Nano-derived products or nanoparticles for agricultural uses play a vital role in enhancing plant growth and crop productivity. Several qualities, such as compact size, easy to carry, easy handling, long time storage, high effectiveness, and nontoxicity make them a preferred option for the farmers than conventional chemicals and techniques. Nano-based commercialization is now growing widely all over the world.
Uses of Nanoparticles In Agriculture
The significant interest of using nanotechnology in agriculture includes specific applications like nano fertilizer and nano pesticides to trail products and nutrient levels to increase the productivity without decontamination of soils, waters, and protection against several insect pests and microbial diseases.
Large-scale use of chemical pesticides is the most concerning global issue since these chemicals lead to serious problems such as biomagnification. Many organophosphate pesticides accumulate in adipose tissue of organisms and affect the food chain. The formulation and use of nanoparticles that have an organic origin and have pesticidal properties is an effective solution to this problem. Major staple crops such as wheat, rice, and maize are highly susceptible to fungal attacks.
In order to curb this problem, nanoparticles can be very effective against several fungal attacks. For example, silver nanoparticles have been found to be very effective against rice blast disease caused by Magnaporthe grisea and copper nanoparticles are effective against Botrytis cinera. Similarly, nanoparticles of zinc oxide and magnesium oxide are very effective against Mucor plumbeus. The effectiveness of various nanoparticles depends upon the concentration.
The maximum inhibitory activity of fungal attack due to silver nanoparticles was observed at 15 mg/L. Rao and Paria reported the inhibitory effect of Sulfur nanoparticles against phytopathogen Fusarium solani which causes apple scab in plants.
Silver nanoparticles consisting of extracts from leaf and stem of Piper nigrum are very effective against Erwinia cacticida. Chinnaperumal et al. have reported the significant larvicidal, antifeedant and pupicidal activity of TiNPs on the cotton bollworm H. armigera after capping it with biocontrol fungus T. viride.
Moreover, synthesized mycogenic TiNPs were found non-toxic to earthworms Eudrilus eugeniae. Aggressive use of chemical herbicides has resulted in environmental contamination. Nanoparticles can substitute the excessive use of chemical herbicides since they are more stable, soluble and easily disintegrate without releasing any harmful residues in soil. These nanoparticle herbicides can be made with active agents such as atrazine with poly (epsilon- caprolectone) nanoparticles.
Prophylactic measures are best to avoid diseases, as is said, “prevention is better than cure”. Diseases can be cured by action of nanoparticles in plants. Nano agrosensors are tiny devices used to investigate various field parameters such as moisture content, pH and concentration of fertilizers in fields.
These sensors are so sensitive that they can detect chemicals at PPB levels (parts per billion). These can help farmers to have keen eye on the entry of pathogens and penetration of infection in the fields. These sensors lead to increase in crop yield.
It has been estimated that 90% of pesticides escape during their application stage in fields which is further more harmful to living beings as well as ecology. “BIOPESTICIDES”, can be used as an alternative. Kumar et al. have reviewed the nano-based application for pest management and figure out the mechanism of monitoring and identification of pest for targeted delivery of nano-pesticide and after that evaluation of its effects on pesticides as well as on beneficial organisms.
The active principles, such as azadirachtin, degulin, melia etc. used in biopesticides are derived from plants. However, the active compounds show less activity in fields due to early degradation in fields by sunlight etc. The activity of active compounds can be enhanced by using nanotechnology.
Nano carriers can be used for exact delivery of these active compounds in fields. This modern system works by proper investigation of pest reactions towards these applie active bio pesticides. Nanotechnology reduces the chances of degradation of active compound (Azadirachtin, rotenone etc) in fields due to UV–rays or microbial attack etc.
Read More: Nanoparticles And Sustainable Agriculture
Seed dormancy is a major problem which leads to reduction in crop yield. This problem can be mitigated by using multi walled carbon nanotubes, which lead to the formation of pores in tough seed coat of seeds. This results in imbibition of water inside seed coat. When crop plants are treated with nano crystals, they enhance the chlorophyll index of treated plants. Shinde et al. have designed the green synthesized magnesium hydroxide nanoparticles [Mg(OH)2NPs] and found it 100% seed germination efficiency and growth of Zea mays in vitro and in vivo.
Similarly, the efficacy of AgNPs was evaluated in vitro with the seedling growth of Boswellia ovalifoliolata and revealed the 10.6 ± 0.3 cm (maximum height) compared to other concentrations and control Savithramma et al. (2012). Interestingly, the nano-based seed priming is gaining more attention for the enhancing of seed germination.
Mahakham et al. 2017 have proposed that AgNPs nanopriming is induced the seed germination as well as nanopores formation for enhanced water uptake, rebooting ROS/antioxidant systems, cell wall loosening by generation of hydroxyl radicals and fastening the starch hydrolysis of seed by nanocatalyst. Seed priming of watermelon with AgNPs was also reported efficient for enhancing the germination, growth, and fruit quality yield via eco-friendly and sustainable nanotechnological approach.
Nanobarcodes are also used to know the expression of various genetic trait inside desired plants. Nano barcodes are made via semi-automated process of electroplating inert metals like- gold and silver which are converted into templates of desired size. After this the formulated nanorods are released from templates and are used to study gene expression in desired organism for any type of biotic and abiotic stresses.
Soil texture is the most important factor which governs the fertility of soil. For weak soils. Nanomaterials are used as a provide a smart, novel, ecofriendly and sustainable option for soils improvement. Alsharef et al. 2016 revealed that the addition of ~0.2% of multiwall carbon nanotube (MWCNTs) and carbon nanofiber (CNFs) to clayey sand soil (UKM soil) enhance the hydraulic conductivity of soils and reduced the soil cracks.
Application of carbon nanotubes to reinforce soil, nano bentonite for drilling fluid additive and for soil mechanic properties, colloidal silica and laponite for mitigation of liquefaction of soils was also reviewed by Huang.
Nano saturated silica can be used to improve the soil texture. Colloidal silica nanoparticles can disperse in liquid medium and therefore allow ground water to disperse equally, improving the soil properties. Another nano particle called as Laponite has specific property of improving soil texture and liquefaction resistance in soil.
Nanoparticles also increase bioavailability of essential nutrients to plants. Cai et al. have studied the impact of magnesium oxide nanoparticles (MgONPs) over a concentration range of 50–250 μg/mL on the tobacco plants and various morpho-physiological changes in root, shoot and leaves, during uptake and accumulation, were observed.
Cai et al. invented a nano clay which when applied to fields in combination with traditional fertilizers can retain nitrogen in soil and stop leaching of nutrients in deeper layer of soil.
Moreover, fabricated xylem vessels are best to check various types of pathogenic populations inhabiting inside host body without destructing the host body or xylem vessels of plants and help us to investigate physio433 chemical and biological interactions between plants and its parasites.
Various methods have been suggested for the measurement of xylem pressure using various probes. With nanotechnology, food products can be made more hygienic, resulting in healthy life of people which is one of the most serious issues of today’s time.
Ground water can be polluted due to increasing use of synthetic fertilizers in fields. Nanotechnology has the potential for providing clean and safe water for drinking and agricultural purposes. Nanoscale Zero-valent iron can be used for treatment of polluted water.
Nano444 oligodynamic metallic particles can be used to make water free from harmful microbes. Silver is used for the synthesis of these nanoparticles because of production of reactive oxygen species (ROS), which can kill both microbes as well as viruses.
Nanotechnology mediated products such as protein – polymer biomimetic membranes, aligned carbon nanotube membranes and thin nano tube nanocomposite membranes help in mitigating the problem of saline water. Zeolite nano membranes are emerging method for sea water desalination. By using these methods, polluted water can be cleaned by disinfection, deodorizing, defouling and can become fit for drinking and agriculture purposes.
Nanotechnology plays a major role in decomposition of slowly degradable compounds like synthetic chemicals and pesticides. Treatment of these compounds is urgently needed because these compounds can affect ecosystem via biomagnifications.
Nanotechnology is used for remediation of uranium, hydrocarbon, waste water and heavy metals from polluted water. It was revealed that TiO2 nanoparticles (TiNPs) degrade the pesticides chlortoluron and
cyproconazole from water by photocatalysis reaction and NH4+ and NO3- ions are produced.
Nano-disinfectants can be used in layers during packaging so they may have better antimicrobial activity against pathogens such as Salmonella sp. The combination of nanotechnology and biosensors give us a very precise device called as nanobiosensors which is modulated to detect the biological activity.
These covert signals from biological form to electrical form and is easily detected by detector device. The detecting signals which are noticed by these devices can be odour, product or a chemical released by biological organisms such as microbes in food samples.
Xiqi et al. have revealed the applicability of nano biosensors. Some of the types of nano biosensors such as Rapid detection biosensors, Enzymatic biosensors, E-nose (Electronic nose), Gold nano Biosensors are in applicability right now. Cheng et al. have detected the botulinum neurotoxin serotypes AB by Rapid detection biosensors with combination of chemiluminescence and electroluminescence.
Enzyme biosensors use the affinity and selectivity of catalytically active proteins, towards their target molecules. When a product released by the pathogen reacts with specific enzymes, signals are generated on the detector device.
Some examples of enzyme biosensors are controlled pore glass beads with optical transducer, polurethane foam with photo terminal transducer, ion selective membrane with potentiometric/ amperometric transducer, screen printed electrode with amperometric transducer.
Interestingly, the E-nose (electronic nose) biosensor is based on the principle similar to that of human nose, is made up of zinc nano wires which can detect the odour of testing sample and calculate the amount of impurities present in sample. Zinc wires have particular data value of particular gas odour. Small fluctuations in experimental data values from true data values detects the impurities in tested sample.
An important application of E-nose is the analysis of food quality. In gold nano Biosensor, the sample is mixed with Gold nanoparticles which leads to change in refractive index of the media surrounding nanoparticles and are generally used in pharmaceuticals, agriculture etc. sectors.
Processing of food raise the food standards and modify food matrix according to need of customers. For easy delivery of useful nutrients in diet we can rely upon delivery system such as nano encapsulation and nano emulsion which leads to easy absorption in body due to small size.
Nano delivery systems enhance the bio availability of active compound, exact active compound release tendency, and also increase the shelf life of active compounds. During food processing various unwanted solutes mix with food and their separation needs huge time and labour.
But nano filtration provides us easy method of unwanted solute separation. Nano filters have membranes which have high permeability for salts and are less permeable for organic solvent such as proteins etc. The basic principle behind nano filtration is electro neutrality.
Nano filters are governed by various characteristics such as pore size and charge density. Nano filters have found wide applications in dairy products for separation of unwanted solutes from commercially important solvent like milk.
Deterioration of food items due to oxidation, led by browning reaction, is a major factor for million-dollar losses of food. By using nanotechnology, such losses can be avoided by using oxygen scavenger films developed by Xiao et al. These films consist titanium dioxide nanoparticles which react with different organic polymers and therefore, low level of oxygen can be maintained, which leads to prevention of rancidity.
Nanotechnology plays a major role in increasing enzyme activity. Nanoparticles make enzyme resistant to various enzyme denaturing compounds such as proteases. Similarly, immobilization of glutamate dehydrogenase and lactose dehydrogenase via silver nanoparticles was reported by Rocchitta et al. Ding et al. have published the opinion for the stability of Enzyme via immobilization on NPs and indicated that the integration of NPs into enzyme carrier schemes has maintained or even enhanced immobilized enzyme performance.
Recycling Of Agricultural Waste
Nanotechnology can be an alternative approach to recycle the agricultural waste in a better way. Agri-wastes can be utilized by the effective processing to produce the nanoproducts. Moreover, generation of nanocomposites, nanocelluloses, biochars etc. from agricultural wastes via postharvest technologies are yet to be implementing nimbly.
Nano lignocellulosic materials are the best examples that are made up via of a combination of nanoparticles and lignin as well as cellulose of plant part. Nanosized cellulosic crystals can be used as light weight reinforcement in polymer matrix, which can be used for construction and packaging etc.
The cellulosic whisker production technology from wheat straw was developed first by Michigan Biotechnology Incorporate (MBI). Nano cellulose is a wise alternate in comparison to fiber glass, plastic. Biggest benefit is that nano cellulose is biodegradable and can solve the problem of waste management very easily.
Interestingly, 110 million tons (Mt) from wheat and 122 Mt of Rice husks are produced as wastes after harvesting and it is the best raw items for the renewable energy, nanosilica and biochar as well as other value-added products. The technological Implementation of these waste mass can be used for the production of nanosilica using nanotechnology method and is opening the best way for the disposal concern of it.
Other Uses Of Nanoparticles In Agriculture
Nano-derived identification tags (barcode technology) are also used in the agriculture sector. Barcodes have various properties such as they are easily coded, tracked and have high durability. These barcodes have both biological and non-biological functions. “Biological barcodes” are used as ID tags, intracellular histopathology and a cheap method of detection of pathogens from food samples. Non-biological barcodes are used as trackers in animal husbandry and agricultural products.
Quantum dots NPs made up of metals like silicon, cadmium, indium which have semiconductor properties are used for detection of diseases such as witches broom in lemon caused by Phytoplasma aurantifolia. These are modern methods of pathogen detection. Earlier staining methods were used for pathogen detection but those were very costly methods.
Quantum dots have various properties, such as they emit effective luminescence, have narrow emission spectra and have excellent photostability. For example, for detection of E. coli 0157:H7, QDs were used as fluorescence marker coupled with immune magnetic separation. Anti E. coli 0157 antibodies made complex with target bacteria and lead to easy identification of E. coli 0157:H7.
Though, a range of NPs are reported for antimicrobial activity, but few of only (such as Ag, TiO2, Zn and ZnO NPs) are predominantly used as microbial inhibitor in plant tissue culture. Kim et al. have reviewed the future prospects of new-age revolutionary nanomaterials such as quantum dots, carbon nanotubes, nanoclusters, polymer dendrimers etc. as an efficient bactericidal and fungicidal agent in plant tissue culture.
Hazards of Nanoparticles
Applications of nanotechnology have widened in recent times, but the concern has arisen about its effects on the environment. Hence, there is an urgent need to investigate the ecotoxicological effects of nanoparticles and the intrinsic as well as extrinsic factors (size, chemical composition, shape, angle of curvature, crystal structure, surface roughness, hydrophobicity etc.) responsible for the toxicity of nanoparticles. It was found that smaller the size of nanoparticles more they are toxic in nature.
It has been also reported that the crystal structure of nanoparticles also influences nano-toxicity. Titanium oxide has 3 mineral ores such as Anatase, Brookite, Rutile. Out of these three, Anatase is most biologically active and causes effects such as cell necrosis and leakage of cell membrane.
Rutile starts apoptosis in cells by triggering ROS. Zinc nano pyramid particles show an inhibitory effect upon the synthesis of beta–galactosidase enzyme and is exemplified the shape dependent inhibition of enzyme.
Nanoparticles when dissolved, release soluble ions. The fate of Zinc nanoparticles in soil and their absorption effects in Vigna unguiculata has been experimented. It has been shown that cationic ions pass via endocytosis across cell membranes.
When carbon nano-tubes bind with persistent chemicals, these decline the potential growth of edible parts of plants and destroy root membranes. Nanoparticles of cerium dioxide reduce nitrogen fixation tendency of leguminous plants by killing the nitrogen fixing bacteria inhabiting roots of leguminous plants.
Hazardous effects of nanoparticles in plants were studied by several researchers. It has been suggested that after attachment of silver nanoparticles with the cell wall of plants, they lead to change in color of treated plants. They observed that the growth rate of plants is inversely proportional to concentration of silver nanoparticles.
Moreover, inhibitory effect of nanoparticles upon the seed germination was also detected. Similarly, Selenium nanoparticles (in high concentrations) trigger oxidative stress in plants leading to generation of superoxides by oxidation of thiols.
But selenium nanoparticles are less toxic in comparison to bulk selenium matter. Recent studies prove that solubility of nanoparticles alters the cell culture response. These nanoparticles adhere to plant roots and cause toxicity to plants at low dosages. Titanium nanoparticles phytotoxicity was revealed by Clement et al.
They have revealed the inhibitory effect on the growth of Lemna paucicostata. Titanium exists in various form such as Anatase, Brookite, Rutile out of which anatase is the most toxic form. Nickle oxide nanoparticles toxicity was studied by Faisal et al. on Lycopersicon esculentum (tomato).
They concluded that nickel ions lead to generation of ROS that causes mitochondrial dysfunction and apoptosis / necrosis. Nickel NPs increase activity of Caspase -3 like protease and therefore lead to activation of intrinsic apoptosis. Zinc oxide nanoparticles phytotoxic effects at cytogenetic level, by studying the genotoxic effects, were carried out by Kumari et al.
Experiments were conducted on Allium cepa and cytotoxic impacts due to inhibition of mitotic index were reported. It was also observed that increased zinc nanoparticles concentration resulted in chromosomes aberration. These defects were mostly visualized at Anaphase586 Telophase stages of cell cycle.
Zinc nanoparticles have also been reported to generate ROS which convert fatty acids to toxic lipids peroxides thus damaging the biological membranes. This damage leads to formation of TBARS (thio barbituric acid reactive species), which effects the membrane permeability.
Hence, it might be speculated that nanoparticles have several negative impacts. Even there are various problems related to marketing of nanoparticles as well as handling and storage of nanoparticles. Therefore, we need to think about a new aspect of nanotechnology that is called as “Sustainable Nanotechnology”. This would allow us to use nanoparticles without any risk.
Conclusion and Future Perspectives
Various aspects of nanotechnology are still untouched and there is immediate need to discover them. Other aspects which need research in nanotechnology are to understand the polymer-polymer and polymer- nutraceutical interactions at molecular level and their impact as delivery system in case of food industry products. Nano agropesticides need to be investigated more.
There has been very less research in literature about functioning of azadirachtin, thymol, curcumin when associated with NPs. European Commission classified nanotechnology under one of the six “Key enabling technologies” which can contribute to sustainable competitiveness and growth in several fields of industrial application.
Source: Singh, R. P., Handa, R., & Manchanda, G. (2021). Nanoparticles in sustainable agriculture: An emerging opportunity. Journal of Controlled Release, 329, 1234-1248.