Evaluating the phytotoxicological effects of bulk and nano forms of zinc oxide on cellular respiration-related indices and differential gene expression in Hordeum vulgare L.

The increasing use of nanoparticles is driving the growth of research on their effects on living organisms. However, studies on the effects of nanoparticles on cellular respiration are still limited. The remodeling of cellular-respiration-related indices in plants induced by zinc oxide nanoparticles (nnZnO) and its bulk form (blZnO) was investigated for the first time. For this purpose, barley (Hordeum vulgare L.) seedlings were grown hydroponically for one week with the addition of test compounds at concentrations of 0, 0.3, 2, and 10 mg mL-1. The results showed that a low concentration (0.3 mg mL-1) of blZnO did not cause significant changes in the respiration efficiency, ATP content, and total reactive oxygen species (ROS) content in leaf tissues. Moreover, a dose of 0.3 mg mL-1 nnZnO increased respiration efficiency in both leaves (17 %) and roots (38 %). Under the influence of blZnO and nnZnO at medium (2 mg mL-1) and high (10 mg mL-1) concentrations, a dose-dependent decrease in respiration efficiency from 28 % to 87 % was observed. Moreover, the negative effect was greater under the influence of nnZnO. The gene transcription of the subunits of the mitochondria electron transport chain (ETC) changed mainly only under the influence of nnZnO in high concentration. Expression of the ATPase subunit gene, atp1, increased slightly (by 36 %) in leaf tissue under the influence of medium and high concentrations of test compounds, whereas in the root tissues, the atp1 mRNA level decreased significantly (1.6-2.9 times) in all treatments. A dramatic decrease (1.5-2.4 times) in ATP content was also detected in the roots. Against the background of overexpression of the AOX1d1 gene, an isoform of alternative oxidase (AOX), the total ROS content in leaves decreased (with the exception of 10 mg mL-1 nnZnO). However, in the roots, where the pressure of the stress factor is higher, there was a significant increase in ROS levels, with a maximum six-fold increase under 10 mg mL-1 nnZnO. A significant decrease in transcript levels of the pentose phosphate pathway and glycolytic enzymes was also shown in the root tissues compared to leaves. Thus, the disruption of oxidative phosphorylation leads to a decrease in ATP synthesis and an increase in ROS production; concomitantly reducing the efficiency of cellular respiration.

Biogeochemical and microscopic studies of soil and Phragmites australis (Cav.) Trin. ex Steud. plants affected by coal mine dumps.

Developed areas of the coal industry are subjected to long-term anthropogenic impacts from the input and accumulation of overburdened coal material, containing potentially toxic heavy metals and metalloids (HMM). For the first time, comprehensive studies of soils and plants in the territory of the Donetsk coal basin were carried out using X-ray fluorescence, atomic absorption analysis, and electron microscopy. The observed changes in the soil redox conditions were characterized by a high sulfur content, and formations of new microphases of S-containing compounds: FeS2, PbFe6(SO4)4(OH)12, ZnSO4·nH2O, revealed the presence of technogenic salinization, increased Сorg content, and low pH contents. Exceedances of soil maximum permissible concentrations of Pb, Zn, Cu, and As in areas affected by coal dumps were apparent. As a consequence of long-term transformation of the environment with changes in properties and chemical pollution, a phytotoxic effect was revealed in Phragmites australis (Cav.) Trin. ex Steud, accompanied by changes in ultrastructural and organization features of roots and leaves such as increases in root diameters and thickness of leaf blades. The changes in the ultrastructure of cell organelles: a violation of the grana formation process, an increase in the number of plastoglobules, a decrease in the number of mitochondrial cristae, and a reduction in the electron density of the matrix in peroxisomes were also observed. The accumulation of large electron-dense inclusions and membrane fragments in cell vacuoles was observed. Such ultrastructural changes may indicate the existence of a P. australis ecotype due to its long-term adaptation to the disturbed environment.

Synthesis and properties of nano-cadmium oxide and its size-dependent responses by barley plant.

Present study included technological methods that made it possible to synthesize CdO nanoparticles and carry out their qualitative and quantitative diagnostics, confirming the as-prepared CdO nanoparticles (NPs) were spherical and had a size of 25 nm. Then, under the conditions of the model experiment the effect of CdO in macro and nanosized particles on absorption, transformation, and structural and functional changes occurring in cells and tissues of Hordeum vulgare L. (spring barley) during its ontogenesis was analyzed. Different analytical techniques were used to detect the transformation of CdO forms: Fourier-transform infrared spectroscopy (FTIR), Dynamic light scattering (DLS), X-ray fluorescence analysis (XRF), Scanning electron microscopy (SEM-EDXMA and TEM), X-ray diffraction (XRD), and X-ray absorption fine structure, consists of XANES - X-ray absorption near edge structure, and EXAFS - Extended X-ray absorption fine structure. Quantitative differences in the elemental chemical composition of barley root and leaf samples were observed. The predominant root uptake of Cd was revealed. CdO-NPs were found to penetrate deeply into barley plant tissues, where they accumulated and formed new mineral phases such as Cd5(PO4)3Cl and CdSO4 according to XRD analysis. The molecular-structural state of the local Cd environment in plant samples corresponding to Cd-O and Cd-Cd. The toxicity of CdO-NPs was found to significantly affect the morphology of intracellular structures are the main organelles of photosynthesis therefore, destructive changes in them obviously reduce the level of metabolic processes ensuring the growth of plants. This study is an attempt to show results how it is possible to combine some instrumental techniques to characterize and behavior of NPs in complex matrices of living organisms.

Effects of bulk and nano-ZnO particles on functioning of photosynthetic apparatus in barley (Hordeum vulgare L.).

The functioning of the photosynthetic apparatus in barley (Hordeum vulgare L.) after 7-days of exposure to bulk (b-ZnO) and nanosized ZnO (n-ZnO) (300, 2000, and 10,000 mg/l) has been investigated. An impact on the amount of chlorophylls, photosynthetic efficiency, as well as the zinc accumulation in chloroplasts was demonstrated. Violation of the chloroplast fine structure was revealed. These changes were generally more pronounced with n-ZnO exposure, especially at high concentrations. For instance, the chlorophyll deficiency under 10,000 mg/l b-ZnO treatment was 31% and with exposure to 10,000 mg/l n-ZnO, the chlorophyll deficiency was already 52%. The expression analysis of the photosynthetic genes revealed their different sensitivity to b-ZnO and n-ZnO exposure. The genes encoding subunits of photosystem II (PSII) and, to a slightly lesser extent, photosystem I (PSI) showed the highest suppression of transcriptional levels. The mRNA levels of the subunits of cytochrome-b6f, NADH dehydrogenase, ribulose-1,5-bisphosphate carboxylase and ATP synthase, which, in addition to linear electron flow (LEF), participate in cyclic electron flow (CEF) and autotrophic CO2 fixation, were more stable or increased under b-ZnO and n-ZnO treatments. At the same time, CEF was increased. It was assumed that under the action of b-ZnO and n-ZnO, the processes of LEF are disrupted, and CEF is activated. This allows the plant to prevent photo-oxidation and compensate for the lack of ATP for the CO2 fixation process, thereby ensuring the stability of photosynthetic function in the initial stages of stress factor exposure. The study of photosynthetic structures of crops is important from the point of view of understanding the risks of reducing the production potential and the level of food security due to the growing use of nanoparticles in agriculture.

Phragmites australis cav. As a bioindicator of hydromorphic soils pollution with heavy metals and polyaromatic hydrocarbons.

The work is devoted to evaluation of the ability of Phragmites australis Сav. to indicate the soil pollution with heavy metals (HMs) and priority polycyclic aromatic hydrocarbons (PAHs) by studying changes in the plant's ultrastructure. The concentration of Mn, Cu, Cr, Cd, Pb, Zn, Ni as well as 16 priority PAHs in hydromorphic soils and macrophyte plants (Phragmites australis Cav.) were increasing with distance decreasing to the power station and approaching to the direction of prevailing wind (northwest). The analyze of distribution of the studied pollutants in plants showed that the highest concentration have prevailed in the roots. A decrease in the diameter of the roots, and an increase in the thickness of the leaf blade was established. The transmission electron microscopy analysis showed that the ultrastructure of P. australis chloroplasts changed affected by accumulation of HMs and PAHs: a rise in the number of plastoglobules; a drop in the number of lamellae in granules, as well as changes in the shape, size, and electron density of mitochondria and peroxisomes. The most serious destructive violations of the main cellular organelles were noted for plants from the site within a 2.5 km from the emissions source and located on the predominant wind rose (north-west) direction. These macrophytes reflect spatial variations of pollutants metals in hydromorphic soils, therefore they are of potential use as bioindicators of environmental pollution.

Uptake of potentially toxic elements and polycyclic aromatic hydrocarbons from the hydromorphic soil and their cellular effects on the Phragmites australis.

The current study provides an information on the combined effect of pollution with potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) in hydromorphic soils on the accumulation, growth, functional and morphological-anatomical changes of macrophyte plant, i.e., Phragmites australis Cav., as well as information about their bioindication status on the example of small rivers of the Azov basin. The territory of the lower reaches of the Kagalnik River is one of the small rivers of the Eastern Azov region was examined with different levels of PTEs contamination in soils, where the excess of the lithosphere clarkes and maximum permissible concentrations (MPC) for Mn, Cr, Zn, Pb, Cu, and Cd were found. The features of the 16 priority PAHs quantitative and qualitative composition in hydromorphic soils and P. australis were revealed. The influence of soil pollution on accumulation in P. australis, as well as changes in the morphological parameters were shown. It has been observed that morphometric changes in P. australis at sites experiencing the сontamination and salinity are reflected with the changes in the ultrastructure of plastids, mitochondria, and EPR elements of plant cells. PTEs accumulated in inactive organs and damaged cell structures. At the same time, PAHs penetrated through the biomembranes and violated their integrity, increased permeability, resulted cell disorganization, meristem, and conductive tissues of roots. The nature and extent of the structural alterations found are dependent on the type and extent of pollution in the examined regions and can be utilized as bioindicators for evaluating the degree of soil phytotoxicity characterized by the accumulation of PTE and PAHs.

Effects of ZnO nanoparticles and its bulk form on growth, antioxidant defense system and expression of oxidative stress related genes in Hordeum vulgare L.

A comparative analysis of physio-biochemical indices and transcriptional activity of oxidative stress genes in barley (Hordeum vulgare L.) seedlings after 7-days exposure to bulk- and nano-ZnO (300 and 2000 mg/L) was carried out. A dose-dependent reduction in the length and weight of roots and shoots, as well as a significant accumulation of Zn in plant parts, was shown. Alterations in the shape and size of organelles, cytoplasmic vacuolization, and chloroplast and mitochondrial disorganization were also revealed. These processes are particularly pronounced when H. vulgare is exposed to the higher concentrations of nano-ZnO. The study of the antioxidant defense system revealed mainly an increase in the level of reduced glutathione and the activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and glutathione S-transferase (GST). The increases in activity, by 4-fold and 3-fold, was found for glutathione transferase in the roots when exposed to 2000 mg/L bulk- and nano-ZnO, respectively. The study of transcriptional activity demonstrated that in the roots under the influence of bulk- and nano-ZnO, along with Mn-SOD, Fe-SOD is highly expressed, mainly associated with the protection of chloroplasts. Analysis of the Cat 1 and Cat 2 gene expression showed that the main contribution to the increase in catalase activity in treated H. vulgare is made by the CAT-1 isozyme. Generally, in response to the impact of the studied ZnO forms, the antioxidant defense system is activated in H. vulgare, which effectively prevents the progression of oxidative stress in early stages of plant ontogenesis. Nevertheless, with constant exposure to bulk- and nano-ZnO at high concentrations, such activation leads to a depletion of the plant's energy resources, which negatively affects its growth and development. The results obtained could be useful in predicting the risks associated with the further transfer of nano-ZnO to the environment.

Biochar-assisted Fenton-like oxidation of benzo[a]pyrene-contaminated soil.

In the present study, the biochar derived from sunflower husks was used as a mediator in the heterogeneous Fenton process. The physical and chemical characteristics were studied in terms of specific surface area, elemental contents, surface morphology, surface functional groups, thermal stability, and X-ray crystallography. The main aim was to evaluate the effectiveness of biochar in a heterogeneous Fenton process catalyzed by hematite toward the degradation of benzo[a]pyrene (BaP) in Haplic Chernozem. The Fenton-like reaction was performed at a pH of 7.8 without pH adjustment in chernozem soil. The effects of operating parameters, such as hematite dosage and H2O2 concentrations, were investigated with respect to the removal efficiency of BaP. The overall degradation of 65% was observed at the optimized conditions where 2 mg g-1 hematite and 1.25 M H2O2 corresponded to the H2O2 to Fe ratio of 22:1. Moreover, the biochar amendment showed an increment in the removal efficiency and promotion in the growth of spring barley (Hordeum sativum distichum). The BaP removal was reached 75 and 95% after 2.5 and 5% w/w addition of biochar, respectively. The results suggested that the Fenton-like reaction's effectiveness would be greatly enhanced by the ability of biochar for activation of H2O2 and ejection of the electron to reduce Fe(III) to Fe(II). Finally, the presence of biochar could enhance the soil physicochemical properties, as evidenced by the better growth of Hordeum sativum distichum compared to the soil without biochar. These promising results open up new opportunities toward the application of a modified Fenton reaction with biochar for remediating BaP-polluted soils.

Influence of soil pollution on the morphology of roots and leaves of Verbascum thapsus L.

The impact of inorganic pollutants in the zone of industrial wastewater settling tanks (South of Russia) was studied. The levels of Mn, Cr, Ni, Cu, Zn, Pb, Cd were determined for Verbascum thapsus L., which are part of the mesophilic succession of wild plants in the studied technogenically polluted territory. The bioavailability of heavy metals (HM) for plants from transformed soils has been established. Anatomical and morphological features in the tissues of the plants affected by HM were analyzed using light-optical and electron microscopic methods. Contamination of the soil cover with Mn, Cr, Ni, Cu, Zn, Pb and Cd has been established with maximum content of Zn. It was revealed that the HM content in the V. thapsus plants exceeded the maximum permissible levels (Russian state standard): Zn by 23, Pb by 2, Cr by 31 and Cd by 3 times. The lower level of HM content in the inflorescences of mullein plants in comparison with the root system, stems and leaves indicates the resistance of generative organs to technogenic pollution. In the root and leaves of the V. thapsus, the anatomical and ultrastructural observation were carried out using light-optical and transmission electron microscopy. Changes in the ultrastructure of plants under the influence of anthropogenic impact have been revealed. The most significant changes of the ultrastructure of the polluted plants were found in the cell organelles of leaves (mitochondria, plastids, peroxisomes, etc.) including spatial transformation of the thylakoid system of plastids during the metal accumulation by plants, which may determine the mechanism of plant adaptation to technogenic pollution.

Effects of Zinc Oxide Nanoparticles on Physiological and Anatomical Indices in Spring Barley Tissues.

The aim of the present work was to investigate the toxic effects of zinc oxide nanoparticles (ZnO NPs, particle size < 50 nm) on the physiological and anatomical indices of spring barley (Hordeum sativum L.). The results show that ZnO NPs inhibited H. sativum growth by affecting the chlorophyll fluorescence emissions and causing deformations of the stomatal and trichome morphology, alterations to the cellular organizations, including irregularities of the chloroplasts, and disruptions to the grana and thylakoid organizations. There was a lower number of chloroplasts per cell observed in the H. sativum leaf cells treated with ZnO NPs as compared to the non-treated plants. Cytomorphometric quantification revealed that ZnO NPs decreased the size of the chloroplast by 1.5 and 4 times in 300 and 2000 mg/L ZnO NP-treated plants, respectively. The elemental analysis showed higher Zn accumulation in the treated leaf tissues (3.8 and 10.18-fold with 300 and 2000 mg/L ZnO NPs, respectively) than the untreated. High contents of Zn were observed in several spots in ZnO NP-treated leaf tissues using X-ray fluorescence. Deviations in the anatomical indices were significantly correlated with physiological observations. The accumulation of Zn content in plant tissues that originated from ZnO NPs was shown to cause damage to the structural organization of the photosynthetic apparatus and reduced the photosynthetic activities.

The toxic effect of CuO of different dispersion degrees on the structure and ultrastructure of spring barley cells (Hordeum sativum distichum).

Nowadays, nanotechnology is one of the most dynamically developing and most promising technologies. However, the safety issues of using metal nanoparticles, their environmental impact on soil and plants are poorly understood. These studies are especially important in terms of copper-based nanomaterials because they are widely used in agriculture. Concerning that, it is important to study the mechanism behind the mode of CuO nanoparticles action at the ultrastructural intracellular level. It is established that the contamination with CuO has had a negative influence on the development of spring barley. A greater toxic effect has been exerted by the introduction of CuO nanoparticles as compared to the macrodispersed form. A comparative analysis of the toxic effects of copper oxides and nano-oxides on plants has shown changes in the tissue and intracellular levels in the barley roots. However, qualitative changes in plant leaves have not practically been observed. In general, conclusions can be made that copper oxide in nano-dispersed form penetrates better from the soil into the plant and can accumulate in large quantities in it.

Bioindication of soil pollution in the delta of the Don River and the coast of the Taganrog Bay with heavy metals based on anatomical, morphological and biogeochemical studies of macrophyte (Typha australis Schum. & Thonn).

The results of biogeochemical and bioindication studies on the resistance of natural populations of macrophyte plant-cattail (Typha australis Schum. & Thonn) on the coast of the Taganrog Bay of the Sea of Azov and the sea edge of the Don River delta with regard to local pollution zones are presented. Plant resistance has been assessed through manifestation of their protective functions in relation to heavy metals. An excess in the lithospheric Clarkes and MPC in Zn, Cd and Pb in Fluvisols has been found. The total index of soil pollution (Zc) has made it possible to identify areas with different categories of contamination within the study area exposed to human impact. High mobility of Zn, Cd, Pb, Cr and Ni in Fluvisols has been revealed, which is confirmed by the significant bioavailability of Zn, Cr and Cd that are accumulated in the macrophyte plant tissues. The absorption of heavy metals by cattail plants is allowed for both the soil and the water of the nearby reservoir, where aquatic systems are a kind of "biological filter" contributing to water purification from pollutants. The impact of the environmental stress factor has been found to be manifested not only in the features of heavy metal accumulation and distribution in plant tissues, but also at the morphological and anatomical level according to the type of prolification. Changes in the cell membranes as well as in main cytoplasmic organelles (mitochondria, plastids, pyroxis, etc.) of the root and leaf cells have been identified, the most significant changes in the ultrastructure being noted in the tissues of leaf chlorenchyma. It is assumed that the identified structural changes contribute to slowing down of the ontogenetic development of plants and reduction in their morphometric parameters when exposed to anthropogenic pollution. Therefore, cattails can be effectively used as biological indicators while determining environmental pressures.

Effects of benzo[a]pyrene toxicity on morphology and ultrastructure of Hordeum sativum.

Many studies have been devoted to investigation of toxic benzo(a)pyrene (BaP) compound, but studies involving changes at the cellular level are insufficient to understand the mechanisms of polycyclic aromatic hydrocarbons (PAHs) effect on plants. To study the toxicity of BaP, a model vegetation experiment was conducted on cultivation of spring barley (Hordeum sativum distichum) on artificially polluted BaP soil at different concentrations. The article discusses the intake of BaP from the soil into the plant and its effect on the organismic and cellular levels of plant organization. The BaP content in the organs of spring barley was determined by the method of saponification. With an increase in the concentration of BaP in the soil, its content in plants also rises, which leads to inhibition of growth processes. The BaP content in the green part of Hordeum sativum increased from 0.3 µg kg-1 in control soil up to 2.6 µg kg-1 and 16.8 µg kg-1 under 20 and 400 ng/g BaP applying in soil, as well as in roots: 0.9 µg kg-1, 7.7 µg kg-1, 42.8 µg kg-1, respectively. Using light and electron microscopy, changes in the tissues and cells of plants were found and it was established that accumulation of BaP in plant tissues caused varying degrees of ultrastructural damage depending on the concentration of pollutant. BaP had the greatest effect on the root, significant changes were found in it both at histological and cytological levels, while changes in the leaves were observed only at the cytological level. The results provide significant information about the mechanism of action of BaP on agricultural plants.

A point mutation in the photosystem I P700 chlorophyll a apoprotein A1 gene confers variegation in Helianthus annuus L.

KEY MESSAGE: Even a point mutation in the psaA gene mediates chlorophyll deficiency. The role of the plastid signal may perform the redox state of the compounds on the acceptor-side of PSI. Two extranuclear variegated mutants of sunflower, Var1 and Var33, were investigated. The yellow sectors of both mutants were characterized by an extremely low chlorophyll and carotenoid content, as well as poorly developed, unstacked thylakoid membranes. A full-genome sequencing of the cpDNA revealed mutations in the psaA gene in both Var1 and Var33. The cpDNA from the yellow sectors of Var1 differs from those in the wild type by only a single, non-synonymous substitution (Gly734Glu) in the psaA gene, which encodes a subunit of photosystem (PS) I. In the cpDNA from the yellow sectors of Var33, the single-nucleotide insertion in the psaA gene was revealed, leading to frameshift at the 580 amino acid position. Analysis of the photosynthetic electron transport demonstrated an inhibition of the PSI and PSII activities in the yellow tissues of the mutant plants. It has been suggested that mutations in the psaA gene of both Var1 and Var33 led to the disruption of PSI. Due to the non-functional PSI, photosynthetic electron transport is blocked, which, in turn, leads to photodamage of PSII. These data are confirmed by immunoblotting analysis, which showed a significant reduction in PsbA in the yellow leaf sectors, but not PsaA. The expression of chloroplast and nuclear genes encoding the PSI subunits (psaA, psaB, and PSAN), the PSII subunits (psbA, psbB, and PSBW), the antenna proteins (LHCA1, LHCB1, and LHCB4), the ribulose 1.5-bisphosphate carboxylase subunits (rbcL and RbcS), and enzymes of chlorophyll biosynthesis were down-regulated in the yellow leaf tissue. The extremely reduced transcriptional activity of the two protochlorophyllide oxidoreductase (POR) genes involved in chlorophyll biosynthesis is noteworthy. The disruption of NADPH synthesis, due to the non-functional PSI, probably led to a significant reduction in NADPH-protochlorophyllide oxidoreductase in the yellow sectors of Var1 and Var33. A dramatic decrease in chlorophyllide was shown in the yellow sectors. A reduction in NADPH-protochlorophyllide oxidoreductase, along with photodegradation, has been suggested as a result of chlorophyll deficiency.

Method for hydrophytic plant sample preparation for light and electron microscopy (studies on Phragmites australis Cav.).

Nowadays there are no well-established, standard methods in electron microscopy despite its 50-year history. An excessive variety of research objects prompt researchers to modify and improve methodological approaches to sample preparation. One of the difficult objects to study by electron microscopy is hydrophytic plants, for example, Phragmites australis Cav. Traditional approaches to fixation and sample preparation do not give satisfactory results due to the peculiarities in structure and physiology of hydrophytic plants. The purpose of present research is modification description of the widespread method developed for double fixation of hydrophytic plant tissue for transmission electron microscopy. Suggested approach takes into account the features of hydrophyte plants. •The developed method allows improving the quality of plant samples by additional fixatives imbibition and removing of air bubbles from aerenchyma tissue using a vacuum.•The new step of sample preparation consisting in the layer-by-layer sample mixing in a special inclined mixer is applied for the embedding media penetrate sufficiently into the sample tissue.•The process of samples inclusion in polymeric resins is carried out in the flat-bottom capsules. Compare to standard conical capsules, flat-bottom capsules allow strictly defined orientation sample pieces, that is permit to produce a semi-thin and ultra-thin slices of perpendicular to the longitudinal structures of the plant. This is especially important to conduct an adequate comparative analysis of dimensions, shape, and electron density of fragments and parts of the studying samples.

Morphological and anatomical changes of Phragmites australis Cav. due to the uptake and accumulation of heavy metals from polluted soils.

The effect of strong chemical contamination of soils on the growth and structure of reed (Phragmites australis Cav.) roots and stems has been investigated. Soils and plants on monitoring plots in the zone of industrial sewage tanks and sludge reservoirs in the city of Kamensk-Shakhtinskii (southern Russia) were studied. Polyelement pollution of soils on the studied monitoring plots was revealed, with exceedances of Clarkes in hundreds of times for Zn and Cd, in tens of times for Pb, and in several times for Cu, Ni, Cr, and Mn. An ecological-geochemical estimation revealed an extremely hazardous level of soil contamination HMs in total. It is shown that the high level of soil contamination decelerates the ontogenetic development of plants and decreases their morphometric parameters. Electron-microscopic study of plants revealed changes in the ultrastructure of cell membranes, as well as the main cytoplasmic organelles of root and stem cells (mitochondria, plastids, etc.). It is suggested that the revealed structural changes in epidermis and mesoderm under the impact of metals hamper the radial migration of fluid in the root from the peripheral parts. These changes are one of the reasons for the decrease in the level of nutrient uptake and translocation from roots to shoots.