Cardoon Plants Research Articles

Chemical composition of cardoon (Cynara cardunculus L. var. altilis) petioles as affected by plant growth stage

In the present study petioles were collected from cultivated cardoon (Cynara cardunculus L. var altilis) plants in central Greece at sixteen harvest dates (samples P1-P16) and nine growth stages (principal growth stages (PGS) 1–9). The main objective of this study was to study the influence of petioles’ growth cycle on their chemical composition. The lipidic content, fatty acids, free sugars, organic acids, and tocopherol composition were analyzed. A total of 27 fatty acids were identified, being the palmitic acid (C16:0, 12.42–50%) the most abundant, except for samples P4 and P5 where linoleic acid revealed the highest relative abundance (C18:2n6c, 46.5 and 39.05%, respectively). The α-, β-, and γ-tocopherols were the identified isoforms of vitamin E, with sample P1 recording the highest tocopherol content. The detected organic acids were oxalic, quinic, malic, citric, and fumaric acids with the highest content being observed in sample P1. Sucrose was the major sugar in all the analyzed samples, followed by fructose, glucose, trehalose, and raffinose. The obtained results allowed us to characterize the chemical composition of cardoon petioles throughout its growth cycle and, consequently, to valorize the species through the exploitation of underutilized plant tissues.

Bioactive Compounds from Cardoon as Health Promoters in Metabolic Disorders.

Cardoon (Cynara cardunculus L.) is a Mediterranean plant and member of the Asteraceae family that includes three botanical taxa, the wild perennial cardoon (C. cardunculus L. var. sylvestris (Lamk) Fiori), globe artichoke (C. cardunculus L. var. scolymus L. Fiori), and domesticated cardoon (C. cardunculus L. var. altilis DC.). Cardoon has been widely used in the Mediterranean diet and folk medicine since ancient times. Today, cardoon is recognized as a plant with great industrial potential and is considered as a functional food, with important nutritional value, being an interesting source of bioactive compounds, such as phenolics, minerals, inulin, fiber, and sesquiterpene lactones. These bioactive compounds have been vastly described in the literature, exhibiting a wide range of beneficial effects, such as antimicrobial, anti-inflammatory, anticancer, antioxidant, lipid-lowering, cytotoxic, antidiabetic, antihemorrhoidal, cardiotonic, and choleretic activity. In this review, an overview of the cardoon nutritional and phytochemical composition, as well as its biological potential, is provided, highlighting the main therapeutic effects of the different parts of the cardoon plant on metabolic disorders, specifically associated with hepatoprotective, hypolipidemic, and antidiabetic activity.

Biochemical diversity of cardoon flowers (Cynara cardunculus L.): Predicting PDO Mediterranean cheese textures

Cardoon flower extract is a vegetable coagulant used in the manufacture of some highly appreciated Mediterranean Protected Designation of Origin (PDO) sheep cheeses, due to their typical flavor and smooth texture. Flowers from 6 cardoon plants (1M–6M), selected on the basis of the total and specific A0, A and B cardosin concentrations were characterized using chromatographic and electrophoretic analysis. Extracts of these flowers were used to investigate the relationship between the biochemical profile and the proteolytic activity on caseins, coagulation properties and cheese texture. Milk-clotting activity and coagulation were measured using an Optigraph. Cheese making trials were done using the traditional protocol of Serra da Estrela PDO cheese manufacture. A multivariate exploratory PCA analysis showed that plants 4M, 5M and 6M with the highest total concentration of cardosins, the prevalence of cardosin A, proteolytic action with Ƙ-casein, and the lowest time of coagulation yielded cheeses with a firmer paste. Plants 1M, 2M and 3M, without the presence of cardosin A, were negatively influenced by the proteolytic action with β-casein, starting flocculation and gel consistency. Plant 3M showed a slow micellar aggregation rate and low gel firmness during milk coagulation, which was reflected in the smooth texture of the cheese. The specific characterization of natural biochemical diversity of cardoon flowers and their influence on cheese texture may help producers to choose the appropriated cardoon flowers to obtain a desired texture.

Assessing the Impact of Water Salinization Stress on Biomass Yield of Cardoon Bio-Energetic Crops through Remote Sensing Techniques

Various species of cultivated thistle, such as Cynara cardunculus L. (cardoon), exhibit interesting features for industrial biomass production as bioenergy crops, given also their advantageous adaptation capacities to typical Mediterranean climate trends, with noticeable resilience to drought and salinization stresses. The in situ hyperspectral reflectance responses of three genotypes of cardoon plants, irrigated with water at different salinity levels, have been tested for assessing the effects on their biophysical parameters, aiming at improving the biomass yield for bioenergy production, minimizing at same time the environmental impacts and the exploitation of soils and waters resources. The leaf and canopy reflectance hyperspectral signatures, acquired at three different growth stages with biometric measurements, were statistically analyzed (ANOVA, Tukey’s test, graphs), as noise-resilient spectral indices, sensible to different plant features of interest. Their broadband versions, based on the Landsat 8 OLI and Sentinel 2 MSI satellite sensors, were also evaluated in perspective of operative and extensive remote crop monitoring from space. The results highlighted significant differences in some spectral index responses, related to different cardoon genotypes and water salt concentration. The biometric data supported by red-edge indices modelling evidenced the impact of the highest salt water concentration (200 mM/L) on the plant growth and yield.

Influence of Nitrogen Application and Drip Irrigation on Greenhouse Gas Emissions and Yield of Cardoon Crop (Cynara cardunculus L.)

Background: Cardoon is a multi-purpose crop with a wide spectrum of potential applications. Objective: The aim of this study was to assess the effects of nitrogen (N) application and drip irrigation practices on emissions of nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) and morphological characterization and biomass production of cardoon crop. Methods: The experiment was run under field conditions from April to August 2018. The field experiment was a randomized complete block design with three replications and four treatments: (i) non-amended soil as control (CONTR); (ii) mineral N fertilizer and non-irrigated (NITRO); (iii) non-fertilized and drip irrigation (IRRIG); and (iv) mineral N fertilizer and drip irrigation by fertigation (FERTI). The fluxes of N2O, CO2 and CH4 were measured by the closed chamber technique and the morphological characteristics and yield of cardoon plants were evaluated per treatment. Results: Results showed that the N2O emissions and global warming potential were not significantly different among the application of mineral N fertilizer itself or by drip fertigation with an emission rate of 0.5% of N applied and -6,8 t CO2-eq. ha-1. The characteristics related to biomass production did not differ significantly (p>0.05) between amended treatments although numerically higher in IRRIG treatment. Conclusion: It was concluded that the application of mineral N fertilizer itself or drip fertigation had no significant effect on N2O emissions and global warming potential. Additionally, the plant growth, including biomass production, increased due to drip irrigation, but not significantly.

Effect of Biochar on Emission of Greenhouse Gases and Productivity of Cardoon Crop (Cynara cardunculus L.)

Cardoon could be cropped for agro-environmental, industrial, and pharmaceutical purposes. The aim of this study was to assess the effects of biochar on emissions of nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4), and productivity of cardoon crop. A pot experiment was run outdoors from April to August 2018, with a cardoon plant per pot. The following four treatments, with four replicates each, were applied: control, soil only; mineral, soil amended with mineral fertilizer (2.5 g N m−2); biochar, soil amended with biochar (1 kg m−2); and mineral+biochar, soil amended with mineral fertilizer (2.5 g N m−2) and biochar (1 kg m−2). The morphological characteristics and biomass production of cardoon plants were evaluated, and the fluxes of N2O, CO2 and CH4 were measured by using the closed chamber technique. The application of biochar combined with mineral reduced N2O emissions by 36% and global warming potential (GWP) by 26% relative to mineral. However, the cumulative CO2 and CH4 emissions as well as yield-scaled GWP were not significantly different among amended soil treatments. Furthermore, the biomass production was increased by 50% by the application of biochar combined with mineral fertilizer relative to mineral. It was concluded that biochar combined with mineral fertilizer is recommended as a pathway mitigation for agro-environmental purposes, because it reduces the global warming potential and could increase the biomass production of cardoon plants.

Improvement of enzymatic antifelting treatment of wool fiber and its effect on dyeing with juglone from a common walnut plant

The objective of this study is to assess an enzymatic effect on the antifelting treatment of yarn and wool fabric. Enzymes, namely, the proteases cardosines A and B, are extracted from the flowers of the cardoon (Cynara cardunculus L) plant. Several conditions of enzymatic treatment are studied in order to optimize the antifelting process and improve shrink proofing. The optimal process is at 40 °C for 2 h in an alkaline medium at pH 10. The results show that the shrinkage of 16.8% for untreated yarn is reduced to 0%, while the shrinkage of 10% for the untreated fabric is reduced to 5%. In addition, the antifelting treatment increases the dye absorbance of a walnut stain (common walnut plant) on the yarn and wool fabric, although the fixation dye rate is decreased. Post oxidation is tested in order to improve the fixation dye rate and the washing fastness of juglone on the wool yarn and fabric.

Cynara cardunculus L. as a Multipurpose Crop for Plant Secondary Metabolites Production in Marginal Stressed Lands.

Cardoon (Cynara cardunculus L.) is a Mediterranean crop, member of the Asteraceae family, characterized by high production of biomass and secondary metabolites and by a good adaptation to climate change, usable in green chemistry, nutraceutical, and pharmaceutical sectors. Recent studies demonstrated the ability of cardoon to grow up in a stressful environment, which is associated with enhanced biosynthesis of biologically active compounds in these plants, and this effect is increased by abiotic stresses (salt, heat, pollution, and drought stress) that characterize many world marginal areas, affected by the climate changes. The plant response to these stresses consists in implementing different processes that modify some plant biological functions, such as alleviating both cellular hyperosmolarity and ion disequilibrium or synthesizing antioxidant molecules. The aim of this work was to investigate different cardoon response mechanisms to abiotic stresses and to evaluate their influence on the biologically active compounds biosynthesis. Following this purpose, we analyzed the ability of cardoon seeds to germinate under different salt stress conditions, and on the sprouts obtained, we measured the total phenol content and the antioxidant activity. Moreover, the growth of cardoon seedlings grown under heavy metals stress conditions was monitored, and the expression levels of heavy metal transport–associated genes were analyzed. The results showed the ability of cardoon plants to tolerate abiotic stress, thanks to different defense mechanisms and the possibility to obtain biomass with high content of biologically active molecules by exploiting the natural tolerance of this species for abiotic stresses. Moreover, we identified some important genes encoding for metal transportation that may be involved in arsenic and cadmium uptake and translocation in C. cardunculus. Then, this species can be considered as a promising crop for green chemistry and energy in marginal lands.

Plant Aspartic Proteases for Industrial Applications: Thistle Get Better.

Plant proteases have a number of applications in industrial processes including cheese manufacturing. The flower of the cardoon plant (Cynara cardunculus L.) is traditionally used as a milk-clotting agent in protected designation of origin cheeses made from goat and sheep milk. Plant-derived rennets are of particular importance to consumers who wish to eat cheeses that are produced without harming any animals. In this review, we have highlighted the importance of plant proteases, particularly aspartic proteases, in industrial processes, as well as exploring more fundamental aspects of their synthesis. We have also reviewed and discussed the production of these enzymes using sustainable and cost-effective alternative platforms.

Growth and chemical constituents of cardoon plant in response to foliar application of various algal extracts

Algal extracts play an important role in metabolic processes in cardoon plant (Cynara cardunculus L.). Cardoon contains phenolic compounds, fixed oil, sesquiterpenes, lactonens, flavones, sterols, coumarins, lignans, inulin, cynarin and silymarin. Also, it has medicinal properties, i.e. reduce the cholesterol, anti-diabetic, and improve the liver functions. The leaves of cardoon plant can inhibit the activity of several human pathogenic bacteria; possibly due to their specific phenolic components which have an antioxidant activity. The aim of this investigation was to evaluate the growth, seed yield and chemical constituents of cardoon due to spray with the algal extracts. Plants were treated with different doses (0, 1, 2 and 3 g/L) of four algal extracts (Spirulina platensis, Chlorella vulgaris, Amphora coffeaeformis and Scenedesmus obliquus). Morphological characters (plant height, leaf number, herb fresh weight, herb dry weight and seed yield) were recorded. Chemical contents (fixed oil, flavonoids, carbohydrates, free radical scavenging activity and phenolic compounds) were evaluated. The highest values of morphological characters were detected under 3 g/L of Spirulina platensis extract. Morphological characters increased by 70.9, 77.1, 45.6, 158.4 and 106.1% in plant height (cm); leaf number/plant, total fresh and dry weights (g/plant) and seed weight (g/plant) respectively, compared to the control. The Scenedesmus obliquus extract at 1 and 3 g/L resulted in the greatest amounts of fixed oil and total carbohydrates, the increase yielded 166.7 and 43.7% than control. Chlorella vulgaris extract in 1 and 2 g/L produced the highest increments in total flavonoids and inhibition of free radical scavenging activity, the increments were 58.8 and 105.5% than control. The highest value of total phenolic compounds was recorded due to the application of Amphora coffeaeformis extract at 3 g/L that produced 311.1% than control. Chlorogenic, caffeic and vanillic were detected as the major fractions of phenolic compounds. Algal extracts caused highly significant changes in major and minor fractions of phenolic compounds. Doses of 2, 3 g/L of Chlorella vulgaris and 2 g/L of Amphora coffeaeformis resulted in the greatest amounts of vanillic, chlorogenic and caffeic acids, these doses yielded 61.1, 31 and 66.7% respectively than control. It can be concluded that highly significant changes were reported in growth, yield and various chemical constituents of cardoon in response to the algal extracts applications.

Phenolic compounds content and antioxidant capacity in cardoon achenes from different head orders

Cardoon inflorescences (heads) contain achenes, which are used for the production of edible oil and biodiesel but also represent a phenolic source. This research aimed at determining the level of bioactive compounds and antioxidant capacity of cardoon achenes and investigating their qualitative and quantitative variations in achenes harvested from heads having different insertion order on main stem. The head order significantly affected the number of achenes per head and one thousand weight but did not affect the achene values of antioxidant capacity and concentrations of total phenolic (107.7–117.4 g gallic acid equivalent kg−1 dry weight), as well as the concentration of chlorogenic and 3,5-di-O-E-caffeoylquinic acids. Conversely, the absolute amounts of these metabolites differed significantly among head order when referred to a single achene or head. About 75% of their absolute values per cardoon plant were produced by achenes belonging to secondary and tertiary heads.

Nutritional Value and Bioactive Compounds Characterization of Plant Parts From Cynara cardunculus L. (Asteraceae) Cultivated in Central Greece.

In the present study, the nutritional value of the edible parts (immature capitula) of cardoon plants was evaluated, while further analyses were carried out in order to assess antioxidant properties and phenolic compounds composition of the various plant parts and seed oils. Cardoon capitula (heads) were a rich source of carbohydrates, with the main detected free sugar being sucrose, as well as of macro- and micro-minerals (K, Ca, Mg, and Fe). Heads were also abundant in saturated fatty acids (palmitic, behenic, linoleic, stearic, caproic, and oleic acid), whereas seed oils in unsaturated fatty acids (linoleic, oleic, palmitic, and stearic acid). Total phenolic compounds (TPC) content and phenolics composition differed between the various plant parts, with heads and leaf blades having higher TPC than midribs and petioles. Moreover, heads and leaf midribs and petioles consisted mainly of phenolic acids (5-O-caffeoylquinic and 3,5-O-dicaffeoylquinic acid), with flavonoids being detected in lower amounts. In contrast, the composition of polyphenols in leaf blades consisted mostly of flavonoids (Luteolin-7-O-glucoside and luteolin-7-O-malonylhexoside), whereas phenolic acids were also detected in considerable amounts (5-O-feruloylquinic and 3-O-caffeoylquinic acid). Regarding antioxidant properties, leaf blades and seeds exhibited the highest potency for all the tested assays which could be partly attributed to the synergistic effects of the phenolic compounds present in each sample. In conclusion, cardoon plant parts may find various uses in the food and pharmaceutical industry, since they contain considerable amounts of bioactive molecules, while seed oils can be considered as alternative vegetable oils for human consumption.

Electromagnetic treatments of cardoon seeds affect plant growth and linoleic acid content

The cardoon plant (Cynara cardunculus L.) is suitable for cultivation in the reclaimed desert lands. A field experiment was carried out during two successive seasons to study the effect of magnetic fields (MF) on cardoon growth and its linoleic acid content. A 75 mT (millitesla) MF was used as follows: MF0 (control) not exposed to the magnetic field, three different MF exposure durations studied as MF1 (T1): 15 min, MF2 (T2): 30 min, or MF3 (T3): 45 min, considered for both non-wetted/dry (D) and wetted seeds (W). The MF had significant effects on most of studied parameters. Plant height (cm), length of the longest leaf (cm), number of offshoots, width and length of the fifth leaf (cm), and number of leaves were all influenced by MF exposure, with significant differences between dry and wet seeds. Of the various MF exposure durations, MF2D and MF3W exhibited the best growth attributes for dry and soaked seeds, respectively. Additionally, the linoleic acid (C18:2) content in produced seeds was significantly influenced by 15 and 30 min of exposure to the MF, in the case of dry seeds. These findings suggest that MF treatments of cardoon seeds have the potential to enhance the plant growth and the linoleic acid content.

Alleviation of arsenic stress in cardoon plants via the supply of a low cadmium concentration

The effect of As (0–80μM) and of As+Cd (0–80μM+5μM) combinations on plant growth, toxicological variables and As and Cd bioaccumulation was studied in cardoon plants under controlled conditions. Plants grown in the presence of As alone showed less reduction in overall root and shoot development than those exposed to As+Cd, although the main root was shorter than in the latter plants. The effective added concentrations of As that reduced shoot or root dry weight by 50% (EC50) and the critical toxic concentration that caused a 10% reduction in plant growth (CTC10%) were higher in plants grown with As alone. In both treatments (As and As+Cd), the CTC10% was higher in the roots, but the root EC50 was lower than the shoot EC50. The presence of Cd increased the accumulation of As in the shoot, but ≥20μM As reduced the shoot bioaccumulation of Cd. Thus, the presence of 5μM Cd with As appears to reduce the tolerance of cardoon plants to the latter element, but it increases their As phytoextraction capacity. Cardoon plants could be used as excluders in As-contaminated sites and as accumulators in those co-contaminated with As and Cd.

Cynara Cardunculus in Large Scale Cultivation. A Case Study in Portugal

Cynara cardunculus L. was installed for biomass production in a total of 8.1 ha in Sesimbra (Portugal), using common agricultural practices and machinery. Installation by sowing was successful, in spite of the extreme drought during the first cycle (only 382 mm). In the second year, the rainfall was 683 mm and the plants developed well, with a mean density of 30 thousand plants per ha. The field presented a heterogeneous distribution of cardoon plants and the aerial photographs showed that 4.9 ha presented an occupation over than 50 %.The yield of biomass was 9.7 tha-1, with plants presenting on average, 2.2 m height, 2.3 cm stalk diameter, and 6.5 capitula per plant. The capitula contained on average 210 seeds, weighing 28 g per 1,000 seeds, and the mean seed yield was 1,065 kg ha-1. The stalks represented 58.7 % of total dry biomass.These results confirm that Cynara crops are suitable for biomass production in Mediterranean regions and that large scale operation can be applied including whole plant harvesting or plant fractionation for seed recovery. There was variation between plants, namely in oil seed production, which suggests potential improvements through breeding.

Proteolytic effect of Cynara cardunculus rennet for use in the elaboration of ‘Torta del Casar’ cheese

The purpose of this work was to analyse the influence of rennet from different Cynara cardunculus plants, selected for its clotting and proteolytic activity on caseins, on the characteristics of manufactured 'Torta del Casar' cheeses. After classifying the cardoon according to proteolytic activity into five groups of greater or lesser activity, 16 batches of cheeses were made with rennet derived from different wild cardoon plants. We observed a major development of the proteolysis during ripening leading to the generation of non-protein nitrogen compounds. Especially noteworthy was the relationship of amino acid nitrogen (AN) generation with rennet clotting activity after 24 h of maceration, and the fact that the production of biogenic amines was not related to the proteolytic activity of the rennet. The activities of the rennet observed 'in vitro' were also developed 'in vivo' in the cheeses, with the different rennets used affecting the final sensory characteristics of cheeses. The rennet with high clotting activity after 24 h of maceration was positively correlated with the creaminess, viscosity, and acceptability of the cheese. However, the high proteolytic activity rennet negatively influenced the acidity, bitterness, and creaminess parameters. Therefore the most appropriate cardoons for making this cheese are those with higher clotting activities and moderate proteolytic activities especially on β-casein. The use of controlled and characterised cardoons in the manufacturing process of Torta del Casar is fundamental to obtaining the homogeneous product demanded by the Torta del Casar Registry of the Protected Designation of Origin.

Responses of Cynara cardunculus L. to single and combined cadmium and nickel treatment conditions

A greenhouse pot experiment was carried out to study the responses of Cynara cardunculus L. (cardoon) to cadmium and nickel. Three groups of 12 pots each were planted with cardoon plants and spiked with single and combined cadmium and nickel aqueous solutions. The bioavailable metal concentrations, measured in soil, ranged widely and were up to 246.7 mg kg −1 for Cd and 61.1 mg kg −1 for Ni. Under Cd treatment, cardoon growth remained unaffected, while increased Ni soil concentrations inhibited plant growth and were lethal to the highly treated plants. In the combined Cd and Ni treatments, an antagonistic effect was observed between the two metals. Cadmium and nickel concentrations in cardoon tissues rose with increasing metal concentrations in the soil. Cadmium and nickel contents in shoots reached 169.3 and 342.3 mg kg −1 in the single treatments while, under the combined Cd and Ni treatments, they were up to 235.0 and 440.7 mg kg −1, respectively. Generally, mean contents of both metals in the shoots were higher than in the roots and the translocation factor was greater than 1. A possible enhancing effect of nickel on cadmium uptake was observed. Cardoon showed characteristics of a Cd accumulator.

Effects of chelates on plants and soil microbial community: Comparison of EDTA and EDDS for lead phytoextraction

Most studies on chelate-induced phytoextraction have focused on EDTA-mediated Pb phytoextraction. But EDTA and the formed EDTA–Pb complexes have low biodegradability and high solubility in soil, resulting in an elevated risk of adverse environmental effects. EDDS is an easily biodegradable chelating agent that has recently been proposed as an environmentally sound alternative to EDTA. Consequently, a greenhouse experiment, using a completely randomized factorial design with four replications, was carried out to compare the potential of EDTA and EDDS for chelate-induced Pb phytoextraction with Cynara cardunculus, as well as to investigate the toxicity of these two chelates to both cardoon plants and soil microorganisms. The effects of chelate addition on soil microbial communities were studied through the determination of a variety of biological indicators of soil quality such as soil enzyme activities, basal and substrate-induced respiration, potentially mineralizable nitrogen, and community level physiological profiles. EDTA was much more efficient than EDDS for the enhancement of root Pb uptake and root-to-shoot Pb translocation. In a soil polluted with 5000 mg Pb kg − 1 , as a result of the addition of 1 g EDTA kg − 1 soil, a value of 1332 mg Pb kg − 1 DW shoot was obtained. EDDS application resulted in a shoot Pb accumulation of only 310 mg kg − 1 DW. Plants treated with EDDS showed lower values of biomass than those treated with EDTA. EDDS proved to be rapidly degraded, and less toxic to the soil microbial community in control non-polluted soils. Pb-polluted EDDS-treated soils showed significantly higher values of basal and substrate-induced respiration than those treated with EDTA. Although EDDS had a lower capacity to enhance Pb phytoextraction than EDTA, it has the advantage of rapid biodegradation.

EDTA-induced heavy metal accumulation and phytotoxicity in cardoon plants

In most metal polluted soils, Pb usually appears together with other heavy metals (HM), such as zinc (Zn) and cadmium (Cd). In addition, in phytoextraction experiments, efficient Pb uptake is generally limited by its low phytoavailability. Then, as part of our studies on chelate-induced phytoextraction, cardoon ( Cynara cardunculus L.) seedlings were hydroponically exposed to a range of ethylenediaminetetraacetic acid concentrations (EDTA: 0, 250, 500, and 750 μM) in the absence and presence of a mixture of heavy metals (300 μM Pb 2+ + 150 μM Zn 2+ + 50 μM Cd 2+). Increasing EDTA concentrations in solution significantly increased shoot Pb accumulation and shoot/root ratios. On the contrary, above 250 μM, EDTA decreased root and shoot Zn and Cd accumulation. Our results suggest a non-selective apoplastic root uptake of metal–EDTA complexes. When supplied independently, both EDTA and the mixture of heavy metals negatively affected plant physiological parameters related to plant water transpiration, such as shoot water content, evapotranspiration, transpiration rate, and stomatal conductance. On the contrary, in the presence of heavy metals, increasing EDTA concentrations led to decreased metal phytotoxicity. The highest total amount of metals in shoots was obtained at 250 μM EDTA, a close to equimolar concentration to the metal with the lowest phytoavailability present in the solution (i.e., Pb). Our results indicate that proper management of the EDTA concentration can reduce metal phytotoxicity, maintain the free uptake of some metals and, at the same time, increase the uptake of metals with low phytoavailability.

EDTA reduces the physiological damage of lead on cardoon plants grown hydroponically

Cardoon seedlings (Cynara cardunculus L.) were grown hydroponically in nutrient solution and exposed to lead (Pb 2+ : 1mM) in the presence of a range of different EDTA concentrations (EDTANa 2 : 0, 0.5, 1 or 2mM). Analyses were performed to establish whether the coordination of Pb 2+ transport by EDTA enhances the mobility of this metal within the plant and to determine the toxic effects of these treatments during a phytoextraction process. Net photosynthesis, transpiration rate and stomatal conductance decreased dramatically in plants treated with Pb 2+ or Pb-EDTA at doses below 1 mM. In these treatments, most of the Pb 2+ accumulated in the roots, and only a very low amount of it was translocated to the shoots. Increasing the EDTA doses up to Pb 2+ equimolarity, increased the Pb 2+ shoot content more than 10-fold without any physiological evidence of toxicity. The treatment with higher doses of EDTA (Pb 2+ 1 mM + EDTA 2 mM) did not show toxicity symptoms, but the Pb 2+ concentration in the aboveground tissues decreased when compared with the equimolar treatment. The interaction with the absorption of some essential cations such as Ca 2+ and phytotoxicity on chelated-assisted phytoextraction is discussed.