Agriculture Reference
In-Depth Information
and are in fact ubiquitous in both the biotic and abiotic compartments
of earth
(Banfield, 2005; Blango, 2009). Emerging research is suggest-
ing that many organisms synthesize nanomaterials. Bacteria in sediments
may synthesize electrically conductive pilli, called nanowires, for sensing
neighbors or for transferring electrons and energy (Bargar et al., 2008;
Fredrickson et al., 2006). Bacterial reduction of urantyl, U
6+
(aq), to U
(IV) oxide (uraninite) is an important bioremediation strategy (Bose et al.,
2009; Manceau et al., 2008) found that wetland plants, or their symbionts,
synthesize copper (Cu) nanoparticles in their rooting zone when grown
in contaminated soils, thereby reducing Cu uptake. Dissimilatory metal-
reducing bacteria even respire on iron oxide nanoparticles in anaerobic
environments (Moore, 2006).
9.8
ENTRY OF NANO-PARTICLES INTO PLANTS
Not much research information is available on interaction of NP with
plants. The uptake of many types of NPs in the bacterial cell (prokary-
otes) is very much limited as they do not have mechanisms for transport
of NPs across the cell wall but in eukaryotes, cellular internalization of
NPs occurs through the process of endocytosis and phagocytosis (Obid-
Obid-
zinska, 1998). Because seed coats have pores that exibit selective perme-
1998). Because seed coats have pores that exibit selective perme-
ability, the interaction between particulate constituents and the plant may
be limited until the radicles emerge and come into direct contact with the
growth medium (Wouterlood et al., 2003). However, intracellular spaces
(<10 µm) in seed coat parenchyma may be filled with aqueous media fa-
cilitating the transport of soluble nutrients as well as small particles to the
embryo (Neill et al., 1999). It is unknown whether intracellular uptake is a
requirement for causing phytotoxity or beneficial effects.
Plants are an important component of the ecological system and may
serve as a potential pathway for NPs transport and a route for bioaccumu-
lation into the food chain. Plant cell wall acts as a barrier for easy entry of
any external agent including nano-particles into plants cells. The sieving
properties are determined by pore diameter of cell wall ranging from 5 to
20 nm (Sigg et al., 2008). Hence, only nano-particles or nanoparticle ag-
gregates with diameter less than the pore diameter of the cell wall could
easily pass through and reach the plasma membrane (Obidzinska, 1998;
Xing, 2008). Certain NPs may increase the permeability of plant cell walls
