nutrients by ENPs-based nano-fertilizers leads to prevention
of eutrophication and water pollution.
3.3 Mode of Action of Nutrient Delivery
Engineered nanoparticles-based nano-fertilizers have been
shown to be adaptable to foliar application. It is considered
as one of the best methods to rectify the nutrient deficiencies,
to increase the quality and yield of crops and also to minimize
the environmental pollution. Conventional fertilizers faced
several barriers, when applied through foliar method, such as
the penetration into the inner tissue becomes difficult, due to
the pore size of cell wall that ranges between 5 and 20 nm.
The nano-coated fertilizers enhance the penetration via
stomata. Nanoparticles having diameter less than the cell wall
pore size can easily enter through it and reach up to the
plasma membrane (Mahil and Kumar 2019). The nanoparticles applied through foliar method get easily transported to
the heterotrophic cells from the site of application, through
the plasmadesmata (having diameter of 40 nm) (Etxeberria
et al. 2016). The uptake of nanoparticles is done by binding to
carrier protein aquaporin, ion channels and endocytosis.
Nanoparticles can also enter the plant cell wall by forming
complexes with membrane transporters (Rico et al. 2011).
Hong et al. (2014) observed that CeO 2 nanoparticles can enter
from atmosphere into the leaf stomata in cucumber leaves,
followed by their redistribution to different parts of the plant
(Hong et al. 2014). Similarly, calcium oxide nanoparticles
were also observed to enter plant cell wall through phloem
tissue of groundnut. On the other hand, nanoparticles are
found in phloem tissues in wheat plants as investigated by
transmission electron microscope (TEM). In Vicia faba,
polymeric nanoparticles of 43 nm diameter were found to
penetrate through stomatal leaf pores, whereas the particles of
1.1 µm were not able to penetrate. These results were obtained
with the help of confocal microscopy by Eichert et al. (2008).
Another group led by Wang et al. (2013) utilized watermelon
plant having large stomata and vessels to study the effect of
several nanoparticles such as TiO 2 , MgO, Fe 2 O 3 and ZnO.
These nanoparticles initially had diameter of 27.3–46.7 nm,
which increased remarkably in the suspension but reduced
during the spraying treatment. They observed that those
nanoparticles can easily penetrate the stomata, whose size
does not exceed 100 nm, from where they are redistributed to
stems via the phloem sieve elements (Wang et al. 2013). After
entering the plant system, nanoparticles move from one cell to
another through plasmodesmata and are carried by aquaporins, ion channels or endocytosis (Mahil and Kumar 2019).
3.4 Types and Applications of Engineered
Nanoparticles-Based Nano-fertilizers
Engineered nanoparticles-based nano-fertilizers can be
classified into macronutrient, micronutrient and non-nutrient
nano-fertilizers based on the requirements of different
nutrients by plants.
3.4.1 Macronutrient Engineered Nanoparticles
Nano-fertilizers
This type of ENPs-based nano-fertilizers have the potential
to fulfil the requirement of large amount of nutrients by
plants, such as N, P, K, Mg, Ca and S. Nano-fertilizers help
in decreasing the loss of nitrogen due to leaching, emissions
and soil microorganisms. These nanoparticles are also efficient in decreasing the toxic effects caused by the overuse of
chemical fertilizers (Vishwakarma et al. 2018). Nanoenabled urea-modified hydroxyapatite and urea-coated zeolite chips were utilized to achieve controlled release of
macronutrients (Chhipa 2017). A nanocomposite of ureamodified hydroxyapatite efficiently releases nitrogen under
pressure into Gliricidia sepium. It was observed that this
nanocomposite release approximately 78% more nitrogen, as
compared to conventional fertilizer. The slow release of
nitrogen results in the increased uptake efficiency, which
further lead to remarkably improved plant yield (Kottegoda
et al. 2011). Another macronutrient nanocomposite involving urea-hydroxyapatite nanohybrid (6:1) with carbonyl and
amine functional groups was used for slow release of
nitrogen (Kottegoda et al. 2017). The foliar application of
NPK-nano-chitosan composite onto wheat significantly
results into shortened plant lifecycle and enhanced grain
yield in comparison to conventional fertilizers (Aziz et al.
2016). The effect of P-K-Fe nano-fertilizer was investigated
on saffron plants grown on a silty-loam soil. This
nano-fertilizer results into increased dry biomass, when
exposed through the leaves (Amirnia et al. 2014).
Nano-CaCO 3 increases the water-content and dry biomass, when applied to Vigna mungo. Similarly, the foliar
application of nano-CaO onto peanuts enhances the accumulation of Ca and development of plant roots relative to
bulk CaO and CaNO 3 (Adisa et al. 2019). The extensive use
of conventional fertilizers results into increased accumulation of N, P, K, Mg, Ca and S, which is extremely harmful
for agro-ecosystems. These macronutrients cause pollution,
when enter the water body. The use of ENPs-based
nano-fertilizers diminish the overall environmental pollution, with benefits of increased crop yield via direct delivery,
and targeted release of nutrients.
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N. Sarkar et al.
of eutrophication and water pollution.
3.3 Mode of Action of Nutrient Delivery
Engineered nanoparticles-based nano-fertilizers have been
shown to be adaptable to foliar application. It is considered
as one of the best methods to rectify the nutrient deficiencies,
to increase the quality and yield of crops and also to minimize
the environmental pollution. Conventional fertilizers faced
several barriers, when applied through foliar method, such as
the penetration into the inner tissue becomes difficult, due to
the pore size of cell wall that ranges between 5 and 20 nm.
The nano-coated fertilizers enhance the penetration via
stomata. Nanoparticles having diameter less than the cell wall
pore size can easily enter through it and reach up to the
plasma membrane (Mahil and Kumar 2019). The nanoparticles applied through foliar method get easily transported to
the heterotrophic cells from the site of application, through
the plasmadesmata (having diameter of 40 nm) (Etxeberria
et al. 2016). The uptake of nanoparticles is done by binding to
carrier protein aquaporin, ion channels and endocytosis.
Nanoparticles can also enter the plant cell wall by forming
complexes with membrane transporters (Rico et al. 2011).
Hong et al. (2014) observed that CeO 2 nanoparticles can enter
from atmosphere into the leaf stomata in cucumber leaves,
followed by their redistribution to different parts of the plant
(Hong et al. 2014). Similarly, calcium oxide nanoparticles
were also observed to enter plant cell wall through phloem
tissue of groundnut. On the other hand, nanoparticles are
found in phloem tissues in wheat plants as investigated by
transmission electron microscope (TEM). In Vicia faba,
polymeric nanoparticles of 43 nm diameter were found to
penetrate through stomatal leaf pores, whereas the particles of
1.1 µm were not able to penetrate. These results were obtained
with the help of confocal microscopy by Eichert et al. (2008).
Another group led by Wang et al. (2013) utilized watermelon
plant having large stomata and vessels to study the effect of
several nanoparticles such as TiO 2 , MgO, Fe 2 O 3 and ZnO.
These nanoparticles initially had diameter of 27.3–46.7 nm,
which increased remarkably in the suspension but reduced
during the spraying treatment. They observed that those
nanoparticles can easily penetrate the stomata, whose size
does not exceed 100 nm, from where they are redistributed to
stems via the phloem sieve elements (Wang et al. 2013). After
entering the plant system, nanoparticles move from one cell to
another through plasmodesmata and are carried by aquaporins, ion channels or endocytosis (Mahil and Kumar 2019).
3.4 Types and Applications of Engineered
Nanoparticles-Based Nano-fertilizers
Engineered nanoparticles-based nano-fertilizers can be
classified into macronutrient, micronutrient and non-nutrient
nano-fertilizers based on the requirements of different
nutrients by plants.
3.4.1 Macronutrient Engineered Nanoparticles
Nano-fertilizers
This type of ENPs-based nano-fertilizers have the potential
to fulfil the requirement of large amount of nutrients by
plants, such as N, P, K, Mg, Ca and S. Nano-fertilizers help
in decreasing the loss of nitrogen due to leaching, emissions
and soil microorganisms. These nanoparticles are also efficient in decreasing the toxic effects caused by the overuse of
chemical fertilizers (Vishwakarma et al. 2018). Nanoenabled urea-modified hydroxyapatite and urea-coated zeolite chips were utilized to achieve controlled release of
macronutrients (Chhipa 2017). A nanocomposite of ureamodified hydroxyapatite efficiently releases nitrogen under
pressure into Gliricidia sepium. It was observed that this
nanocomposite release approximately 78% more nitrogen, as
compared to conventional fertilizer. The slow release of
nitrogen results in the increased uptake efficiency, which
further lead to remarkably improved plant yield (Kottegoda
et al. 2011). Another macronutrient nanocomposite involving urea-hydroxyapatite nanohybrid (6:1) with carbonyl and
amine functional groups was used for slow release of
nitrogen (Kottegoda et al. 2017). The foliar application of
NPK-nano-chitosan composite onto wheat significantly
results into shortened plant lifecycle and enhanced grain
yield in comparison to conventional fertilizers (Aziz et al.
2016). The effect of P-K-Fe nano-fertilizer was investigated
on saffron plants grown on a silty-loam soil. This
nano-fertilizer results into increased dry biomass, when
exposed through the leaves (Amirnia et al. 2014).
Nano-CaCO 3 increases the water-content and dry biomass, when applied to Vigna mungo. Similarly, the foliar
application of nano-CaO onto peanuts enhances the accumulation of Ca and development of plant roots relative to
bulk CaO and CaNO 3 (Adisa et al. 2019). The extensive use
of conventional fertilizers results into increased accumulation of N, P, K, Mg, Ca and S, which is extremely harmful
for agro-ecosystems. These macronutrients cause pollution,
when enter the water body. The use of ENPs-based
nano-fertilizers diminish the overall environmental pollution, with benefits of increased crop yield via direct delivery,
and targeted release of nutrients.
156
N. Sarkar et al.