Industrial Crops and Products

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1 Industrial Crops and Products 35 (2012) Contents lists available at ScienceDirect Industrial Crops and Products journa l h o me page: New approaches concerning the utilization of natural amendments in cadmium phytoremediation Alina Stingu a, Irina Volf a,, Valentin I. Popa a, Irina Gostin b a Gheorghe Asachi Technical University of Iasi, Faculty of Chemical Engineering and Environmental Protection, 73 Prof. dr. Doc. Dimitrie Mangeron Street, Iasi, Romania b Al. I. Cuza University of Iasi, Faculty of Biology, Bd. Carol I 20A, , Romania a r t i c l e i n f o Article history: Received 28 February 2011 Received in revised form 3 June 2011 Accepted 4 June 2011 Available online 7 July 2011 Keywords: Biologically active compounds Natural amendments Heavy metal Phytoremediation a b s t r a c t Different vegetal biomass resources such as Picea abies bark, Castanea sativa chestnuts shell and Asclepias syriaca plant were considered to provide a source of natural bioactive compounds, which can be properly used in several directions such as: plant growth regulators and amendments in bioremediation. Having in mind a complex processing biomass technology, these raw materials are used in a first step to separate bioactive compounds by an aqueous extraction. The obtained extracts containing polyphenols were tested in germination tests to evaluate their influence on cadmium bioaccumulation in oat plant (Avena sativa). It was observed that the mentioned extracts modulated cadmium bioaccumulation, photosynthesizing pigments biosynthesis, plant growth and its development depending on metal ion concentration (5, 12.5, 25 mg/l), and extracts composition determined by vegetal raw material and their total polyphenols content (130, 122, 114 mg/l related to gallic acid). FTIR spectra and histo-anatomical cross section of the roots certify that P. abies bark and A. syriaca plant extracts amendments stimulated cadmium bioaccumulation, promoting the translocation of heavy metals to the aerial part of the plant, meanwhile chestnuts shell extract reduced the mobility of cadmium determining in situ inactivation of heavy metal ions Elsevier B.V. All rights reserved. 1. Introduction It is known that cadmium is associated with industrial processes such as metal plating and the production of nickel cadmium batteries, pigments, plastics and other synthetics. Cadmium is a potential environmental hazard and it is one of the most dangerous heavy metals that exist in the polluted fields. The high values of cadmium concentration observed in many agricultural soils are due to long term use of phosphatic fertilizers and sewage sludge applications (Irtelli and Navari-Izzo, 2006; Shamsi et al., 2008). In these conditions a cost effective procedures are needed to remove cadmium from the contaminated soil environment. At the same time phytoremediation is a cost effective and eco-friendly green remediation technology for environmental cleanup. In this context, the technologies for metals phytoremediation include phytoextraction which aims to remove trace elements from soil through their uptake and accumulation by plants (Nascimento and Xing, 2006). The resulted plant biomass can then be harvested, thereby removing the metals from the site. This technique is only effective if the plants accumulate large concentrations of metals/metalloids in shoots and have a reasonable Corresponding author. addresses: astingu@ch.tuiasi.ro (A. Stingu), iwolf@ch.tuiasi.ro (I. Volf), vipopa@ch.tuiasi.ro (V.I. Popa), irinagostin@yahoo.com (I. Gostin). biomass production (McGrath and Zhao, 2003). Phytoextraction is best suited for the remediation of diffusely polluted areas, where pollutants occur in a relatively low concentration and superficially (Rulkens et al., 1998). Phytostabilisation is considered to be another phytoremediation technique aiming at establishing a vegetation cover and determining in situ inactivation of trace elements by combining the use of metal-tolerant plants with soil amendments that have as a consequence reducing the mobility and toxicity of pollutants and simultaneously increasing soil fertility and improving plant establishment. The plants recommended for phytostabilisation should retain the metals at the root level restricting their transport to aerial parts (Baker, 1981) thus avoiding further transfer into the food chain (Wenzel et al., 1999). At the same time, natural organic acids have been proposed to enhance phytoextraction due to their higher biodegradability and Nascimento (2006) noticed that citric, oxalic, vanillic and gallic acids, applied in dosage of 10 or 20 mm/kg, solubilized significant amounts of Zn, Ni, and Cd from soil. On the other side, studies carried by Popa et al. (2010a) and Ignat et al. (2011) provided that aqueous polyphenolic extracts obtained from different raw materials such as spruce wood bark and grape red seeds contain significant concentrations of phenolic acids. These could be used as sequestrants to form chelates with heavy metals. Increasing interest in the replacement of synthetic chelators has determined to research into natural sources of chelating agents, especially using plants as raw materials. This will allow a /$ see front matter 2011 Elsevier B.V. All rights reserved. doi: /j.indcrop

2 54 A. Stingu et al. / Industrial Crops and Products 35 (2012) possibility to valorize of waste industrial products which represent an important challenge of sustainable development based on environmentally friendly processes correlated with complex processing of biomass. In these conditions we have in view that there are huge amounts of spruce bark and chestnuts shell residues which are readily available at low prices. Thus for spruce of pulpwood size, bark volumes are usually between 12% and 24% of total processed wood and in the case of chestnuts shell represent around 10% by weight of them which is removed in the peeling process and it is used as fuel. Therefore, these residues due to their significant content of polyphenols can be used as a raw material for the production of high-value bioactive substances (Popa et al., 2010b). Polyphenols are secondary plant metabolites mostly derivatives, and/or isomers of flavones, isoflavones, flavonols, catechins, and phenolic acids with a vast array of possible functions, including antioxidative activity, antifeedants, attractants for pollinators, contributors to plant pigmentation (Tahara, 2007; Naczk and Shahidi, 2006). Phenolics could be properly use in food industry, health protecting, plants growth and development, bioremediation (Naczk and Shahidi, 2006; Stingu et al., 2009a). Besides being radical scavengers, flavonoids, for example are able to function as chelators for metals, depending on the molecular structure (Korkina, 2007). Keilig and Ludwig-Müller (2009) study shown that flavonoids could be an additional factor in heavy metal tolerance in Arabidopsis thaliana. The accessibility of these compounds determined us to develop new applications in the field of phytoremediation. From this point of view in this study we followed a situation in which cadmium tolerance/bioaccumulation could be enhanced by adding natural bioactive compounds obtained by aqueous extraction from Picea abies bark, Castanea sativa chestnuts shell of and Asclepia syriaca plant. The relation established between polyphenolic compounds and heavy metal tolerance/bioaccumulation was investigated in the case of Avena sativa which could be correlated with the possibilities to use polyphenols as metal chelators or as heavy metal biosolubilizer. The possibility of using natural polyphenolic extracts as natural amendments in cadmium phytoremediation was investigated through all specific evaluation analysis: biometric measurements and quantitative determination of plantlet biomass, physiological and anatomical cross-sections analysis. 2. Material and methods 2.1. Aqueous extraction P. abies bark was provided by a pulp mill, C. sativa chestnuts shell was collected in Iasi, Romania, in October 2009 from Anastasie Fatu Botanical Garden and dry steams of Asclepias syriaca plant were obtained from an energetically crop (1998) in a research program of Gheorghe Asachi Technical University of Iasi, Natural and Synthetic Polymer department. All of these raw materials were grinded in a mill and reduced to a fine powder of 0.5 mm. 5, 10, 20 g of grounded P. abies bark, C. sativa chestnuts shell and A. syriaca biomass were extracted with125 ml distilled water in a water bath, 45 min at C for three times and the extracts were cumulated to a final volume of 500 ml using distilled water. 2005). About 1 ml of plant extracts was mixed with 500 L of the FC reactive, 2 ml of 10% sodium carbonate and 5 ml of water. The mixture was shaken thoroughly and was allowed to stand for 90 min. Then the absorbance at 765 nm was determined against a blank which contain all reagents without the samples or the gallic acid at the same conditions. The total phenolic content is expressed as the number of equivalents of gallic acid (GAE). Then all obtained extracts were characterized from the point of view of total content of tannins, flavonoids, flavonols and antocyanins using selected samples with about the same content in total polyphenols. The total content of tannins was determined using a method based on the precipitation of tannins with casein. The tannins content was established using FC method and expressed as the difference between the initial content of polyphenols and the content after the precipitation with casein (El-Sayed, 2009). The total contents of flavonoids and flavonols were determined by aluminium chloride method using rutin as a reference compound according to Makris et al. (2007), respectively El-Sayed (2009) based on the formation of a complex flavonoid aluminium having the maximum of absorption at 510 nm for flavonoids and 440 nm for flavonols. The colour intensity of the extracts was determined by reading the absorbance at fixed wavelength, 420, 520, 620 nm according to MA-F-AS2-07-CARCHR (2006) Experimental assay Germination test were carried out in Petri dishes, each one containing 8 oat seeds pre-disinfected with NaOCl 1% for 15 min and 10 ml tested sample solution. Tested solutions were: control tap water; three different concentrations of cadmium salt: Cd-5, Cd-12.5, Cd-25 corresponding to 5, 12.5, 25 mg/l CdCl 2 cadmium contamination level and the same cadmium concentrations but in the presence of the polyphenolic extracts: P. abies bark: PA-Cd-5, PA-Cd-12.5, PA-Cd-25; C. sativa chestnuts shell: CS-Cd-5, CS-Cd-12.5, CS-Cd-25; A. syriaca plant: AS-Cd-5, AS-Cd-12.5, AS-Cd-25. It has been used CdCl 2 2H 2 O salt to prepare solution and induce cadmium stress. The experiment was carried out in triplicates and an average value was reported Plantlet analysis After 10 days from the beginning of the experiments, the oat plantlets were separated into roots, coleoptiles and primary leaves and measured to evidence the different effects of natural extracts on plants growth and development. Separated plantlet samples were oven dried at 70 C until constant values of mass was reached and dry biomass was quantified Photosynthesizing pigments Photosynthesizing pigments were spectrophotometrical quantified, using a UV-VIS SP-8001, Metertech Inc. spetrophotometer, by reading the absorbance of fresh primary leaves extracted in 80% acetone, at 470, 646, 663 nm wavelengths and using the extinction coefficients proposed by Lichtenthaler and Wellburn (1983). Chlorophyll content was expressed in g/g green biomass Characterization of the extracts Each aqueous extract was characterized in terms of total dry matter and organic matter content and total polyphenolic content using Folin Ciocalteau (FC) method (Stingu et al., 2009a; Bao et al., 2.6. Metal content analysis For the quantification of heavy metal concentration in oat plant tissues, dry samples were mineralized in HNO 3 (65%) and H 2 O 2 (30%) on a hot plate (120 C) for at least 5 h until the volume was

3 A. Stingu et al. / Industrial Crops and Products 35 (2012) Table 1 Aqueous polyphenolic extracts characterization. Raw material (g) Dry matter content (g/l extract) Organic matter content (g/l extract) Total polyphenolic content (mg/l extract) PA PA PA CS CS CS AS AS AS PA Picea abies bark extract, CS Castanea sativa chestnuts shell extract, AS Asclepias syriaca plant extract. The gray scale mark the selected treatment solution which will further be tested in the germination experiment. less than 1 ml. This volume was made up to 25 ml with bi-distilled water and than heavy metal concentration was determined using a GBC Avanta Atomic Absorption Spectrophotometer (Stingu et al., 2009b). Statistical analysis was carried out using the Excel XP, SPSS Sampling and chemical analyses were examined in triplicate in order to decrease the experimental errors and to increase the experimental reproducibility. The confidence of data generated in the present investigations has been analyzed by standard statistical methods to determine the mean values and standard deviation (S.D.). The values in figures were expressed as mean ± S.D. of the three replicates FTIR spectroscopy FTIR spectra were obtained for the dry roots of the oat plantlet resulted in 25 mg/l cadmium stress conditions and in the contaminated growth medium supplemented with P. abies bark, C. sativa chestnuts shell and A. syriaca extracts to evaluate the influence of the natural extracts on oat plant development. The oven dried plant samples were ground into a fine powder by using an agate mortar and the FT-IR spectra were recorded using Bruker IFS-66v model FT-IR spectrometer in the region cm 1 by employing standard KBr pellet technique (2.5% sample) Histo-anatomical examination of cross sections Histo-anatomical cross section was examined only for oat roots grown in 25 mg/l Cd 2+ stress conditions and also for the case of introducing the polyphenolic extracts as amendments. The roots were fixed and conserved in 70% ethanol. Free hand sections were performed using a razor blade. The sections were coloured with ruthenium red and iodine green. The photos were taken with an Olympus E-330 photo camera, using an Olympus BX51 research microscope. Fig. 1. The influence of different polyphenolic extracts treatment on oat plantlet growth in cadmium contaminated environment. Symbols are presented in experimental protocol. 3. Results and discussion 3.1. Characteristics of aqueous extracts P. abies bark (PA), C. sativa chestnuts shell (CS) and A. syriaca plant (AS) polyphenolic extracts characteristics are presented in Table 1. From the obtained data it could be observed that as a function of raw materials nature the aqueous extracts were characterized by a different content in total polyphenols. To make a comparison, from all extracts it was selected for experiments those containing the same total polyphenolic content as the following: PA from 5 g, CS from 5 g and AS from 20 g raw material, to test their influence on cadmium bioaccumulation. The selected aqueous extracts were individually characterized in terms of total content of tannins, flavonoids and flavonols, colour intensity, ph and the results were summarized in Table 2. The highest value for total content of tannins (mg/100 g EAG) was obtained for C. sativa chestnuts shell extract, meanwhile the total content of flavonoids (mg/100 g RE) corresponded to P. abies bark aqueous extract. A. syriaca plant extract was characterized by the highest values of the total content of flavonols (mg/100 g RE) and of ph Oat plantlet growth and development The presence of the polyphenolic compounds in the growth medium ameliorated oat coleoptiles growth and dry biomass accumulation in the case of contamination with solutions of 12.5 and 25 mg/l cadmium concentrations (Figs. 1 and 2) and determined stimulation effects comparing with results obtained without amendments application. Not the same things could be said about the roots and primary leaves growth and development which were inhibited under cadmium stress, even in the presence of all tested aqueous extracts. The most significant stimulation effects on coleoptiles elongation and dry biomass yield were found when P. Table 2 Characteristics of selected aqueous polyphenolic extracts. Extract Total content of tannins mg/100 geag Total content of flavonoids mg/100 g RE Total content of flavonols mg/100 g RE Colour intensity ph PA CS AS PA Picea abies bark extract, CS Castanea sativa chestnuts shell extract, AS Asclepias syriaca plant extract.

4 56 A. Stingu et al. / Industrial Crops and Products 35 (2012) Fig. 2. The influence of different polyphenolic extracts treatment on oat plantlet dry biomass in cadmium contaminated environment. Fig. 3. Cadmium bioaccumulation in oat plant under different polyphenolic extracts treatment. abies bark and A. syriaca extracts were applied in culture medium contaminated with solutions of 12.5 and 25 mg/l cadmium concentrations Photosynthesizing pigments The biosynthesis of photosynthesizing pigments was significantly stimulated by the presence of polyphenolic extracts, depending on cadmium concentration in the growth medium. Thus, the most obvious stimulation effects on total chlorophyll content were evidenced when AS extract amendment was used for all cadmium concentrations. Regarding carotene pigments, the same effect was registered in the presence of CS extract but only for concentrations of 5 and 25 mg/l cadmium environment contamination (Table 3) Heavy metal content Tables 4 and 5 summarized the values determined for cadmium ions concentrations ( g/g dry mass) and metal content ( g/plant) in oat plantlet. The highest cadmium concentrations ( ; ; g/g dry weight) were found when the P. abies bark polyphenolic extract was added in the growth medium for all three tested cadmium concentrations (5, 12.5, 25 mg/l Cd 2+ ). The highest values for cadmium content (heavy metal concentration reported to the whole plant weight) were observed under the influence of A. syriaca plant extract amendments (12.62; g/plant) when solutions of 12.5 and 25 mg/l cadmium concentrations were used to induce stress conditions. Metal concentrations and its plant content seem to be increased with increasing cadmium ions concentrations in the medium and also in the presence of P. abies bark and A. syriaca plant aqueous extracts. The highest heavy metal concentration effect and its plant content were predominantly found into the roots zone, followed by coleoptiles and primary leaves. The presence of aqueous extracts provides an increasing trend in cadmium concentration effect and its content into higher part of the oat plantlet compared with the situation when polyphenols were absent. The lower values for cadmium concentration (34.94 g/g dry weight) and content (1.24 g/plant) were obtained during oat seeds germination test when C. sativa chestnuts shell bioactive compounds were applied in 25 mg/l cadmium contaminated environment. For the other two concentration of cadmium ions (5 and 12.5 mg/l Cd 2+ ) the values determined for metal concentration and content were also lower in the presence of C. sativa chestnuts shell extracts compared with the case of no polyphenolic extracts addition or P. abies bark and A. syriaca plant extract administrated to the same cadmium concentrations. The values were: and 2011 g/g dry weight for cadmium concentration and 2.76; 4.65 g/plant for cadmium content in oat plantlet. Analyzing the obtained results it could be observed that the bioaccumulation which represent the proportion between ( g metal/g dry weight plant) and ( g metal/ml solution) (Singh et al., 2009) varied with cadmium ions contamination of the growth medium and the nature of polyphenolic extracts (Fig. 3). It could be noticed that P. abies bark and A. syriaca extracts increased cadmium bioaccumulation in A. sativa and translocation (Translocation factor (TF) = The ratio of the metal concentration in shoots/the ratio of the metal concentration in roots) (Sun et al., 2009) of heavy metal to the upper parts of oat plantlet (Fig. 4). P. abies bark and A. syriaca extracts promoted the solubilization of high amounts of cadmium ions and allowed them to be accumulated in oat plantlet. The presence of P. abies bark extract in the growth medium provide a bioaccumulation (441.8) of heavy metal ions in oat with 65% higher than control represented by the results obtained with solution of 5 mg/l cadmium concentration. In the case of 12.5 mg/l cadmium contaminated environment the highest bioaccumulation was observed under AS extract treatment (382.7), being with 74% higher than control (219.2). Increasing the cadmium concentration, PA extract stimulate the bioaccumulation with 37% (263.29) based on the reference represented by 25 mg/l cadmium ions (191.2). C. sativa chestnuts shell extract act as a chelator agent for cadmium ions as long as the presence of this extract in the growth medium decrease the bioaccumulation process and block the heavy metals access to the upper parts of the plant by stocking them at the Fig. 4. Translocation factor of cadmium ions in oat plantlet under different polyphenolic extracts treatments.

5 A. Stingu et al. / Industrial Crops and Products 35 (2012) Table 3 Photosynthetic pigments content ( g/g) for oat plantlet grown under cadmium stress conditions and polyphenolic extracts amendments. Tested solution Chl a Chl b Carotene Chl a + b Chl a/b Control ± ± ± Cd ± ± ± PA-Cd ± ± ± CS-Cd ± ± ± AS-Cd ± ± ± Cd ± ± ± PA-Cd ± ± ± CS-Cd ± ± ± AS-Cd ± ± ± Cd ± ± ± PA-Cd ± ± ± CS-Cd ± ± ± AS-Cd ± ± ± PA Picea abies bark extract, CS Castanea sativa chestnuts shell extract, AS Asclepias syriaca plant extract. Bold and grey shade highlight the highest values obtained for the mentioned parameters (Carotene and Chl a + b). Table 4 Rootlets, coleoptiles, primary leaves concentration ( g/g dry mass) of cadmium in oat plantlet under polyphenolic extracts treatment. Tested solution Concentration ( g/g dry weight) Roots Coleoptiles Leaves Total Cd ± ± ± PA-Cd ± ± ± CS-Cd ± ± ± AS-Cd ± ± ± Cd ± ± ± PA-Cd ± ± ± CS-Cd ± ± ± AS-Cd ± ± ± Cd ± ± ± PA-Cd ± ± ± CS-Cd ± ± ± AS-Cd ± ± ± PA Picea abies bark extract, CS Castanea sativa chestnuts shell extract, AS Asclepias syriaca plant extract. level of rootlets. This could be correlated with the smallest values for translocation factor (Fig. 4). The metal recovery, increased in the presence of P. abies bark and C. sativa chestnuts shell extracts but decreased considerably under A. syriaca extracts amendment in a environment contaminated with 5 and 12.5 mg/l Cd 2+. For a higher contamination level (25 mg/l Cd 2+ ), the recovery was reduced in the presence of natural polyphenolic extracts, especially in the case of P. abies bark and A. syriaca ones (Fig. 5) FTIR analysis The FTIR spectra of oat plant roots are shown in Fig. 6 and those presented similarly aspects with a lignin characteristic spectrum. In the plant cell wall, lignin is intertwined and covalently bounded with macromolecules of cellulose and hemicelluloses, thus forming supramolecular structures such as microfibrils and lamellae as constituents of cell plant wall membranes. The linkage types include ether bonds between aryl carbons in the lignin and the carbohydrate, ester bonds between aryl carbons, and also uronic acid residues and lignin hemicelluloses matrix encrusts and protects the cellulose component of the cell wall from microbial attacks (Popescu et al., 2006). The major chemical functional groups identified include hydroxyl, methoxyl, carbonyl and carboxyl groups. Oat plant roots spectra evidence two important region as for lignins spectra, clearly differentiated: the bands in the cm 1 region assigned to the OH groups of the physically absorbed water or bonded in aliphatic and aromatic groups, as Table 5 Rootlets, coleoptiles, primary leaves content ( g/plant) of cadmium in oat plantlet under polyphenolic extracts treatment. Tested solution Content ( g/plant) Roots Coleoptiles Leaves Total Cd ± ± ± PA-Cd ± ± ± CS-Cd ± ± ± AS-Cd ± ± ± Cd ± ± ± PA-Cd ± ± ± CS-Cd ± ± ± AS-Cd ± ± ± Cd ± ± ± PA-Cd ± ± ± CS-Cd ± ± ± AS-Cd ± ± ± PA Picea abies bark extract, CS Castanea sativa chestnuts shell extract, AS Asclepias syriaca plant extract.

6 58 A. Stingu et al. / Industrial Crops and Products 35 (2012) Fig. 5. Cadmium recovery (%) in oat plant under different polyphenolic extracts treatment. well as to the methyl groups, and the bands in the cm 1 region, assigned mainly to the guaiacyl and syringyl structural units, but also for other functional groups (Popescu et al., 2006). The very strong absorption band observed around cm 1 represents a bound hydroxyl group in phenolic and aliphatic structures (Sawalha et al., 2007). The medium absorption band appearing at 2924 cm 1 for all samples of tested oat roots is due to CH stretching in aromatic methoxyl groups and in aliphatic methyl/methylene groups of side chains. The lone C O stretching vibration band corresponding to native carbonyl and ester groups stretching 1728 cm 1 is present, with a medium absorption intensity, only in the roots collected from the cadmium contaminated growth medium supplemented with spruce bark polyphenolic extract (Popescu et al., 2006; Sawalha et al., 2007). Absorbance changes observed at 1639 cm 1, 1633 cm 1 were assigned to a chelated form of the carbonyl on the carboxyl group. In some studies this absorption band was described as the region of both ionized non-coordinated and ionized coordinated COO group (Sawalha et al., 2007; McNear et al., 2010). The absorption band at 1539 cm 1 was evidenced only in the case of plant roots samples grown in a 25 g/ml Cd (II) and in the case of growth medium supplementation with chestnuts shell aqueous extract. This band it is charactherized by the C C stretching of the aromatic syringil ring. The bands assigned to the valence vibrations of the aromatic ring in guaiacyl group at 1519 cm 1, 1514 cm 1 and C H asymetric deformation in OCH 3 at 1423 cm 1, 1419 cm 1 are the most representative ones for lignins and were observed with strong intensity, in all FTIR spectra registered for all oat roots samples. The very strong band occurring at 1382 cm 1 ş i 1388 cm 1, identified only in FTIR spectra of oat roots plant grown in a 25 g/ml Cd(II) contaminated medium and supplemented with chestnuts shell, respectively A. syriaca plant extracts, could be attributed to symmetric C H bending from methoxyl group, O H and C O of phenols and tertiary alcohol. The bands at cm 1 assigned to the C 1 O vibration in syringil derivatives. In general, the IR features occuring between cm 1 are attributed to aromatic C O stretching vibrations. All spectra evidence vibration charactheristic for guaiacyl units, other than those discussed before such us: 1255 cm 1, 1155 cm 1, 1156 cm 1, 1159 cm 1 ; and vibrations charactheristic for the syringyl units at 1319 cm 1. The very strong band occurring at 1056 cm 1 (P. abies bark amendment and control sample), 1058 cm 1 (A. syriaca plant extract amendment) and 1049 cm 1 (C. sativa chestnut shell extract amendment and 25 g/ml Cd 2+ ) shows the presence of alkyl O ether vibrations methoxyl and -O-4 in guaiacol (Popescu et al., 2006). The absorption at 1048 cm 1 indicates the presence of polysaccharides. Many C O C groups exhibit characteristics bands in the cm 1 spectral range and generally the strong band at 1026 cm 1 is assigned to the vibration of C O in alcohol hydroxyl group (Cavalu and Cîntă Pînzaru, 2005). FTIR spectroscopy was used to clarify the reaction of Cd (II) in oat roots. The characteristic changes in the FTIR spectra were detected as a response to reaction between Cd (II) and polyphenolic aqueous extract. Characteristic pick of FTIR spectra registered for oat root plant were summarized in Table Microscopic characteristic of cross-sections For microscopic characterization cross section of A. sativa roots were used. The micrographs are presented in Fig. 7. Fig. 6. FT-IR spectrum of roots vegetative parts of oat plant grown in 25 mg/l Cd 2+ stress conditions and in the presence of different polyphenolic natural extracts.

7 A. Stingu et al. / Industrial Crops and Products 35 (2012) Table 6 Wave number (cm 1 ) of dominant peak obtained from absorption spectra. Samples Spectral region 3425 cm cm cm cm cm cm cm cm cm cm cm cm cm 1 Control VS M S M S S S S VS M W M 25 g/ml Cd VS M S M S S S S VS W W M (II) P. abies bark VS M M S S S S S S VS M W M extract PA A. syriaca VS M S M S S S S VS W W M extract AS C. Sativa shell extract CS VS M S M S S S S VS M W M VS very strong intensity, S strong intensity, M medium intensity, W weak intensity, PA Picea abies bark extract, CS Castanea sativa chestnuts shell extract, AS Asclepias syriaca plant extract. Cross-sections of roots characteristics for reference plants revealed the typical pattern of a monocotyledon roots (Fig. 1A). This consisted of an outer epidermis, a cortex with large parenchymatic cells (5 6 cells layers). The endodermis is uniseriate with tertiary structure. The vascular cylinder was surrounded by a pericycle (one cell-layer) and contained 7 phloemic and 7 xylemic vascular bundles. The root centre is occupied by a metaxylem vessel. In V1 V4 do not appear major changes regarding the anatomical Fig. 7. Cross sections through the root: (A) control, (B) V1 (Picea abies bark extract amendments), (C E) V2 (Asclepias syriaca plant extract amendments), (F) V3 (Castanea sativa chestnuts shell extract amendments), (G) V4 (25 g/ml Cd 2+ ), scale bar A, B, C, F, G 100 m, D, E 50 m.

8 60 A. Stingu et al. / Industrial Crops and Products 35 (2012) structure. However, some changes can be highlighted. In V1 and V2, some disintegration areas in the cortex could be observed. This could be caused by the higher bioaccumulation of cadmium ions by oat plant in the case of P. abies bark and A. syriaca plant aqueous extracts. In V2 root hairs with an abnormal conformation (twisted and branched) appear. The vascular bundles (especially the xylem ones) are less developed in V3 and this confirm the inhibitory effects of C. sativa chestnuts shell extract observed on plantlet elongation and vegetal biomass accumulation, especially into the roots area. This effect could also be correlated with the lowest values registered for bioaccumulation. The presence of CS extracts into a 25 mg/l Cd 2+ contaminated environment block the metal ions into the roots area, affecting its proper development. 4. Conclusions The data obtained evidenced that the metabolism of the plants cultivated in the presence of aqueous extracts containing polyphenols a cadmium ions is very complex. Thus, bioactive compounds existing in aqueous extracts modulated the bioaccumulation process of cadmium ions in A. sativa depending on heavy metal concentrations and polyphenolic extracts compositions determined by raw materials. Oat plant response to cadmium stress conditions in the presence of different bioactive compounds extracts, characterized through biometric measurements of plantlet length, biomass yield, physiological and morphological analysis, FT-IR analysis, cadmium concentrations and bioaccumulation in different parts of oat plant, allowed to remark the following: P. abies bark and A. syriaca plant extracts stimulated cadmium bioaccumulation, promoting the translocation of heavy metals to the aerial part of the plant. The polyphenolic extracts could properly be used in bioremediation, P. abies bark and A. syriaca plant extracts could be used as natural amendments, increasing the solubilization of heavy metals improving the phytoextraction process. C. sativa chestnuts shell extract act as a chelator of cadmium ions, reducing their mobility, decreasing thus translocation and determining in situ inactivation of heavy metal ions being suitable in phytostabilisation. Despite the structural modifications induced by A. syriaca extracts, they are not so important to affect the growth and surviving of the oat plantlets. P. abies bark extract does not induce significant changes in the plantlet structure. These conclusions can be correlated with plant behavior appreciated by photosynthesizing pigments biosynthesis influenced by the presence of polyphenols as plant growth stimulators and with cadmium ions as stress agents in plant development. The effects of these factors could be reflected in plant metabolism which will be further followed by the study of enzymes involved in the process and by chemical modification in biomass composition. Acknowledgements This paper was realized with the support of BRAIN Doctoral Scholarships as an investment in intelligence projects, financed by The European Social Found and Romanian Government. References Baker, A.J.M., Accumulators and exluders-strategies in response of plants to heavy metals. J. Plant Nutr. 3, Bao, J.S., Cai, Y., Sun, M., Wang, G.Y., Corke, H., Anthocyanins, flavonols, and free radical scavenging activity of Chinese bayberry (Myrica rubra) extracts and their color properties and stability. J. Agric. Food Chem. 53, Cavalu, S., Cîntă Pînzaru, S., Qualitative and quantitative aspects in analysis of ginseng pharmaceuticals using vibrational spectroscopy. Rom. J. Biophys. 15, El-Sayed, S.A.H., Total phenolic contents and free radical scavenging activity of certain Egyptian Ficus species leaf samples. Food Chem. 114, Ignat, I., Stingu, A., Volf, I., Popa, V.I., Characterization of grape seeds aqueous extract and possible application in biological system. Cellulose Chem. Technol. 45, Irtelli, B., Navari-Izzo, F., Influence of sodium nitrilotriacetate (NTA) and citric acid on phenolic and organic acids in Brassica juncea grown in excess of cadmium. Chemosphere 65, Keilig, K., Ludwig-Müller, J., Effect of flavonoids on heavy metal tolerance in Arabidopsis thaliana seedlings. Bot. Stud. 50, Korkina, L.G., Phenylpropanoids as naturally occurring antioxidants: from plant defense to human health. Cell. Mol. Biol. 53, Lichtenthaler, H.K., Wellburn, A.R., Determinations of total carotenoids and chlorophylls a and b of leaf extracts in different solvents. Biochem. Soc. Trans. 11, Makris, D.P., Boskou, G., Andrikopoulos, N.K., Recovery of antioxidant phenolics from white vinification solid by-products employing water/ethanol mixtures. Bioresour. Technol. 98, McGrath, S.P., Zhao, F.J., Phytoremediation of metals and metalloids from contaminated soils. Curr. Opin. Biotechnol. 14, McNear, D.H., Chaney, R.L., Sparks, D.L., The hyperaccumulator Alyssum murale uses complexation with nitrogen and oxygen donor ligands for Ni transport and storage. Phytochemistry 71, Naczk, M., Shahidi, F., Phenolics in cereals, fruits and vegetables: occurrence, extraction and analysis. J. Pharmaceut. Biomed. 41, Nascimento, C.W.A., Organic acids effects on desorption of heavy metals from a contaminated soil. Sci. Agric. 6, Nascimento, C.W.A., Xing, B., Phytoextraction: a review on enhanced metal availability and plant accumulation. Sci. Agric. 63, Popa, V.I., Ignat, I., Volf, I., 2010a. A comparison concerning separation and characterization of polyphenols from spruce wood bark. In: Proc. 11th European Workshop on Lignocellulosics and Pulp, Hamburg, Germany, pp Popa, V.I., Stingu, A., Volf, I., 2010b. Lignins an polyphenols in bioremediation. In: Fulekar, M.H. (Ed.), Bioremediation Technology. Springer, pp Popescu, C.M, Vasile, C., Popescu, M.C., Singurel, G., Popa, V.I., Munteanu, B.S., Analytical methods for lignin characterization. II. Spectroscopic studies. Cellulose Chem. Technol. 40, Recueil international des methodes d analyses OIV, MA-F-AS2-07-CARCHR, vol. 1. Rulkens, W.H., Tichy, R., Grotenhuis, J.J.C., Remediation of polluted soil and sediment: perspectives and failures. Water Sci. Technol. 37, Sawalha, M.F., Peralta- Videa, J.R., Saupe, G.B., Dokken, K.M., Gardea-Torresdey, J.L., Using FTIR to corroborate the identity of functional groups involved in the binding of Cd and Cr to saltbush (Atriplex canescens) biomass. Chemosphere 66, Shamsi, I.H., Wei, K., Zhang, G.P., Jilani, G., Hassan, M.J., Interactive effects of cadmium and aluminum on growth and antioxidative enzymes in soybean. Biol. Plant. 52, Singh, A., Eapen, S., Fulekar, M.H., Potential of Medicago sativa for uptake of cadmium from contaminated environment. Rom. Biotechnol. Lett. 14, Stingu, A., Volf, I., Popa, V.I., 2009a. Chestnuts (Castanea sativa) extracts a potential plant growth regulator. Bull. Polytech. Inst. Is. 4, Stingu, A., Volf, I., Popa, V.I., 2009b. Study of copper and cadmium accumulation by bean. J. Environ. Eng. Manage. 5, Sun, Y., Zhou, Q., Liu, W., An, J., Xu, Z., Wang, L., Joint effects of arsenic and cadmium on plant growth and metal bioaccumulation: a potential Cdhyperaccumulator and As-excluder Bidens pilosa L. J. Hazard. Mater. 161, Tahara, S., A journey of twenty-five years through the ecological biochemistry of flavonoids. Biosci. Biotechnol. Biochem. 71, Wenzel, W.W., Lombi, E., Adriano, D., Biogeochemical processes in the rhizosphere: role in phytoremediation of metal-polluted soils. In: Prasad, N., Hagemeyer, J. (Eds.), Heavy Metal Stress in Plants From Molecules to Ecosystems. Springer Verlag, Heidelberg, pp