but not of copper phytotoxicity in plants.

The objective of this study was to evaluate whether the oxidative stress caused by aluminum (Al) toxicity is a symptom that can trigger root growth inhibition in oat genotype seedlings. Oat seedlings were grown in a nutrient solution (pH 4.0) with 0 and 370 μM Al. At 12, 24, and 36 h after Al addition, growth (root length) and biochemical parameters (catalase - CAT, ascorbate peroxidase - APX, and superoxide dismutase - SOD activities, lipid peroxidation, ascorbic acid (ASA) and non-protein thiol group (NPSH) concentration) were determined. The aluminum content was measured in oat seedlings. Regardless of the exposure time, root of the tolerant genotype grew normally with any Al treatments. Al supply caused lipid peroxidation only in the Al-sensitive genotype in roots and shoots (at 12, 24, and 36 h). In sensitive genotype seedlings, CAT, APX, and SOD were activated only at 24 or 36 h. In tolerant and intermediate genotypes, CAT, APX, and SOD were activated at 12, 24, and 36 h. Data for root growth and lipid peroxidation suggested that lipid peroxidation in the sensitive genotype may be an effect of Al toxicity on root growth. Therefore, the tolerant, intermediate, and sensitive genotypes differ in the expression of the amount, type of antioxidants, and speed of activation of antioxidant system, suggesting a varying capacity of these genotypes to deal with oxidative stress, which resulted in varying sensitivity and tolerance to Al., (© 2013.)

Plantlets of Pfaffia glomerata (Spreng.) were exposed for 28 days to three different metal/metalloid (Hg, Pb and As) with different levels (Hg 1; As 25, 50, 100 and Pb 100 and 400 μM) to analyze the possible phytochelatin initiation and affects on growth and photosynthetic pigments vis-à-vis metal accumulation potential of plants. The plantlets showed significant Hg, As and Pb accumulation in roots (150, 1267.67 and 2129 μg g(-1) DW respectively); however, a low root to shoot metal translocation was observed. It was interesting to note that all tested macronutrient (Mg, K, Ca) was higher in shoots and just opposite in case of micronutrients (Cu, Fe, Zn), was recorded highest in roots. The growth of plantlets (analyzed in terms of length and dry weight) was negatively affected by various metal treatments. In addition, the level of photosynthetic pigments alters significantly in response to all metal/metalloid treatment. In response to all tested metal/metalloids in plants only As induced phytochelatins (PC2, PC3 and PC4) in roots, and in shoots, GSH was observed in all tested metal/metalloids. In conclusion, P. glomerata plantlets could not cooperatively induce phytochelatins under any of Hg and Pb levels.

The present study investigated changes in both the growth parameters and the enzymatic and non-enzymatic antioxidant systems of maize (Zea may L.) plants grown in Typic Hapludalf soil containing an accumulation of Cu and Zn. This accumulation developed because the soil received nineteen applications of pig slurry in no-tillage system over seven years. In this study, the maize plants were grown for fifteen and 25 days after emergence (DAE) in pots containing undisturbed and disturbed soil samples collected from a field experiment that received the rates 0, 20, 40 and 80m(3)ha(-1) of pig slurry, which totalized the amount of 0, 380, 760 and 1520m(3)ha(-1) of pig slurry in seven years, respectively, and phosphorus (P)+potassium (K) treatment (in disturbed soil samples). The maize plants grown in the undisturbed soil samples with an accumulation of Cu and Zn did not indicate an apparent decrease in growth. However, when compared to the treatment with PK fertilization, the maize plants grown in the disturbed soil with pig slurry treatments indicated higher lipid peroxidation and a number of senescent leaves, as well as a significant decrease in plant height. Additionally, when compared to the PK treatment, the leaf superoxide dismutase and ascorbate peroxidase activities decreased and increased, respectively, with the addition of pig slurry treatments in the disturbed soil at 25 DAE. In general, when compared to the treatments with 20m(3)ha(-1) of pig slurry and PK at fifteen and 25 DAE, the leaf ascorbic acid and non-protein thiol groups concentrations decreased with the addition of 40 and 80m(3)ha(-1) of pig slurry. This result suggests that the excess of Cu and Zn in the pig slurry significantly changed the antioxidant system of the maize plants., (Copyright © 2013 Elsevier Inc. All rights reserved.)

This study investigated the cadmium (Cd) intoxication on cognitive, motor and anxiety performance of rats subjected to long-term exposure to diet with Cd salt or with Cd from contaminated potato tubers. Potato plantlets were micropropagated in MS medium and transplanted to plastic trays containing sand. Tubers were collected, planted in sand boxes and cultivated with 0 or 10 μM Cd and, after were oven-dried, powder processed and used for diet. Rats were divided into six groups and fed different diets for 5 months: control, potato, potato+Cd, 1, 5 or 25 mg/kg CdCl2. Cd exposure increased Cd concentration in brain regions. There was a significant decrease in the step-down latency in Cd-intoxicated rats and, elevated plus maze task revealed an anxiolytic effect in rats fed potato diet per se, and an anxiogenic effect in rats fed 25 mg/kg Cd. The brain structures of rats exposed to Cd salt or Cd from tubers showed an increased AChE activity, but Na+,K+-ATPase decreased in cortex, hypothalamus, and cerebellum. Therefore, we suggest an association between the long-term diet of potato tuber and a clear anxiolytic effect. Moreover, we observed an impaired cognition and enhanced anxiety-like behavior displayed by Cd-intoxicated rats coupled with a marked increase of brain Cd concentration, and increase and decrease of AChE and Na+,K+-ATPase activities, respectively., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

This work aimed to study the process of stress adaptation in root and leaves of different developmental stages (apex, middle and basal regions) of Pluchea sagittalis (Lam.) Cabrera plants grown under exposure to five Pb levels (0, 200, 400, 600 and 1000 μM) for 30 days. Pb concentration and content in roots, stems, and leaves of different developmental stages increased with external Pb level. Consumption of nutrient solution, transpiration ratio, leaf fresh weight, leaf area, and shoot length decreased upon addition of Pb treatments. However, dry weight of shoot parts and roots did not decrease upon addition of Pb treatments. Based on index of tolerance, the roots were much more tolerant to Pb than shoots. δ-aminolevulinic acid dehydratase activity was decreased by Pb treatments, whereas carotenoid and chlorophyll concentrations were not affected. Lipid peroxidation and hydrogen peroxide concentration both in roots and leaves increased with increasing Pb levels. Pb treatments increased ascorbate peroxidase activity in all plant parts, while superoxide dismutase activity increased in leaves and did not change in roots. Catalase activity in leaves from the apex shoot was not affected by Pb, but in other plant parts it was increased. Pb toxicity caused increase in non-protein thiol groups concentration in shoot parts, whereas no significant difference was observed in roots. Both root and shoot ascorbic acid concentration increased with increasing Pb level. Therefore, it seems that Pb stress triggered an efficient defense mechanism against oxidative stress in P. sagittalis but its magnitude was depending on the plant organ and of their physiological status. In addition, these results suggest that P. sagittalis is Pb-tolerant. In conclusion, P. sagittalis is able to accumulate on average 6730 and 550 μg Pb g(-1) dry weight, respectively, in the roots and shoot, a physiological trait which may be exploited for the phytoremediation of contaminated soils and waters.

The possible role of zinc (Zn) to reverse the oxidative stress caused by mercury (Hg) was investigated in Pfaffia glomerata plantlets. Thirty-day-old acclimatized plantlets of P. glomerata were exposed to four treatments: control, 50 μM Zn, 50 μM Hg and 50 μM Zn + 50 μM Hg for 9 days. In Zn + Hg treatment, shoot and root Hg concentrations were 59 and 24% smaller than that plants exposed to 50 μM Hg added alone. An increase in the Zn concentration in the shoot of plants exposed to Zn + Hg occurred, although in the roots Zn concentration was not altered, when compared to the control. Fresh and dry weights, as well as the activity of δ-aminolevulinic acid dehydratase (δ-ALA-D) in Hg-treated plants were significantly reduced. Percentage survival, fresh and dry weights and δ-ALA-D activity of plants treated by 50 μM Zn + 50 μM Hg were greater than of that treated by Hg alone. Moreover, Zn treatment reduced the lipid peroxidation caused by Hg, being this effect related to increased root superoxide dismutase activity, and shoot catalase and ascorbate peroxidase activities. In conclusion, the presence of Zn in the substrate caused a significant reduction in the oxidative stress induced by Hg.

Plantlets of Pfaffia glomerata (Spreng.) were exposed in vitro for 30 days to five lead levels (0-400 μM) to analyze the effects on growth and oxidative stress and responses of various antioxidants vis-à-vis lead accumulation. The plantlets showed significant lead accumulation in roots (1,532 μg g(-1) DW) with a low root to shoot lead translocation (ca. 3.6%). The growth of plantlets was negatively affected by various lead treatments, although the level of photosynthetic pigments did not alter significantly in response to any lead treatment. However, plantlets suffered from oxidative stress as suggested by the significant increase in malondialdehyde levels in root (8.48 μmol g(-1) FW) and shoot (3.20 μmol g(-1) FW) tissues with increasing lead treatments. In response to the imposed toxicity, increases in the activities of catalase in root (4.14 ∆E min(-1) mg(-1) protein) and shoot (3.46 ∆E min(-1) mg(-1) protein) and superoxide dismutase in root (345.32 units mg(-1) protein) and shoot (75.26 units mg(-1) protein), respectively, were observed, while the levels of non-protein thiols and ascorbic acid were not affected significantly in either roots or shoots.

The phytotoxic effects of aluminum and the mechanisms of genetically-based Al tolerance have been widely investigated, as reported in many papers and reviews. However, investigations on many Al-sensitive and Al-resistant species demonstrate that Al phytotoxicity and Al-resistance mechanisms are extremely complex phenomena. The objective of the present study was to analyze the effects of aluminum on the activity of antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), and ascorbate peroxidase (APX). Also was evaluated the lipid peroxidation, H(2)O(2) content, levels of ascorbic acid (ASA), non-protein thiols (NPSH) and Al content in three genotypes of oat, Avena sativa L. (UFRGS 930598, UFRGS 17, and UFRGS 280). The genotypes were grown in different concentrations of Al ranging from 90 to 555 μM for 5 days. The antioxidant system was unable to overcome toxicity resulting in negative effects such as lipid peroxidation and H(2)O(2) content in UFRGS 930598. The results showed that UFRGS 930598 was the most sensitive genotype. UFRGS 17 and UFRGS 280 were more resistant to Al toxicity. These results suggest that UFRGS 17 has mechanisms of external detoxification and UFRGS 280 has mechanisms of internal detoxification. The different behavior of enzymatic and non-enzymatic antioxidants of the genotypes showed that aluminum resistance in UFGRS 17 and UFRGS 280 may be related to oxidative stress.

We evaluated the antiproliferative effect of infusions from Pluchea sagittalis using the Allium cepa test. Infusions in three concentrations (2.5, 5, and 25 g dm-3) of leaves cultivated in three environments (in vitro, acclimatized growth chamber, and field) were used. Six onion bulbs were used for each of the eight treatments, and the mitotic index was obtained from 6000 cells per treatment. In conclusion, leaf infusions of P. sagittalis cultivated in the field have a high antiproliferative activity, as well as the cultivation system influences the antiproliferative potential.

Aluminum (Al) is one of the most abundant elements of the planet and exposure to this metal can cause oxidative stress and lead to various signs of toxicity in plants. Plants are essential organisms for the environment as well as food for humans and animals. The toxic effect of aluminum is the major cause of decreased crop productivity. Thus, the objective of the present study was to analyze the effects of aluminum on the activity of antioxidant enzymes such as catalase (CAT - E.C. 1.11.1.6), superoxide dismutase (SOD - E.C.1.15.1.1) and ascorbate peroxidase (APX - E.C. 1.11.1.11), and on lipid peroxidation, electrolyte leakage percentage (ELP) and chlorophyll and protein oxidation levels in Cucumis sativus L. (cv. Aodai). Seedlings were grown at different concentrations of aluminum ranging from 1 to 2000 microM for 10 days. The increase in ELP and H(2)O(2) production observed in the seedlings may be related to the decreased efficiency of the antioxidant system at higher aluminum concentrations. The antioxidant system was unable to overcome toxicity resulting in negative effects such as lipid peroxidation, protein oxidation and a decrease in the growth of Cucumis seedlings. Aluminum toxicity triggered alterations in the antioxidant and physiological status of growing cucumber seedlings., (Copyright 2010 Elsevier Masson SAS. All rights reserved.)

Oxidative stress caused by mercury (Hg) was investigated in Pfaffia glomerata plantlets grown in nutrient solution using sand as substrate. Thirty-day-old acclimated plants were treated for 9 days with four Hg levels (0, 1, 25 and 50 microM) in the substrate. Parameters such as growth, tissue Hg concentration, toxicity indicators (delta-aminolevulinic acid dehidratase, delta-ALA-D, activity), oxidative damage markers (TBARS, lipid peroxidation, and H(2)O(2) concentration) and enzymatic (superoxide dismutase, SOD, catalase, CAT, and ascorbate peroxidase, APX) and non-enzymatic (non-protein thiols, NPSH, ascorbic acid, AsA, and proline concentration) antioxidants were investigated. Tissue Hg concentration increased with Hg levels. Root and shoot fresh weight and delta-ALA-D activity were significantly decreased at 50 microM Hg, and chlorophyll and carotenoid concentration were not affected. Shoot H(2)O(2) concentration increased curvilinearly with Hg levels, whereas lipid peroxidation increased at 25 and 50 microM Hg, respectively, in roots and shoots. SOD activity showed a straight correlation with H(2)O(2) concentration, whereas CAT activity increased only in shoots at 1 and 50 microM Hg. Shoot APX activity was either decreased at 1 microM Hg or increased at 50 lM Hg. Conversely, root APX activity was only increased at 1 microM Hg. In general, AsA, NPSH and proline concentrations increased upon addition of Hg, with the exception of proline in roots, which decreased. These changes in enzymatic and non-enzymatic antioxidants had a significant protective effect on P. glomerata plantlets under mild Hg-stressed conditions.

The present study was designed to study the process of stress adaptation in roots and shoot of Zea mays seedlings grown under hydroponic conditions during exposure to lead (Pb) (0-200 microM) for 1-7 d. The alterations in growth and in the level of various biochemical parameters were accessed vis-à-vis Pb accumulation. The accumulation of Pb increased in a concentration-duration-dependent manner, however its translocation from root to shoot was low. At the same time, the level of malondialdehyde (MDA) increased with increasing Pb concentration. However, growth parameters, such as dry weight and root length did not show a significant decline to any of the Pb concentrations. In addition, the level of photosynthetic pigments decreased only upon exposure to high Pb concentrations. These results suggested an alleviation of the stress that was presumably being achieved by antioxidants viz., superoxide dismutase (SOD) and catalase (CAT) as well as ascorbic acid (AsA), which increased linearly with increasing Pb levels and exposure time. However, the level of non-protein thiols (NP-SH) in roots, in general, showed a decline beyond 4d that could be attributed to their consumption for the purpose of Pb detoxification. In conclusion, Zea mays can be used as an indicator species for Pb, and the various antioxidants might play a key role in the detoxification of Pb induced toxic effects.

A hydroponic experiment was carried out to characterize the oxidative stress responses of two potato cultivars (Solanum tuberosum L. cvs. Asterix and Macaca) to cadmium (Cd). Plantlets were exposed to four Cd levels (0, 50, 100, 150 and 200 microM) for 7 days. Cd concentration was increased in both roots and shoot. Number of sprouts and roots was not decreased, whereas Cd treatment affected the number of nodal segments. Chlorophyll content and ALA-D activity were decreased in both cultivars, whereas carotenoids content was decreased only in Macaca. Cd caused lipid peroxidation in roots and shoot of both cultivars. Protein oxidation was only verified at the highest Cd level. H(2)O(2) content was increased in roots and shoot of Asterix, and apparently, a compensatory response between roots and shoot of Macaca was observed. SOD activity was inhibited in roots of Asterix at all Cd treatments, whereas in Macaca it was only increased at two highest Cd levels. Shoot SOD activity increased in Asterix and decreased in Macaca. Root CAT activity in Asterix decreased at 100 and 150 microM, whereas in Macaca it decreased only at 50 microM. Shoot CAT activity was decreased in Macaca. Root AsA content in Macaca was not affected, whereas in shoot it was reduced at 100 microM and increased at 200 microM. Cd caused increase in NPSH content in roots and shoot. Our results suggest that Cd induces oxidative stress in both potato cultivars and that of the two cultivars, Asterix showed greater sensitivity to Cd levels.

In order to evaluate the effect of cadmium (Cd(2+)) toxicity on mineral nutrient accumulation in potato (Solanum tuberosum L.), two cultivars named Asterix and Macaca were cultivated both in vitro and in hydroponic experiments under increasing levels of Cd(2+) (0, 100, 200, 300, 400 and 500 microM in vitro and 0, 50, 100, 150 and 200 microM in hydroponic culture). At 22 and 7 days of exposure to Cd(2+), for the in vitro and hydroponic experiment, respectively, the plantlets were separated into roots and shoot, which were analyzed for biomass as well as Cd(2+), and macro (Ca(2+), K(+) and Mg(2+)) and micronutrient (Cu(2+), Fe(2+), Mn(2+) and Zn(2+)) contents. In the hydroponic experiment, there was no reduction in shoot and root dry weight for any Cd(2+) level, regardless of the potato cultivar. In contrast, in the in vitro experiment, there was an increase in biomass at low Cd(2+) levels, while higher Cd(2+) levels caused a decrease. In general, Cd(2+) decreased the macronutrient and micronutrient contents in the in vitro cultured plantlets in both roots and shoot of cultivars. In contrast, the macronutrient and micronutrient contents in the hydroponically grown plantlets were generally not affected by Cd(2+). Our data suggest that the influence of Cd(2+) on nutrient content in potato was related to the level of Cd(2+) in the substrate, potato cultivar, plant organ, essential element, growth medium and exposure time.

The objective of this study was to evaluate whether the oxidative stress caused by aluminum (Al) toxicity is an early symptom that can trigger root growth inhibition in Macaca (Al-sensitive) and SMIC148-A (Al-tolerant) potato clones. Plantlets were grown in a nutrient solution (pH 4.00) with 0, 100 and 200mg Al L(-1). At 24, 72, 120 and 168h after Al addition, root length and biochemical parameters were determined. Regardless of exposure time, root length of the Macaca clone was significantly lower at 200mg Al L(-1). For the SMIC148-A clone, root length did not decrease with any Al treatments. Al supply caused lipid peroxidation only in Macaca, in both roots (at 24, 72, 120 and 168h) and shoot (at 120 and 168h). In roots of the Macaca, catalase (CAT) and ascorbate peroxidase (APX) activity decreased at 72 and 120h, and at 24, 72 and 120h, respectively. At 168h, both activities increased upon addition of Al. In roots of the SMIC148-A, CAT activity increased at 72 and 168h, whereas APX activity decreased at 72h and increased at 24, 12 and 168h. The Macaca showed lower root non-protein thiol group (NPSH) concentration at 200mg Al L(-1) in all evaluations, but the SMIC148-A either did not demonstrate any alterations at 24 and 72h or presented higher levels at 120h. This pattern was also observed in root ascorbic acid (AsA) concentration at 24 and 120h. The cellular redox status of these potato clones seems to be affected by Al. Therefore, oxidative stress may be an important mechanism for Al toxicity, mainly in the Al-sensitive Macaca clone.

In this study, the effects of exogenous mercury (HgCl(2)) on time-dependent changes in the activities of antioxidant enzymes (catalase and ascorbate peroxidase), lipid peroxidation, chlorophyll content and protein oxidation in cucumber seedlings (Cucumis sativus L.) were investigated. Cucumber seedlings were exposed to from 0 to 500microM of HgCl(2) during 10 and 15 days. Hg was readily absorbed by growing seedlings, and its content was greater in the roots than the in shoot. Time and concentration-dependent reduction in root and shoot length was observed at all concentrations tested, equally in the roots and shoot, at both 10 and 15 days. At 50microM HgCl(2), root fresh weight of 15-day-old seedlings increased, and at other concentrations, it reduced. For 10-day-old seedlings, reduction in root and shoot fresh biomass was observed. At 15 days, only at 50microM HgCl(2) was there no observed reduction in shoot fresh biomass. Dry weight of roots increased at 500microM both at 10 and 15 days, though at 250microM HgCl(2) there was only an increase at 15 days. There was a significant effect on shoot dry weight at all concentrations tested. Hg-treated seedlings showed elevated levels of lipid peroxides with a concomitant increase in protein oxidation levels, and decreased chlorophyll content when exposed to between 250 and 500microM of HgCl(2). At 10 days, catalase activity increased in seedlings at a moderately toxic level of Hg, whereas at the higher concentration (500microM), there was a marked inhibition. Taken together, our results suggest that Hg induces oxidative stress in cucumber, resulting in plant injury.