Salts affect the interaction of ZnO or CuO nanoparticles with wheat

Abstract

Exposure to nanoparticles (NPs) that release metals with potential phytotoxicity could pose problems in agriculture. The authors of the present study used growth in a model growth matrix, sand, to examine the influence of 5 mmol/kg of Na, K, or Ca (added as Cl salts) and root exudates on transformation and changes to the bioactivity of copper(II) oxide (CuO) and zinc oxide (ZnO) NPs on wheat. These salt levels are found in saline agricultural soils. After 14 d of seedling growth, particles with crystallinity typical of CuO or ZnO remained in the aqueous fraction from the sand; particles had negative surface charges that differed with NP type and salt, but salt did not alter particle agglomeration. Reduction in shoot and root elongation and lateral root induction by ZnO NPs were mitigated by all salts. However, whereas Na and K promoted Zn loading into shoots, Ca reduced loading, suggesting that competition with Zn ions for uptake occurred. With CuO NPs, plant growth and loading was modified equally by all salts, consistent with major interaction with the plant with CuO rather than Cu ions. Thus, for both NPs, loading into plant tissues was not solely dependent on ion solubility. These findings indicated that salts in agricultural soils could modify the phytotoxicity of NPs.

The effects of metallic engineered nanoparticles upon plant systems: An analytic examination of scientific evidence

“…It should be noted that while lateral root induction is related to auxin regulation, this phenomenon is not unique to nanoparticles. Stewart et al (2015)have reported similar findings for ZnO NPs and metal ions.…”

Rhizosphere interactions between copper oxide nanoparticles and wheat root exudates in a sand matrix: Influences on copper bioavailability and uptake

“…The CuONPs were modeled with a finite type IV solid phase of crystalline tenorite, calculated as total mass of CuONPs added initially to the Magenta boxes per volume of solution at the end of the growth period. X‐ray diffraction analysis of the CuONPs showed the patterns typical for a monoclinic structure of tenorite (Stewart et al ). Currently, the stability constant for nanoparticulate tenorite is not reported in the literature.…”

Fortification of micronutrients for efficient agronomic production: a review

“…In a study involving bean, a reduction of the shoot levels of Fe, Mn, and Zn was observed in the presence of CuO NPs, but cotreatment of the CuO NP-exposed plants with ZnO NPs lowered the shoot level of Cu from CuO NPs, likely due to the alleviation by ZnO NPs of the inhibition of Fe reductase activity induced by CuO NPs in the plant . Secondly, as shown in a study with wheat, the induction of lateral root proliferation occurs with certain micronutrients, whether as ions or NPs (Stewart et al 2015 and references therein). These findings indicate the role that ions released from NPs might be playing.…”