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.

Positive effects of night warming on physiology of coniferous trees in late growing season: Leaf and root

“…& Tech. Co., Ltd., Beijing, China with a backfilling solution and an ion-selective liquid cocktail as reported by Luo et al (2013aLuo et al ( , 2013b. Prior to the flux measurements, the ion-selective electrodes were calibrated by a standard solution (1 mM KCl, 0.1 mM CaCl 2 and 0.1 mM NH 4 NO 3 ) with two extra NH 4 NO 3 concentrations of 0.05 and 0.5 mM for NH 4 þ and NO 3 À , pH 5.5 and pH 6 for H þ , and O 2 concentrations of 0% and 0.21% for oxygen-microelectrode, respectively.…”

“…performed according to the method of Luo et al (2013b).The maximal root net ion uptake of P. asperata and A. faxoniana were detected in the region of 16.5e18 and 11e12 mm, respectively. Therefore, net fluxes of NH 4 þ and NO 3 À were measured in this region of both species.…”

Populus deltoides females are more selective in nitrogen assimilation than males under different nitrogen forms supply

“…Many studies have been reported that different plant species, genotypes, growing conditions, and lifespan showed different responses to different N forms (Claussen and Lenz 1999;Strojny 1999;Munzarova et al 2006;Luo et al 2013b). For the poplar, there were some conflicting results which had been reported by (Rennenberg et al 2010).…”

Effects of nitrogen and phosphorus supply on growth and physiological traits of two Larix species

“…Previous studies have showed that N and P deficiencies cause negative effects on plants (Boyce et al, 2006;Turnbull et al, 2007;Kant et al, 2011;Warren, 2011;Zhang et al, 2014), and photosynthesis always decreases under N and P deficiencies (Zhang et al, 2014;Luo et al, 2015). N is a vital constituent in proteins, nucleic acids, chlorophylls and many secondary metabolites of plants (Luo et al, 2013a), and therefore it plays an essential role in the enzymatic activities of photosynthetic processes (Güsewell, 2004). A strong linear relationship between leaf N concentration and photosynthetic capacity has been well established (Field and Mooney, 1986;Evans, 1989;Wright et al, 2004;Takashima et al, 2004;Zhang et al, 2014).…”