Agriculture Reference
In-Depth Information
and the properties of growth media as well as the plant species all play important
roles in the altered accumulation of organic compounds by plants.
In addition to the mediation of uptake and accumulation of coexisting environ-
mental organic compounds, Servin et al. (
2012
) showed that TiO
2
NPs increased the
nitrogen content in cucumber root by 51.2 % compared with control cucumber root,
but the nitrogen content in leaf tissues are comparable between control and
TiO
2
NPs-treated plants. These authors also reported that TiO
2
NPs drastically
modified the levels of macro- and micronutrients in cucumber fruits (Servin
et al.
2013
). For example, treatment of cucumber with 500 mg/L of TiO
2
NPs
increased the potassium content by 35 % and phosphorous content by 34 % in
cucumber seedlings. Jacob et al. (
2013
) also reported that plant uptake of
micronutrients such as Mn and Mg in nutrient solution coexisted with TiO
2
NPs
was altered due to the presence of TiO
2
NPs.
14.6 Future Perspectives
With the continuing exploration and applications of ENMs in agricultural industry
and many other industries in society, it is reasonable to anticipate that the chances
for agricultural crops to encounter ENMs will continually increase in the future.
However, ENMs in the actual environment is not expected to reach the levels used
in most lab studies in the foreseeable future. But these ENMs will linger in the
environment for a long time and affect not only the earlier stages of agricultural
crops (e.g., seed germination, root elongation) but will likely affect the whole
growth stages of these crops and even many generations of plant development if
the sources are not removed. Therefore, it remains essential to understand how
environmentally relevant concentrations of ENMs will affect the long-term growth
of agricultural crops and what are the subsequent implications for our food security.
Uptake and accumulation of ENMs by agricultural crops, especially the edible
tissues, is always a concern which needs to be explicitly addressed. Current
technologies are insufficient to tackle the challenges raised by ENMs. For example,
most microscopic imaging techniques only allow qualitative investigation on a tiny
fraction of plant tissues, which are often not representative of the whole plant
tissues. In addition, these techniques have high detection limits, requiring the
exposure of plants to unrealistically high concentrations. While tissue extraction
techniques such as ICP-MS or ICP-OES allow quantitative determination of metal-
lic ENMs, detailed information on the state and localization of ENMs in plant
tissues is lost after the acid extraction. For nonmetallic ENMs such as CNTs,
quantitative determination on plant tissues is still elusive. A recent publication
concerning the analysis of CNTs in plant root tissues with microwave-assisted
temperature measurement is a welcome development for CNT analysis (Irin
et al.
2012
); however, a long way is still ahead. Techniques or a combination of
techniques which allow mass analysis of ENMs in plant tissues at relatively low
