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14СЕЛЬСКОХОЗЯЙСТВЕННЫЕ НАУКИ
PACS number(s): 87.17.Ee; 61.46.+w IMPACT OF METAL-BASED NANOPARTICLES ON WHEAT (TRITICUM AESTIVUM L.) PLANT MORPHOLOGY AND ANTIOXIDANT ENZYME ACTIVITY
BABANLI SAFIYAKHANIM TOFIG
Doctoral student, Baku State University, Department of Biophysics and Biochemistry, Faculty
of Biology, Baku, Azerbaijan
AHMADOV ISMAT SULEYMAN
Professor, Baku State University, Center of excellence for research, development and innovation, Nanoresearch Laboratory, Baku, Azerbaijan
AZIZOV IBRAGIM VAHAB
Corresponding member of ANAS, Professor, Azerbaijan National Academy of Sciences, Institute of Molecular Biology and Biotechnologies, Laboratory of photochemistry of chloroplasts,
Baku, Azerbaijan
SHAHBAZOVA FARIDA AZAD
Doctoral student, State Border Service Academy, Baku, Azerbaijan
Abstract.. In the presented research, the effect of nanoparticles such as CuO, AI2O3, Fe2O3, ZnO and TiO2 on the morphophysiological parameters of the wheat plant was studied. Experiments were conducted both in laboratory conditions and in field conditions. It was clear from the results of experiments that nanoparticles affect the energy of germination and the percentage of seed germination.ZnO from applied nanoparticles has a better effect. Al nanoparticles, on the contrary, negatively affect both the energy of seed germination and the percentage of germination. Fe2O3 nanoparticles stimulate development of seedlings.Relatively low concentrations of CuO have a better effect on the germination energy of wheat grains. ZnO nanoparticles showed a greater stimulating effect than ТЮ2 and Fe2O3 nanoparticles, increase the average number of grains in one spike. Both forms of chlorophyll pigment were positively affected by Fe2O3 nanoparticles. ZnO and TiO2 nanoparticles slightly increased the pigment content. Apparently, nanoparticles increase the amount of pigments in plants under drought condition. The results showed that all three applied nanoparticles, TiO2, ZnO and Fe2O3, increased SOD activity. But Fe2O3 nanoparticles increased more.
Keywords: nanoparticles; field experiments, wheat plants, plant seedlings; chlorophyll; enzyme activity
1. INTRODUCTION
Recent studies show that, with the application of nanotechnology, it is possible to improve the mineral nutrition of plants, reduce the harmful effects of insects and pests, control pathogens and weeds, regulate moisture levels, control soil fertility and temperature in agricultural fields, and develop sensor equipment or devices for detecting and field condition measurements. This will allow nanotechnology to become an important technology for creating precision farming, which in the field will provide increased yields [10]. Since the early 1990s, the intensive development of nanotechnology has made it possible to produce a huge number of interesting nanomaterials with unique physical and chemical characteristics. Nanoparticles (NPs) as nanomaterials are due to the extreme dependence of properties (electronic, magnetic, optical, mechanical, etc.) on the size and shape of particles in the range of 1-100 nm [1]. Much attention is paid to nanosized materials, since
their structure and properties differ significantly from the properties of atoms and molecules, as well as bulk materials [18]. Engineering nanoparticles are designed in such a way as to have properties that the original samples of the same materials do not have. Towards a definition of inorganic nanoparticles from an environmental, health and safety perspective [2]. There are three types of nanoparticles: natural, accidently and engineered. Metal nanoparticles are mainly engineered nanoparticles and have not only unique physicochemical properties, but also various biological effects. The reactivity of nanoparticles with biomolecules depends on several factors, including: nanoparticle size, core composition, shape, surface properties, purity, stability, and manufacturing method [25,28].
Currently, metal-based nanoparticles are widely used in various areas of human activity and there are high risks of their release into the environment, so it is necessary to monitor their potential toxic effects on ecosystems, the abundance and diversity of flora and fauna. For example, some nanoparticles are estimated to be taken up by plants 15-20 times more than their bulk particles [20]. When exposed to plants, nanoparticles can retain the main characteristics of their original materials, so it is necessary to take into account the influence of the original material when studying the interaction of nanoparticles in the environment, for example, heavy metals are toxic to plants, while silicon as a metalloid has been seen to be beneficial to plants [9,26,30]. In recent years, nanoparticles of metals and metal oxides have been used in various industries, including agriculture. From the research results of recent years, it can be seen that the use of nanomaterials, mainly in the form of nanoparticles in wheat production is still at an early stage. However, these new materials are being used to provide effective nutrients in fertilizers, to combat undesirable productivity limiting factors such as the effects of pests and diseases, temperature and humidity, salinity and drought, and to develop next generation pesticides.
According to the data of a number of authors, silver nanoparticles at low concentrations can enhance the energy of germination and seed germination, growth and development, respiration rate, and activity of enzyme systems [11,19]. It is noted that silver nanoparticles mainly accumulate in the roots of plants. Studies with TiO2 , AhO3 , and Fe3O4 nanoparticles have shown that, depending on the concentration, these nanoparticles can have different effects [3]. In these experiments, iron nanopowders at low concentrations increased the yield and grain quality of cereal crops. In [4] seed soaking with titanium, aluminum, and iron nanoparticles did not affect seed germination and plant growth. It is assumed [12] that in the process of growth and development, plants can use the surface energy of nanoparticles coming from outside, which can affect the functions of the molecular structures of the cell. The experiments of Zhu and his colleagues showed that the toxic effect of ZnO nanoparticles on wheat plants is not very strong, however, ZnO nanoparticles cause degradation of chlorophyll, damage the root system of seedlings, as a result of which the development of seedlings is weakened, the formation and growth of leaves is delayed. They concluded that When studying the effect of ZnO nanoparticles on wheat plants, the range of concentrations should be taken into account [34].
Zhang Zhenyan, while investigating the effect of Cu nanoparticles and Cu ions on the wheat plant in his experiments, found that both Cu nanoparticles and its ionic form caused serious changes in its morphology and physiology. They explained the change in the morphology of wheat roots by the lack of regulation of auxin transport and the destruction of cells. They determined that Cu nanoparticles accumulate more in the roots of wheat than in its sprouts. Transcriptome analysis showed that Cu nanoparticles accelerate protein transcription. Oxidative stress and root growth inhibition of Cu nanoparticles as well as Cu ions were their main toxicity. As a result, they found that Cu nanoparticles show less toxicity than Cu ions. It was clear from their experiments that the toxic effects of Cu nanoparticles and Cu ions occur through different molecular mechanisms [33].
In another experiment, they determined that the effect of CuO nanoparticles in the early stages of wheat plant development depends on its concentration. Thus, CuO nanoparticles at a concentration of 0.01 g/l have a positive effect on the development of wheat sprouts. They also determined that Cuo
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nanoparticles at concentrations of 0.1 and 1 g/l have a small effect on the activity of enzymes of the antioxidant system [31]. The effect of silver, copper and iron nanoparticles on wheat (Triticum aestivum) seeds was studied in laboratory conditions. The germination and strength index of wheat seedlings were determined. Wheat seeds were treated with silver, copper, and iron nanoparticles under various conditions. The length of root shoots and the percentage of germination were calculated. The results of these experiments showed that the percentage of germination decreases when wheat seeds are treated with silver and copper nanoparticles, while the maximum percentage of germination was observed when iron nanoparticles were used. In addition, the growth of roots and shoots also increased with the use of iron nanoparticles. On the contrary, when exposed to copper nanoparticles, a sharp reduction in the length of roots and shoots was observed. Thus, it was found that copper nanoparticles have an inhibitory effect, and iron has a stimulating effect on the germination and growth of wheat [5]. The effect of titanium dioxide (TiO2) nanoparticles on the growth and development of wheat at concentrations of 20, 40, 60, 80, 100 mg/kg of soil was also studied. The control for the experiments was untreated soil with nanoparticles. It was revealed that the effect of TiO2 nanoparticles is positive at concentration levels up to 60 mg/kg. Nanoparticles at a concentration of 60 mg/kg increased the length of roots and shoots, as well as the total fresh and dry biomass, but decreased at higher concentrations. Nanoparticle migration from the soil and accumulation in leaves were observed. According to the results of these experiments, it was concluded that TiO2 nanoparticles can have an inhibitory effect and cause cell damage at concentrations above 60 mg/kg TiO2 nanoparticles [17].
And in the work of Soran M.-L et al., the effects of TiO2 nanoparticles on the ultrastructure of wheat leaves, biologically active compounds and the elemental composition of wheat were studied. They determined the concentration of phenolic compounds, assimilation pigments, antioxidant capacity, element content, and ultra structural changes in wheat plants grown in the presence or absence of TiO2 nanoparticles. Ultra structural analysis in the leaves of plants treated with TiO2, no significant changes were observed. In plants grown in the presence of TiO2 nanoparticles, the amount of assimilating pigments and the amount of polyphenols decreased compared to the control sample, and the antioxidant activity of plants grown in the corrected soil was higher than in plants grown in the control soil. When a TiO2 nanoparticle was introduced into the soil, a pronounced reaction of the plant to stress conditions was found. This was manifested by a decrease in chlorophyll, the amount of polyphenols, carotenoids, and an increase in the antioxidant activity of plants [21].
There are attempts to use nanoparticles as fertilizers to increase crop yields. Attracts attention with their higher efficiency and less environmental hazard. A study by Sana Ullah and colleagues examined the effects of TiO2 nanoparticles at 0, 30, 50, and 100 mg/kg in combination with soil application of phosphate fertilizers at 0, 25, and 50 mg/kg on wheat. The physiological parameters of plants and the activity of their antioxidant enzymes (SOD, POD) were measured. It was found that the use of the elements Ca (316%), Cu (296%), Al (171%) and Mg (187%) with 50 mg/kg TiO2 nanoparticles, even in the absence of phosphorus fertilizer in the soil, the concentration of phytoavailable phosphorus significantly increased to 63, 3%. Along with the introduction of phosphorus, TiO2 nanoparticles caused the activity of SOD (2.06-33.97%) and POD (up to 13.19%) and the formation of H2O2 (50.6-138.8%). These results of these experiments indicate that TiO2 nanoparticles may have some similarity with phosphate compounds and metal ions in soil, converting them into a soluble form, which increases their bioavailability [27].
Indian scientists in their recent study have found that the Indo-Gangetic Plains region has very high levels of ozone at ground level, which led to significant crop losses, especially wheat. It has been established that O3 penetrating into the stomata and, after dissolving in the apoplast, forming reactive oxygen species (ROS) causes damage that leads to oxidative stress or premature aging [22]. O3 affects plant metabolism, adversely interfering with photosynthetic carbon assimilation, stomata conductance, and overall plant growth [15]. To prevent crop losses from abiotic stresses, as well as from ozone exposure, it is proposed to use nanotechnologies. The Rekha Kannaujia study evaluated
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the antiozonant efficacy of biogenic silver nanoparticles (B-AgNP) and compared them with a model antiozonant ethylenediurea (EDU) against ozone phytotoxicity. Growth, physiology, antioxidant protection, and yield parameters were studied in two wheat varieties (HD-2967 and DBW-17) treated with B-AgNP (25 mg/L and 50 mg/L) at both the vegetative and reproductive stages. They found that Ag nanoparticles at optimal concentrations are effective as EDUs and therefore could be promising ozone protector for wheat [12]. Nanoparticles can change not only the physiological parameters of plants, but also the nutritional composition of wheat. In the work of C. M. Rico and his colleagues, the effect of cerium oxide (nCeO2) nanoparticles on the growth, yield and nutritional composition of wheat (Triticum aestivum L.) was studied. Plants were cultivated to obtain grain in the soil with the application of 0, 125, 250, and 500 mg nCeO2/kg (control, nCeO2-L, nCeO2-M, and nCeO2-H, respectively). During harvesting, grain and plant tissues were analyzed for fatty acids, minerals and amino acids. The results of their experiments showed that CeO2-H nanoparticles improved plant growth, shoot biomass, and grain yield by 9.0%, 12.7%, and 36.6%, respectively, compared to control. With an increase in the concentration of nCeO2, the accumulation of cerium in the roots increased. CeO2- nanoparticles modified the amino acid composition and increased the content of linolenic acid to 6.17% [16].
Thus, nanotechnology (including metals/nanoparticles) is a major source of innovation with important economic implications. However, the potential health and environmental risks of nanotechnology applications and procedures have not only emerged, but have increased at the national and international levels. Past experience with sanitary, technological and environmental risks has shown that trying to deal with them after the fact is the wrong policy. Therefore, it is extremely important to assess the risks as early as possible. Thus, new methodological approaches were sought not only for nanotechnologies in general, but also for nanoparticles in particular, including metal nanoparticles. The aim of this work was to study the effect of nanoparticles of biogenic metal oxides on the germination energy, germination, growth and development, the content of photosynthetic pigments, the activity of photosystems and antioxidant enzymes of plants.
2. MATERIALS AND METHODS
2.1 Material.
The object of the study was seedlings and plants of the soft wheat variety (Triticum aestivum L) Mirbashir-128. The Mirbashir-128 wheat variety was obtained from the intraspecific hybridization of the Bezostaya-1 variety with the "S-271" variety of Pakistani origin of the Azerbaijan Scientific Research Institute of Agriculture. The variety is resistant to dormancy and has a height of 95-100 cm. The variety has medium maturity and ripens at the same time as the Bezosta-1 variety. It is resistant to wilting. The bush is compact, the sprouts and the plant are dark green. The spike is of medium length and medium density. Spike scales are semicircular, the spike lets are short, weakly spreading and rough. The average productivity of the variety is 63.4 s/ha under irrigation. Potential productivity is 60-70 s/ha. The grain is large and the weight of 1000 grains is 37-47 g. The amount of protein in the grain is 14.7-15.3%, the amount of gluten is 28-30%. It is weakly and moderately susceptible to fungal diseases. Drought resistance is average. The optimal sowing period in the boiling conditions is from September 20 to October 10, and in the irrigation conditions from October 20 to November 10. 80-100 kg of phosphorus, 40-60 kg of potassium, 80-100 kg of nitrogen fertilizers are applied per hectare.
2.2. Nanoparticles.
The nanoparticles (CuO, Al2O3, Fe2O3, ZnO and TiO2) in powder form were purchased from Sky Spring Nanomaterials, Inc (USA). The characteristics of the particles were as follows. Average particle size: 18 nm, purity: 99.9% and surface area > 80 (m2/g) as reported by the commercial agent. Wheat seeds were dusted with nanoparticle powder before sowing. For this, 1 mg of each nanoparticle was added to a 50 ml glass for 10 seeds, and the seeds were processed in a shake for 10 minutes.
2.3 Experimental design
Before coating the seeds with dust of nanoparticles, their surface was sterilized. The seed surface was kept in 10% sodium hypochlorite solution for 10 minutes and dried. The seeds are then coated with nanoparticle powder in a vortex mixer. Seeds coated with nanoparticles were placed on filter paper in Petri dishes for germination. Petri dishes are sealed with adhesive tape and placed in an incubator for 5 days. Then the percentage of seed germination was calculated, the length of the roots and shoots of the seedlings was measured. The germination energy and seed germination, morphometric parameters, the content of chlorophylls a and b, carotenoids, and plant productivity were determined. In the process of further plant growth, morphometric parameters, the content of chlorophyll a and b, carotenoids, the activity of photosystem 2, and the antioxidant enzymes superoxide dismutase and catalase were determined.
An alcoholic extract of the leaves was used to determine the content of pigments. The content of pigments was determined on an SF-26 spectrophotometer by absorption at wavelengths of 665, 649, and 440 nm. The amount of pigments was calculated by the Vernon method [23]. The activity of photosystem II was determined with exceptional sensitivity and reproducibility the Photosynthesis Yield analyzer MINI-PAM (Germany). It is the reliable determination of the YIELD-parameter AF/Fm (Genty-parameter).
The activity of the enzyme superoxide dismutase was determined according to the method [24], the activity of catalase - polarographically, by the release of oxygen. Static data processing was carried out using the program "Statistica for windows".
Figure 1. The Photosynthesis Yield Analyzer MINI-PAM
The alcoholic extract of the leaves was used to determine the content of pigments. The pigment content was measured on an SP-2000 spectrophotometer at 665, 649, and 440 nm. The amount of pigments was calculated according to the method [29].
3. RESULTS
3.1. Physiological parameters of wheat sprouts germinated in laboratory conditions
In our experiments, we initially investigated the effect of nanoparticles on the sowing qualities of seeds. It is known that under the sowing qualities of seeds understand the signs and properties that characterize the suitability of seeds for sowing. The main parameters characterizing the quality of seeds include germination energy, germination percentage, viability, purity, weight of 1000 seeds, humidity, infestation with pests and diseases, and varietal purity. The two main of these parameters -germination energy and germination - determine the suitability of seeds for sowing. Germination vigor refers to the number of normally germinated seeds expressed as a percentage of the number of seeds taken in a given short period of time. The higher the number of sprouts from the seeds sown, the higher the yield. The percentage of germination is understood as the number of normally developed germinated seeds under optimal conditions for a certain period of time. To assess the effect of nanoparticles on the germination energy and the percentage of germination of wheat seeds, 100 seeds were counted, the seeds were treated with nanoparticle powder and germinated in Petri dishes. On fig. 2 shows the germination of wheat seeds.
Figure 2. The effect of nanoparticles on the germination of Mirbashir-128 wheat variety
seeds
When determining the germination and germination energy of seeds, it was found that nanoparticles have a different effect on these indicators. The results of the experiment are given in table 1. From the results of the experiments, it was clear that ZnO from the applied nanoparticles has a better effect on the germination energy and germination percentage of the seeds than the other nanoparticles. However, Al nanoparticles, on the contrary, have a negative effect on both the germination energy of seeds and the germination percentage compared to the control (table 1). Nanoparticles also had different effects on the development of seedlings. Seedling height was stimulated by Fe2O3 nanoparticles, but Al nanoparticles significantly retarded seedling development.
Table 1. Effect of nanoparticles on seed germination and morphological and physiological parameters of wheat seedlings_
Experimenta Germinatio Germination Seedling Fv
l variants n energy, % , % growth (cm) / Fm
14 1
day 9 day
Control 70 90 3, 1 0,
CuO 70 80 5 1 8
TiO2 85 90 4, 1 0,
ZnO 90 100 5 2 6
Fe2O3 85 90 6, 1 0,
Al 60 80 5 4 7
6, 1 0,
5 4 7
7, 1 0,
0 5 7
4, 7 0,
5 7
While clarifying the effect of nanoparticles on the germination percentage of seeds, it was interesting that it depends on the concentration of nanoparticles. For this, 0.01, 0.1 and 1.0 mg/l solutions of CuO nanoparticles were prepared. Then the seeds were germinated in these solutions. The analysis of the effect of CuO nanoparticles on the germination of wheat seeds showed that a high concentration of nanoparticles in the solution caused an increase in the value of the studied parameter by 14%, 15% and 18%, respectively, compared to the control (Figure 3). The evaluation of the
morphometric characteristics of sprouts of wheat seeds germinated in different concentrations of CuO nanoparticles is shown in Figure 4. The length of roots and stems of 14-day-old seedlings was measured. From the analysis of the measurements, it was clear that the length of the roots at the concentration of 0.01 mg/l was about 2 times greater than the control. However, as the amount of concentration increased, the length of the roots decreased compared to the control. The length of the stem of the seedlings was also measured. It was clear from the measurements that the length of the stem was greater than the control at the concentration of 0.01 mg/l. The increase was again 2 times. Thus, almost the maximum increase is observed at the lowest concentration of nanoparticles.
Figure 3. Effect of CuO nanoparticles on the cermination capacity of wheat seeds
Figure 4. The effect of CuO nanoparticles on vegetative characteristics of wheat seedlings
3.2 Physiological parameters of wheat cultivated under field conditions Experiments devoted to the study of the interaction of nanoparticles with plants and the physiological and biochemical effects they cause are mainly carried out with plants grown in laboratory conditions. A large number of interesting results have been obtained in this area. Experiments carried out with laboratory plants mainly study the initial stages of plant development. The movement of nanoparticles in plant organs, their localization, influence on important physiological and biochemical processes, important experimental results related to the role of nanoparticles in plant resistance to stress factors are already known, and research in this area continues. These experiments are becoming more in-depth and carried out at the molecular, even gene level. However, one of the main questions in all these experiments is the question of the impact of nanotechnology on plant productivity. Therefore, in recent years, the boundaries of experiments have already expanded and experiments on the effect of nanomaterials on plants began to be carried out in the field. It has always been interesting to what extent the results of laboratory experiments with
nanoparticles are applicable in the field. Therefore, it was interesting for us to conduct experiments conducted in the laboratory with wheat in the field. The field experiments were conducted at the experiment area of the Chloroplast Photochemistry laboratory of the Institute of Molecular Biology and Biotechnology of MoE. The soil of experimental locality were brown forest soils where intensive soil-cultivation enables annual maize rotation. Experimental plots were presented in an area of 2 and 2 m2 with two repetitions of each treatment. Two experimental options (control - irrigated site and site created by drought) were installed randomly located, perpendicularly separated blocks (Figure. 1). The experimental plot prior to our experiment was used for growing wheat in the season. The usual plowing procedure was carried out and fertilizer was applied to the soil only before sowing, during the growing season fertilizer was not applied. Each blocks that received different irrigation treatments. For the irrigation was used tap water. Both blocks from planting to the end of the 4th week was irrigated. Irrigation was thereafter discontinued in the test block. At this time, the control block was watered 2 times a week, and the test block was watered every 2 weeks.
Table 2. Influence of nanoparticles on seed germination and morphophysiological indicators of wheat plants grown in field conditions_
Experimen tal variants Germinati on energy, % Germinati on, % Height of sprouts (cm) Л Fv / Fm
14 day 19 day
Control 70 90 3.5±0 11± 0,
TiO2 85 90 ,2 ,9 8
ZnO 90 100 6.5±0 14±0 0,
Fe2O3 85 90 ,5 ,9 7
6.5±0 14±0 0,
,5 .8 7
7.0±0 15±0 0,
,8 ,9 7
In preliminary experiments, the effect of TiO2, ZnO and Fe2O3 nanoparticles on seec
germination energy and germination percentage was studied. As mentioned, the seeds were planted in the field after being treated with the powder of these nanoparticles. Evaluation of germination energy and germination of seeds was performed 14 days after sowing. The length of the sprouts was measured on the 14th and 19th day. The results of the experiment are given in table 2. It is clear from the table that ZnO nanoparticles have a different effect on these indicators. Fe2O3 nanoparticles have a better effect on the development of sprouts and their height is relatively high. AF/Fm directly measures the quantum yield of PSII electron transfer and is an extremely useful parameter in the field. AF/Fm parameter was determined on the 19th day of wheat development. Samples (5 cm2) were taken from the leaves of both sites, irrigated and drought-exposed plants, and measured with a PAM device after keeping them in the dark for 20 minutes. The results of measurements are given in tables 2.
Table 3. Effect of nanoparticles on photosynthetic pigments in field-grown wheat seedlings (mg/g wet weight)_
Experimental Chl a Chl b Chl Chl Carotenoids
variants a+b a/b
Control 1.8 0.55 2.35 3.27 2.2
TiO2 1.9 0.71 2.61 2.67 3.2
ZnO 1.9 0.69 2.59 2.75 3.5
Fe2O3 2.1 0.72 2.82 2.92 3.7
The measurement of chlorophyll content were conducted by standard methods, fresh leaves samples were taken from both variants and weighted, finely chopped, and homogenized in 5 mL acetone (90%, v/v). Another 5 mL 90% acetone was added and the mixtures were placed in darkness for 24 h at room temperature. After that, the mixtures were centrifuged for 10 min at 3600 rpm. The supernatant was collected, and the absorbance was recorded at 664, 647 nm using a Carry 50 UV-vis spectrometer. The contents of chlorophyll a and chlorophyll b were calculated based on the following equations.
chlorophyll a V 11:93 A664 — 1:93 A647
chlorophyll b V20:36 A647 — 5:50 A664
where A664 and A647 were represented as the absorbance measured at 664 and 647 nm, respectively.
The results of these measurements are given in table 3. Controls were samples taken from plants obtained from seeds exposed to drought but without nanoparticle application. As can be seen from the table, both forms of chlorophyll pigment were positively affected by Fe2O3 nanoparticles. ZnO and TiO2 nanoparticles slightly increased the pigment content. Apparently, nanoparticles increase the amount of pigments in plants under drought condition.
It is well known that the productivity of plants affected by drought is low, weak development, and physiological parameters change dramatically. Various physiological, biochemical and genetic methods and factors have been developed to increase plant resistance to drought. They have made significant progress in this area. Great hopes are placed on the application of nanotechnologies in this area. Intensive research is underway to improve the drought tolerance of plants through the use of nanomaterials, including nanoparticles. In our experiments, TiO2, ZnO, and Fe2O3 nanoparticles were applied to a medium drought-resistant wheat variety Mirbashir-128 and some indicators of its productivity were studied. Samples were taken during the period of wheat ripening and measurements were taken. These indicators were the length of the stem, the length of the ear and the number of grains in one ear. The measurement results are shown in Table 4 and Figure 5. It was seen that ZnO nanoparticles showed a greater stimulating effect than TiO2 and Fe2O3 nanoparticles. Thus, the average number of grains in one ear was 22 more than in the control.
Table 4. Influence of nanoparticles on yield indicators of wheat
Experimental variant s Length of stem cm Length of spike cm The number of grains in one spike number
Control 30±1 6±1 30±2
TiO2 36±2 9±1 51±3
ZnO 44±2 10±1 63±4
Fe2O3 41±1 8±1 52±2
3.2. Effect of nanoparticles on Antioxidant Enzyme Activities
It is well known that ROS generation and quenching are always balanced by enzymatic and non-enzymatic antioxidants at all stages of plant development. However, in stress situations,
including drought conditions, the excess of ROS can disrupt redox homeostasis. There are reports that nanoparticles can also induce an oxidative stress effect, leading to the strengthening of the antioxidant system. Therefore, they consider it possible to apply nanoparticles to protect against the interference caused by oxidative stress during drought stress. Application of nanoparticles significantly improved antioxidant enzyme activity in drought-stressed maize plants as compared to untreated seeds. Experiments show that nanoparticles cause the increase of reactive oxygen species (ROS) in plants as abiotic stress and consequently the activation of antioxidant enzymes. However, the effect of nanoparticles depends on their application method and concentration. Low concentrations of nanoparticles in plants lead to reduced antioxidant activity due to low oxidative stress. However, when oxidative stress is high, the activity of the enzyme in the antioxidant defense system increases. In other words, the effect of nanoparticles is similar to the effect of stress factors such as drought and salinity. Thus, in plants, antioxidant enzymes such as Catalase (CAT), Ascorbate Peroxidase (APX), Guaiacol Peroxidase (GPX) and Glutathione Reductase (GR) functions to interrupt the cascades of uncontrolled oxidation in some organelles.
12
Control ZnO Fe,03 ТЮ2
Figure 6. Influence of nanoparticles on activity of superoxide dismutase (SOD) in wheat
seedling leaves
Enzyme activity was measured by standard biochemical methods. The activity of the superoxide dismutase enzyme was determined using the method of Syrota T.V. The method for determining the antioxidant activity of superoxide dismutase and chemical compounds. The patent of the Russian Federation No. 2144674 [24].
Leaf samples from drought-exposed plots were taken at the tuber stage of plants. The result of the measurements is given in figure 6. The results showed that all three applied nanoparticles, TiO2, ZnO and Fe2O3, increased SOD activity. But Fe2O3 nanoparticles increased more. Thus, it can be said that during drought stress, it is possible to balance the activity of enzymes against ROS through nanoparticles.
4. CONCLUSION
The presented experiments revealed changes in the morphology and physiology of wheat under the influence of a nanoparticle. The treatment of wheat seeds with nanoparticles significantly changed the physiological and biochemical characteristics of plants. It is shown that with the use of nanoparticles they affect the energy of germination and the percentage of seed germination. ZnO from applied nanoparticles has a better effect on the germination energy and percentage of seed germination than other nanoparticles. However, Al nanoparticles, on the contrary, negatively affect both the energy of seed germination and the percentage of germination compared to the control (Table 1). Nanoparticles also affected the development of seedlings in different ways. The height of seedlings was stimulated by Fe2O3 nanoparticles, but Al nanoparticles significantly slowed down the development of seedlings. Change in root morphology, possibly due to changes in nitrate-regulated
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auxin transport and cell death in roots. An analysis of the effect of CuO nanoparticles on the germination of wheat seeds showed that an increase in the value of the studied parameters has a concentration dependence. Relatively low concentrations of CuO have a better effect on the germination energy of wheat grains.
One of the main purposes of the application of nanoparticles in the agricultural industry is to increase the resistance of plants to stress factors. One of these stress factors is drought. It is known that drought stress causes serious changes in all developmental stages of plants, slows down their development, causes a number of morphophysiological changes, drought reduces plant height, biomass, root length, number of leaves, water capacity, seriously affects stomata activity, photosynthesis and antioxidant system. Experiments show that the drought resistance of plants can be increased by applying nanoparticles. For example, application of SiO2 NPs in drought-stressed plants achieves higher SOD activity, which increases the efficiency of the antioxidant system protecting drought-stressed plants from oxidative damage. Therefore, SiO2 NPs partially compensate the negative effects of drought on plants by increasing the activity of SOD, glutathione reductase [7] and catalase [32] enzymes. On the other hand, protein accumulation modulates the response to drought stress. Drought stress reduces starch deposition in wheat grain, resulting in increased grain size. protein content [8]. Some researchers reported that drought stress increased total protein content in rice [6]. In our experiments with wheat, it is proven once again that ZnO, TiO2 and Fe2O3 nanoparticles significantly increase the SOD activity in wheat plants cultivated under drought conditions compared to the control. Increased SOD activity plays an important role in increasing drought resistance.
Thus, it can be concluded that with the application of nanoparticles, the development of the wheat plant can be improved, it will enable it to realize its potential productivity, and its resistance to stress factors can be increased.
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