Remodeling of root morphology by CuO and ZnO nanoparticles: effects on drought tolerance for plants colonized by a beneficial pseudomonad.

Formulations that include nanosized-CuO and -ZnO are being considered for agricultural applications as fertilizers because they act as sources of Cu or Zn. Currently, few studies of the effects of these nanoparticles (NPs) consider the three way interactions of NPs with the plant plus its microbiome. At doses that produced root shortening by both nanoparticles (NPs), CuO NPs induced proliferation of elongated root hairs close to the root tip and ZnO NPs increased lateral root formation in wheat seedlings (Triticum aestivum). These responses occurred with roots colonized by a beneficial bacterium, Pseudomonas chlororaphis O6 (PcO6), originally isolated from roots of wheat grown under dryland farming in calcareous soils. The PcO6- induced tolerance to drought stress in wheat seedlings was not impaired by the NPs. Rather growth of the PcO6-colonized plants with NPs resulted in systemic increases in expression of genes associated with tolerance to water stress. Increased expression in shoots of other genes related to metal stress was consistent with higher Cu and Zn levels in PcO6-colonized shoots grown with the NPs. The work illustrates that the plants grown with CuO or ZnO NPs showed cross protection for different challenges of metal stress and drought.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author