title: Utilization of (15)NO3 (-) by nodulated soybean plants under conditions of root hypoxia.
abstract: Waterlogging of soils is common in nature. The low availability of oxygen under these conditions leads to hypoxia of the root system impairing the development and productivity of the plant. The presence of nitrate under flooding conditions is regarded as being beneficial towards tolerance to this stress. However, it is not known how nodulated soybean plants, cultivated in the absence of nitrate and therefore not metabolically adapted to this compound, would respond to nitrate under root hypoxia in comparison with non-nodulated plants grown on nitrate. A study was conducted with (15)N labelled nitrate supplied on waterlogging for a period of 48 h using both nodulated and non-nodulated plants of different physiological ages. Enrichment of N was found in roots and leaves with incorporation of the isotope in amino acids, although to a much smaller degree under hypoxia than normoxia. This demonstrates that nitrate is taken up under hypoxic conditions and assimilated into amino acids, although to a much lesser extent than for normoxia. The similar response obtained with nodulated and non-nodulated plants indicates the rapid metabolic adaptation of nodulated plants to the presence of nitrate under hypoxia. Enrichment of N in nodules was very much weaker with a distinct enrichment pattern of amino acids (especially asparagine) suggesting that labelling arose from a tissue source external to the nodule rather than through assimilation in the nodule itself.
authors: Departamento de Biologia Vegetal, Universidade Estadual de Campinas, C.P. 13083-862 Campinas, SP Brazil ; Laboratório de Botânica e Zoologia, Universidade Potiguar, C.P. 59056-000 Natal, RN Brazil.
authors: Luciana
authors: L
authors: Nunes Menolli Lanza
authors: Departamento de Bioquímica, Universidade Federal do Rio Grande do Norte, C.P. 59078-970 Natal, RN Brazil.
authors: Daniel Carlos
authors: DC
authors: Ferreira Lanza
authors: Departamento de Biologia Vegetal, Universidade Estadual de Campinas, C.P. 13083-862 Campinas, SP Brazil.
authors: Ladaslav
authors: L
authors: Sodek
keywords: 15N; Amino acids; Glycine max; Hypoxia; Nitrate; Nodules