273
residues of the cell wall and also enhanced the ROS content (Liu et al. 2013).
Graphene has induced intracellular ROS generation and mitochondrial dysfunctioning in A. thaliana cells. Mitochondrial damage and reduced membrane integrity
because of increased ROS generation accounted for cell death on graphene exposure. Actually, increased permeability of the outer mitochondrial membrane has
enhanced outflux of cytochrome c and other apoptogens from the outer chamber. It
has also activated caspases that initiated the process of apoptosis/necrosis (Begum
and Fugetsu 2013).
CeO 2 NPs and In 2 O 3 NPs induced oxidative stress in A. thaliana. However, the
less toxicity of In 2 O 3 NPs as compared to CeO 2 NPs was due to higher expression
of glutathione synthase (GS) genes that are responsible for plant stress management. Hence, plants exposed to In 2 O 3 NPs experienced less oxidative stress as compared to CeO 2 NPs (Ma et al. 2013). ZnO NPs induced H 2 O 2 production and reduced
the level of antioxidant enzymes to induce oxidative stress in P. sativum leaves
(Mukherjee et al. 2014). CeO 2 and TiO 2 induced ROS generation in H. vulgare.
ROS further induced chromatin modification in the root and shoot cells (Mattiello
et al. 2015). Ag NPs induced oxidative stress to reduce the vegetative growth of
C. abyssinica. Transgenic C. abyssinica plants containing bacterial
γ-glutamylecysteine synthase (γ-ECS) were not affected by Ag NP exposure.
Actually, transgenic plants contained more glutathione (GSH) content that detoxified the oxidative stress induced by Ag NPs (Ma et al. 2015). The oxidative stress
induced by NPs may also be plant growth stage-dependent. CeO 2 NPs induced H 2 O 2
generation during the floral growth stage of Brassica rapa. H 2 O 2 generation was not
observed during vegetative growth (Ma et al. 2016). So, increased oxidative stress
is a strong reason for toxic effects of NPs on various plants.
NPs, in addition to inducing toxicity, can also enhance the absorption or accumulation of other toxic pollutants present in soil, water, and air. In such a study,
MWCNTs induced oxidative stress and nutrient imbalance in V. faba seedlings. The
oxidative stress was enhanced when seedlings were exposed to MWCNTs in the
presence of toxic metal, lead, and cadmium. MWCNTs further enhanced the accumulation of lead and cadmium. As a result, the presence of toxic compounds
enhanced the oxidative stress due to MWCNTs as compared to the sole exposure of
MWCNTs (Wang et al. 2014). Ag NPs induced growth inhibition and root damage
in T. aestivum via Ag ions released from NPs. Exposure of NPs altered the level of
proteins mainly involved in primary metabolism and abiotic stress management
(Vannini et al. 2014). ZnO NPs induced oxidative stress mediated inhibition of
F. esculentum growth. The activity of ROS enzyme and antioxidant enzymes was
increased in NP-treated plants (Lee et al. 2013).
NPs Disturbed the Nutritional Status of Plants
CeO 2 NP exposure was found to reduce the nutritional quality of plants. The accumulation of micro- and macronutrients such as iron, prolamin, glutelin, lauric acid,
valeric acid, and starch in grains of NP-treated rice seedlings was significantly
10 Phytoresponse to Nanoparticle Exposure
residues of the cell wall and also enhanced the ROS content (Liu et al. 2013).
Graphene has induced intracellular ROS generation and mitochondrial dysfunctioning in A. thaliana cells. Mitochondrial damage and reduced membrane integrity
because of increased ROS generation accounted for cell death on graphene exposure. Actually, increased permeability of the outer mitochondrial membrane has
enhanced outflux of cytochrome c and other apoptogens from the outer chamber. It
has also activated caspases that initiated the process of apoptosis/necrosis (Begum
and Fugetsu 2013).
CeO 2 NPs and In 2 O 3 NPs induced oxidative stress in A. thaliana. However, the
less toxicity of In 2 O 3 NPs as compared to CeO 2 NPs was due to higher expression
of glutathione synthase (GS) genes that are responsible for plant stress management. Hence, plants exposed to In 2 O 3 NPs experienced less oxidative stress as compared to CeO 2 NPs (Ma et al. 2013). ZnO NPs induced H 2 O 2 production and reduced
the level of antioxidant enzymes to induce oxidative stress in P. sativum leaves
(Mukherjee et al. 2014). CeO 2 and TiO 2 induced ROS generation in H. vulgare.
ROS further induced chromatin modification in the root and shoot cells (Mattiello
et al. 2015). Ag NPs induced oxidative stress to reduce the vegetative growth of
C. abyssinica. Transgenic C. abyssinica plants containing bacterial
γ-glutamylecysteine synthase (γ-ECS) were not affected by Ag NP exposure.
Actually, transgenic plants contained more glutathione (GSH) content that detoxified the oxidative stress induced by Ag NPs (Ma et al. 2015). The oxidative stress
induced by NPs may also be plant growth stage-dependent. CeO 2 NPs induced H 2 O 2
generation during the floral growth stage of Brassica rapa. H 2 O 2 generation was not
observed during vegetative growth (Ma et al. 2016). So, increased oxidative stress
is a strong reason for toxic effects of NPs on various plants.
NPs, in addition to inducing toxicity, can also enhance the absorption or accumulation of other toxic pollutants present in soil, water, and air. In such a study,
MWCNTs induced oxidative stress and nutrient imbalance in V. faba seedlings. The
oxidative stress was enhanced when seedlings were exposed to MWCNTs in the
presence of toxic metal, lead, and cadmium. MWCNTs further enhanced the accumulation of lead and cadmium. As a result, the presence of toxic compounds
enhanced the oxidative stress due to MWCNTs as compared to the sole exposure of
MWCNTs (Wang et al. 2014). Ag NPs induced growth inhibition and root damage
in T. aestivum via Ag ions released from NPs. Exposure of NPs altered the level of
proteins mainly involved in primary metabolism and abiotic stress management
(Vannini et al. 2014). ZnO NPs induced oxidative stress mediated inhibition of
F. esculentum growth. The activity of ROS enzyme and antioxidant enzymes was
increased in NP-treated plants (Lee et al. 2013).
NPs Disturbed the Nutritional Status of Plants
CeO 2 NP exposure was found to reduce the nutritional quality of plants. The accumulation of micro- and macronutrients such as iron, prolamin, glutelin, lauric acid,
valeric acid, and starch in grains of NP-treated rice seedlings was significantly
10 Phytoresponse to Nanoparticle Exposure