Phytotoxicity of Metal Oxide Nanoparticles is Related to Both Dissolved Metals Ions and Adsorption of Particles on Seed Surfaces

Abstract

This study assesses the biological effects of nanoparticles (NPs) based on seed germination and root elongation tests. Lettuce, radish and cucumber seeds were incubated with various metal oxide NPs (CuO, NiO, TiO 2 , Fe 2 O 3 , Co 3 O 4), of which only CuO and NiO showed deleterious impacts on the activities of all three seeds. The measured EC 50 for seed germinations were: lettuce seed (NiO: 28 mg/L; CuO: 13 mg/L), radish seed (NiO: 401 mg/L; CuO: 398 mg/L), and cucumber seed (NiO: 175 mg/L; CuO: 228 mg/L). Phytotoxicity of TiO 2 , Fe 2 O 3 and Co 3 O 4 to the tested seeds was not significant, while Co 3 O 4 NP solution (5 g/L) was shown to improve root elongation of radish seedling. Metal oxide NPs tended to adsorb on seed surfaces in the aqueous medium and released metal ions near the seeds. Therefore, metal oxide NPs had higher phytotoxicity than free metal ions of the equivalent concentrations. Further, the surface area-to-volume ratio of seeds may also affect NPs phytotoxicity, whereby small seeds (i.e., lettuce) were the most sensitive to CuO and NiO NPs in our experiments.

The impact of engineered cobalt, iron, nickel and silver nanoparticles on soil bacterial diversity under field conditions

“…When taken collectively, the results of current study clearly indicate that while different NPs migrate through the soil matrix at different rates, their impact on microbial diversity may be dependent on the environmental parameters beyond the properties of the soil. Numerous studies have shown that NPs undergo chemical transformation in the soil including oxidation and ionization [15,[21][22][23]. The environmental parameters directly influence the rate of chemical transformation of NPs [24], and depending on whether the microbial toxicity of NPs is through direct interaction with the cells, indirect mechanisms or combination thereof, the fate determines the impact of NPs on soil microbial community.…”

Phytotoxicity of ionic, micro- and nano-sized iron in three plant species

“…Engineered nanoparticles (ENPs) have a promising use in many areas including catalysis, optics, biology, agriculture, and microelectronics (Wu et al, 2012;Libralato et al, 2013;Corsi et al, 2014;Libralato, 2014;Minetto et al, 2014). Further applications are currently focused on environmental remediation due to their likely performance in contamination removal and toxicity mitigation (Gavaskar et al, 2005;Tratnyek and Johnson, 2006).…”

“…Mushtaq (2011) observed that concentrations of Fe 3 O 4 ENPs within 100-5000 mg/L were able to significantly reduce Cucumis sativus root development compared to controls suggesting the presence of stressing conditions. Phytotoxic effects of Fe 3 O 4 ENPs were assessed in lettuce (Lactuca sativa), radish (Raphanus sativus) and cucumber (C. sativus) (Wu et al, 2012) evidencing median effective concentrations (EC50) of more than 5000 mg/L for lettuce and radish, and of 1682 mg/L for cucumber, respectively. For all species, the germination index was significantly different from standard conditions showing seedling inhibition effects.…”

Effects of Nano Silver Oxide and Silver Ions on Growth of Vigna radiata

“…However, this aspect need to be confirmed experimentally as toxicity varies with seed type, NP type, and exposure conditions. For example, (Ma et al 2010) reported that root growth depends on plant species and nanoparticles types and (Wu et al 2012) showed that toxicity to seeds depend on surface area-to-volume ratio of seeds. Further research is needed to study the uptake during full growth of the plant.…”