Singh and Lee 2016). Salinity or salt stress decreases the
various growth and physiological parameters in Triticum
aestivum which was reversed upon application of NPs
(Shalata et al. 2001; Darko et al. 2017).
TiO 2 -NPs application ultimately improve plant tolerance
to extreme climate events by increasing proline and other
amino acids, nutrients level and water uptake, and activities
of antioxidant enzymes (Ghosh et al. 2010; Ebrahimi et al.
2016). Besides, they might also control expression of
stress-related genes. In a study, cDNA-AFLP analysis performed on two genotypes of chickpea (Sel96Th11439, cold
tolerant, and ILC533, cold susceptible), Amini et al. (2017)
reported an increased level of transcript–derived fragments
(TDF) which control cold tolerance along with defense and
damage indices like electrolyte leakage level in TiO 2 -
NP-treated chickpea during cold stress (4 °C). Overexpression or upregulation of some recognized genes in TiO 2 -
NP-treated plants may be regarded as efficient markers in
adaptation process in Vigna radiata against cold stress.
Plant’s tolerance to stress involves groups of various genes
participated in several metabolism pathways, cellular
defense system, cell signaling, protein synthesis and chromosomal structure. Further, TiO 2 -NPs effectively alleviate
the stress-induced toxicity through changing the levels of
phytochemical production, activation of antioxidants
defense system and stability of plastid pigments. Thus,
application of TiO 2 -NPs suggested to control the damage
due to climate change in fields and to increase crop
productivity.
5 Conclusions and Future Recommendations
Due to wide array of application in various fields, release
and accumulation of TiO 2 -NPs into environment become
unavoidable. Hence, TiO 2 -NPs pollution arises as a potential
threat for ecosystem structure and functioning that resulted
in declining food quality and yield, and health of human
being. In this respect, a comprehensive understanding of
TiO 2 -NPs transfer through the ecosystem and its impacts on
plants is very important.
In the last few years, a large number of studies have been
conducted to understand the phytotoxicity of TiO 2 -NPs and
their interaction to plants; however, there are still some area
which needs to be more explanation.
1. Toxicological studies revealed both the beneficial and
harmful impacts of TiO 2 -NPs on morphological, physiological, cellular and molecular aspects of plants, but
further research is required to provide more information
regarding their uptake, translocation and internalization
in plant cells. These conflicting results point out the
complexity of plants response to TiO 2 -NPs that are not
only vary with TiO 2 -NPs properties (i.e., size, concentration, shape, surface coating size, shape, surface coating, etc.) but are also dependent on the plant species and
its various developmental stages and experimental conditions (type of medium, exposure method, exposure
duration, etc.).
2. A clear understanding about TiO 2 -NPs uptake and
translocation mechanisms, i.e., about how the NPs with
different shapes and size get enter into the cells, how they
translocate from cortex to stelar region, and how they
cross Casparian strips present in endodermal cells, etc.,
are still need more explanation.
3. A number of studies are available related to impacts of
TiO 2 -NPs on plants, but most of these studies are short
period of time and experiments were conducted under
controlled conditions in laboratory settings that are likely
very differ from actual field conditions. Therefore, there
is a need of long-term, well-designed, plant life cycle
experiments to evaluate TiO 2 -NPs impacts on plants
under real field conditions so that their environmentally
relevant implications can be advocated.
4. From the foregoing studies, it is noticed that different
plant species may activate different detoxification
mechanisms in response to TiO 2 -NPs exposure to mitigate its toxicity, however, our knowledge about the role
of ROS as a signaling molecule in plants under TiO 2 -NPs
stress is still in primary stage.
5. In addition, paucity of literature is available on role of
different ‘omics’ methodologies, such as transcriptomics,
proteomics and metabolomics that can give an authentic
data to comprehensively evaluate TiO 2 -NPs toxicity and
tolerance mechanisms in plants.
6. Besides, due to several unique properties, TiO 2 -NPs have
attracted attention for its potential application as a growth
promoter, nanofertilizer, nanopesticides and so on in
agriculture. However, our knowledge regarding TiO 2 -
NPs uptake capacity and its permissible limit is still
sketchy. However, the application of TiO 2 -NPs in agriculture is very new and in its evolving stage and progress
in research is still at bench-top scale. There is an urgent
need to unravel the fate and behavior of TiO 2 -NPs
applications in agriculture to enhance plant growth and
productivity and also to assess unforeseeable risks on
environments.
7. The foreseen potential of TiO 2 -NPs in near future
includes their application for controlled and targeted
release of chemicals or fertilizers, as encapsulated pesticides, as nanosensor and nanoherbicides as well to
develop TiO 2 -NP-based formulations to improve crop
quality and yield by improving resistance/tolerance
against various abiotic as well as biotic stresses under
the present scenario of climate change and to fulfill the
unforeseen demand of food supply.
Interaction of Titanium Dioxide Nanoparticles …
67
various growth and physiological parameters in Triticum
aestivum which was reversed upon application of NPs
(Shalata et al. 2001; Darko et al. 2017).
TiO 2 -NPs application ultimately improve plant tolerance
to extreme climate events by increasing proline and other
amino acids, nutrients level and water uptake, and activities
of antioxidant enzymes (Ghosh et al. 2010; Ebrahimi et al.
2016). Besides, they might also control expression of
stress-related genes. In a study, cDNA-AFLP analysis performed on two genotypes of chickpea (Sel96Th11439, cold
tolerant, and ILC533, cold susceptible), Amini et al. (2017)
reported an increased level of transcript–derived fragments
(TDF) which control cold tolerance along with defense and
damage indices like electrolyte leakage level in TiO 2 -
NP-treated chickpea during cold stress (4 °C). Overexpression or upregulation of some recognized genes in TiO 2 -
NP-treated plants may be regarded as efficient markers in
adaptation process in Vigna radiata against cold stress.
Plant’s tolerance to stress involves groups of various genes
participated in several metabolism pathways, cellular
defense system, cell signaling, protein synthesis and chromosomal structure. Further, TiO 2 -NPs effectively alleviate
the stress-induced toxicity through changing the levels of
phytochemical production, activation of antioxidants
defense system and stability of plastid pigments. Thus,
application of TiO 2 -NPs suggested to control the damage
due to climate change in fields and to increase crop
productivity.
5 Conclusions and Future Recommendations
Due to wide array of application in various fields, release
and accumulation of TiO 2 -NPs into environment become
unavoidable. Hence, TiO 2 -NPs pollution arises as a potential
threat for ecosystem structure and functioning that resulted
in declining food quality and yield, and health of human
being. In this respect, a comprehensive understanding of
TiO 2 -NPs transfer through the ecosystem and its impacts on
plants is very important.
In the last few years, a large number of studies have been
conducted to understand the phytotoxicity of TiO 2 -NPs and
their interaction to plants; however, there are still some area
which needs to be more explanation.
1. Toxicological studies revealed both the beneficial and
harmful impacts of TiO 2 -NPs on morphological, physiological, cellular and molecular aspects of plants, but
further research is required to provide more information
regarding their uptake, translocation and internalization
in plant cells. These conflicting results point out the
complexity of plants response to TiO 2 -NPs that are not
only vary with TiO 2 -NPs properties (i.e., size, concentration, shape, surface coating size, shape, surface coating, etc.) but are also dependent on the plant species and
its various developmental stages and experimental conditions (type of medium, exposure method, exposure
duration, etc.).
2. A clear understanding about TiO 2 -NPs uptake and
translocation mechanisms, i.e., about how the NPs with
different shapes and size get enter into the cells, how they
translocate from cortex to stelar region, and how they
cross Casparian strips present in endodermal cells, etc.,
are still need more explanation.
3. A number of studies are available related to impacts of
TiO 2 -NPs on plants, but most of these studies are short
period of time and experiments were conducted under
controlled conditions in laboratory settings that are likely
very differ from actual field conditions. Therefore, there
is a need of long-term, well-designed, plant life cycle
experiments to evaluate TiO 2 -NPs impacts on plants
under real field conditions so that their environmentally
relevant implications can be advocated.
4. From the foregoing studies, it is noticed that different
plant species may activate different detoxification
mechanisms in response to TiO 2 -NPs exposure to mitigate its toxicity, however, our knowledge about the role
of ROS as a signaling molecule in plants under TiO 2 -NPs
stress is still in primary stage.
5. In addition, paucity of literature is available on role of
different ‘omics’ methodologies, such as transcriptomics,
proteomics and metabolomics that can give an authentic
data to comprehensively evaluate TiO 2 -NPs toxicity and
tolerance mechanisms in plants.
6. Besides, due to several unique properties, TiO 2 -NPs have
attracted attention for its potential application as a growth
promoter, nanofertilizer, nanopesticides and so on in
agriculture. However, our knowledge regarding TiO 2 -
NPs uptake capacity and its permissible limit is still
sketchy. However, the application of TiO 2 -NPs in agriculture is very new and in its evolving stage and progress
in research is still at bench-top scale. There is an urgent
need to unravel the fate and behavior of TiO 2 -NPs
applications in agriculture to enhance plant growth and
productivity and also to assess unforeseeable risks on
environments.
7. The foreseen potential of TiO 2 -NPs in near future
includes their application for controlled and targeted
release of chemicals or fertilizers, as encapsulated pesticides, as nanosensor and nanoherbicides as well to
develop TiO 2 -NP-based formulations to improve crop
quality and yield by improving resistance/tolerance
against various abiotic as well as biotic stresses under
the present scenario of climate change and to fulfill the
unforeseen demand of food supply.
Interaction of Titanium Dioxide Nanoparticles …
67