Nitrogen metabolism of two contrasting poplar species during acclimation to limiting nitrogen availability

Abstract

To investigate N metabolism of two contrasting Populus species in acclimation to low N availability, saplings of slow-growing species (Populus popularis, Pp) and a fast-growing species (Populus alba × Populus glandulosa, Pg) were exposed to 10, 100, or 1000 μM NH4NO3. Despite greater root biomass and fine root surface area in Pp, lower net influxes of NH4 + and NO3 – at the root surface were detected in Pp compared to those in Pg, corresponding well to lower NH4 + and NO3 – content and total N concentration in Pp roots. Meanwhile, higher stable N isotope composition (δ15N) in roots and stronger responsiveness of transcriptional regulation of 18 genes involved in N metabolism were found in roots and leaves of Pp compared to those of Pg. These results indicate that the N metabolism of Pp is more sensitive to decreasing N availability than that of Pg. In both species, low N treatments decreased net influxes of NH4 + and NO3 –, root NH4 + and foliar NO3 – content, root NR activities, total N concentration in roots and leaves, and transcript levels of most ammonium (AMTs) and nitrate (NRTs) transporter genes in leaves and genes involved in N assimilation in roots and leaves. Low N availability increased fine root surface area, foliar starch concentration, δ15N in roots and leaves, and transcript abundance of several AMTs (e.g. AMT1;2) and NRTs (e.g. NRT1;2 and NRT2;4B) in roots of both species. These data indicate that poplar species slow down processes of N acquisition and assimilation in acclimation to limiting N supply.

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

“…which was largely dependent on the soil pH (DesRochers et al 2003). Luo et al (2013a) found that the different uptake abilities of NO 3 -and NH 4 ? of two contrasting poplar species were also dependent on the roots position.…”

“…can be directly assimilated into amino acids in the roots by the Glutamine synthetase-glutamate synthase (GS-GOGAT) system to form glutamine and glutamate (Dluzniewska et al 2007), whereas NO 3 -needs to be reduced to NH 4 ? by nitrate reductase (NR) and nitrite reductase (NiR) before incorporation into amino acids mainly in leaves (Rennenberg et al 2010;Nunes-Nesi et al 2010;Luo et al 2013a). Thus, ammonium ions are assimilated in the roots and transported as amino acids and amides to the leaves, while nitrate ions are transported to the leaves largely as nitrate (Arnozis and Findenegg 1986;Shelp 1987).…”

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.…”

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

“…The fast-growing ones possess greater N and P use efficiencies and higher enzymatic activities related to N assimilation and P mobilization (Gan et al, 2015). The fast-growing broadleaved tree Populus alba  P. glandulosa is more sensitive to increasing N availability (Li et al, 2012), while the slowly growing P. popularis is more sensitive to decreasing N availability (Luo et al, 2013b). Also, fast growing P. deltoides females are more sensitive to inorganic nitrogen forms than the slow growing male trees .…”