261
reduction in biomass of lower leaf, stem, and root was noticed (Antisari et al. 2015).
Likewise, Ag NPs retarded the growth of Brassica campestris and Vigna radiata
plants. Further, transmission electron microscopy evidenced the breakage of the cell
wall on Ag NP exposure (Mazumdar 2014). A comparative study of Ag
+
ion and Ag
NP exposure revealed more toxic effects of NPs on A. thaliana as compared to Ag
+
ions. Ag NP exposure decreased the root length, chlorophyll content, and water
homeostasis of A. thaliana plants. Ag NPs also disturbed the thylakoid structure of
chloroplasts and reduced the transcript expression of antioxidant and aquaporin
genes (Qian et al. 2013). CeO 2 NPs induced oxidative stress and growth inhibition
in A. thaliana. The chlorophyll content of CeO 2 NP-exposed plants was also
reduced. Exposure of In 2 O 3 NPs did not alter the biomass, total chlorophyll, and
antioxidant potential of A. thaliana plants. Only minor root growth inhibition was
observed on exposure of In 2 O 3 NPs (Ma et al. 2013). Si NPs induced chlorosis and
reduction in rosette diameter, biomass, and stem length in A. thaliana (Slomberg
and Schoenfisch 2012).
NP-Induced Oxidative Stress on Plants
The antioxidant potential of plants protects them from internal and external oxidative stress. If NPs disturb the antioxidant potential of plants, their growth and development will be directly or indirectly affected. A few studies reported negative effect
on plant growth mainly due to oxidative stress induced by NPs. In such a study,
graphene exposure induced oxidative stress and inhibited the germination, growth,
and biomass accumulation of cabbage, red spinach, and tomato plants. Interestingly,
graphene showed no ill effect on the growth and development of lettuce plants
(Begum et al. 2011). Exposure of MWCNTs increased the generation of reactive
oxygen species (ROS) in spinach plants. MWCNT-treated plants showed cell damage and alteration in leaf and root anatomy. However, supplementing the plant
growth medium with ascorbic acid, an antioxidant compound was found to alleviate
the oxidative stress induced by MWCNTs (Begum and Fugetsu 2012). Likewise,
graphene oxide sheets induced oxidative stress in V. faba plants (Anjum et al. 2013).
CeO 2 exposure induced oxidative stress and has negative effect on growth of rice
seedlings (Rico et al. 2013a). CeO 2 NP exposure also induced the formation of
ROS. NPs also inhibited the germination and root growth of lettuce (Cui et al.
2014). Graphene exposure was reported to induce apoptosis in T87 A. thaliana cell
lines (Begum and Fugetsu 2013). ZnO NPs have no effect on the shoot growth,
although oxidative stress was induced in leaves of green pea (Pisum sativum).
However, root elongation was induced on ZnO NP exposure (Mukherjee et al. 2014).
10 Phytoresponse to Nanoparticle Exposure
reduction in biomass of lower leaf, stem, and root was noticed (Antisari et al. 2015).
Likewise, Ag NPs retarded the growth of Brassica campestris and Vigna radiata
plants. Further, transmission electron microscopy evidenced the breakage of the cell
wall on Ag NP exposure (Mazumdar 2014). A comparative study of Ag
+
ion and Ag
NP exposure revealed more toxic effects of NPs on A. thaliana as compared to Ag
+
ions. Ag NP exposure decreased the root length, chlorophyll content, and water
homeostasis of A. thaliana plants. Ag NPs also disturbed the thylakoid structure of
chloroplasts and reduced the transcript expression of antioxidant and aquaporin
genes (Qian et al. 2013). CeO 2 NPs induced oxidative stress and growth inhibition
in A. thaliana. The chlorophyll content of CeO 2 NP-exposed plants was also
reduced. Exposure of In 2 O 3 NPs did not alter the biomass, total chlorophyll, and
antioxidant potential of A. thaliana plants. Only minor root growth inhibition was
observed on exposure of In 2 O 3 NPs (Ma et al. 2013). Si NPs induced chlorosis and
reduction in rosette diameter, biomass, and stem length in A. thaliana (Slomberg
and Schoenfisch 2012).
NP-Induced Oxidative Stress on Plants
The antioxidant potential of plants protects them from internal and external oxidative stress. If NPs disturb the antioxidant potential of plants, their growth and development will be directly or indirectly affected. A few studies reported negative effect
on plant growth mainly due to oxidative stress induced by NPs. In such a study,
graphene exposure induced oxidative stress and inhibited the germination, growth,
and biomass accumulation of cabbage, red spinach, and tomato plants. Interestingly,
graphene showed no ill effect on the growth and development of lettuce plants
(Begum et al. 2011). Exposure of MWCNTs increased the generation of reactive
oxygen species (ROS) in spinach plants. MWCNT-treated plants showed cell damage and alteration in leaf and root anatomy. However, supplementing the plant
growth medium with ascorbic acid, an antioxidant compound was found to alleviate
the oxidative stress induced by MWCNTs (Begum and Fugetsu 2012). Likewise,
graphene oxide sheets induced oxidative stress in V. faba plants (Anjum et al. 2013).
CeO 2 exposure induced oxidative stress and has negative effect on growth of rice
seedlings (Rico et al. 2013a). CeO 2 NP exposure also induced the formation of
ROS. NPs also inhibited the germination and root growth of lettuce (Cui et al.
2014). Graphene exposure was reported to induce apoptosis in T87 A. thaliana cell
lines (Begum and Fugetsu 2013). ZnO NPs have no effect on the shoot growth,
although oxidative stress was induced in leaves of green pea (Pisum sativum).
However, root elongation was induced on ZnO NP exposure (Mukherjee et al. 2014).
10 Phytoresponse to Nanoparticle Exposure