title: Effect of nitrogen species supply and mycorrhizal colonization on organosulfur and phenolic compounds in onions.
abstract: The aim of the present study was to test whether variations in the root environment affect the content of health-related organosulfur compounds, total phenolic compounds, and flavonol glycoside concentrations in onions. For this purpose, greenhouse-grown onions ( Allium cepa L.) were either inoculated with a commercial arbuscular mycorrhizal inoculum or a sterile inoculum and were provided with two NH(4)(+):NO(3)(-) ratios as a nitrogen source. Onion growth, arbuscular mycorrhizal colonization rate, sugars, and nutrient element concentrations were also quantified. The plant antioxidant activity and quercetin monoglucoside and organosulfur compound concentrations increased with dominant nitrate supply. Furthermore, mycorrhizal colonization increased the antioxidant activity and also concentrations of the major quercetin glucosides. The present study provides clear evidence that antioxidant activity, quercetin glycosides, and organosulfur compounds can be increased in sufficiently supplied onion plants by dominant nitrate supply or application of arbuscular mycorrhizal fungi. This was probably due to increased precursor production and induced defense mechanisms.
authors.affiliation: Department of Plant Nutrition, Institute of Vegetable and Ornamental Crops e.V. Grossbeeren, Theodor Echtermeyer Weg 1, D-14979 Grossbeeren, Germany. perner@igzev.de
authors.forename: Henrike
authors.initials: H
authors.lastname: Perner
authors.forename: Sascha
authors.initials: S
authors.lastname: Rohn
authors.forename: Gregor
authors.initials: G
authors.lastname: Driemel
authors.forename: Natalie
authors.initials: N
authors.lastname: Batt
authors.forename: Dietmar
authors.initials: D
authors.lastname: Schwarz
authors.forename: Lothar W
authors.initials: LW
authors.lastname: Kroh
authors.forename: Eckhard
authors.initials: E
authors.lastname: George
mesh_terms: D000975:Antioxidants / Q000032:analysis; D044948:Flavonols / Q000032:analysis; D008903:Minerals / Q000032:analysis; D038821:Mycorrhizae / Q000254:growth & development*; D009566:Nitrates / Q000008:administration & dosage*; D019697:Onions / Q000737:chemistry* / Q000254:growth & development / Q000382:microbiology*; D010636:Phenols / Q000032:analysis*; D018517:Plant Roots / Q000737:chemistry / Q000254:growth & development / Q000382:microbiology; D013457:Sulfur Compounds / Q000032:analysis*
chemical_list: D000975:Antioxidants; D044948:Flavonols; D008903:Minerals; D009566:Nitrates; D010636:Phenols; D013457:Sulfur Compounds; C006568:ammonium nitrate