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Three garden vegetables—radish, carrot and lettuce—were cultivated in a pot experiment using two soils from the Příbram area polluted mainly by cadmium (Cd), zinc (Zn), lead (Pb) and chromium (Cr). The soils of the Příbram district, Czech Republic, are heavily polluted as a result of the atmospheric deposition of toxic elements originating from historic lead–silver mining and smelting activities. The results showed that lettuce absorbed the highest amounts of toxic elements (Cd 28 and 30, Cr 12 and 13, Zn 92 and 205 mg·kg−1 DW), except Pb, which was higher in radish (30 and 49 mg·kg−1 DW). Changes in macronutrient contents in edible parts were not found, except for sulfur. A higher total free amino acids (fAAs) accumulation was shown in all vegetables in more contaminated soil, with the highest fAA content being in radish. A group of essential fAAs reached 7–24% of total fAAs in vegetables. The risk to human health was characterized using the target hazard quotient and total hazard index (HI). The cumulative effect of the consumption of vegetables with HI > 1 showed possible non-carcinogenic health effects for lettuce and carrot. HI decreased in the order Cd > Pb > Cr > Zn. The carcinogenic risk of toxic elements decreased in the order Cd > Cr > Pb (0.00054, 0.00026, 0.00003). These values showed a carcinogenic risk from the consumption of lettuce and carrot and confirmed that the adult population of the studied area is at high risk if lettuce and carrot cultivated in this area are consumed daily.

The present study investigated the effect of arsenic (As) on photosynthesis and other selected physiological parameters in two ferns. The ferns (Pteris cretica 'Albo-lineata' and 'Parkerii') subjected to As doses of 100 and 250 mg kg-1 for three months, showed different As accumulation, which was higher in Albo-lineata. Overall, the obtained results indicated significant differences between studied ferns. The individual effects of As and growing period on all parameters were very variable. However, As doses generally caused a decrease of net photosynthetic rate, stomatal conductance, transpiration rate, maximum quantum yield of PSII, and photosynthetic pigments. The sampling period effect was significant for magnesium content of Parkerii (decrease) and contents of photosynthetic pigments of Albo-lineata (increase) and Parkerii (decrease). Results showed that Parkerii had higher sensitivity to As doses than Albo-lineata, which was also reflected by the higher free glycine content and its increase by As doses.

Arsenic is a ubiquitous toxic element that can be accumulated into plant parts. The present study investigated the response of Pteris cretica and Spinacia oleracea to As treatment through the analysis of selected physiological and metabolic parameters. Plants were grown in pots in As(V) spiked soil (20 and 100 mg/kg). Plants’ physiological condition was estimated through the determination of elements, gas-exchange parameters, chlorophyll fluorescence, water potential, photosynthetic pigments, and free amino acid content. The results confirmed differing As accumulation in plants, as well as in shoots and roots, which indicated that P. cretica is an As-hyperaccumulator and that S. oleracea is an As-root excluder. Variations in physiological and metabolic parameters were observed among As treatments. Overall, the results revealed a significant effect of 100 mg/kg As treatment on the analysed parameters. In both plants, this treatment affected growth, N, Mg, S, Mn, and Zn content, as well as net photosynthetic rate, chlorophyll fluorescence, and total free amino acid content. In conclusion, the results reflect the similarity between P. cretica and S. oleracea in some aspects of plants’ response to As treatment, while physiological and metabolic parameter changes related to As treatments indicate the higher sensitivity of S. oleracea.

Background Arsenic toxicity induces a range of metabolic responses in plants, including DNA methylation. The focus of this paper was on the relationship between As-induced stress and plant senescence in the hyperaccumulator Pteris cretica var. Albo-lineata (Pc-Al). We assume difference in physiological parameters and level of DNA methylation in young and old fronds as symptoms of As toxicity. Results The As accumulation of Pc-Al fronds, grown in pots of haplic chernozem contaminated with 100 mg As kg− 1 for 122 days, decreased with age. Content of As was higher in young than old fronds for variants with 100 mg As kg− 1 (2800 and 2000 mg As kg− 1 dry matter, respectively). The highest As content was determined in old fronds of Pc-Al grown in pots with 250 mg As kg− 1. The increase with age was confirmed for determined nutrients – Cu, Mg, Mn, S and Zn. A significant elevation of all analysed nutrients was showed in old fronds. Arsenic accumulation affected DNA methylation status in fronds, but content of 5-methylcytosine (5mC) decreased only in old fronds of Pc-Al (from 25 to 12%). Determined photosynthetic processes showed a decrease of fluorescence, photosynthetic rate and chlorophylls of As treatments in young and old fronds. Water potential was decreased by As in both fronds. Thinning of the sclerenchymatous inner cortex and a reduction in average tracheid metaxylem in the vascular cylinder was showed in roots of As treatment. Irrespective to fronds age, physiological parameters positively correlated with a 5mC while negatively with direct As toxicity. Opposite results were found for contents of Cu, Mg, Mn, S and Zn. Conclusions The results of this paper point to changes in the metabolism of the hyperaccumulator plant Pc-Al, upon low and high exposure to As contamination. The significant impact of As on DNA methylation was found in old fronds. Irrespective to fronds age, significant correlations were confirmed for 5mC and As toxicity. Our analysis of the very low water potential values and lignification of cell walls in roots showed that transports of assimilated metabolites and water between roots and fronds were reduced. As was showed by our results, epigenetic changes could affect studied parameters of the As hyperaccumulator plant Pc-Al, especially in old fronds.

Pollution and poisoning with carcinogenic arsenic (As) is of major concern globally. Interestingly, there are ferns that can naturally tolerate remarkably high As concentrations in soils while hyperaccumulating this metalloid in their fronds. Besides Pteris vittata in which As-related traits and molecular determinants have been studied in detail, the As hyperaccumulation status has been attributed also to Pteris cretica. We thus inspected two P. cretica cultivars, Parkerii and Albo-lineata, for As hyperaccumulation traits. The cultivars were grown in soils supplemented with 20, 100, and 250 mg kg−1 of inorganic arsenate (iAsV). Unlike Parkerii, Albo-lineata was confirmed to be As tolerant and hyperaccumulating, with up to 1.3 and 6.4 g As kg−1 dry weight in roots and fronds, respectively, from soils amended with 250 mg iAsV kg−1. As speciation analyses rejected that organoarsenical species and binding with phytochelatins and other proteinaceous ligands would play any significant role in the biology of As in either cultivar. While in Parkerii, the dominating As species, particularly in roots, occurred as iAsV, in Albo-lineata the majority of the root and frond As was apparently converted to iAsIII. Parkerii markedly accumulated iAsIII in its fronds when grown on As spiked soils. Considering the roles iAsV reductase ACR2 and iAsIII transporter ACR3 may have in the handling of iAs, we isolated Albo-lineata PcACR2 and PcACR3 genes closely related to P. vittata PvACR2 and PvACR3. The gene expression analysis in Albo-lineata fronds revealed that the transcription of PcACR2 and PcACR3 was clearly As responsive (up to 6.5- and 45-times increase in transcript levels compared to control soil conditions, respectively). The tolerance and uptake assays in yeasts showed that PcACRs can complement corresponding As-sensitive mutations, indicating that PcACR2 and PcACR3 encode functional proteins that can perform, respectively, iAsV reduction and membrane iAsIII transport tasks in As-hyperaccumulating Albo-lineata.

Given the close relationship between cytokinins (CKs), photosynthesis and nitrogen metabolism, this study assessed the effect of arsenic (As) contamination on these metabolic components in the As-hyperaccumulators Pteris cretica L. var. Albo-lineata (Pc-A) and var. Parkerii (Pc-P) as well as the As-non-hyperaccumulator Pteris straminea Mett. ex Baker (Ps). The ferns were cultivated in a pot experiment for 23 weeks in soil spiked with As at the levels 20 and 100 mg·kg-1. For the purpose of this study, the CKs were placed into five functionally different groups according to their structure and physiological roles: bioactive forms (bCKs; CK free bases); inactive or weakly active forms (dCKs; CK N-glucosides); transport forms (tCKs; CK ribosides); storage forms (sCKs; O-glucosides); and primary products of CK biosynthesis (ppbCKs; CK nucleotides). An important finding was higher CKs total content, accumulation of sCKs and reduction of dCKs in As-hyperaccumulators in contrast to non-hyperaccumulator ferns. A significant depletion of C resources was confirmed in ferns, especially Ps, which was determined by measuring the photosynthetic rate and chlorophyll fluorescence. A fluorescence decrease signified a reduction in the C/N ratio, inducing an increase of bioactive CKs forms in Pc-P and Ps. The impact of As on N utilization was significant in As-hyperaccumulators. The glutamic acid/glutamine ratio, an indicator of primary N assimilation, diminished in all ferns with increased As level in the soil. In conclusion, the results indicate a large phenotypic diversity of Pteris species to As and suggest that the CKs composition and the glutamic acid/glutamine ratio can be used as a tool to diagnose As stress in plants.

Background Arsenic (As) toxicity induces a range of metabolic responses in plants, including DNA methylation. The focus of this paper was on the relationship between As-induced long-term stress and plant senescence in the hyperaccumulator Pteris cretica var. Albo-lineata ( Pc -Al).Results We showed that Pc -Al grown in pots of haplic chernozem contaminated with 100 mg As kg -1 (As 100 ) for 122 days could accumulate more than 2000 and 2800 mg As kg -1 dry matter in old and young fronds, respectively. Analysis of 5-methylcytosine (5mC) in Pc -Al confirmed that the overall DNA methylation status in fronds of As 100 ferns was reduced in contrast to control treatment. Compared with controls, the overall DNA methylation status in fronds of As 100 ferns was reduced (by 6% in young and 10% in old fronds); however, the decrease was significant only in old fronds. The significant correlations for 5mC, in contrast to direct As toxicity, showed that decreases of chlorophylls, fluorescence and photosynthetic rate could be affected by epigenetic changes. Photosynthetic processes were determined in As 100 treatment and showed a reduction of gas-exchange parameters, and a decrease in carotenoids and chlorophylls (by 5% and 26%, respectively). Hyperaccumulation of As resulted in a significant elevation of all analysed nutrients (Cu, Mn, Zn, Mg, S) in old fronds, but not in young fronds.Conclusions The results of this paper point to complex changes in the metabolism of the hyperaccumulator plant Pc -Al, upon exposure to As contamination. The most significant impact was found in young fronds. The physiological parameters correlated more significantly with a decrease of DNA methylation than with direct As toxicity. Our analysis of the very low water potential values and lignification of cell walls in roots showed that transports of assimilated metabolites and water between roots and fronds were reduced.

Changes of amino acid (AAs) contents (glutamic acid – Glu, aspartic acid – Asp) and fatty acids profile (FAs) in spinach under cadmium (Cd) soil contamination (Cd1 = 30, Cd2 = 60, Cd3 = 90 mg/kg soil) are reported here. Spinach plants were sampled 25, 40, 55 and 75 days after sowing. Growing Cd soil contamination was associated with the strong inhibition of above-ground biomass (23.5–6.3 g dry matter per pot) and with the enhancement of Cd content (0.60–72.38 mg/kg dry matter) in leaves. During 55 days of plant growing the increase of Glu and Asp content was associated with the enhancement of Cd content. The highest accumulation of AAs was determined on Cd3 treatment after 55 days of cultivation. Strong decreases of both AAs were confirmed in the last sampling peri od for Cd treatments (reduction of Glu content of Cd3 treatment to ca. 64% and Asp content to ca. 72% in contrast to control). The content of saturated fatty acids increased (mainly palmitic acid) and the content of unsaturated fatty acids decreased in spinach aboveground biomass with increasing Cd concentration. Results of multivariate analysis of variance MANOVA showed the significant effect of Cd contamination for FAs metabolism, but the most significant effect was confirmed for plant growing period.

Changes in the fatty acid (FAs) composition in response to the extent of Cd contamination of soils (0, 30, 60 and 90 mg Cd kg(-1)) differed between ecotypes of Noccaea caerulescens originating from France - Ganges, Slovenia - Mežica and Austria - Redlschlag. Mežica ecotype accumulated more Cd in aboveground biomass compared to Ganges and Redlschlag ecotypes. Hyperaccumulators contained saturated fatty acids (SFAs) rarely occurring in plants, as are cerotic (26:0), montanic (28:0), melissic (30:0) acids, and unusual unsaturated fatty acids (USFAs), as are 16:2, 16:3, 20:2 and 20:3. Typical USFAs occurring in the family Brassicaceae, such as erucic, oleic and arachidonic acids, were missing in tested plants. Our results clearly indicate a relationship between Cd accumulation and the FAs composition. The content of SFAs decreased and the content of USFAs increased in aboveground biomass of Ganges and Mežica ecotypes with increasing Cd concentration. Opposite trend of FAs content was determined in Redlschlag ecotype. Linoleic (18:2n-6), α-linolenic (18:3n-3) and palmitic (16:0) acids were found in all ecotypes. The results observed in N. caerulescens ecotypes, showed that mainly Mežica ecotype has an efficient defense strategies which can be related on changes in FAs composition, mainly in VLCFAs synthesis. The most significant effect of ecotype on FAs composition was confirmed using multivariate analysis of variance.

A pot experiment was conducted to compare the responses of a non-transgenic tobacco plant (WT) and plants with genetically prolonged life-span (SAG) to risk elements of As, Cd and Zn. Plants were grown in control soil and in soil with higher levels of risk elements. The pigment contents were established by HPLC and chlorophyll fluorescence parameters were measured from slow kinetics after a 15 min dark period with the PAM fluorometer. Top (i.e. young) leaves of both WT and SAG plants were more sensitive to photoinhibition caused by these risk elements but plants showed acclimation to such elements in the bottom leaves. Plants differed in the participation of individual pigments of xanthophyll cycle: increased levels of risk elements seem to stimulate especially first (violaxanthin to antheraxanthin) and second (anhtheraxanthin to zeaxanthin) steps of the cycle in WT plants. In SAG plants, toxic elements caused an increase in the content, particularly of the initial compound of the cycle — violaxanthin.

In the past two decades, many pathways of nitric oxide biosynthesis have been described. This review offers the general knowledge of mechanisms of plant nitric oxide biosynthesis.

Increased endogenous plant cytokinin (CK) content through transformation with an isopentyl transferase (ipt) gene has been associated with improved plant stress tolerance. The objective of this study is to determine amino acid changes associated with elevated CK production in ipt transgenic tobacco (Nicotiana tabacum L., cv. Wisconsin 38). Nontransformed (WT) and transformed tobacco plants with ipt gene controlled by senescence-activated promoter (SAG) were exposed to zinc soil contamination (tested levels Zn1=250, Zn2=500, Zn3=750 mg kg−1 soil). The Zn effect on plant stress metabolism resulted in changes in levels of selected free amino acids playing an important role in adaptation to stress and plant senescence (alanine, leucine, proline, methionine and γ-aminobutyrate) and differed for transformed and nontransformed tobacco plants. Analyses of amino acids confirmed that SAG tobacco plants had improved zinc tolerance compared with the WT plants. The enhanced Zn tolerance of SAG plants was associated with the maintenance of accumulation of proline, methionine and γ-aminobutyrate. The concentrations of leucine and alanine did not show significant differences between plant lines.

Physiological and biochemical processes in plants are regulated by phytohormones. Phytohormone profiles are unknown in the fern family Pteridaceae. In this work, we analysed phytohormones in fronds and roots of three Pteris fern varieties with differing abilities in arsenic (As) accumulation. The ferns (hyperaccumulating P. cretica var. Albo-lineata and var. Parkerii, and non-hyperaccumulating P. straminea) were cultivated in a pot experiment with low contaminated soil (Astotal 16 mg kg−1, Aswater soluble 0.15 mg kg−1) for 185 days and harvested four times during growth. Phytohormone profiles were determined using high-performance liquid chromatography coupled to a hybrid triple quadrupole/linear ion trap mass spectrometer. We found twenty-five phytohormones and their structural and functional analogues (including growth and stress hormones) at detectable levels in fronds and roots. Interactions between growth hormones promoted the growth of ferns in the absence of environmental stress. Cytokinins of cis-zeatin type affected biomass yield, especially in the non-hyperaccumulator P. straminea. Phytohormone correlations between fern fronds and roots indicate a significant role for xylem-phloem transport and highlight the importance of transport in stress response. We observed similarities in phytohormone correlation profiles in the hyperaccumulators P. cretica var. Albo-lineata and var. Parkerii. In P. cretica var. Albo-lineata, interaction between jasmonic and abscisic acids was demonstrated, representing significant feedback of the defence response against oxidative stress by As. On the other hand, we did not find significant correlation among stress phytohormones in P. straminea. Profiling of growth and stress hormones in ferns confirms that they have specific phenotypic regulation. Hormonal regulations in the hyperaccumulator P. cretica var. Albo-lineata significantly differed from the non-hyperaccumulator P. straminea. A greater number of phytohormone correlations in the two hyperaccumulators suggests they use biosynthesised phytohormones more effectively.

Nitric oxide (NO) is an important signalling molecule with diverse physiological functions in plants. In plant cell, it is synthesised in several metabolic ways either enzymatically or nonenzymatically. Due to its high reactivity, it could be also cytotoxic in dependence on concentration. Such effects could be also mediated by NO-derived compounds. However, the role of NO in photosynthetic apparatus arrangement and in photosynthetic performance is poorly understood as indicated by a number of studies in this field with often conflicting results. This review brings a short survey of the role of exogenous NO in photosynthesis under physiological and stressful conditions, particularly of its effect on parameters of chlorophyll fluorescence.

We applied the alkaline version of the single-cell gel electrophoresis (comet assay) to seedlings of heterozygous tobacco (Nicotiana tabacum L. var. xanthi) treated with zinc acetate dihydrate (20 to 80 mM Zn2+ for 2 h or 2 to 12 mM Zn2+ for 24 h). A dose dependent increase in DNA damage expressed by the tail moment values were observed in nuclei isolated from the roots after 2 and 24 h Zn2+ treatments. In contrast, Zn2+ did not induce significant DNA damage to leaf nuclei, with the exception of 10 or 12 mM Zn2+ for 24 h. Somatic mutations, identified as dark green, yellow, and dark green/yellow double sectors on the pale green tobacco leaves were not detected after any Zn2+ treatments. The accumulation of Zn in roots and shoots was determined by inductively coupled plasma optical emission spectrometry and the Zn content in roots was about three times higher than in shoots.

Cadmium (Cd) toxicity affects numerous metabolic processes in plants. In the presence of Cd, plants accumulate specific amino acids which may be beneficial to developing Cd tolerance. Our study aimed to characterize the changes in the metabolism of selected free amino acids that are associated with Cd tolerance, and investigate the levels of selected microelements in order to relate these changes to the adaptation strategies of two metallophytes-Noccaea caerulescens (Redlschlag, Austria) and Noccaea praecox (Mežica, Slovenia). The plants were exposed to Cd contamination (90 mg Cd/kg soil) for 120 days in a pot experiment. Our results showed higher Cd accumulation in N. praecox compared to N. caerulescens. Cadmium contamination reduced the zinc and nickel levels in both species and a mixed effect was determined for copper and manganese content. Differences in free amino acid metabolism were observed between the two metallophytes growing under Cd-free and Cd-loaded conditions. Under Cd-free conditions, aromatic amino acids (phenylalanine, tryptophan and tyrosine) and branched-chain amino acids (leucine, isoleucine and valine) were accumulated more in the leaves of N. praecox than in N. caerulescens. Cd stress increased the content of these amino acids in both species but this increase was significant only in N. caerulescens leaves. Marked differences in the responses of the two species to Cd stress were shown for alanine, phenylalanine, threonine and sarcosine. Cadmium contamination also induced an increase of threonine as alanine and sarcosine decrease, which was larger in N. caerulescens than in N. praecox. All these factors contribute to the higher adaptation of N. praecox to Cd stress.

Relatively little is known about why odd-numbered fatty acids (OFAs) can be synthesized only by some plant species. We aimed at determining whether there is a relationship between the effects of Cd-induced oxidative stress on unsaturated fatty acids (USFAs) and their degradation products, especially OFAs. Plants with different ability to accumulate Cd - Noccaea praecox from Mežica, Slovenia (Me) and two ecotypes of Noccaea caerulescens from Ganges, France (Ga) and Redlschlag, Austria (Re) were cultivated in pot experiments. Only Me plants contained OFA 13:0, while all plants contained OFAs 15:0, 17:0 and 23:0 but in different proportions. Mutual correlations showed a significant effect of Cd contamination on the content of OFAs and USFAs in Me, a less pronounced effect in Re and the lowest one in Ga plants. The most significant correlation between the contents of USFAs and OFAs was also calculated for Me plants. The correlations between OFAs and USFAs indicate an active participation of OFA in FAs metabolism. Increased efficiency of utilization of the assimilated carbon via OFAs metabolism of Me plants in contrast to Re and Ga is also reflected in the increase of tolerance of Me plants to Cd toxicity in plant cells.

In the present study, the content of risk elements and content of free amino acids were studied in spinach (Spinacia oleracea L.) and mustard (Sinapis alba L.) subsequently grown on uncontaminated and contaminated soils (5 mg Cd/kg, 1000 mg Pb/kg and 400 mg Zn/kg) with the addition of activated carbon (from coconut shells) or biochar (derived from local wood residues planted for phytoextaction) in different seasons (spring, summer and autumn). The results showed that activated carbon and biochar increased biomass production on contaminated site. Application of amendments decreased Cd and Zn uptake by spinach plants. Mustard significantly increased Pb accumulation in the biomass as well in subsequently grown autumn spinach. Glutamic acid and glutamine were major free amino acids in leaves of all plants (15–34% and 3–45%) from total content. Application of activated carbon and biochar increased content of glutamic acid in all plants on uncontaminated and contaminated soils. Activated carbon and biochar treatments also induced an increase of aspartic acid in spinach plants. Biochar produced from biomass originated from phytoextraction technologies promoted higher spinach biomass yield comparing unamended control and showed a tendency to reduce accumulation of cadmium and zinc and thus it is promising soil amendment.

This study aims to reveal and to compare effect of two various systems of nitrogen nutrition, namely injection and sidedress application, on the levels of NO 3 – and phytohormones (cytokinins, abscisic acid (ABA), indole-3-acetic acid (IAA)) in Festulolium plants. Calcium nitrate (CN) or ammonium sulphate (AS) were used as N source in the pot experiment. The yield of Festulolium above and below ground biomass was more substantially enhanced after sidedress application of both AS or CN in comparison with injection application. The levels of endogenous cytoki nins peaked 5 days after application regardless the form of N source and the method of application. The increased concentration of endogenous cytokinins as well as the enhanced content of selected free amino acid suggest that N applied sidedress can maintain better distribution patterns of nutrients and provide improved conditions for growth and nitrogen uptake. The nitrogen application affected ABA concentrations on all tested treatments. The correlation between NO 3 and ABA concentrations ranged from 0.77 to 0.89. A significant IAA increase was re corded in plants after ammonium nitrogen sidedress application and it was confirmed that applications of nitrate reduced IAA concentration (correlation between NO 3 and IAA for AS treatment R 2 = 0.77–0.94).

This study aims to reveal and to compare effects of two different systems of nitrogen (N) nutrition (sidedress ap plication or injection application) on toxicity of NH 4 and mixed nutrition. We investigated whether NH 4 + or mixed (NH 4 NO 3 ) application causes significant changes in the endogenous levels of cytokinins (CK), whole plant N and their effects on yield of selected plants. Ammonium sulphate or ammonium nitrate were used as N source in the pot experiment. The yield of Festulolium and Trifolium pratense L. above-ground biomass and roots was more substantially enhanced after sidedress application of both ammonium sources in comparison with injection application. Our results confirmed that the accumulation of CKs in plants is in correlation with their N content (R 2 = 0.66–0.98). Proportions between individual CK forms remained relatively steady and their dynamics exhibited similar trends after N application. Our results indicate that the negative effect of the application of NH 4 + on the growth of Festulolium and clover plants could be effectively modulated by the presence of NO 3 .

For metabolomic analysis of maize plants growing under different nitrogen nutrition sequential extraction of fresh biomass was used and isolated fractions were characterized and evaluated using IR spectra. The IR spectra of in dividual fractions were evaluated in relation to the nitrogen rates (2 g or 4 g N), to applied fertilizers (ammonium nitrogen or urea ammonium nitrate solution) and sampling period. For butanol fraction, typical bands of flavo noids, polar phospholipids, steryl glycosides, analogues of ecdysteroids were characterized. The IR spectra of BuOH fraction showed changes of relative contents of isolated compounds mainly affected by nitrogen rates. For water fraction bands of organic acids, salts of organic acids, flavonoid glycosides and oligopeptides (phytochelatins and/ or glutathione) were the most significant. The results showed an increased induction of oxalic acid in plants after 4 g N application. Degradation of this acid induced oxidative stress, therefore strong correlation among contents of oxalic acid, flavonoids and compounds with amide nitrogen (glutathione) was observed in plants growing under 4 g nitrogen nutrition. The glutathione-ascorbate cycle protects plants against oxidative damage.

Changes of amino acid concentrations (proline, glutamate, asparagine, aspartate, alanine) and glutamate kinase activity (GKA) in plants under arsenic chronic stress reported here reveal their role in plant arsenic stress adaptation. Results of the pot experiment confirmed the toxic effect of arsenic at tested levels (As1=25 mg As kg(-1) soil, As2=50 mg As kg(-1) soil, As3=75 mg As kg(-1) soil) for spinach. Growing available arsenic contents in soil were associated with the strong inhibition of above-ground biomass and with the enhancement of As plant content. The changes of glutamate, asparagine, aspartate and proline levels in the plants showed strong linear dependences on arsenic concentration in plants (R2=0.60-0.90). Compared to the untreated control, concentrations of free proline and aspartate of As3 treatment were enhanced up to 381% and 162%, respectively. The significant changes of glutamate were observed on As2 and As3 treatments (increased level up to 188, i.e. 617%). Arsenic in plants was shown to be an inhibitor of glutamase kinase activity (R2=0.91). Inhibition of GKA resulted in an increase in the content of glutamate that is used in synthesis of phytochelatins in plant cells. Concentration of alanine did not have a confirmed linear dependence on arsenic concentration in plant (R2=0.05). The changes of its concentrations could be affected by changes of pH in plant cell or induction of alanine aminotransferase by hypoxia.

Mixture of plants (Festulolium: Trifolium pretense L.) was grown in the pot experiment with different forms of nitrogen nutrition. The fertilizers (ammonium sulphate or calcium nitrate or ammonium nitrate) were applied conventionally or according to the CULTAN method (Controlled Uptake Long Term Ammonium Nutrition). The abso lute growth rate (AGR) and contents of free asparagine and proline in the aboveground biomass were determined. Additional nitrogen increased the dry weight of biomass and AGR of the plants treated with sidedress application in comparison with plants treated with the CULTAN method. The results suggest increased levels of free proline in CULTAN-treated plants while those of asparagine did not increase. The significance of these observations to the loss of potential yield and the relationship between methods of application is considered.

The effect of nitrogen nutrition on phytosterol and amino acid content in aboveground biomass of maize (Zea mays l.) was investigated in a pot experiment. For cultivation of maize plants nitrogen dose (2 or 4 g n/pot) was applied in the form of ammonium nitrate (an) for control treatments or urea ammonium nitrate solution (Uan). Uan solution was applied according to the CUltan method (Controlled Uptake long term ammonium nutrition). The content of amino acids as important nitrogen-containing compounds in plant biomass was affected by nitrogen nutrition. an increase of glutamine and asparagine levels in maize aboveground biomass was observed after Uan solution application. The results of free β-sitosterol analyses by HPlC showed its 94% increasing concentration after Uan application in contrast to an treatments. our results confirmed that sterol interconversions are controlled by environmental conditions and they are involved in the regulation of membrane properties in response to changing growth conditions.

The aim of the study was to assess how the extraradical mycelium (ERM) of arbuscular mycorrhizal (AM) fungi contributes to Cd immobilization in the rhizosphere. Substrates prepared by cultivation of AM and non-mycorrhizal tobacco (Nicotiana tabacum L.) in quartz sand in two experiments were amended with Cd in a range of concentrations and Cd immobilization was assessed as Cd toxicity using root growth tests. Split-root plants, inoculated at one part of the root system, and hyphal compartments colonized by ERM only were used to separate the effects of ERM from plant-mediated effects of mycorrhiza and from the effects of roots. AM decreased Cd toxicity in the substrates obtained by 12 weeks of cultivation (Experiment 1), while the effect was less clear after 8 weeks (Experiment 2). No indication was found for an involvement of plant-mediated effects; in contrast, the effect of ERM could be clearly demonstrated. Lower Cd toxicity in the substrates colonized by ERM was related to ERM-induced alkalinization, but not directly to ERM density. It is concluded that the ERM of AM fungi may enhance Cd immobilisation in soil not only due to its high Cd sorption capacity but also by its activity.

The experiment assessed the variability of in seven clones of willow plants of high biomass production (Salix smithiana S-218, Salix smithiana S-150, Salix viminalis S-519, Salix alba S-464, Salix ’Pyramidalis’ S-141, Salix dasyclados S-406, Salix rubens S-391). They were planted in a pots for three vegetation periods in three soils differing in the total content of risk elements. Comparing the calculated relative decrease of total metal contents in soils, the phytoextraction potential of willows was obtained for cadmium (Cd) and zinc (Zn), moderately contaminated Cambisol and uncontaminated Chernozem, where aboveground biomass removed about 30% Cd and 5% Zn of the total element content, respectively. The clones showed variability in removing Cd and Zn, depending on soil type and contamination level: S. smithiana (S-150) and S. rubens (S-391) demonstrated the highest phytoextraction effect for Cd and Zn. For lead (Pb) and arsenic (As), the ability to accumulate the aboveground biomass of willows was found to be negligible in both soils. The results confirmed that willow plants show promising results for several elements, mainly for mobile ones like cadmium and zinc in moderate levels of contamination. The differences in accumulation among the clones seemed to be affected more by the properties of clones, not by the soil element concentrations or soil properties. However, confirmation and verification of the results in field conditions as well as more detailed investigation of the mechanisms of cadmium uptake in rhizosphere of willow plants will be determined by further research.

The glutamate kinase activity was investigated as a plant stress response to Cd, Zn, As or sewage sludge application to soil in the pot and field experiments with spinach (Spinacia oleracea L.). Allosteric regulation of glutamate kinase activity by free proline creates a possibility for an increase in glutamic acid content due to the synthesis of glutathione and phytochelatines in plant cells. For this reason the high rates of As, Cd and Zn applied into soil strongly decreased the glutamate kinase activity. Allosteric regulation of the glutamate kinase activity did not inhibit the synthesis of proline and hydroxyproline under stress condition caused by organic pollutants after application of sewage sludge. Formed proline was bound to stress proteins and therefore glutamate kinase activity was not inhibited.

Composition of native vegetation on a polychlorinated biphenyls (PCB)-contaminated soil dumpsite at Lhenice, South Bohemia (Czech Republic), was determined and species variability in the accumulation of PCBs in plant biomass was investigated. Soil stripping contaminated by PCBs originated at a factory producing electrical transformers that mostly used the commercial PCB mixture Delor 103 and 106. The PCB content of soil in the most contaminated part of the dumpsite reached 153 mg kg(-1) dry soil. Low diversity of plant species was found on the dumpsite. Results showed three grass species, Festuca arundinacea Schreb., Phalaroides arundinacea (L.) Rauschert., and Calamagrostis epigeios (L.) Roth., to be the major components of the vegetation and confirmed their high tolerance toward PCB contamination. The highest content of PCB in plant biomass--813.2 microg kg(-1) dry biomass--was determined in Festuca aboveground biomass. For phytoextraction purposes especially, Festuca can be recommended due to its high biomass yield, but its bioconcentration factor was very low (0.006). Tripleurospermum maritimum (L.) Sch. Bip. and Cirsium arvense (L.) Scop. grew mainly at the margins of the most contaminated part of the dumpsite. The PCB content determined in their aboveground biomass-278.7 and 289.5 microg kg(-1) dry biomass, respectively--was nonsignificantly lower compared to grass species Phalaroides and Calamagrostis. Salix (Salix viminalis L. and Salix caprea L.) was monitored among plant species composition at this site as a representative of woody species.

Most of the works published since the beginning of the 20 th century have brought interesting results about beneficial effects of titanium (Ti) on plants, but much less is known about its phytotoxic effects at higher doses. Here we demonstrate the influence of Mg treatment on the phytotoxic effects of Ti. Mg, Ti + Mg and two different concentrations of Ti leaf sprays were applied on oats (Avena sativa L. cv. Zlaťak) grown on three different soil types (Fluvisol, Luvisol and Chernozem). Physiological parameters of oats as well as some essential elements contents were analyzed. The foliar applications of Ti caused significant toxic manifestations on oats at ≥ 10 mg/kg concentrations. Mg partially ammeliorates these toxic effects if applied together with Ti. The effect was strong on Fluvisol, but we aker on Chernozem and Luvisol. Ti effects are more significant the further the soil is from the nutritional optimum of the plants. This is most evident in the case of Fluvisol, which is deficient in Mg, Fe, Mn, and Zn. It seems that Ti possesses a generally equalizing effect on the elements content in the plant.

Two pot experiments were conducted to investigate the effect of inoculation with the arbuscular mycorrhizal (AM) fungus Glomus intraradices on Pb uptake by two clones of Nicotiana tabacum plants. Non-transgenic tobacco plants, variety Wisconsin 38, were compared in terms of Pb uptake with transgenic plants of the same variety with inserted gene coding for polyhistidine anchor in fusion with yeast metallothionein. Bioavailability of Pb in experimentally contaminated soil was enhanced by the application of a biodegradable chelate ethylenediaminedissuccinate (EDDS). EDDS addition (2.5 and 5.0 mmol kg−1 substrate) increased Pb uptake from the substrate and enhanced Pb translocation from the roots to the shoots, with shoot Pb concentrations reaching up to 800 mg kg−1 at the higher chelate dose. Application of a single dose of 5 mmol kg−1 proved to be more efficient at increasing shoot Pb concentrations than two successive doses of 2.5 mmol kg−1, in spite of a marked negative effect on plant growth and phytotoxicity symptoms. Pb amendment (1.4 g kg−1 substrate) connected with either dose of EDDS decreased significantly plant biomass as well as reduced the development of AM fungi. AM inoculation promoted the growth of tobacco plants and partly alleviated the negative effect of Pb contamination, mainly in the case of root biomass. No consistent difference in Pb uptake was found between transgenic and non-transgenic tobacco plants. The effect of AM inoculation on Pb concentrations in plant biomass varied between experiments, with no effect observed in the first experiment and significantly higher root Pb concentrations and increased root–shoot ratio of Pb concentrations in the biomass of inoculated plants in the second experiment. Due to probable retention of Pb in fungal mycelium, the potential of AM for phytoremediation resides rather in Pb stabilisation than in phytoextraction.