and proteomics. The results revealed high toxicity in treated
seedlings due to oxidative stress parameters by ionic Ag than
nanosilver. The root cells showed the presence of silver in
the nanoparticle form. The leaf chloroplasts of treated
plantlets were changed that altered rate of photosynthesis.
The majority of primary metabolism proteins was
up-regulated that helped to cope with silver-induced toxicity
through enhanced energy production and reinforced defense
in treated plants (Stefanic et al. 2020).
Kokina et al. (2020) demonstrated that the five-weeks-old
yellow medick (Medicago falcata L.) plants grown using
hydroponics with Fe 3 O 4 -NPs. The results of treatment
induced increase in root length, chlorophyll a fluorescence in
yellow medick. The parameters that conferred resistance to
powdery mildew disease (fungal) were reduced genome
instability, genotoxicity and expression of miR159c (Kokina
et al. 2020).
Responses of nanoparticles treated paddy
Peng et al. (2020) examined the effects on paddy soil and
rice plants under flooded condition by ZnO, CuO and CeO 2
nanoparticles (NPs) for the bioavailability and translocation.
The results showed that test NPs enhanced redox potential of
paddy soil. The NPs induced the elements (Cu and Ce)
accumulation in rice roots. The Zn concentration in shoots
was high by ZnO-NPs with translocation factor—1.5. The
root cortex accumulated Zn and Cu was accumulated in the
root exodermis in the NPs treated plants (Peng et al. 2020).
Wu et al. (2020) reported hydroponic cultivation of rice
(Oryza sativa L.) seedlings for comparative evaluation of the
metallic (AgO-NPs) and sulfidized (Ag 2 S-NPs) silver
nanoparticles. The test NPs were investigated for iron plaque
formation and effects of silver uptake in seedlings. The
results revealed iron plaque in seedlings and the AgO and
Ag 2 S-NPs bioavailability. The study alarmed concern for the
wetland plants for Ag 2 S-NPs exposure. The high Fe levels
facilitate bioavailability of Ag 2 S-NP in Fe-rich environments
(Wu et al. 2020). The rice seedlings in a hydroponic were
investigated for arsenite (As(III)) or arsenate (As(V)) and
CuO-NPs or Cu(II) accumulation by Wang et al. (2019). Cu
in both forms were found to reduce the total As accumulation, and Cu(II) was more effective than CuO-NPs in rice
tissues. The results proved that nano-enabled agrichemicals
were alternative to conventional metal salts in agriculture for
safe application (Wang et al. 2019).
Zhang et al. (2020a, b) reported on the heavy metals
chemical speciation and micronutrient bioavailability in
paddy soil by TiO 2 -NPs, ZnO-NPs and CuO-NPs by
flooding–drying simulation. The results showed that the NPs
addition increased pH, Eh and electrical conductivity (EC) in
soil. The acid-soluble fraction showed increase in the Zn and
Cu concentrations that led to enhanced bioavailability of test
metals in the soil. The NPs treated soil showed decrease in
Cd bioavailability with the TiO 2 -NPs and increase by ZnO
and CuO-NPs (Zhang et al. 2020a, b). The ZnO-NPs toxicity
in rice seedlings by using sodium nitroprusside (SNP, a NO
donor) was investigated for the regulatory mechanisms of
nitric oxide (NO) in counteracting test NPs toxicity by Chen
et al. (2015). The results showed reduced accumulation of
Zn, production of reactive oxygen species and lipid peroxidation. The test seedlings showed increase in reduced glutathione and activities by peroxidase, catalase and ascorbate
peroxidase. The study provided evidence for NO in amelioration of test NPs phytotoxicity in rice seedlings (Chen
et al. 2015).
The germination and growth of rice (O. sativa L., cv.
Swarna) seedlings were evaluated by Gupta et al. (2018) for
phytostimulatory effect by silver nanoparticles (AgNPs). The
results showed that tested concentrations of NPs promoted
both the shoot and root growth and increased the length and
biomass, phenolic metabolites, chlorophyll-a and carotenoid
contents of seedlings. The study showed changes in activities of catalase (CAT), ascorbate peroxidase (APX) and
glutathione reductase (GR) and gene expression of antioxidative enzymes in seedlings (Gupta et al. 2018).
The study by Zhang et al. (2020a, b) evaluated the phytotoxicity and cadmium (Cd) migration in O. sativa by TiO 2 -
NPs in the soil–rice system. The high Cd content decreased
the height and biomass of test plants and metal enrichment in
paddy soil. The increase in height, biomass and the total
chlorophyll in the leaves was reported at tillering stage. The
booting stage showed reduction of malondialdehyde
(MDA) by 15–32% and the peroxidase (POD) activity 24–
48%. The leaves (booting and heading stage) and the catalase (CAT) activity in the tillering stage were reduced. The
results suggested that Cd migration was found promoted by
TiO 2 -NPs in the soil–rice system (Zhang et al. 2020a, b).
Responses of nanoparticle-treated wheat plants
The wheat (Triticum aestivum L.) plants were investigated
for bioaccumulation and translocation of NPs, growth,
photosynthesis and gas exchange by application of biochar
supplemented with cerium oxide nanoparticles (CeO 2 NPs)
by Abbas et al. (2020). The results indicated that CeO 2 NPs
promoted the plant growth by triggering photosynthesis,
transpiration and stomatal conductance in dose-dependent
manner. The biochar amendment with CeO 2 NPs reduced the
accumulation of Ce and alleviated the phytotoxic effects on
wheat plant growth. The findings proved that NPs
bioavailability to plants could be inhibited by supplementation of biochar (Abbas et al. 2020).
Khan et al. (2020a, b) investigated the wheat (T. aestivum
L.) plant growth and uptake of Cd grown in pot under
ambient conditions in Cd-contaminated soil by Si-NPs at
92
A. A. H. Khan
seedlings due to oxidative stress parameters by ionic Ag than
nanosilver. The root cells showed the presence of silver in
the nanoparticle form. The leaf chloroplasts of treated
plantlets were changed that altered rate of photosynthesis.
The majority of primary metabolism proteins was
up-regulated that helped to cope with silver-induced toxicity
through enhanced energy production and reinforced defense
in treated plants (Stefanic et al. 2020).
Kokina et al. (2020) demonstrated that the five-weeks-old
yellow medick (Medicago falcata L.) plants grown using
hydroponics with Fe 3 O 4 -NPs. The results of treatment
induced increase in root length, chlorophyll a fluorescence in
yellow medick. The parameters that conferred resistance to
powdery mildew disease (fungal) were reduced genome
instability, genotoxicity and expression of miR159c (Kokina
et al. 2020).
Responses of nanoparticles treated paddy
Peng et al. (2020) examined the effects on paddy soil and
rice plants under flooded condition by ZnO, CuO and CeO 2
nanoparticles (NPs) for the bioavailability and translocation.
The results showed that test NPs enhanced redox potential of
paddy soil. The NPs induced the elements (Cu and Ce)
accumulation in rice roots. The Zn concentration in shoots
was high by ZnO-NPs with translocation factor—1.5. The
root cortex accumulated Zn and Cu was accumulated in the
root exodermis in the NPs treated plants (Peng et al. 2020).
Wu et al. (2020) reported hydroponic cultivation of rice
(Oryza sativa L.) seedlings for comparative evaluation of the
metallic (AgO-NPs) and sulfidized (Ag 2 S-NPs) silver
nanoparticles. The test NPs were investigated for iron plaque
formation and effects of silver uptake in seedlings. The
results revealed iron plaque in seedlings and the AgO and
Ag 2 S-NPs bioavailability. The study alarmed concern for the
wetland plants for Ag 2 S-NPs exposure. The high Fe levels
facilitate bioavailability of Ag 2 S-NP in Fe-rich environments
(Wu et al. 2020). The rice seedlings in a hydroponic were
investigated for arsenite (As(III)) or arsenate (As(V)) and
CuO-NPs or Cu(II) accumulation by Wang et al. (2019). Cu
in both forms were found to reduce the total As accumulation, and Cu(II) was more effective than CuO-NPs in rice
tissues. The results proved that nano-enabled agrichemicals
were alternative to conventional metal salts in agriculture for
safe application (Wang et al. 2019).
Zhang et al. (2020a, b) reported on the heavy metals
chemical speciation and micronutrient bioavailability in
paddy soil by TiO 2 -NPs, ZnO-NPs and CuO-NPs by
flooding–drying simulation. The results showed that the NPs
addition increased pH, Eh and electrical conductivity (EC) in
soil. The acid-soluble fraction showed increase in the Zn and
Cu concentrations that led to enhanced bioavailability of test
metals in the soil. The NPs treated soil showed decrease in
Cd bioavailability with the TiO 2 -NPs and increase by ZnO
and CuO-NPs (Zhang et al. 2020a, b). The ZnO-NPs toxicity
in rice seedlings by using sodium nitroprusside (SNP, a NO
donor) was investigated for the regulatory mechanisms of
nitric oxide (NO) in counteracting test NPs toxicity by Chen
et al. (2015). The results showed reduced accumulation of
Zn, production of reactive oxygen species and lipid peroxidation. The test seedlings showed increase in reduced glutathione and activities by peroxidase, catalase and ascorbate
peroxidase. The study provided evidence for NO in amelioration of test NPs phytotoxicity in rice seedlings (Chen
et al. 2015).
The germination and growth of rice (O. sativa L., cv.
Swarna) seedlings were evaluated by Gupta et al. (2018) for
phytostimulatory effect by silver nanoparticles (AgNPs). The
results showed that tested concentrations of NPs promoted
both the shoot and root growth and increased the length and
biomass, phenolic metabolites, chlorophyll-a and carotenoid
contents of seedlings. The study showed changes in activities of catalase (CAT), ascorbate peroxidase (APX) and
glutathione reductase (GR) and gene expression of antioxidative enzymes in seedlings (Gupta et al. 2018).
The study by Zhang et al. (2020a, b) evaluated the phytotoxicity and cadmium (Cd) migration in O. sativa by TiO 2 -
NPs in the soil–rice system. The high Cd content decreased
the height and biomass of test plants and metal enrichment in
paddy soil. The increase in height, biomass and the total
chlorophyll in the leaves was reported at tillering stage. The
booting stage showed reduction of malondialdehyde
(MDA) by 15–32% and the peroxidase (POD) activity 24–
48%. The leaves (booting and heading stage) and the catalase (CAT) activity in the tillering stage were reduced. The
results suggested that Cd migration was found promoted by
TiO 2 -NPs in the soil–rice system (Zhang et al. 2020a, b).
Responses of nanoparticle-treated wheat plants
The wheat (Triticum aestivum L.) plants were investigated
for bioaccumulation and translocation of NPs, growth,
photosynthesis and gas exchange by application of biochar
supplemented with cerium oxide nanoparticles (CeO 2 NPs)
by Abbas et al. (2020). The results indicated that CeO 2 NPs
promoted the plant growth by triggering photosynthesis,
transpiration and stomatal conductance in dose-dependent
manner. The biochar amendment with CeO 2 NPs reduced the
accumulation of Ce and alleviated the phytotoxic effects on
wheat plant growth. The findings proved that NPs
bioavailability to plants could be inhibited by supplementation of biochar (Abbas et al. 2020).
Khan et al. (2020a, b) investigated the wheat (T. aestivum
L.) plant growth and uptake of Cd grown in pot under
ambient conditions in Cd-contaminated soil by Si-NPs at
92
A. A. H. Khan