In a developing country like India, with significant number of people living under poverty line, agriculture is the mainstay for the livelihood of more than 50 per cent population. To meet the food requirement of increasing population, although a large acreage of land is under cultivation of a range of crop species, the average yield every year, however, has not been as anticipated. Plants have failed to realize their full growth potential owing to varying abiotic stress conditions like high salinity, drought, extreme temperatures, presence of heavy metals, water logging etc. Efforts have been made and are underway to devise strategies/methodologies that could evoke defensive response in plants when exposed to stress conditions. In the recent past, the use of nanoparticles has emerged as a ray of hope in providing solution for combating this obstacle that hamper crop plants from realizing their full growth potential. Nanoparticles are small particles with dimensions satisfying the nanometer scale. Although nanoparticles have been synthesized using physical and chemical methods, these methods are not only expensive, but also are non-eco-friendly and hazardous to health. Of late, a safer approach (green approach) of synthesizing nanoparticles, using plant extracts, have been adopted and has found wide acceptance among the agricultural scientists. Nanoparticles have large surface area, show quick absorbance/penetration with precision delivery to the target site. Use of nanoparticles like Fe, Cu, Zn, Ag, Au, silica etc. have shown positive response in plants manifested in increased germination, high chlorophyll content, increased proline synthesis, photosynthesis etc. The encouraging response seen in plants has led to the resurgence in efforts to try a range of nanoparticles synthesized from myriad plant species. This communication reviews the efforts made by various scientific groups using nanoparticles and the results achieved
Keywords: Green synthesis; Plant, Nanoparticles, Biotic and abiotic stress
The ever-increasing population in the world and particularly in the developing countrylike India, has intensified the demand for enhanced food production. With the population expected to escalate by 34 percent by 2050, The global crop production will have to rise from the present 2.1 billion tons to about 3 billion tons [1]. Although to cater to the needs of ever-increasing population, a vast area of land has been brought under cultivation of various food crops, the agricultural yield, every year, has not been up to the mark due to varying biotic and abiotic stresses. Among the common natural abiotic stresses, that has despicably thwarted efforts to have a bumper harvest, have been the soil salinity, drought, and extreme temperatures.
Although to overcome these obstacles, efforts have been and are being made to devise and/or strategize scientific methods that could ameliorate the growth conditions of the crop
plants, the results obtained, have been far from satisfactory. Of
late, Nanotechnology has emerged as a potent tool that has helped
in resolving a range of problems hither- to-fore unresolved [2].
It has offered an eco-friendly mechanism that has proved pivotal
in overcoming some of the problems confronting the agricultural
scientist. It uses the physio-chemical properties of a substance at
molecular level to explore biological and material world at nano
meter scale. Nanoparticles, being tiny in size (1-100nm), show
unique physio-chemical characters such as large surface area,
improved/enhanced reactivity, increased solubility and penetrance
via the membranes that enable them target any cell organelle and
diverse morphology as compared to bulk particles [3,4].
Owing to all these attributes that the small size bestows on a
chemical component, the nanoparticles are suitable for chemical
delivery that has the quality of reaching the target site with precision.
For example, the chemical fertilizers, which are applied in large
doses to enhance the productivity of crop, usually are not target
specific and/or are not absorbed completely by plants resulting in
their accumulation in soil making it toxic. Use of nanoparticles has
given a fillip to the plant growth and productivity by enhancing the
availability and absorption/penetration of nutrients into the plants.
Nanotechnology holds promise in overcoming the stress related
problem faced by the crop plants. However, it can be effectively
used once its full potential is identified and particularly, their role
in mitigation of various types of stresses faced by plants and their
mechanism of action [5]. Realizing the pivotal role that plant based
nanoparticles can play in alleviating the problems confronting the
mankind, it was considered worthwhile to write this review in
order to summarize and address the advancements in the field of
green synthesis of nanoparticles.
Nanoparticles, on account of its unique physiochemical
properties, have wide applications in agriculture, engineering,
environmental remediation, biotechnology, microbiology,
medicine, electronics, mechanics, optics, and material science [6].
Methods employed thus far, to synthesize nanoparticles, can be
broadly categorised into two. The first category includes the topdown
approach and the second includes the bottom-up approach.
While in top-down approach, bulk materials are reduced to the
nano-dimensions by employing lithographic techniques or etching,
mechanical processes such as high energy ball milling, laser pyrolysis
method, machining, grinding, etc., in the bottom-up approach, the
chemical methods such as gas phase method, hydrothermal method,
sol-gel method etc. are used for the synthesis of nanoparticles from
simple atoms or molecules [7,8]. The bottom-up approach seems
more promising and effective method for synthesis of nanoparticles,
as it provides the options to form nanoparticles of desired shape
and size depending upon the subsequent application by controlling
the precursor concentrations, pH, temperature etc. [6,7].
Need for green synthesis
Various approaches adopted for the synthesis of nanoparticles
have its limitations. The mechanical and physical methods are
not able to give nanoparticles of expected size. Moreover, the
maintenance of high temperature and pressure required during
the synthesis incurs heavy expenditure. The chemical methods
involve use of organic solvents and a range of other chemicals as
capping and reducing agents which are non-ecofriendly, toxic
health hazard and hard to degrade. Commonly used chemicals in
the synthesis process include sodium borohydride and hydrazine
hydrate. This apart, while chemicals like ammonium ions, citric
acid, carbon monoxide, formaldehyde, hydrogen, hydrogen
peroxide, hydroxylamine hydrochloride, sodium carbonate etc.
are used as reducing agents, Cetyltrimethylammonium bromide
(CTAB), Dodecyl amine (DDA), Ethylene diamine tetra acetic acid
(EDTA), Oleic acid, Polyetherimide (PEI), Polyethylene glycol
(PEG), Polyamidation (PAMAM), Polyacrylic acid (PAA) etc. work as
capping agents.
Realizing the serious consequences, the continuous use of
nanoparticles synthesized using physical and chemical methods
can lead to, it became imperative to invent an alternative method(s)
which was least invasive. Of late there has been a resurgence
in efforts in adopting a greener approach toward nanoparticle
synthesis [8,9]. The greener methods (Green chemistry) involve the
use of natural products (plant extracts/ bacterial- fungal extracts)
restricting the use of toxic chemicals to the minimum.
The principles of green chemistry were established in 1998
considering the main objectives to reduce environmental hazards,
and risk to human health with enhanced next generation applications.
Environmentally benign, green method of nanoparticle synthesis is
simple and cost effective with high rate of reproducibility of more
stable material concomitant with low risk of contamination of the
product [8,10]. Furthermore, it is very straightforward to scale up.
Although the green methods of nanoparticle synthesis encompass
the use of various microorganisms (bacteria, fungi, yeast, etc.)
besides the plants, the methods involving exclusively the microbes
(bio-assisted methods) is slow with less reproducibility and offers
limited number of size and shape when compared to routes that use
plant-based active ingredients [8].
The use of plant extracts as the production assembly of various
types of nanoparticles have drawn attention, due to the active
ingredients of plant metabolites like polyphenols, flavonoids,
tannins, saponins, resins, essential oils, terpenes, terpenoids etc.,
which help in conversion of metal ions into nanoparticles by behaving
as reducing and capping agents [11]. The plant extracts provide a
rapid, non-toxic, non-pathogenic, biodegradable and economical
single step technique for the biosynthetic processes involved in
making of various metallic and non-metallic nanoparticles. (Table
1) lists the plants that have facilitated nanoparticle synthesis.
Table 1: Plant mediated green synthesis of silver, gold, iron and copper nanoparticles.
Limitations of plant mediated green synthesis
Although the use of plant extracts as source of nanoparticles
holds promise, there is no clarity about the exact mechanism of
nanoparticle synthesis using plant extracts [8,11]. Here it will be apt
to mention that the plants of the same species occupying varying
habitats vary in their chemical compositions that may lead to
different results and interpretations in different laboratories. This
can be considered as a major limitation associated with plant based
biogenic methods. However, the green method of nanoparticle
synthesis has far more advantages than these minor limitations.
The effect of nanoparticles, whether harmful or advantageous,
depends upon the type and concentration of nanoparticles used as
well as the plant species [11-200].
Uptake and translocation mechanism of nanoparticles in crops
Figure 1: Shows the mechanism of absorption, uptake, transport and penetration of nanoparticles in plants. (A)
Treatment methods of nanoparticles: Foliar spray (Flowers, leaves, hydathodes etc.) and irrigation through roots.
(B) Uptake of nanoparticles is hampered by many barriers such as cuticle, epidermis, endodermis, casparian strips.
Roots hairs on roots, stomata, hydathods and lenticels provide passage to nanoparticles into the plant system.
(C) Nanomaterials can follow the apoplastic,symplastic and or apo-symplastic pathways for moving up and down
the plant (D) Nanoparticles penetrate into the plant cell through several mechanisms such as endocytosis, pore
formation, through plasmodesmata and can be mediated by carrier proteins.
Source: Modified after Pérez-de-Luque [208].
Generally, lateral roots of the plant absorb the nanoparticles
from the soil from where they enter into the vascular system
through the cortex and pericycle of the roots [201]. While the
nanoparticles that are smaller than the pore of the cell wall
passeasily through it [202,203], the larger nanoparticles fail to
penetrate the cell wall of root cells. Instead, the cell wall opening of
flowers, stigmas, hydathodes, and stomata provide an easy passage
to the larger nanoparticles which interfere with the metabolic
pathways of these cells (Figure 1) [204]. A body of data is available
which suggest that nanoparticles move within the plant body by 1)
Binding with ion channel proteins, (2) endocytosis through newly
formed pores, (3) binding with some organic molecule, and/or by
aligning with membrane transporters [205-207]. Nevertheless,
further investigation is required to explain the selectivity and
uptake mechanism of nanoparticles among types of plants, which
is still not very clear.
Mechanistic Interaction of Nanoparticles under abiotic
stress in plants
Plants, owing to their rooted and sedentary nature, cannot
escape unpredictable changes happening within and outside
the lithosphere. Any exposure to stress conditions result in an
outburst of Reactive Oxygen Species (ROS) that cause the oxidative
breakdown of myriad biomolecules central to the structural
integrity of the cell and its photosynthetic machinery/metabolism
[209]. Although plants are fortified with an inbuilt defence
mechanism to overcome the negative effects of stress conditions,
by way of inducing a battery of genes/ proteins into action and/
or by stimulating the production of stress busting molecules like
proline, glycerol, inositol, glycine, trehalose etc., the decline in
overall growth and productivity despite all the defences, more often
than not, get accentuated [210]. While soil salinity and drought lead
to osmotic stress in plants, waterlogging creates hypoxia conditions
for roots which is usually overcome by a shift in starch metabolism
to fermentation that manifests in reduced growth. Similarly, the
presence of heavy metals in soil stimulates the accumulation of
metal chelates, polyphosphates and organic acids which extenuates
the severity of impact, the growth, nevertheless, is affected.
Nanoparticles, owing to various structural/functional
attributes, have the potential to mitigate the disruptive effects
of abiotic stresses on plants by 1) imitating the activities of
antioxidant enzymes that scavenge the ROS [211], 2) by binding to
the heavy metals thereby preventing it from getting incorporated
into the plant system, 3) by improving the rate of photosynthesis
by protecting the photosystems [212], [213], and 4) by alteration
of expression of the genes involved in plant defence responses.
However, the response of plants to nanoparticle types and the
concentration used varied from species to species [214]. This has
opened many avenues to explore a range of nanoparticles that
could help plants overcome the abiotic stress induced barriers. In
the recent times there has been a spate of reports which prove the
potential of nanoparticles in mitigation of abiotic stresses in plants.
(Table 2) sum-up the role of nanoparticles in circumventing abiotic
stresses.
Table 2:Role of nanoparticles in mitigation of abiotic stresses in crop plants.
Salinity stress:Saline soils are physiologically dry soils. High
concentration of salt in soil makes the soil water potential more
negative that reduces the potential gradient between the soil and
the roots. This hampers the uptake by roots that culminates in
the build-up of ionic toxicity and nutritional imbalance in plants.
Besides, vital processes like lipid metabolisms, protein synthesis,
photosynthesis are also affected [215]. Reports are available on the
potential of Si and SiO2 nanoparticles and silicon fertilizer in the
alleviation of salt stress in several plants such as Basil [216]; Tomato
[212,217]; Wheat [218]; Rice [219]; Lentil [220]; Common Bean
[221]; Potato [222,223]; Cucumber [224] etc. A significant increase
in the plant growth, chlorophyll content, proline level, antioxidant
enzyme system, photosynthetic rate and other vital processes,
subsequent to nanoparticle treatment, have been observed.
Silica nanoparticles help in the mitigation of salinity stress by
decreasing the Na+ absorption by different plant tissues. Decreased
levels of Na+ concentration in tissues maintain the osmotic potential
of plants which improves the absorption of water and minerals
from the soil, that stimulates the plant growth and development
under salt stress [225]. In broccoli, use of multiwalled carbon
nanotubes helped in alleviation of salt stress by slight alteration
in plasma membrane properties and aquaporin transduction,
transportation that increased water uptake and net assimilation
of CO2 [226]. Other nanoparticles used effectively in mitigation of
salt stress includes iron nanoparticles in Grapes [227], chitosan in
Tomato [228], Copper oxide in Tomato [229], silver in Wheat [230],
ZnO in Wheat [231], Maghnemite in peppermint [232] etc. which
showed the similar response like silica nanoparticle.
Drought stress:Drought causes wilting of plants. With little or
no water available in the surroundings although some plant species
undergo rolling of leaves to prevent the loss of water by exposing
less leaf surface to dry air, this nevertheless, reduces growth,
vigour and the rate of photosynthesis [233]. Treatment of silicon
in Sorghum and silica nanoparticles in hawthorn (Crataegus sp.)
showed improved drought tolerance. The seedlings of hawthorn
treated with different concentrations of silica nanoparticles,
showed a positive response on photosynthesis, water, proline,
carbohydrate, Malondialdehyde (MDA) and chlorophyll content
[234]. Similarly, treatment of two cultivars of Sorghum with silicon
nanoparticles improved the water uptake by improving shoot to
root ratio in both the cultivars irrespective of their susceptibility
for drought stress [235,236]. The use of silica nanoparticles have
also helped in mitigating the adverse effects of drought stress in
Tomato, Prunus and Cucumis by improving the water uptake and
mineral absorption [212,234,237]. In drought stressed soybean
seeds enhancement in seed germination and shoot to root ratio was
observed upon treatment with ZnO nanoparticles [236].
Due to drought and salinity stress, it becomes difficult to absorb
iron from the soil which is an important micronutrient for the
plants. The deficiency of iron besides causing significant damage
to metabolism, leads to chlorosis in plants. Several studies have
been conducted to reveal the mitigating effects of Fe nanoparticles
under drought stress. Foliar application of iron nanoparticles in
safflower and irrigation of strawberry with solution containing
iron nanoparticles improved the resistance against drought in both
the plants [227,238]. Similar results were obtained when Brassica
napus and sunflower seeds were treated with γ-Fe2O3 (Maghemite
nanoparticles) [239,240]. Promising role of nanoparticles in the
improvement of physicochemical attributes and agronomic traits
under drought conditions have also been recorded in Lentil, Barley,
Soybean and Wheat upon treatment with silver nanoparticles,
multiwalled carbon nanotubes, CeO2 and TiO2 nanoparticles,
respectively [241-244]
Chilling stress:Exposures to very cold temperatures have had
varying effects on the functioning of plants. Freezing temperature
damages the plant cell by distortion of permeability and leakage
of ions from the membrane which reduces the germination of
seeds and the growth of plants [245]. Chilling stress also adversely
affects photosynthesis in plants by damaging rubisco enzyme
and by reducing chlorophyll content, CO2 assimilation and rate
of transpiration [247,248]. It is only the cold tolerant species
that show less damaging effect of chilling [246]. Application of
nanoparticles helps in the alleviation of damaging effects of chilling
stress by (1) decreasing the membrane damage and reducing the
ion leakage [249]; (2) Enhanced production of Rubisco enzyme and
gene expression of chlorophyll binding gene [250], (3) Increasing
ability of chloroplast to immerse light [251], (4) Increasing the
antioxidant enzyme activity [252] and by (5) inhibiting the ROS
production [253]. Application of TiO2 in Chickpea [250,254] and
silver nanoparticles in Arabidopsis [255] increased upregulation
of stress related genes that increased tolerance against cold stress.
Heat Stress:Exposure to high temperatures cause denaturation
of proteins that hinder metabolic processes. Heat stress increases
oxidative stress, which causes degradation of membrane lipids,
leakage of ions, reduced rate of photosynthesis, decreased
chlorophyll content and protein degradation [256,257]. Although,
plants have overcome the harmful effects of elevated temperatures
by the production of molecular chaperones and heat shock proteins
(HSPs), the adverse effects of heat stress persist still in some plants.
The use of nanoparticles like Cerium oxide and TiO2 in Maize
[258,260], Selenium in Tomato [259] and silver nanoparticles
in Wheat [261] improved the tolerance of plants against heat
stress. Application of Selenium, CeO2, TiO2 and multiwalled carbon
nanotubes have been reported to enhance the upregulation of
heat shock proteins such as HSP70 and HSP90 [258,260,262].
Treatment with Spherical Cerium oxide nanoparticles (Nanoceria)
in Arabidopsis reduced the stress caused by light, heat, dark and
chilling conditions [263].
Heavy metal stress and other stresses:Heavy metal stress
disturbs the uptake of nutrients and vital supplements by the
plants. This apart, besides suppressing the activity of the enzyme,
it disturbs the uptake causing reduced plant growth due to the
deficiency of essential nutrients [264]. Presence of heavy metals
in environment cause oxidative stress in plants which degrade
the plant metabolism. Treatment of TiO2 and Al2O3 nanoparticles
in tobacco plants increased the upregulation of miRNA expression
which in result improved the plant tolerance against heavy
metal stress [265,266]. Similarly, while application of silicon
nanoparticles in maize reduced the arsenate toxicity [267], in
Pea and bamboo it reduced chromium toxicity and lead toxicity
respectively [268,269]; SeO2 reduced boron toxicity in Sunflower
[270]; Silver nanoparticles reduced lead and cadmium toxicity in
Moringa [271].
Waterlogging chokes the root system by depleting the oxygen
content of soil. This causes accumulation of carbon dioxide which
ceases germination and growth. Application of silver nanoparticles
in Saffron and Soybean and Al2O3 nanoparticles in Soybean has
improved the corm and seed germination, respectively, and
increased the plant growth under water logging stress [272,273].
Treatment of Cd-telluride quantum dots and silicon nanoparticles
in wheat proved successful in alleviating the UV-B stress by redu
oxidative stress [274,275]. A similar response was observed in
spinach with the treatment of Anatase-TiO2 nanoparticles under
UV-B stress [276,277].
The chemical and physical interaction of nanoparticles with
biological systems such as plants is mainly due to their intrinsic
catalytic reactivity, nano size and large surface area. Generation
of reactive oxygen species (ROS), during the interaction of
nanoparticles with plants under abiotic stress, is a common
phenomenon [260,278]. Besides inducing ROS, nanoparticles have
triggered the upregulation of a number of stress related genes
[211]. Furthermore, it can imitate the antioxidant enzymes and
other signalling molecules that result in transcriptional changes
and alteration in secondary metabolite production. Changes in
the metabolic pathway subsequent to nanoparticle treatment has
improved the tolerance of plants against the stress conditions
[279]. There are very few studies on the effect of nanoparticles
on antioxidant enzymes and their interaction at the molecular
level. Antioxidant enzymes play an important role in the defence
mechanism of plants against all stresses. It helps in the scavenging
of ROS and reactive nitrogen species (RNS) which cause oxidative
stress in biological systems. The commonly present antioxidant
enzymesinclude catalase (CAT), peroxidase (POD), superoxide
dismutase (SOD), ascorbate peroxidase (APX), guaiacol and
glutathione reductase (GR), glutathione peroxidase (GPX) etc.
Application of gold nanoparticles in Brassica juncea [280]; CeO2
nanoparticles in kidney bean [281] and silver nanoparticles
in Spirodela polyrhiza have enhanced the production of these
enzymes [282].
Under stress conditions, the defence system is activated
by signalling network. Calcium ions play a major role in signal
transduction pathway and are called the second messenger.
Stimulus of any kind of stress elevates the level of cytosolic Ca2+
concentration through calcium ion channels which eventually bind
with Ca2+ -binding protein (CaBP) and activate them (Figure 2).
The activated CaBPs directly bind to promoters of specific stress
related genes and causes the repression or induction of their
expression and accordingly, induce tolerance against the stress.
Nanoparticles can imitate Ca2+ ions and bind with the CaBPs. It can
cause overexpression of CaBPs that triggers the activation of plant
defence system through expression of stress related genes [283].
Silver nanoparticles bind with Ca+/Na+ ion pumps via calcium
ion receptors or calcium ion channels and instigate the signaling
cascade in plants [284]. In addition, C60 nanocrystals activates the
Ca+/calmodulin-dependent protein kinase II [285]; cadmium sulfide
QDs induced overexpression of calcium-binding protein CML45 as
well as calcium-dependent protein kinase 23 [286]. These CaBPs
play an important role in the development of resistance in plants
against abiotic stresses [287,288].
Figure 2: Shows the mechanism of action of nanoparticles in plants under stress stimulus. NP- Nanoparticles; CCa2+
ions; CaBPs- Calcium binding proteins; ROS- Reactive oxygen species.
Source: Modified after Khan et al. [283].
Figure 3: Percentage of salinity in coastal water samples.
It has been observed that Nitric Oxide (NO) modulates the
antioxidant gene expression and suppresses the generation of
ROS and eventually reduces lipid peroxidation. Treatment of
nanoparticles can elevate the level of Ca2+ in the cytosol which
induces the synthesis of Nitric oxide (NO). In addition, nanoparticles
can increase the nitrate reductase enzyme activity in plants which
enhances the concentration of NO to activate the immune response
in plants under biotic and abiotic stress conditions [289,290]
Under biotic stress conditions plant induces two types of
resistance (1) Acquired systemic resistance (ASR) via the Salicylic
acid (SA) signaling pathway and (2) induced systemic resistance
(ISR) through the Jasmonic acid (JA) and/or ethylene signaling
pathways [291]. Jasmonates and salicylic acid interact with
hormones such as Auxins, Ethylene, and Gibberellins that regulate
plant growth as well as defense responses to various stresses
[292,293]. Application of Chitosan nanoparticles induces plant
defense response through the SA pathway under biotic stress
[294] and the JA pathway under abiotic stress conditions [295].
In a study the activation of ISR in wheat through JA pathways
with the treatment of TiO2 nanoparticles was reported [296]. In
another study, Chitosan-PVA and Chitosan-PVA + Cu NPs promote
the expression of SOD genes and JA in tomato under salinity stress
[228].
The mechanism of action of nanoparticles is still not well known.
However, it is envisaged that the genomic and proteomic studies can
help in elucidation of the exhaustive mechanism of nanoparticles
under abiotic stress conditions. In a study the modification in the
proteins involved in the metabolism of sulphur in roots of Eruca
sativa following the treatment with silver nanoparticles was
reported [297]. Application of polyvinylpyrrolidone (PVP) coated
silver nanoparticles induced the expression of stress related genes
in Arabidopsis thaliana [298]. The transcriptional response of
this model plant was analyzed by cDNA expression microarrays
which showed the upregulation of 286 genes including metal and
oxidative stress related genes and downregulation of 81 genes
including ethylene signalling pathway. Treatment of TiO2 and Al2O3
nanoparticles on tobacco plants showed the upregulation of miRNA
which playsa significant role in abiotic stresses [265,266].
The proteomic study of rice with the treatment of silver
nanoparticles showed 1) The upregulation of stress related genes,
2) Ca2+ regulation and signalling, 3) Induction of oxidative stress
response pathway, 4) Cell division and cell wall synthesis, 5) Protein
degradation, and 6) Apoptosis [284]. The exposure of ZnO, TiO2, and
fullerene soot in the roots of Arabidopsis thaliana and multiwalled
carbon nanotubes in Tomato resulted in the upregulation of biotic
and abiotic stress related genes [299,300]. Sores et al. reported that
NiO nanoparticles induced oxidative stress in Hordeum while the
treatment of NiO in combination with SiO2 nanoparticles helped in
mitigation of oxidative stress indicating the protective role of SiO2
nanoparticles in abiotic stress [301].
Nanoparticles have emerged as potent tool endowed with
qualities of eliciting the defensive response in plants under stress
conditions. Its small size, large surface area, easy absorbance/
penetration and the ease of finding the target site has given it an
edge over the other conventional methods employed to overcome
stress related problems. The positive response shown by a range of
crop species under varying stress conditions like high salinity [302-
315], presence of heavy metals, extreme temperatures, and drought
conditions, subsequent upon nanoparticle treatment, underpins
the positive role played by the nanoparticles in alleviating stress
induced complications. Although nanoparticles are being widely
used, its mechanism of action is still not yet clear. It is surmised that
any insight gained into the mechanism of nanoparticle action will
be pivotal realizing that agriculture in India contribute about 18
per cent of the GDP while providing employment to more than 50
per cent workforce. A thorough understanding of the mechanism
of nanoparticle action will pave the way for developing new
strategies to tackle a range of stress related problems confronting
the agriculturists.
Dr. Savita- Searching of literature and compilation of data in the
form of tables.
Dr. Anju Srivastava: Editing and expert inputs.
Dr. Reena Jain: Editing and expert inputs.
Dr. Pratap Kumar Pati: Editing and expert inputs.
Dr. K.K. Koul: Editing and expert inputs.
FAO (2009) High level expert forum-how to feed the world in 2050. Economic and Social Development, Food and Agricultural Organization of the United Nations, Italy.
Anbukkarasi V, Srinivasan R, Elangovan N (2015) Antimicrobial activity of green synthesized zinc oxide nanoparticles from Emblica Officinalis. International Journal of Pharmaceutical Sciences Review and Research 33(2): 110-115.
TC P, Mathew L, Chandrasekaran N, Ashok M, Mukherjee A (2010) Biomimetic synthesis of nanoparticles: Science, technology applicability. Biomimetics Learning from Nature.
Kumar N, Vazhacharickal P, Mathew J, Joy J (2015) Synthesis of silver nano particles from neem leaf (Azadirachta indica) extract and its antibacterial activity CIB tech. J Biotechnol 4: 20-31.
Sharma P, Babu PJ, Bora U (2012) Sapindus mukorossi aqueous fruit extract as reducing, capping and dispersing agents in synthesis of gold nanoparticles. Micro Nano Lett 7(12): 1296-1299.
Prabhu SN (2015) Green route synthesis of stable isotropic gold nanoparticles using leaf extract of Curcuma longa and their characterization. Adv Appl Sci Res 6(8): 167-169.
Laokul P, Maensiri S (2009) Aloe vera solution synthesis and magnetic properties of Ni-Cu-Zn ferrite nanopowders. J Optoelectron Adv Mater 11: 857-862.
Gowayed MH, Al Zahrani HSM, Metwali EMR (2017 ) Improving the salinity tolerance in potato (Solanum tuberosum) by exogenous application of silicon dioxide nanoparticles. Int J Agric Biol 19(1): 183-192.
Karami A (2017) Multiwalled carbon nanotubes and nitric oxide modulate the germination and early seedling growth of barley under drought and salinity. Agric Conspec Sci cus 82(4): 331-339.
Gunjan B, Zaidi MGH, Sandeep A (2014) Impact of gold nanoparticles on physiological and biochemical characteristics of brassica juncea. J Plant Biochem Physiol 2(3).
Almutairi ZM (2016) Effect of nano-silicon application on the expression of salt tolerance genes in germinating tomato (Solanum lycopersicum L.) seedlings under salt stress. POJ 9(1): 106-114.
Moshabaki FI, Tahmourespour A, Hoodaji M, Ataabadi M, Mohammadi A (2018) Influence of exopolysaccharide-producing bacteria and SiO2 nanoparticles on proline content and antioxidant enzyme activities of tomato seedlings (Solanumlycopersicum L.) under salinity stress. Polish J Environ Stud 28(1): 153-163.
Emary FE, Amer M(2018) Role of nano-silica in amelioration salt stress effect on some soil properties, anatomical structure and productivity of faba bean (Vicia faba L.) and maize (Zea mays L.) Plants. J Plant Prod 9(11): 955-964.
Professor, Chief Doctor, Director of Department of Pediatric Surgery, Associate Director of Department of Surgery, Doctoral Supervisor Tongji hospital, Tongji medical college, Huazhong University of Science and Technology
Senior Research Engineer and Professor, Center for Refining and Petrochemicals, Research Institute, King Fahd University of Petroleum and Minerals (KFUPM), Dhahran, Saudi Arabia
Interim Dean, College of Education and Health Sciences, Director of Biomechanics Laboratory, Sport Science Innovation Program, Bridgewater State University