Variation of antioxidants and secondary metabolites in nitrogen-deficient barley plants.
Barley (Hordeum vulgare cv. Bojos) plants cultured in low nitrogen (N) containing Hoagland solution (20 mg/l) were exposed to N deficiency (-N) over 15 days. Plants revealed relatively high tolerance to total N deficit because shoot length was not altered and dry biomass was depleted by ca. 30% while root length increased by ca. 50% and dry biomass remained unaffected. Soluble proteins and free amino acids decreased more pronouncedly in the roots. Antioxidants (glutathione and ascorbic acid) decreased in the shoots but increased or were not affected in the roots. Ascorbate peroxidase and glutathione reductase activities were depleted in shoots and/or roots while guaiacol peroxidase activity was stimulated in the shoots. In accordance, fluorescence signal of reactive oxygen species (ROS) and nitric oxide was elevated in shoots but no extensive changes were observed in roots if +N and -N treatments are compared. At the level of phenolic metabolites, slight increase in soluble phenols and some phenolic acids and strong elevation of flavonoid homoorientin was found in the shoots but not in the roots. Fluorescence microscopy in terms of detection of phenols is also discussed. We also briefly discussed accuracy of quantification of some parameters owing to discrepancies in the literature. It is concluded that N deficiency induces increase in shoot phenolics but also elevates symptoms of oxidative stress while increase in root antioxidants probably contributes to ROS homeostasis aimed to maintain root development.
Institute of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemědělská 1, 613 00 Brno, Czech Republic. Electronic address: jozkovacik@yahoo.com.
Jozef
J
Kováčik
Institute of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemědělská 1, 613 00 Brno, Czech Republic.
Bořivoj
B
Klejdus
Department of Natural Drugs, Faculty of Pharmacy, University of Veterinary and Pharmaceutical Sciences Brno, Palackého 1/3, 612 42 Brno, Czech Republic.
Petr
P
Babula
Institute of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemědělská 1, 613 00 Brno, Czech Republic.
Markéta
M
Jarošová
D000975:Antioxidants / Q000378:metabolism*; D001467:Hordeum / Q000737:chemistry / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism
D000975:Antioxidants; D017382:Reactive Oxygen Species; D009584:Nitrogen
Fluorescence microscopy; Mineral nutrition; Oxidative stress; Phenolic metabolism; Reactive oxygen species