Agriculture Reference
In-Depth Information
2.3 Potential Fate and Effects of Nanotechnology
in Fertilizer Inputs
As the applications of nanotechnology become more and more ubiquitous, the
toxicity and the environmental impact of these novel materials must be addressed.
In the case where nanomaterials will be intentionally applied, as in the case with
nanofertilizers, it is particularly important to understand their fate and effects. As
farm crops serve as a potential pathway for nanoparticle transport and a route of
bioaccumulation into the food chain, studies on the effects of nanoparticles on
plants are needed. Information on whether nanoparticles will bioaccumulate in
plants up through the food chain and end up in higher-level organisms, however,
is limited. A recent review examined potential uptake, translocation, and biotrans-
formation pathways for nanoparticles in plant systems as well as the positive and
negative effects observed in a variety of food crops (Rico et al.
2011
). In contrast to
the studies showing that nanoparticles can be used to boost plant growth, there are a
number of studies that report on the negative impacts of nanoparticles on higher
plants. Recent studies on silver nanoparticle-amended sand have demonstrated a
disruption in the growth of wheat plants (Dimkpa et al.
2013
). Phytotoxicity studies
of nanoscale alumina (nano-Al
2
O
3
) powders indicated that uncoated alumina par-
ticles could inhibit root elongation in crops such as corn, cucumber, soybean,
cabbage, and carrot, while coated particles showed less of an effect (Yang and
Watts
2005
). High concentration of nanosized iron oxide particles inhibited
Zea
mays
growth (R˘cuciu and Creang˘
2007
). In another study, the effects of five types
of nanoparticles (multiwalled carbon nanotubes, aluminum, aluminum oxide, zinc,
and zinc oxide) on seed germination and root growth of radish, rapeseed, ryegrass,
lettuce, corn, and cucumber were examined (Lin and Xing
2007
). At concentrations
of 2,000 mg/L, nano-Zn was found to inhibit seed germination in ryegrass, while
nano-ZnO negatively affected corn. The same concentrations of those two
nanoparticles terminated root elongation in all tested plant species. Nano-Al
2
O
3
was shown to have a modest effect on root growth for corn. Nano-Al promoted root
growth in radish and rapeseed but significantly retarded growth in ryegrass and
lettuce. Recently, the effects of colloidal suspensions of clay or titanium dioxide
nanoparticles on hydroponic maize seedlings were investigated. It was found that
nanoparticle accumulation at the root surface led to rapid partial inhibition of cell-
wall pore size, leaf growth, water transport, and transpiration (Asli and Neumann
2009
). Unlike carbon nanotube studies presented in Sect.
2.2
, negative effects on
root elongation were observed in tomato, cabbage, carrot, and lettuce exposed to
carbon nanotubes (Canas et al.
2008
). Another study looked at the uptake and
translocation of zinc oxide nanoparticles in a hydroponic ryegrass system. ZnO
nanoparticles (20
5 nm) were found in the endodermal and vascular cells of the
ryegrass root. Ryegrass exposed to the nanoparticles had significantly reduced
biomass, shrunken root tips, and collapsed root epidermal and cortical cells (Lin
and Xing
2008
). In other cases, no effect could be observed despite nanoparticle
accumulation. For example, pumpkin plants (
Cucurbita maxima
) were chosen for a
