The effect of nanoparticles on soil and rhizosphere bacteria and plant growth in lettuce seedlings

Nanomaterials are increasingly being considered for use in agricultural applications, where they have been suggested for a range of uses including fertilizer and pesticide applications. Among nanomaterial applications, agricultural use has a particularly high likelihood of introducing significant quantities of nanomaterials to the environment. The focus of this work was on conducting preliminary experiments examining how nanomaterials might influence rhizosphere bacteria, and in turn influence plant growth. For this work, buttercrunch lettuce seeds were grown in the presence of suspensions of three different nanoparticles. Two of the studied nanomaterials, amine-modified polystyrene nanospheres and titanium dioxide nanoparticles, caused significant decreases in both rhizosphere bacterial counts and plant root and stem growth. In contrast, sulfate-modified polystyrene nanospheres actually increased rhizosphere bacterial counts, but had no significant impact on growth. Only the amine-modified polystyrene nano spheres were found to attach to root surfaces, suggesting that nanomaterial attachment to root surfaces is not a requirement for hindered plant growth. It was hypothesized that attachment of amine-modified polystyrene and TiO2 nanomaterials to bacteria themselves could be changing the bacteria surface properties, and ultimately reducing bacterial affinity for root surfaces. (C) 2019 Elsevier Ltd. All rights reserved.