Certain amino acids inhibit growth of tobacco (Nicotiana tabacum L. var. xanthi), tomato (Lycopersicon esculentum) carrot (Daucus carota), and soybean (Glycerine max L. co. Mandarin) cell cultures when nitrate or urea are the nitrogen sources but not when ammonia is the nitrogen source. These amino acids also inhibit development of nitrate reductase activity (NADH:nitrate oxidoreductase EC 1.6....

NtcA is a transcriptional activator involved in global nitrogen control in cyanobacteria. In the absence of ammonium it regulates the transcription of a series of genes encoding proteins required for the uptake and assimilation of alternative nitrogen sources (I. Luque, E. Flores, and A. Herrero, EMBO J. 13:2862-2869, 1994). ntcA, present in a single copy in the marine Synechococcus sp. strain ...

Instream processing may substantially alter nutrient export from forested watersheds. This study tested how instream uptake of N and P were affected by successional differences in the accumulation of large wood and debris dams in a 66-year chronosequence formed by five watersheds within the Hubbard Brook Experimental Forest (HBEF), NH. Nutrient enrichment releases in summer 1998 were used to me...

Nitrate utilization and ammonium utilization were studied by using three algal isolates, six bacterial isolates, and a range of temperatures in chemostat and batch cultures. We quantified affinities for both substrates by determining specific affinities (specific affinity = maximum growth rate/half-saturation constant) based on estimates of kinetic parameters obtained from chemostat experiments...

The enrichment of denitrifying phosphate accumulating organisms (DNPAOs) is the prerequisite for the denitrifying phosphate removal process. This study investigated the effect of nitrate concentration on the enrichment of DNPAOs was studied with batch experiments. The Sequencing Batch Reactor (SBR) was set-up with acetate as the sole carbon source. The addition of nitrate solution and the anoxi...

The effects of elevated CO2 (750 ppm vs. 390 ppm) were evaluated on nitrogen (N) acquisition and assimilation by three Medicago truncatula genotypes, including two N-fixing-deficient mutants (dnf1-1 and dnf1-2) and their wild-type (Jemalong). The proportion of N acquisition from atmosphere and soil were quantified by (15)N stable isotope, and N transportation and assimilation-related genes and ...

The high affinity nitrate transport system in Arabidopsis thaliana involves one gene and potentially seven genes from the NRT1 and NRT2 family, respectively. Among them, NRT2.1, NRT2.2, NRT2.4 and NRT2.7 proteins have been shown to transport nitrate and are localized on the plasmalemma or the tonoplast membranes. NRT2.1, NRT2.2 and NRT2.4 play a role in nitrate uptake from soil solution by root...