magnetite in epidermal cell wall via apoplastic route. Fairly large quantities of magnetite
in the range of 2.01–8.07 mg g
À1 iron were found in wheat roots. Since no paramagnetic
signal was detected in stem and leaves, it suggested that nanoparticles were not
translocated through vascular tissues. Nanoparticle penetration into the roots of wheat
seedlings have been facilitated by 2–10 nanometer average citrate-coated magnetite
nanoparticles, favoring nanoparticle uptake by plants. Nanoparticle uptake might be
enhanced by the enlargement of existing pores, induction of new cell wall pores,
internalization during endocytosis in the plasma membrane, or crossing the cell membrane using transport carrier proteins or through ion channels (López-Luna et al. 2016).
5.3 Seed Germination, Growth and Development
Nanoparticle containing essential metals is considered in formulations of fertilizers
to enhance nutrient absorption in plants with low metal bioavailability. Carbon
nanotubes have acquired an important position due to unique mechanical, electrical,
thermal, and chemical properties. Carbon nanotubes act as nanotransporters for
delivery of DNA and dye molecules into plants cells (Srinivasan and Saraswathi
2010). However, in various studies researchers have reported that multi-walled
carbon nanotubes have a unique potential to influence the seed germination and
plant growth. Multi-walled carbon nanotubes induce the water and essential calcium
and iron nutrient uptake efficiency that could enhance the seed germination and plant
growth and development (Villagarcia et al. 2012; Tiwari et al. 2014). Miralles et al.
(2012) demonstrated that industrial-grade multi-walled carbon nanotubes enhanced
germination and root elongation of wheat. Remarkably, carbon nanotubes were
adsorbed onto the root surfaces of wheat without significant uptake or translocation.
In another study, Tripathi and Sarkar (2014) noticed that water-soluble carbon
nanotubes inside the wheat plants were able to induce the root and shoot growth in
light and dark conditions. Hu and Zhou (2014) reported a novel and biocompatible
hydrated graphene ribbon could promote germination of wheat seed and enhance
resistance to oxidative stress. The metabolomics analysis indicated that hydrated
graphene ribbon could upregulate carbohydrate, amino acid, and fatty acid metabolism that determined secondary metabolism, nitrogen sequestration, cell membrane
integrity, permeability, and oxidation resistance.
Titanium dioxide nanoparticles are promising as efficient nutrient source for
plants to improve biomass production due to enhanced nitrogen assimilation, photoreduction activities of photosystem II and electron transport chain, and scavenging
of reactive oxygen species (Lyu et al. 2017; Raliya et al. 2015; Morteza et al. 2013).
The exposure of wheat plant to titanium dioxide nanoparticles causes enhancement
in root elongation without influencing seed germination, vegetative growth, and
photosynthesis. These are short-term effects of titanium dioxide nanoparticles, but
during the whole cycle of the plant, it may have some adverse effect (Larue et al.
2012b). Mahmoodzadeh and Aghili (2014) showed that a titanium dioxide nanoparticle at its optimal concentration has a stimulating effect, and high concentrations
170
P. L. Kashyap et al.
in the range of 2.01–8.07 mg g
À1 iron were found in wheat roots. Since no paramagnetic
signal was detected in stem and leaves, it suggested that nanoparticles were not
translocated through vascular tissues. Nanoparticle penetration into the roots of wheat
seedlings have been facilitated by 2–10 nanometer average citrate-coated magnetite
nanoparticles, favoring nanoparticle uptake by plants. Nanoparticle uptake might be
enhanced by the enlargement of existing pores, induction of new cell wall pores,
internalization during endocytosis in the plasma membrane, or crossing the cell membrane using transport carrier proteins or through ion channels (López-Luna et al. 2016).
5.3 Seed Germination, Growth and Development
Nanoparticle containing essential metals is considered in formulations of fertilizers
to enhance nutrient absorption in plants with low metal bioavailability. Carbon
nanotubes have acquired an important position due to unique mechanical, electrical,
thermal, and chemical properties. Carbon nanotubes act as nanotransporters for
delivery of DNA and dye molecules into plants cells (Srinivasan and Saraswathi
2010). However, in various studies researchers have reported that multi-walled
carbon nanotubes have a unique potential to influence the seed germination and
plant growth. Multi-walled carbon nanotubes induce the water and essential calcium
and iron nutrient uptake efficiency that could enhance the seed germination and plant
growth and development (Villagarcia et al. 2012; Tiwari et al. 2014). Miralles et al.
(2012) demonstrated that industrial-grade multi-walled carbon nanotubes enhanced
germination and root elongation of wheat. Remarkably, carbon nanotubes were
adsorbed onto the root surfaces of wheat without significant uptake or translocation.
In another study, Tripathi and Sarkar (2014) noticed that water-soluble carbon
nanotubes inside the wheat plants were able to induce the root and shoot growth in
light and dark conditions. Hu and Zhou (2014) reported a novel and biocompatible
hydrated graphene ribbon could promote germination of wheat seed and enhance
resistance to oxidative stress. The metabolomics analysis indicated that hydrated
graphene ribbon could upregulate carbohydrate, amino acid, and fatty acid metabolism that determined secondary metabolism, nitrogen sequestration, cell membrane
integrity, permeability, and oxidation resistance.
Titanium dioxide nanoparticles are promising as efficient nutrient source for
plants to improve biomass production due to enhanced nitrogen assimilation, photoreduction activities of photosystem II and electron transport chain, and scavenging
of reactive oxygen species (Lyu et al. 2017; Raliya et al. 2015; Morteza et al. 2013).
The exposure of wheat plant to titanium dioxide nanoparticles causes enhancement
in root elongation without influencing seed germination, vegetative growth, and
photosynthesis. These are short-term effects of titanium dioxide nanoparticles, but
during the whole cycle of the plant, it may have some adverse effect (Larue et al.
2012b). Mahmoodzadeh and Aghili (2014) showed that a titanium dioxide nanoparticle at its optimal concentration has a stimulating effect, and high concentrations
170
P. L. Kashyap et al.