title: Effect of zinc oxide (ZnO) nanoparticles on physiology and steviol glycosides production in micropropagated shoots of Stevia rebaudiana Bertoni.
abstract: This study aims to address the effects of different concentrations (0, 0.1, 1.0, 10, 100 or 1000 mg L-1) of engineered zinc oxide (ZnO) nanoparticles (34 nm in size) on growth parameters, steviol glycosides (rebaudioside A and stevioside) production and antioxidant activities in the tissue culture grown shoots of Stevia rebaudiana Bertoni. The highest percentage of shoot formation (89.6%) at 1 mg L-1of ZnO nanoparticles concentration suggests a positive influence of ZnO nanoparticles on S. rebaudiana growth as compared to other treatments with or without ZnO nanoparticles. Additionally, HPLC results illustrate a significant enhancement of steviol glycosides (almost doubled as compared to the control) in micropropagated shoots grown under an oxidative stress of 1 mg L-1of ZnO nanoparticles. This finding is further affirmed by an increased 2,2-diphenyl-1-picryl hydrazyl (DPPH) scavenging activity, total anti-oxidant capacity, total reducing power, total flavonoid content and total phenolic content, with an ascending oxidative pressure and generation of reactive oxygen species (ROS). However, the antioxidant activities, formation of secondary metabolites and the physiological parameters showed a sudden decline after crossing a threshold of 1 mg L-1concentration of ZnO nanoparticles and falls to a minimum at 1000 mg L-1, elucidating maximum phytotoxic effect of ZnO nanoparticles at this concentration. This is the first study evaluating both the favorable and adverse effects of ZnO nanoparticles employed to a highly valuable medicinal plant, S. rebaudiana.
authors.affiliation: Department of Biology, Faculty of Art & Science, Abant Izzet Baysal University, 14030 Bolu, Turkey; Department of Biotechnology, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad 45320, Pakistan.
authors.forename: Rabia
authors.initials: R
authors.lastname: Javed
authors.affiliation: Department of Physics, Faculty of Natural Sciences, Quaid-i-Azam University, Islamabad 45320, Pakistan; Department of Physics, School of Science and Engineering, Lahore University of Management Sciences, Lahore 54729, Pakistan.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Usman
authors.affiliation: Department of Seed Science & Technology, Faculty of Natural & Agricultural Sciences, Abant Izzet Baysal University, 14030 Bolu, Turkey.
authors.forename: Buhara
authors.initials: B
authors.lastname: Yücesan
authors.affiliation: Department of Biotechnology, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad 45320, Pakistan.
authors.forename: Muhammad
authors.initials: M
authors.lastname: Zia
authors.affiliation: Department of Biology, Faculty of Art & Science, Abant Izzet Baysal University, 14030 Bolu, Turkey. Electronic address: gurel.ekrem@gmail.com.
authors.forename: Ekrem
authors.initials: E
authors.lastname: Gürel
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D045786:Diterpenes, Kaurane / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005419:Flavonoids / Q000378:metabolism; D016166:Free Radical Scavengers / Q000737:chemistry / Q000494:pharmacology / Q000633:toxicity; D006027:Glycosides / Q000378:metabolism*; D053768:Metal Nanoparticles / Q000008:administration & dosage* / Q000737:chemistry / Q000633:toxicity; D010636:Phenols / Q000378:metabolism; D063245:Plant Development / Q000187:drug effects; D018520:Plant Shoots / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D017382:Reactive Oxygen Species; D013053:Spectrophotometry; D017550:Spectroscopy, Fourier Transform Infrared; D036625:Stevia / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D014961:X-Ray Diffraction; D015034:Zinc Oxide / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity
chemical_list: D000975:Antioxidants; D045786:Diterpenes, Kaurane; D005419:Flavonoids; D016166:Free Radical Scavengers; D006027:Glycosides; D010636:Phenols; D017382:Reactive Oxygen Species; C012042:steviol; D015034:Zinc Oxide
keywords: Oxidative stress; Phytotoxicity; Reactive oxygen species (ROS); Stevia rebaudiana; Steviol glycosides; Zinc oxide nanoparticles