title: Net fluxes of ammonium and nitrate in association with H+ fluxes in fine roots of Populus popularis.
abstract: Poplar plants are cultivated as woody crops, which are often fertilized by addition of ammonium (NH4(+)) and/or nitrate (NO3(-)) to improve yields. However, little is known about net NH4(+)/NO3(-) fluxes and their relation with H(+) fluxes in poplar roots. In this study, net NH4(+)/NO3(-) fluxes in association with H(+) fluxes were measured non-invasively using scanning ion-selective electrode technique in fine roots of Populus popularis. Spatial variability of NH4(+) and NO3(-) fluxes was found along root tips of P. popularis. The maximal net uptake of NH4(+) and NO3(-) occurred, respectively, at 10 and 15 mm from poplar root tips. Net NH4(+) uptake was induced by ca. 48 % with provision of NO3(-) together, but net NO3(-) uptake was inhibited by ca. 39 % with the presence of NH4(+) in poplar roots. Furthermore, inactivation of plasma membrane (PM) H(+)-ATPases by orthovanadate markedly inhibited net NH4(+)/NO3(-) uptake and even led to net NH4(+) release with NO3(-) co-provision. Linear correlations were observed between net NH4(+)/NO3(-) and H(+) fluxes in poplar roots except that no correlation was found between net NH4(+) and H(+) fluxes in roots exposed to NH4Cl and 0 mM vanadate. These results indicate that root tips play a key role in NH4(+)/NO3(-) uptake and that net NH4(+)/NO3(-) fluxes and the interaction of net fluxes of both ions are tightly associated with H(+) fluxes in poplar roots.
authors.affiliation: College of Life Sciences, Northwest Agriculture and Forestry University, Yangling, 712100, Shaanxi, People's Republic of China.
authors.forename: Jie
authors.initials: J
authors.lastname: Luo
authors.forename: Jingjing
authors.initials: J
authors.lastname: Qin
authors.forename: Fangfang
authors.initials: F
authors.lastname: He
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.forename: Tongxian
authors.initials: T
authors.lastname: Liu
authors.forename: Andrea
authors.initials: A
authors.lastname: Polle
authors.forename: Changhui
authors.initials: C
authors.lastname: Peng
authors.forename: Zhi-Bin
authors.initials: ZB
authors.lastname: Luo
mesh_terms: D064751:Ammonium Compounds / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D009566:Nitrates / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism*; D032107:Populus / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D052584:Xylem / Q000378:metabolism
chemical_list: D064751:Ammonium Compounds; D009566:Nitrates; D006180:Proton-Translocating ATPases