The diameters of inhibition growth zones (mm).
Post-modern society is viewed nowadays as a technologized society, where the great solutions to human problems can be solved by the progress of technology in economics from classical industry to communications. In the last years, nanotechnology is called to play an important part in the global food production, food security and food safety in the sense that the use of nanoscale micronutrients conduced to suppressing crop disease and the relationship between nutritional status and plant diseases is investigated. Nanomaterials are capable to penetrate into cells of herbs; they can carry DNA and other chemical compounds in the cells extending the possibility in plant biotechnology to target special gene manipulation. It is important to note that the concentration, plant organ or tissue, exposure rate, elemental form, plant species, and exposure dosage (chronic/acute) affect the plant response and in particular the distinct stress response. The complex process of utilization nanoparticles in agriculture has to be monitored to a level that avoids further environmental contamination. The present and future use of nanoparticles as micronutrients is affected by different risks related to nanotoxicity of micronutrients, a problem to be solved by an appropriate and safe circuit of nanoparticles in soil, water, plants and at last in human organism.
Post-modern society is viewed nowadays as a technologized society, where the great solutions to human problems can be solved by the progress of technology in economics from classical industry to communications. In this regard, nanotechnology was viewed from the beginning as the manipulation of matter at atomic, molecular and supramolecular scale leaved the established field of microfabrication, semiconductor physics, energy storage to extended surface science, organic chemistry and molecular biology applications. Nanotechnology presents the ability to create new materials with dimensions on the nanoscale together with a large range of applications in new domains as nanomedicine, nanoelectronics or biomaterials. From this point of view, in the last years nanotechnology is called to play an important part in the global food production, food security and food safety in the sense that the use of nanoscale micronutrients conduced to suppressing crop disease and the relationship between nutritional status and plant diseases are investigated. The large use of nanotechnology raises the problem of the toxicity of the new materials involved and their use in economics, this problem is associated with a poor legislation in the field regarding accidental release, atmospheric deposition, deliberate disposal in the environmental as pesticides, remediators, including the use of soil amendments containing nanomaterials (manuers, sludge) or water contamination for irrigation. In spite of this toxicological concern, the agriculture-nanotechnology is viewed as a solution, as a technological advancement in order to use efficiently the natural agriculture resources, i.e. water, nutrients or chemicals while farming. Besides the possible benefits of enhancing the crop yield, nanotechnology presents itself that having the ability to maximize the benefits of natural agriculture resources, through efficient products in the form of pesticides for pest and disease management and for sensors that monitors the soil quality and plant health, in the other words to solve a problem of environmental pollution. In this regard, over the last decade an important number of patents have been proposed and different products on the market that incorporated nanomaterials have been used in agricultural practice, e.g., nanopesticides, nanofertilizers or nanosensors.
As a general aspect, of world-wide society characterized by a constantly growing of population number, there exists the most important challenge that of higher agriculture yields. The aim of application of nanomaterials in agriculture is to reduce the applied amount of plan protection products, to minimize nutrient losses in fertilization and increased the yields through an optimized nutrient management. Classical active substances used nowadays can be lost during application due to different processes as runoff, evaporation, photolysis, and hydrolysis or microorganisms degradation. Different nanomaterials used as additives are characterized by large surface area and as a consequence they are appropriate to sorption process minimizing in this way the losses by reducing runoff and decreasing releases kinetics. Special designed nanoparticles can protect the active ingredients from photodegradation or can enhance uptake into leaves and other parts of the plant. Nanomaterials characteristics conduced to the substitution hazardous organic solvents present in some plant protection products and can reduce the application rates through their enhanced reactivity. As it was expressed before, despite of these positive impacts some nanomaterials have properties that classified them as potentially hazardous. The use of nanomaterials in agriculture and especially in plant protection and fertilization may pose unpredictable risks due to the fact that their application is accompanied by an intentional input of nanomaterials in the environment. In this regard, the human and environmental exposure due to nanomaterial residues in crops and soil might increase due to bioaccumulation of nanomaterials in the environment and food chain . The requirements of a growing food market implied the existence of an urgent demand for products containing nanomaterials due to a process of regulation. At the beginning of twenty-first century the most popular agriculture application of nanotechnology is focused on plant protection and fertilization. It is stated  that higher plants have an ability to develop mechanisms to perform satisfactory under hard atmospheric and soil conditions. In order to help plants growth one of the novel methods is the use of nanomaterials that possesses physicochemical characteristics to enhance the metabolism of plants. In this view, the fertilization that used nanotechnology can amplify the plant production by delivering the micronutrients on request and control the development of plants. Nanomaterials are capable to penetrate into cells of herbs, they can carry DNA and other chemical compounds in the cells , extending the possibility in plant biotechnology to target special gene manipulation.
One of the most serious and important problems of agri-nanotechnology is the absence of analytical methods to quantify the concentration of nanomaterials in water, soil and air, in order to define an exposure limit. Part of difficulties is related to extraction and separation from soil matrix and interfering constituents, and the presence of very low concentrations, more over for metallic nanomaterials there exist different natural constituents as counterparts. However, the analysis techniques indicates possibility to extract these low concentrations by processes as X-ray based techniques, chemothermal oxidation, thermogravimetry or mass spectrometry, these techniques been used generally coupled on a measurement line. The evaluation risk of organic compounds used in plants protection products, namely the evaluation of persistence, bioaccumulation and toxicity is based on specific end points and parameters obtained from laboratory and field experiments. For instance, the persistence is evaluated considering the dissipation of 50% of initial concentration, bioaccumulation properties are measured of octanol-water partition coefficient and the evaluation of toxicity is based on aquatic toxicity namely the intrinsic toxicity of the compounds.
In the agri-nanotechnology the enhanced yield is related to the potential nutritional value of nanomaterials, especially for the essential micronutrients necessary for host defense. The permanent search for new solutions to global food problem conduced to the application of nanotechnology to enhance the efficiency and sustainability of agriculture practice.
2. Nanomaterials in plant growth
The increase requirement of global food production is related nowadays with the necessity of application new technology for enhancing crop yield in order to satisfy the global food security. As a modern trend in this view, the application of nanotechnology solutions can bring a response to grave problem of different deficiencies in human population as deficiencies of iron, zinc, selenium, calcium, phosphorus or vitamin A. The nanotechnology can offer solutions as micronutrients in agriculture in order to optimize the deficient presence of these substances in soil, by their use in fertilization. Besides the possible studied benefits, it is stated  that the nanomaterials use in agriculture may pose unforeseeable risks due to the intentional input of nanomaterials in the environment that can led to human exposure related to bioaccumulation in crops and soil and as a consequence in the food chain.
The great challenge of modern agriculture related to the use of nanotechnology is to regulate the products with the nano content in the condition where the nanomaterials pose problems to the regulatory bodies and on the other hand there is a lack of knowledge to the possible effect on the plant growth, i.e. to the genetics of plants. The possible use of nanomaterials in agriculture is a new nanotechnology solution under development now for a dozen years [4, 5] as studies regarding the use of nanoscale nutrients (metals, metal oxides, carbon) to suppress crop diseases . In this view, the problem of agriculture in managing the crop disease is related to different attempts as genetic breeding, new pesticides products or new eradication protocols with the effect of the development of host plant resistance. Genetically modified plants raises different ethical problems related to the effect to the metabolism of human body, and this is a serious public concern.
A possible alternative for suppressing crop disease is the managing of plant nutrition statue and in this perspective the major limitation is that different crops have different nutrients requirements and the nutrient interacts with the level of plant disease in variable ways. As an example, the micronutrients are critical in the defense against crop disease where tissue infection induced reactions that conduced to the production of inhibitory secondary metabolites. These metabolites are generally generated by enzymes that requires activation by micronutrients cofactors, e.g. Mn, Cu and Zn as activating host defense enzymes i.e. phenylalanine or ammonia lyase. The availability of micronutrients level is related to soil characteristics, e.g. Fe, Mn, Zn are deficient in alkaline soils which limit uptake by roots and by consequence exposed roots to infections. Another way for enhancing disease defense is connected to non-essential elements, e.g. Al or Si, that offers resistance to a number of foliar and root pathogens although their presence in soil (e.g. Si) is frequently limited. As regarding Al, its application has been limited due to the fact that the over-application can cause significant crop damage and yield reduction, and insufficient presence modifies the acidity of soil . The important characteristics of the nanoscale metals and metal oxides is the greatly their availability and translocation within plants. In the process of producing nanomaterials to be applied in agriculture there are used besides chemical and physical methods for synthesis the biosynthesis using plant extracts. The traditional method is the synthesis on chemical route, namely the reduction in liquid phase with common reducing agents as; citric acid, hydroxylamine, cellulose, hydrogen peroxide, sodium carbonate and sodium hydroxide. In the solutions are added stabilizing agents in order to assure uniform particle distribution and dispersion, agents such as: polyvinyl alcohol and sodium polyacrylate. The physical methods for synthesis include laser ablation, chemical vapor deposition (CVD), sonochemical reduction, supercritical fluids or gamma radiation. In the case of carbon, the fullerene synthesis is realized in arc discharge or gas combustion and carbon nanotubes are produced by CVD in the decomposition process of gaseous hydrocarbons. Different nano products that can be used as fertilizers have been patented in the last years as: active nano-grade organic fine humic (CN 1472176-A, Wu et al.); oxide nano rare earth (CN1686957-A, Wang et al.), carbon nanomaterials (US 0174032-A1, Lui et al.); nanosilver (KR 000265-A, Kim et al.); nano diatomite and zeolite (US 0115469-A1, Yu et al.), nano-selenium (US 0326153-A1, Yin et al.) or nano-silicon carrier (US 0225412-A1, Sardari et al.). The high-surface area nanoscale materials conduced to a more efficient retain of nutrients and represents a stable reservoir to plants , raising the potential for enhanced plants growth. The use of traditional is characterized by fertilizers with active ingredients that have low water solubility, the result being an inefficient availability to plants and furthermore a lack of control to pathogen agents. The nanofertilizers offer controlled release and synchronization of the nutrient flux over time with the uptake, minimizing the wasteful interactions with soil or air that conduced to nutrients loss. From the roots of the plants the nanomaterials as ZnO, TiO2, CeO2, Fe3O4, Ni(OH)2, C70 fullerenes, Al, Cu, Ag, carbon nanotubes (CNT), are uptake and translocated to plant stem where partly are deposited (C70, Fe3O4,CeO2, Ni(OH)2) or partly are foliar deposited (Al, Ag, Cu, Zn, ZnO, CeO2, Fe3O4, C70). The root cell of a plant has different absorption zones for different kinds of nanomaterials, for instance Fe3O4 has absorption areas in epidermis, cortex and cambium; Ni(OH)2 in epidermis, cortex, cambium and metaxylem, Ag in epidermis and cortex or Ag2+ in epidermis, cortex, endodermis, and metaxylem.
Regarding nanomaterials exposure there exists a positive experience impact on crop growth and pathogen inhibitions, as related to antimicrobial activity for Ag, ZnO, Mg, Si or TiO2. The effect on different plants of the foliar exposure to nanomaterials as ZnO conduced to increase in shoot length (15.1%), root length (4.2%) , increase in chlorophyll (24.4%) soluble leaf protein (38.7%) or increase in acid phosphatase (76.9%), alkaline phosphatase (61.7%) and phytase (>3x). The effect of tobacco culture cell exposure to MWCNT (multiple wall carbon nano tubes) conduced to enhanced cell growth and regulate cell division by activating water channel protein  and the effect of 50 μg/ml on tomato roots to MWCNT conduced to enhanced fresh and dry mass besides changes in gene expression (water channel protein) . The foliar and root application of nanoparticles of Fe2O3 conduced to the increasing of root elongation and to the increase of photosynthetic parameters by foliar application . The application of Mn in concentration 0.05–1 mg/L on Mung bean roots in a Hoagland culture solution conduced to an increase in shoot and root length, dry and fresh biomass and rootlet number . The effect of spinach roots exposure to TiO2 nanoparticles present in soil conduced to an enhanced growth rate and chlorophyll as well as an enhanced rubisco activity and photosynthetic rate . The silver nanoparticles exhibit an intense inhibitory activity to microorganisms, in this regard Ag NPs damaged and penetrate the cell membrane subsequently reducing the infection . Another nanomaterial with intense antimicrobial activity is ZnO NPs that is effective to pathogen control growth, also characterized by a lower toxicity in comparison to Ag and with benefits on soil fertility. The application of ZnO NPs conduced to systemic disruption of cellular function of pathogens as
It is worth to mention, that in general the discussion to nanomaterials in agriculture refers also to a most prominent fraction of nanomaterials that are non-solids comprising nanoscale structures that can encapsulate an active ingredient in plan protection product. Generally active substances have poor solubility in water and at room temperature are brought to solution with organic (co)solvents. In order to avoid the use of organic (co)solvents one solution is stated  the use of oil/water emulsions. Generally the physical appearance of non-solid nanomaterials are lipid base in liposomes, micelles or cochleates, in polymer based in micelles, nanosphere, nanocapsules and polymersomes or in emulsions base as liquid crystals and microemulsions. The nanomaterials in non-solid forms enhance the solubility and the coverage of the hydrophobic leaf surface together with the penetration of the active substances through the cuticula.
As presented, the characteristics of solid and non-solid nanomaterials have been investigated in the last decade in order to understand the effect of nanonutrients in culture fertilization as well as in plant protection with promising results together with various studies regarding the toxicity of nanoparticles in the environment.
3. Nanoparticles and their action on plants
The nanotechnology application in agriculture is for our world one of the most important domains of study due to the possibility of increasing for different culture production and assisted plant protection against pests and diseases together with the monitoring of pathogenic agents. In this regard, the application of nanotechnology in the control of crop yield and crop protection is relatively recent compared to organic or chemical nutrients and different drug delivery or pharmaceuticals [31, 32].
One of the most important nutrients for humans and plants is iron (Fe) where iron deficiency is common in nowadays human diet affecting over 2 billion people in the world  Iron is essential for plant development and plays an important part in photosynthetic process being implied in redox reaction as well as generating reactive oxygen species . Due to its properties iron containing nanoparticles have been used as nano-fertilizer for nutrition of plants. As an example there was observed  a positive effect of nano-FeO and nano-ZnCuFe oxide on the growth of mung (
One of the elements that results from the rapid industrialization is cadmium-Cd and as a consequence there exists an irreversible exposure in the environment, especially in the soil. The Cd absorption in the plants from soil or air through aerial deposition and its transfer into different parts of the plants can cause several abnormalities in plants as reduced growth and yield . The major entry gate of Cd in plants is the roots while the toxic element entry in the human body is the consumption of contaminated food. The excess of Cd in plants affected the plant growth by reducing the production of reactive species, electrolyte leakage, hydrogen peroxide and malondialdehyde concentrations in plants . As a solution to reduce the Cd content in soil is the application of biochar, as a carbon rich pyrolyzed organic biomass that is effective in reducing bioavailability of metals in soil . These properties are based on biochar high pH, cation exchange capacity, nutrient retention capacity including water retention capacity and lower bulk density . The use of nanotechnology in agriculture can rise different problems as the role of foliar application of ZnO nanoparticles combined with soil applied biochar in Cd accumulation by plants , in this regard it was stated that compared to other cereals maize (
The effect of nano-boron (B) fertilizer on the mineral nutrition and fruit yield was put into evidence by on pomegranate trees culture . It was observed that a foliar spray of nano-B (concentration 6.5 mg BL−1) in combination with nano-Zn increased significantly the fruit yield up to 34% depending on treatment, with an accent to nano-B fertilizer. Also, the foliar application of these nano-fertilizers increased the number of fruits per tree, without an effect upon fruit cracking. As regards the fruit size physical parameters as fruit diameter, fruit calvyx diameter or average weight, they are not affected significantly for the treated trees, but the pH pomegranate juice increased to 0.62 pH units under fertilization. Concentrated nano-B foliar application caused small (1%) but statistically constant changes in the amount of total phenolic compounds in pomegranate juice whereas the antioxidant activity is not affected. The total amount of sugar in pomegranate fruit juice increased up to 4.6% at discussed nano-B concentration with no significantly increase in total anthocyanins under treatment. The action of nano-B fertilizers is also efficient in fruit crops as almond, apple, pear, persimmon or peach.
Calcium (Ca) is an important macro-element that plays an important role in plants including structural functions of cell walls, stabilization of cell membrane, maintenance of cell turgor pressure and counter-ion for inorganic and organic anions in vacuoles, as well as cytoplasmic messenger. Calcium cannot be transferred through from the older tissue to other parts of plant on the basic phloem pathway and Ca xylem translocation depends on unidirectional transpiration stream . Studies of foliar application of nano-Ca on pomegranate trees shows no significant effect on fruit yield and to the number of fruits per trees . Nano-Ca fertilization increased the Ca leaf concentration, whereas the foliar treatment decreased significantly pomegranate fruit cracking. The total phenolic compounds in pomegranate fruit juice is decreased in nano-Ca fertilization but with no significant effect on antioxidant activity and total anthocyanin content. Foliar application of Ca reduces the fruit cracking due to its role on cell wall, in enhancing the mechanical properties of plant tissue. However, the foliar fertilization of Ca had no significant effect on yields for kiwifruit, strawberry, grape and cherry.
Manganese (Mn) is a micronutrient required by most of the plants die to its implication in biochemical reactions, as those required by dehydrogenases, decarboxylases, kinases, oxidases, peroxidases enzymes and to their role in fighting oxygen reactive species in plants. Plants required 20–40 mg Mn/kg of dry weight for its various functions e.g. in tricarboxylic acid cycle, oxidative and non-oxidative decarboxylation reactions and for different synthesis as carotenoids, sterols or gibberellic acid. The most important process of photosynthesis, implied the final conversion of absorbed light to energy via enzymatic reactions. Among them, a studied Mn-containing enzyme, is found in PSII oxygen evolving complex, a multi-step enzymatic pathway where Mn is required, as a cofactor in both lower and higher plants for the Hill reaction-the water splitting and oxygen evolving system . Mn plays an important role in the synthesis of fatty acids and carotenoids, as well as in cell division and elongation. A normal function of the plant as biological system is affected by abiotic stress defined any adverse force or condition that affects its normal functioning. Abiotic stresses as drought, flood, salinity or harsh temperature conduced to an excessive amounts of reactive oxygen species that potentially injure proteins, membrane lipids, carbohydrates and DNA. The application of Mn increased the leaf area, photosynthesis rate and stomatal conductance in drought stress conditions, reducing the production of reactive oxygen species in plants. These reactive species also accumulated in inside the plants under thermal stress as harsh temperatures, that causes damage to cellular compounds and metabolic processes. It was suggested  that salinity inhibits the uptake of Mn inside plants inducing deficiency, in this case the foliar application increased stem diameter, fresh and dry biomass, number of seeds and different biochemical parameters as total protein or Hill reaction activity. The application of Mn nanoparticles on wheat applied by foliar exposure or soil amendment showed  no inhibition of vegetative or reproductive development, further more Mn nanoparticles significantly reduced Mn accumulation in shoots but increased the translocation efficiency in grains compared to classical Mn fertilizers due to a greater reactivity and non-toxicity due to a slower and a continuously availability of soluble Mn from Mn nanoparticles as compared to ionic Mn salt. The Mn nanoparticles greater photophosphorylation and oxygen evolution compared to bulk Mn suggested its novel potential nano modulator of the photochemical pathway in agriculture . Furthermore Mn nanoparticles are viewed as a stimulant of plant growth and of metabolic processes as alkaloids production. In infested soils, foliar exposure to Mn oxide nanoparticles reduces disease up to 28% as compared to controls , the plants can have cross-tolerance between abiotic and biotic stresses, and in this regard stress tolerance can help plants to form faster and more resistant manner to additional environmental changes. The propose mechanism for the distribution of Mn nanoparticles through the plant incudes transportation from the root through the vascular system, a process considered as active-transporting as long as includes signaling, recycling and plasma membrane regulation. Generally the excess amounts of Mn in plants is not benefic to their health by interfering with the uptake, transport and utilization of other minerals as Ca, Fe or Mg as being competitive for the same ion transport.
Copper nanoparticles at low concentrations (<0.25 mg L−1) stimulated plant photosynthesis in a percentage of 35% on waterweed (
Magnesium (Mg) is essential for plant growth as it plays an important role in the photosynthesis process as central component of chlorophyll and also acts as a phosphorus carrier as an important element for phosphate metabolism. Mg is necessary in cell division and protein formation in activation of several enzyme systems and is essential for plant respiration. The effect of foliar application of magnesium and iron nanoparticles solutions upon black-eyed pea (
Silver (Ag) is known as an element with antiseptic characteristics and it is important to understand its effect upon soil microbial community. Microorganisms are key regulators of biogeochemical recycling of nutrients in the environment and assist in maintaining the overall health and function of ecosystems . The soil is regarded as a complex system and its physicochemical characteristics as pH, texture and organic matter content can influence the nanoparticles properties introduced in it, a fact that can conduce to an increased or a decreased bioavailability and toxicity of nanoparticles. The effect of Ag nanoparticles on the microbial diversity and enzyme activity of soil is regarded as a significant decrease in microbial mass as a function of increasing Ag nanoparticles concentration. . Ag nanoparticles had impact on vascular plants, presenting positive or negative effects on seed germination, root growth and plant biomass . In Ag nanoparticles application on wheat plants, there was not observed a significant effect with the exception of root fresh weight and root length that presents a negative response at 75 ppm treatment while in cowpea and
Titanium oxide (TiO2) mineral is naturally occurred in four natural polymorphs: akaogiite (monoclinic), brookite (orthorhombic), anatase (tetragonal) and rutile (tetragonal). TiO2 nanoparticles are explored due their use as an antimicrobial agent and photocatalyst in order to remove organic compounds from contaminated air, soil, and water. Ti is not an essential element for plants, therefore TiO2 nanoparticles are not viewed as plant nutrients but plays a potential role in plant protection and at lower doses its effective to its properties as a photocatalysts or an UV protector. It was stated  that exposure of naturally aged spinach seeds to TiO2 nanoparticles (rutile) at concentration of 250–4000 mg L−1 significantly increased the germination rate, the germination index, the dry weight of seedlings and vigor index of seeds. It was observed that under hydroponic conditions on agar, TiO2 nanoparticles generally cause positive or non-consequential effects on plant growth for different food crops. For example, in hydroponic conditions it was observed a significant increase in the root and shoot length of
Selenium (Se) is an essential trace element for humans and animals and is beneficial for plants at low concentrations particularly under stress conditions acting like an antioxidant. Cereals are a good source of Se as it is present in the form of Se-methionine . The total concentration of Se in most of soils is 0.1–2 mg kg−1, with factors that affects Se solubility as: soil pH, redox potential, calcium carbonate level, cation exchange capacity, organic carbon, iron and aluminum level as well as the plants capability to produce root exudates. Selenium is most available in alkaline soils in the form of selenite, in acidic poorly aerated Se occurs in insoluble selenide forms, the lower limit for Se concentration in soil is 0.5 mg kg−1. Selenium fertilization rate and its chemical form directly influenced Se grain concentration affecting the yield, its application form being foliar or liquid on the soil surface. Low concentrations of Se had a positive effect on growth of ryegrass, lettuce and potato due to its antioxidant action. It was stated  that 10 g Se selenite per ha can increase wheat Se concentration from a base level of 30–100-200 μg kg−1 to recommended level of 300 μg kg−1 as a minimum target. Agronomic use efficiency is higher for foliar application than soil application. Agronomic bio-fortification is an inexpensive method for the increase of Se intake by humans but the limited Se resources indicated that fertilization strategies had to increase agronomic use efficiency in environmental conditions by improving agro-technical measures.
Silicon dioxide (SiO2) is a form of silicon oxide that had abundance in environmental mostly in the soil. Lower amounts of nano-SiO2 increased germination of seeds in tomato , or of
Regarding the nanotoxicity of nanoparticles action, the involved mechanism is not entirely understand, this mechanism is assumed in the sense by the changes related to the chemical structure, particles size and active surface area of nanoparticles. It is stated  that the toxicity action is focused on two directions: i.e. (a) a chemical toxicity based on the chemical composition as the released of toxic ions and (b) stress or stimuli caused by the surface, size or shape of particles. As viewed from chemical physics processes, the solubility of oxide nanoparticles affects the cell culture response and nanoparticle mediated toxicity is partly explained by the release of dissolved components of them . In comparison to metal toxicity in plants and animals, the nanoparticles pathway is different, a problem solved by the introduction of different parameters in experimental tests to evaluate the nanoparticles dynamics. In a plant culture exposed to nanoparticles, the gain and losses related to the development, growth and productivity are not exclusively part of nanoparticles effect but they can be viewed as a participation of the primary ions to biological processes active in plants. Regarding the presence of nanoparticles in soil, as culture area for plants, had to be considered the interaction with the microorganisms in soil because they can positively interact with plants e.g. arbuscular mycorrhizal fungi . The nanoparticles interaction with plants e.g. accumulation in plant biomass affects their fate and transport in the environment. There exists a first report  in 2007 regarding the negative effects of nanoparticles upon several plants as corn, cucumber, soybean, cabbage and carrot at relatively low dosage. At microscopic scale, the analysis of the chromosome morphology showed a relation between increased number of aberrations and the increased concentration of nanoparticles e.g. the appearance of stick chromosomes . The phyto-toxicity was observed at molecular and nuclear cell level because the occurrence of stick chromosomes might be related to the degradation or de-polymerization of chromosomal DNA . The extended development of modern agriculture brings besides some true benefits regarding crop productivity increasing problems related to environmental contamination with toxic elements e.g. metals or pesticides compounds and from this point of view nanoparticles used can aggravate the situation. The process of heavy metals accumulation by plants is related for the large majority of plants to roots accumulation and only a small part is translocated to the aboveground of the plants . There are evidence  to a translocation process from the roots to the fruits, without the existence of changes due to biochemical processes. It is important to note that the concentration, plant organ or tissue, exposure rate, elemental form, plant species, exposure dosage (chronic/acute) affects the plant response and in particular the distinct stress response. This is the reason why the complex process of utilization nanoparticles in agriculture has to be monitored to a level that avoids further environmental contamination i.e. soil, water and air.
4. Hydroxyapatite and essential oils
One of the essential problems that limits crop production is the low availability of phosphorous (P) in many agricultural regions. In order to increase the phosphorous content in the soil it is necessary to apply P fertilizers, because phosphorous is an essential element for plant growth. Besides classical fertilizers, nanotechnology can offer a solution to supply the micronutrients deficiencies for plants development. In this regard, it was suggested  the use of hydroxyapatite nanoparticles Ca10(PO4)6(OH)2, nano-HAp, as potential fertilizers. Tests on the potential use of nano-HAp (15 nm) on soybean (
Among other important plants for the use in medicine are those conducted to the extraction of essential oils as basil and lavender. Essential oils are complex biostructures and contain a lot of chemical compounds from different classes as: terpenoids, ketones, aldehydes and esters with a composition depending on the plant’s origin and quality, harvest time, climate, soil and extraction method. About 90% of the bioactive components of essential oils are monoterpenes and in the oxygenated form the bioactivity is enhanced. The medical use of essential oils is based on their properties such as antibacterial, antifungal and their characteristic to prevent the growth of different pathogens. The antibacterial activity of HAp samples and HAp samples coated with essential oil of basil and lavender was tested on methicillin_resistant
The evolution in the cell growth of
Antimicrobial qualitative assay revealed that the peppermint had a significant inhibition effect on the microbial growth of the tested microorganisms, with the inhibition diameter ranging from 6 to 22 mm. The solvent DMSO did not affect the growth on solid media of any tested microbial strains. HAp had no inhibitory effect on the growth of the tested microorganisms and the most pronounced inhibition was observed in the case of
The lavender EO inhibited the growth of all tested bacterial strains, as indicated the formation of inhibition zone ranged from 16 mm (
The possibility of covering hydroxyapatite with different molecules, e.g. essential oils offer a solution to apply in food industry, in the idea that HAp is an essential component of human organism. In this regard, the potential use in medicine e.g. bone reconstruction could help the reducing of postoperative infections after different implants. In the case of hydroxyapatite nanotechnology have opened the gate to different applications in agriculture, food industry, medicine with the final target of improving human health and resistance to a continuous modification of pathogen agents.
As it was presented, in the last few decades, nanotechnology reveals its benefit usage in different activity fields and in particular in biotechnology and agriculture. Fertilizer compounds are essential for our quality of soil and water for the development of plants in order to increase the crops in order to cover what is needed to sustain the food necessities all over the world. Therefore there exist a necessity to decrease nutrient casualties in fertilization, and to amplify the plant product by the operation of novel uses with assistance of nanotechnology and nanomaterials. This type of fertilization delivers the nutrients on request, control the use of chemical fertilizers that regulate growth and development of plants and raise the activity of target vegetal organism. In this regard have been presented the effects of different nanomaterials and nanoparticles upon selected plants culture as wheat, maize, soybean, etc. taking into account their growth morphological parameters and the nanoparticles influence upon plant metabolism. The present and future use of nanoparticles as micronutrients is affected by different risks related to nano-toxicity of micronutrients, a problem to be solved by an appropriate and safe circuit of nanoparticles in soil, water, plants and at last in human organism. In this regard, it is important to quantify nanomaterials concentration in water, soil and air, where the concentration of relevant nanomaterials is essential to define exposure, a problem to be solved by the modeling of environmental concentrations. Due to the rapid development of manufactured nanomaterials it is important to evaluate their environmental and health impact, and it was stated to assure a safe circuit from micronutrients used for plants crop increasing to the beneficiaries of these plants, i.e. animals and humans. The present work is an approximately extensive presentation of the present status of the application of nanomaterials and nanoparticles in agriculture i.e. in plants fertilization with accent to the plants growth parameters, possible toxic risks and application to the antimicrobial activity.
The authors thank for financial support to Romanian Ministry of Research and Innovation Contract No. 43PCCDI/2018 and Contract No. 23PCCDI/2018.