Agriculture Reference
In-Depth Information
of plants while the soil-material-associated nanomaterials interact with the roots.
Therefore, it is expected that the plants having higher leaf area indexes (LAI) also
have a higher interception potential for air-borne nanomaterials, which in turn in-
crease their entrance into trophic webs. Once the nanomaterials are applied on the
leaf surface, they might penetrate the plants via the bases of trichomes or through
stomatal openings and get translocated to different tissues. Due to stomata obstruc-
tion, the accumulation of nanomaterials in photosynthetic surfaces might provoke
foliar heating which results in alteration of the gas exchange (Da Silva et al.
2006
).
This heating might produce changes in various physiological and cellular functions
of plants (Da Silva et al.
2006
).
5 Nanomaterials for Crop Improvement
5.1 Carbon-Based Nanomaterials
Carbon-based nanomaterials such as single-walled carbon nanotubes (SWCNTs),
multi-walled carbon nanotube (MWCNTs), carbon buckyballs, etc., have found vast
applications in the field of agriculture and food. Canas et al. (
2008
) reported the
effects of functionalized SWCNTs and non-functionalized SWCNTs on root elonga-
tion of six different crop species, such as cabbage (Brassica oleracea), cucumber (Cu-
cumissativus), carrot (Daucuscarota), onion (Allium cepa), lettuce (Lactuca sativa),
and tomato (Solanumlycopersicum). They showed that the root elongation in onion
and cucumber was enhanced by non-functionalized SWCNTs, and the interaction of
both functionalized SWCNTs and non-functionalized SWCNTs with root surface,
resulted in the formation of nanotube sheets on cucumber root surface, without enter-
ing into the roots. However, cabbage and carrot remained unaffected by either form
of nanotubes. Furthermore, functionalized SWCNTs inhibited the root elongation of
lettuce, while tomato was found to be most sensitive to non-functionalized SWCNTs
with significant root length reduction, whereas a positive response has been shown
on the seed germination and growth of tomato plants upon interaction with MW-
CNTs (Khodakovskaya et al.
2009
). They showed that the presence of MWCNTs
increased water uptake by seeds which in turn enhanced the germination process
(Fig.
11.10a
,
b
). Tomato seeds placed on medium with different concentrations of
MWCNTs germinated on the third day, while the tomato seeds placed on regular MS
(Murashige and Skoog) medium did not germinate at that time (Fig.
11.10b
).
Similar positive effects of MWCNTs on seed germination and root growth of
six different crop species—radish (Raphanussativus), rye grass (Loliumperenne),
rape (Brassica napus), lettuce (Lactuca sativa), corn (Zea mays) and cucumber (Cu-
cumissativus)—was also reported (Lin et al.
2007
). Very recently, Remya et al.
(
2010
) also reported the positive effects of both SWCNTs and MWCNTs on the
germination of rice seeds and observed an enhanced germination for seeds germi-
nated in the presence of nanotubes. But, the interaction of different nanomaterials
with plants and their mechanism for genetic and molecular modification of plants
