In the Southern Ocean, the nitrogen (N) isotopes of organic matter and the N and oxygen (O) isotopes of nitrate (NO3 ) have been used to investigate NO3 assimilation and N cycling in the summertime period of phytoplankton growth, both today and in the past. However, recent studies indicate the significance of processes in other seasons for producing the annual cycle of N isotope changes. This s...

[1] Biogeochemical cycling of N and S was examined at two watersheds in the Adirondack Mountains, New York, to better understand the retention and loss of these elements during winter and spring snowmelt. We analyzed stable isotope compositions of NO3 (dN-NO3 , dO-NO3 ) and SO4 2 (dS-SO4 2 , dO-SO4 2 ), along with concentrations and fluxes of NO3 and SO4 2 , in precipitation, throughfall, snowp...

In acid forest soils nitrate (NO3 ) from anthropogenic nitrogen deposition is retained at levels beyond what can be explained by known biological mechanisms. A number of researchers have hypothesized that abiotic NO3 – incorporation into soil organic matter might be responsible for this phenomenon, however studies have been limited to a few temperate forest sites. The goal of this study was to ...

Mobilization of natural nitrate (NO3-) deposits in the subsoil by irrigation water in arid and semiarid regions has the potential to produce large groundwater NO3-concentrations. The use of isotopes to distinguish between natural and anthropogenic NO3- sources in these settings could be complicated by the wide range in delta15N values of natural NO3-. An approximately 10 000 year record of pale...

The morphological plasticity of root systems is critical for plant survival, and understanding the mechanisms underlying root adaptation to nitrogen (N) fluctuation is critical for sustainable agriculture; however, the molecular mechanism of N-dependent root growth in rice remains unclear. This study aimed to identify the role of the complementary high-affinity NO3(-) transport protein OsNAR2.1...

We examined the hypothesis that elevated CO2 concentration would increase NO3- absorption and assimilation using intact wheat canopies (Triticum aestivum cv. Veery 10). Nitrate consumption, the sum of plant absorption and nitrogen loss, was continuously monitored for 23 d following germination under two CO2 concentrations (360 and 1000 micromol mol-1 CO2) and two root zone NO3- concentrations (...

Root development is extremely sensitive to variations in nutrient supply, but the mechanisms are poorly understood. We have investigated the processes by which nitrate (NO3-), depending on its availability and distribution, can have both positive and negative effects on the development and growth of lateral roots. When Arabidopsis roots were exposed to a locally concentrated supply of NO3- ther...

The effect of Ca2+ on NO3- assimilation in young barley (Hordeum vulgare L. var CM 72) seedlings in the presence and absence of NaCl was studied. Calcium increased the activity of the NO3- transporter under saline conditions, but had little effect under nonsaline conditions. Calcium decreased the induction period for the NO3- transporter under both saline and nonsaline conditions but had litt...

Nitric oxide (NO) in oxygen-containing aqueous solution has a short half-life that is often attributed to a rapid oxidation to both NO2- and NO3-. The chemical fate of NO in aqueous solution is often assumed to be the same as that in air, where NO is oxidized to NO2 followed by dimerization to N2O4. Water then reacts with N2O4 to form both NO2- and NO3-. We report here that NO in aqueous soluti...

Since increasing the NO3 and NH4 make eutrophication in waterbodies, microalgae tolerance tohigh concentrations of NO3 and NH4 and their growth in these levels indicate the bioremediationpotential of nitrogen-rich wastewaters and produce efficient algal biomass in freshwaterenvironments. To evaluate the tolerance of green algae, Scenedesmus quadricauda to different NO3and NH...