(2017) reported the germination and early growth of oak
(Quercus macdougallii) by application of citrate coated two
types of Fe 3 O 4 -NPs. The germination was increased 33%,
and the growth, dry biomass and chlorophyll concentration
were enhanced. The study suggested that NPs treatments
could improve reforestation of threatened forestry species
(Pariona et al. 2017).
The investigation of ZnO and TiO 2 nanomaterial synthesis was attempted to increase the rate of transplant production in eggplant, pepper and tomato. The results showed
the effect of nanomaterials gel-coated seedlings on parameters like mean germination time, and germination coefficient
of variation was reduced. The performance of growing
transplants was efficient for the safer production of transplants by gel-coated nanomaterials on test plants (Younes
et al. 2020).
Increased plant biomass
The effects on hydroponically grown Nigella arvensis L.
by application of engineered aluminum and nickel oxide
(Al 2 O 3 and NiO-NPs) nanoparticles on parameters like
growth, oxidative stress and activities of antioxidants were
investigated by Chahardoli et al. (2020). The less concentrations increased plant biomass, and the high levels of the
test nanoparticles decreased N. arvensis biomass. There was
an increase of enzymatic antioxidants such as ascorbate
peroxidase (APX), catalase (CAT), superoxide dismutase
(SOD) and peroxidase (POD) in roots and shoots. The
parameters like scavenging activity by 2,2-diphenyl-1-picryl
hydrazyl (DPPH), capacity of total antioxidant, reducing
power, iridoids, saponin and phenols in treated plants were
increased by test NPs. The application of NiO-NPs on test
plants inhibited the antioxidant activities, secondary
metabolites formation, total antioxidant capacity, scavenging
activity by DPPH and total saponin content (Chahardoli
et al. 2020).
Effect on plant microbiota
Vitali et al. (2019) explored the poplar (Populus nigra)
plants for the effect of silver nanoparticles (AgNPs) application. The test plant microbiota levels in leaf and root were
evaluated after NP treatment. The results showed increase in
bacteria and fungi in the treated leaf and reduced the bacterial and fungal biodiversity in the root. The study showed
the phyllosphere and rhizosphere poplar-associated microbiota of a tree species from a polluted environment (Vitali
et al. 2019).
Increase in plant root and shoot
The sludge conditioned in soil with single and binary mixture of nanoparticles (Ag 2 O, TiO 2 ) was investigated by
Singh and Kumar (2020a, b) for effect on spinach plants
grown in pot experiments. The Ag 2 O NPs treated plants
showed no growth effects. The root length and fresh weight
were increased in spinach at high concentration of single and
binary mixture of TiO 2 NPs. The binary mixture and TiO 2
increased total chlorophyll content and decreased with
higher tendency of root surface adsorption by Ag 2 O. The
study of single and binary mixture of NPs reported no acute
toxicity in the treated spinach. The spinach leaves grown in
sludge enriched with NPs were found unsafe for consumption due to accumulation of Ag and Ti metals (Singh and
Kumar 2020a, b).
The study assessed the role of nano-zerovalent iron (FeO
nanoparticles) on sunflower (Helianthus annuus) plants
cultivated in soil with hexavalent chromium (Cr IV). The
amelioration of Cr toxicity in sunflower plants by application
of test NPs was evaluated by Mohammadi et al. (2020). The
results revealed that the higher concentration of test
nanoparticles increased plant morphological and physiological parameters and decrease in Cr uptake. The factors like
bioaccumulation (BAF) and translocation (TF) in root and
shoot tissues were reduced. The results of NP-treated plants
under Cr toxicity were found through reduced Cr uptake and
increased activity by SOD, CAT, POX and APX detoxification enzymes (Mohammadi et al. 2020).
Mitigation of chilling stress
The effects on sugarcane leaves treated with NPs of silicon
dioxide (nSiO 2 ), zinc oxide (nZnO), selenium (nSe), graphene nanoribbons (GNRs) as foliar sprays were investigated by Elsheery et al. (2020a, b). The ameliorative effects
of NPs against chilling stress in test plants for photosynthesis
and photoprotection were evaluated. The results of NPs
application reduced the adverse chilling effects in treated
seedlings by the increased PS-II photochemical efficiency
(Fv/Fm), maximum photo-oxidizable PS-I (Pm), photosynthetic gas exchange and the chlorophyll and carotenoid
content. It was proved that among the tested NPs, nSiO 2
showed higher amelioration effects to mitigate chilling stress
in sugarcane (Elsheery et al. 2020a, b).
Improved defenses
The foliar spray of Fe 3 O 4 -NPs on Nicotiana benthamiana
plant was reported for the increased (both dry and fresh)
weights, activation of antioxidants and upregulation of salicylic acid (SA) synthesis. The accumulation of endogenous
SA in test plants conferred the plant resistance against
Tobacco Mosaic Virus (TMV) infection (Cai et al. 2020).
The exposure of tobacco (Nicotiana tabacum) seedlings to
AgNPs and ionic silver was investigated by Stefanic et al.
(2020) for the physiological effects, changes in ultrastructure
Plant Physiological Responses to Engineered Nanoparticles
91
(Quercus macdougallii) by application of citrate coated two
types of Fe 3 O 4 -NPs. The germination was increased 33%,
and the growth, dry biomass and chlorophyll concentration
were enhanced. The study suggested that NPs treatments
could improve reforestation of threatened forestry species
(Pariona et al. 2017).
The investigation of ZnO and TiO 2 nanomaterial synthesis was attempted to increase the rate of transplant production in eggplant, pepper and tomato. The results showed
the effect of nanomaterials gel-coated seedlings on parameters like mean germination time, and germination coefficient
of variation was reduced. The performance of growing
transplants was efficient for the safer production of transplants by gel-coated nanomaterials on test plants (Younes
et al. 2020).
Increased plant biomass
The effects on hydroponically grown Nigella arvensis L.
by application of engineered aluminum and nickel oxide
(Al 2 O 3 and NiO-NPs) nanoparticles on parameters like
growth, oxidative stress and activities of antioxidants were
investigated by Chahardoli et al. (2020). The less concentrations increased plant biomass, and the high levels of the
test nanoparticles decreased N. arvensis biomass. There was
an increase of enzymatic antioxidants such as ascorbate
peroxidase (APX), catalase (CAT), superoxide dismutase
(SOD) and peroxidase (POD) in roots and shoots. The
parameters like scavenging activity by 2,2-diphenyl-1-picryl
hydrazyl (DPPH), capacity of total antioxidant, reducing
power, iridoids, saponin and phenols in treated plants were
increased by test NPs. The application of NiO-NPs on test
plants inhibited the antioxidant activities, secondary
metabolites formation, total antioxidant capacity, scavenging
activity by DPPH and total saponin content (Chahardoli
et al. 2020).
Effect on plant microbiota
Vitali et al. (2019) explored the poplar (Populus nigra)
plants for the effect of silver nanoparticles (AgNPs) application. The test plant microbiota levels in leaf and root were
evaluated after NP treatment. The results showed increase in
bacteria and fungi in the treated leaf and reduced the bacterial and fungal biodiversity in the root. The study showed
the phyllosphere and rhizosphere poplar-associated microbiota of a tree species from a polluted environment (Vitali
et al. 2019).
Increase in plant root and shoot
The sludge conditioned in soil with single and binary mixture of nanoparticles (Ag 2 O, TiO 2 ) was investigated by
Singh and Kumar (2020a, b) for effect on spinach plants
grown in pot experiments. The Ag 2 O NPs treated plants
showed no growth effects. The root length and fresh weight
were increased in spinach at high concentration of single and
binary mixture of TiO 2 NPs. The binary mixture and TiO 2
increased total chlorophyll content and decreased with
higher tendency of root surface adsorption by Ag 2 O. The
study of single and binary mixture of NPs reported no acute
toxicity in the treated spinach. The spinach leaves grown in
sludge enriched with NPs were found unsafe for consumption due to accumulation of Ag and Ti metals (Singh and
Kumar 2020a, b).
The study assessed the role of nano-zerovalent iron (FeO
nanoparticles) on sunflower (Helianthus annuus) plants
cultivated in soil with hexavalent chromium (Cr IV). The
amelioration of Cr toxicity in sunflower plants by application
of test NPs was evaluated by Mohammadi et al. (2020). The
results revealed that the higher concentration of test
nanoparticles increased plant morphological and physiological parameters and decrease in Cr uptake. The factors like
bioaccumulation (BAF) and translocation (TF) in root and
shoot tissues were reduced. The results of NP-treated plants
under Cr toxicity were found through reduced Cr uptake and
increased activity by SOD, CAT, POX and APX detoxification enzymes (Mohammadi et al. 2020).
Mitigation of chilling stress
The effects on sugarcane leaves treated with NPs of silicon
dioxide (nSiO 2 ), zinc oxide (nZnO), selenium (nSe), graphene nanoribbons (GNRs) as foliar sprays were investigated by Elsheery et al. (2020a, b). The ameliorative effects
of NPs against chilling stress in test plants for photosynthesis
and photoprotection were evaluated. The results of NPs
application reduced the adverse chilling effects in treated
seedlings by the increased PS-II photochemical efficiency
(Fv/Fm), maximum photo-oxidizable PS-I (Pm), photosynthetic gas exchange and the chlorophyll and carotenoid
content. It was proved that among the tested NPs, nSiO 2
showed higher amelioration effects to mitigate chilling stress
in sugarcane (Elsheery et al. 2020a, b).
Improved defenses
The foliar spray of Fe 3 O 4 -NPs on Nicotiana benthamiana
plant was reported for the increased (both dry and fresh)
weights, activation of antioxidants and upregulation of salicylic acid (SA) synthesis. The accumulation of endogenous
SA in test plants conferred the plant resistance against
Tobacco Mosaic Virus (TMV) infection (Cai et al. 2020).
The exposure of tobacco (Nicotiana tabacum) seedlings to
AgNPs and ionic silver was investigated by Stefanic et al.
(2020) for the physiological effects, changes in ultrastructure
Plant Physiological Responses to Engineered Nanoparticles
91