Table 5.

Phytotoxic pathways of AgNP on plants.

Plants	Main action of AgNP*	Ref.
Zucchini	Decrease in plant biomass and transpiration.	[7]
Jasmine rice	AgNP trapped in the roots rather than transported to the leaves. Cause leaf cell deformation.	[11]
Wheat	Suppress the photosynthetic activity with a destruction of photosystems. Lead an improper regulation of PSI electron transport.	[14]
Maize	AgNP reduced transpiration and assimilation rate.	[16]
Cabbage	Increase ROS generation, malondialdehyde production, anthocyanin biosynthesis, and decrease chlorophyll content. Induce most of the genes related to secondary metabolism (glucosinolates, anthocyanin) and antioxidant activities.	[19]
Pea	Stimulate the activities of SOD and ascorbate peroxidase while inhibited activities of glutathione reductase and dehydroascorbate reductase. Declined the total ascorbate and glutathione contents and severely damage leaf and root anatomical structures.	[21]
Mung bean	Reduced Total chlorophyll content but increased proline content. Increased H2O2 level and lipid peroxidation levels in roots.	[22]
Turnip	Anthocyanin, malondialdehyde, and hydrogen peroxide levels were increased. ROS production and DNA damage were significantly elevated.	[23]
Wheat	Accumulation of Ag in the shoots. AgNP caused oxidative stress in roots, as indicated by accumulation of oxidized glutathione, and induced expression of a gene encoding a metallothionein involved in detoxification by metal ion sequestration.	[26]
Thale cress	Accumulate in leaves. Disrupt the thylakoid membrane structure and decrease chlorophyll content. Alter the transcription of antioxidant and aquaporin genes, changing the balance between the oxidant and antioxidant systems.	[30]
Wormwood	Enhance secondary metabolites production. Increase total phenolic AND flavonoid contents, antioxidant activity and SOD activity.	[33]
Kinnow	Enhance antioxidant activity and SOD activity. Total phenolic and flavonoid contents were significantly high.	[34]
Pine, Oak	Chloroplasts shape changed from lenticular to round. AgNP-treated oaks contained large starch granules while treated pines exhibit plastoglobules.	[35]
English oak	Disturbances in the shape of plastids, plastoglobules and the starch content of oak leaves. Showed the high degree of mycorrhization.	[36]
Castor bean	Cause an enhanced enzymatic activity of ROS enzymes and phenolic content in seedlings.	[39]
Maize	A significant change in metaxylem count.	[43]
Wheat	Increase in the quantum efficiency of energy trapping in the PSII reaction center. Accumulate in roots of seedlings and translocation to aerial parts.	[51]
Wheat	Proteins related to photosynthesis and protein synthesis increased, while glycolysis, signaling, and cell wall related proteins decreased. Proteins related to redox and mitochondrial electron transport chain also decreased. Glycolysis associated proteins (glyceraldehyde-3-phosphate dehydrogenase) increased, while phosphoenol pyruvate carboxylase decreased.	[52]
Rice	Increase in chlorophyll a and carotenoid contents. A low level of ROS concomitant with decreased amount of lipid peroxidation and H2O2 content.	[61]
Mustard	Improved photosynthetic quantum efficiency and higher chlorophyll contents in leaves. Levels of malondialdehyde and hydrogen peroxide decreased in the seedlings. Reduce ROS levels and decrease proline content.	[62]
Wheat	Morphological changes induced oxidative stress in plant cells as a consequence of the osmotic stress action.	[63]
Scots pine	High concentration inhibited the formation of mycorrhizae. Low concentration increased mycorrhizal colonization and the dry mass of roots.	[64]
Wheat	The wheat variety sensitive to pathogen action, showed a substantial increase in the TBARS contents, while other varieties showed less changes.	[65]
Rice	An enhancement in the activities of the antioxidant enzymes catalase, superoxide dismutase, ascorbate peroxidase, glutathione reductase and glutathione peroxidase generally occurred in primed seedlings.	[66]
Soybean	The abundances of glyoxalase II 3 and fermentation related proteins were time-dependently decreased. The alcohol dehydrogenase 1 and pyruvate decarboxylase 2 genes were downregulated.	[67]
Arabidopsis	AgNP were taken up by the root and primarily localized at the cell wall and intercellular spaces. Auxin accumulation was reduced in the root tips. AgNP inhibited root gravitropism with a reduction in auxin accumulation and expression of auxin receptors.	[68]
Common grass	Increased root and shoot Ag content but inhibited seedling growth. Seedlings fail to develop root hairs, with highly vacuolated and collapsed cortical cells and broken epidermis and root cap.	[69]

Main actions include accumulation in roots and/or leaves, suppression of photosynthesis and/or transpiration, alteration of metabolism and proteomic expression.

Abbreviations: ROS, reactive oxygen species; SOD, superoxide dismutase; TBARS, 2-thiobarbituric acid reactive substances.