235
9.4 Uptake, Bioaccumulation, and Biomagnification
of Nanomaterials in Food
Recently, nanotechnology is incorporated into the agricultural and food industries.
As mentioned before, the current increase in the production and application of
nanomaterials has exposed plants to these materials; therefore, plants, as the first
producers in consumers’ food pyramid, are regarded as the main route of nanoparticles entry into the food chain.
Despite the exposure of plants to the undesirable environmental nanomaterial
pollutants, the application of nanomaterials in the agricultural industry has gained
credit at least in laboratory scales. Nanomaterials, especially nano-fertilizers or pesticides, successfully helped in increasing germination, plant growth and crop quality, photosynthesis enhancement, plant nutrient use efficiency and higher water
uptake inside seeds (Khodakovskaya et al. 2012; Harrison 1996; Nair et al. 2010;
Giraldo et al. 2014; Kottegoda et al. 2011; Milani et al. 2012; Wilson et al. 2008;
Tripathi et al. 2011).
Accumulation and absorption of nanomaterials by plants may affect the food
chain and harm human health. The uptake, accumulation, and transformation of
nanomaterials in food crops are yet ambiguous. Notably, few plant studies have
revealed that the nanomaterials characteristics, plant species, and even experimental
conditions can significantly influence on nanomaterials–plant interactions (Rico
et al. 2011; Monica and Cremonini 2009).
It has been shown that some plants absorb nanomaterials using stomata of leaves,
which are in contact with air and foliar sprays and also their roots. They store them
in their tissues and transfer them to other parts (Ingale and Chaudhari 2018; Anjum
et al. 2016; Dhoke et al. 2013). Following the root uptake and epidermal cell penetration of nanomaterials, further transportation of nanomaterial to the xylem is necessary for their circulation. It seems that three routes are involved in nanomaterial
transportation: (i) cell wall pores, (ii) the apoplastic pathway, or (iii) 40-nm plasmodesmata channels that connect adjacent plant cells, which is called the symplastic
pathway (Luttge 1971; Tilney et al. 1991). The translocation of nanomaterials from
the roots to the plant aerial parts has been studied. Intra- and/or extracellular movement of nanomaterials through tissues brings them to the xylem (Fig. 9.3). Passage
of nanomaterials across the root might not be as simple as we think; it can be
affected by the endodermis cell wall between cortex and stele called Casparian strip
in the root that prevents the apoplastic transport of external materials (Luttge 1971;
Seeger et al. 2009). If this cell-wall incrustation was continuous, the symplastic
pathway is the only way of crossing nanomaterial from the plasma membrane and
reaching the stele; however, root apex or the damaged endodermal cells are the
probable substitute paths for nanomaterials (Tester and Leigh 2001; Nowack and
Bucheli 2007; Wang et al. 2012). Upon getting into the vascular system, the transpiration stream could translocate nanomaterials to the aerial parts of the plant (Lin
et al. 2009).
9 Impact of Nanomaterials on the Food Chain
9.4 Uptake, Bioaccumulation, and Biomagnification
of Nanomaterials in Food
Recently, nanotechnology is incorporated into the agricultural and food industries.
As mentioned before, the current increase in the production and application of
nanomaterials has exposed plants to these materials; therefore, plants, as the first
producers in consumers’ food pyramid, are regarded as the main route of nanoparticles entry into the food chain.
Despite the exposure of plants to the undesirable environmental nanomaterial
pollutants, the application of nanomaterials in the agricultural industry has gained
credit at least in laboratory scales. Nanomaterials, especially nano-fertilizers or pesticides, successfully helped in increasing germination, plant growth and crop quality, photosynthesis enhancement, plant nutrient use efficiency and higher water
uptake inside seeds (Khodakovskaya et al. 2012; Harrison 1996; Nair et al. 2010;
Giraldo et al. 2014; Kottegoda et al. 2011; Milani et al. 2012; Wilson et al. 2008;
Tripathi et al. 2011).
Accumulation and absorption of nanomaterials by plants may affect the food
chain and harm human health. The uptake, accumulation, and transformation of
nanomaterials in food crops are yet ambiguous. Notably, few plant studies have
revealed that the nanomaterials characteristics, plant species, and even experimental
conditions can significantly influence on nanomaterials–plant interactions (Rico
et al. 2011; Monica and Cremonini 2009).
It has been shown that some plants absorb nanomaterials using stomata of leaves,
which are in contact with air and foliar sprays and also their roots. They store them
in their tissues and transfer them to other parts (Ingale and Chaudhari 2018; Anjum
et al. 2016; Dhoke et al. 2013). Following the root uptake and epidermal cell penetration of nanomaterials, further transportation of nanomaterial to the xylem is necessary for their circulation. It seems that three routes are involved in nanomaterial
transportation: (i) cell wall pores, (ii) the apoplastic pathway, or (iii) 40-nm plasmodesmata channels that connect adjacent plant cells, which is called the symplastic
pathway (Luttge 1971; Tilney et al. 1991). The translocation of nanomaterials from
the roots to the plant aerial parts has been studied. Intra- and/or extracellular movement of nanomaterials through tissues brings them to the xylem (Fig. 9.3). Passage
of nanomaterials across the root might not be as simple as we think; it can be
affected by the endodermis cell wall between cortex and stele called Casparian strip
in the root that prevents the apoplastic transport of external materials (Luttge 1971;
Seeger et al. 2009). If this cell-wall incrustation was continuous, the symplastic
pathway is the only way of crossing nanomaterial from the plasma membrane and
reaching the stele; however, root apex or the damaged endodermal cells are the
probable substitute paths for nanomaterials (Tester and Leigh 2001; Nowack and
Bucheli 2007; Wang et al. 2012). Upon getting into the vascular system, the transpiration stream could translocate nanomaterials to the aerial parts of the plant (Lin
et al. 2009).
9 Impact of Nanomaterials on the Food Chain