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Negative Effect on Seed Germination and Root and Shoot Elongation
Roots are the foremost and prime plant tissue that comes in contact with the NPs on
exposure. NPs are initially accumulated in the roots and later transported to various
plant tissues. This process of uptake and transport of NPs can induce several morphological, anatomical, and physiological plant responses.
As mentioned earlier, reduction in plant root length on NP exposure demonstrates their phytotoxicity on plants. Exposure of alumina NPs has been documented
to inhibit the root elongation in maize, Cucumis sativus, Glycine max, Brassica
oleracea, and Daucus carota (Yang and Watts 2005). Nonfunctionalized and poly- 3aminobenzenesulfonic acid-functionalized SWCNTs inhibited the elongation of
tomato and lettuce roots, respectively (Canas et al. 2008). Yb 2 O 3 , Gd 2 O 3 , and La 2 O 3
NP exposure reportedly inhibited the root elongation of lettuce, rape, and wheat
plants. However, CeO 2 NPs hampered the growth of only lettuce roots (Ma et al.
2010). Palladium (Pd), copper (Cu), Si, and Au NPs have also been documented for
root growth retardation in lettuce (Shah and Belozerova 2009). Lanthanum oxide
(La 2 O 3 ) NPs were also reported to induce toxicity to cucumber plants (Ma et al.
2011). Au NPs has also induced leaf necrosis in tobacco plants (Sabo-Attwood et al.
2012). In another study, the seed germination and root elongation of ryegrass and
corn was inhibited in the presence of Zn and ZnO NPs (Lin and Xing 2007).
SWCNTs were found to inhibit the growth of root hair in maize (Yan et al. 2013).
CdS QDs were observed to inhibit the growth and physiology of wild and Ds element expressing mutant A. thaliana plants (Marmiroli et al. 2014).
Fullerene exposure was observed to reduce hypocotyl length and root length of
germinated A. thaliana seedlings. Further, root gravitropism responses of exposed
roots were also inhibited (Liu et al. 2010). Copper oxide (CuO) exposure has
reduced the root length followed by reduced shoot length of P. vulgaris (Dimkpa
et al. 2015). ZnO NP exposure also induced inhibition of seed germination and
growth in rapeseed (Brassica napus). ZnO NPs inhibited the root–shoot elongation
and dry weight of the exposed shoots (Kouhi et al. 2014).
Exposure of Ag NPs was found to reduce the germination and growth of rice
seedlings. Further, the shoot–root growth of NP-exposed seedlings was considerably inhibited (Thuesombat et al. 2014). In a comparative toxicity study, polyvinyl
pyrollidone- and gum arabic-coated Ag NPs inhibited seed germination and vegetative growth of Phytolacca americana (Yin et al. 2012). Ce-coated Ag NPs were
observed to inhibit the growth of P. radiatus and Sorghum bicolour in agar and soil
medium. The phytotoxic responses were lowered when NPs were exposed through
soil (Lee et al. 2012). Cu NPs inhibited the growth of P. radiatus and Triticum aestivum plants. However, growth inhibition was more pronounced in P. radiatus than
in T. aestivum (Lee et al. 2008).
Ag NPs inhibited seedling growth and development of root hairs in Lolium multiflorum (Yin et al. 2011). Fullerenes have inhibited the vegetative growth of tobacco
(Liu et al. 2013). Exposure of Ag NPs was found to prolong the vegetative growth
of A. thaliana plants by 2–3 days, while their reproductive growth was shortened by
3–4 days as compared to untreated plants. The seed germination of treated plants
10 Phytoresponse to Nanoparticle Exposure
Negative Effect on Seed Germination and Root and Shoot Elongation
Roots are the foremost and prime plant tissue that comes in contact with the NPs on
exposure. NPs are initially accumulated in the roots and later transported to various
plant tissues. This process of uptake and transport of NPs can induce several morphological, anatomical, and physiological plant responses.
As mentioned earlier, reduction in plant root length on NP exposure demonstrates their phytotoxicity on plants. Exposure of alumina NPs has been documented
to inhibit the root elongation in maize, Cucumis sativus, Glycine max, Brassica
oleracea, and Daucus carota (Yang and Watts 2005). Nonfunctionalized and poly- 3aminobenzenesulfonic acid-functionalized SWCNTs inhibited the elongation of
tomato and lettuce roots, respectively (Canas et al. 2008). Yb 2 O 3 , Gd 2 O 3 , and La 2 O 3
NP exposure reportedly inhibited the root elongation of lettuce, rape, and wheat
plants. However, CeO 2 NPs hampered the growth of only lettuce roots (Ma et al.
2010). Palladium (Pd), copper (Cu), Si, and Au NPs have also been documented for
root growth retardation in lettuce (Shah and Belozerova 2009). Lanthanum oxide
(La 2 O 3 ) NPs were also reported to induce toxicity to cucumber plants (Ma et al.
2011). Au NPs has also induced leaf necrosis in tobacco plants (Sabo-Attwood et al.
2012). In another study, the seed germination and root elongation of ryegrass and
corn was inhibited in the presence of Zn and ZnO NPs (Lin and Xing 2007).
SWCNTs were found to inhibit the growth of root hair in maize (Yan et al. 2013).
CdS QDs were observed to inhibit the growth and physiology of wild and Ds element expressing mutant A. thaliana plants (Marmiroli et al. 2014).
Fullerene exposure was observed to reduce hypocotyl length and root length of
germinated A. thaliana seedlings. Further, root gravitropism responses of exposed
roots were also inhibited (Liu et al. 2010). Copper oxide (CuO) exposure has
reduced the root length followed by reduced shoot length of P. vulgaris (Dimkpa
et al. 2015). ZnO NP exposure also induced inhibition of seed germination and
growth in rapeseed (Brassica napus). ZnO NPs inhibited the root–shoot elongation
and dry weight of the exposed shoots (Kouhi et al. 2014).
Exposure of Ag NPs was found to reduce the germination and growth of rice
seedlings. Further, the shoot–root growth of NP-exposed seedlings was considerably inhibited (Thuesombat et al. 2014). In a comparative toxicity study, polyvinyl
pyrollidone- and gum arabic-coated Ag NPs inhibited seed germination and vegetative growth of Phytolacca americana (Yin et al. 2012). Ce-coated Ag NPs were
observed to inhibit the growth of P. radiatus and Sorghum bicolour in agar and soil
medium. The phytotoxic responses were lowered when NPs were exposed through
soil (Lee et al. 2012). Cu NPs inhibited the growth of P. radiatus and Triticum aestivum plants. However, growth inhibition was more pronounced in P. radiatus than
in T. aestivum (Lee et al. 2008).
Ag NPs inhibited seedling growth and development of root hairs in Lolium multiflorum (Yin et al. 2011). Fullerenes have inhibited the vegetative growth of tobacco
(Liu et al. 2013). Exposure of Ag NPs was found to prolong the vegetative growth
of A. thaliana plants by 2–3 days, while their reproductive growth was shortened by
3–4 days as compared to untreated plants. The seed germination of treated plants
10 Phytoresponse to Nanoparticle Exposure