Agriculture Reference
In-Depth Information
mended with Ag nanoaprticles for the seed germination and root growth of zucchini
plants, showed no negative effects, whereas on prolonging their growth in the pres-
ence of Ag NPs, a decrease in plant biomass and transpiration was observed (Rehm
et al.
1997
).
5.4 Metal Oxide-Based Nanomaterials
5.4.1 ZnO Nanoparticles
Zinc (Zn) is one of the necessary micronutrients required for the optimum growth
of plants. It plays an important role in driving many metabolic reactions within the
plants. Zn is also a part of several other enzymes such as super oxides dismutase
and catalase, which prevent oxidative stress in plant cells. Growth and development
would stop if specific enzymes were not present in the plant tissues (Vitosh et al.
1994
). Important role of Zn can be decided as it controls the synthesis of indole
acetic acid (IAA), a phytohormone which significantly regulates the plant growth.
It also helps in the chlorophyll synthesis and carbohydrate formation (Adiloglu
et al.
2002
) and enables the plants to withstand lower air temperatures. Zn helps
in the biosynthesis of cytochrome, a pigment and maintains the plasma membrane
integrity, and the synthesis of leaf cuticle. Additionally, the enhancement of Zn nu-
tritional status helps in reducing harmful heavy metals uptake which hinders their
toxicity in plants, such as Cd (Pandey et al.
2010
). Pandey et al. (
2010
) studied the
effect of ZnO nanoparticles consisting of oxygen vacancies on the seed germina-
tion and root growth of
C. arietinum
seeds. They observed that due to oxygen
vacancies, the oxygen deficient, i.e., Zn-rich ZnO nanoparticles increased the level
of IAA in roots (sprouts), which in turn indicated the increase in the growth rate
of plants.
Due to the presence of very small quantity of Zn, the amount of Zn utilized
byplant is very less, this ensures a controlled delivery of Zn to the plant, hence the
excess of Zn that may toxicate the plant is avoided. Furthermore, its excess amount
would least spoil the soil quality as ZnO is an eco-friendly and bio-friendly material
which can be used as a green reagent.
5.4.2 TiO
2
Nanoparticles
Owing to its photocatalytic nature, TiO
2
nanoparticles under light are able to generate
an oxidation-reduction reaction, and produce superoxide anion radical and hydrox-
ide (Crabtree et al.
1998
; Hong et al.
2005a
). Photosterilization by TiO
2
nanopar-
ticles improves the growth and development of plants. Hong et al. (
2005b
) reported
the effects of TiO
2
nanoparticles (rutile phase) on the photochemical reaction of
chloroplasts of Spinaciaoleracea. They found that the treatment of TiO
2
nanopar-
ticles enhanced the Hill reaction and chloroplasts activity, which accelerated FeCy
