Investigation of cellular redox changes in plants in response to changing the inorganic nitrogen source

Nitrogen is a primary important element present in all the life stages and processes of plants, from metabolic pathways to the distribution of resources; therefore, identification of the changes of nitrogen utilization in plants is difficult and precise identification could not be done. The aim of this study was to identify the changes due to the nitrogen source in the various redox reactions taking place, to identify biochemical variations in plant cells, and to determine the role of nitrogen assimilation pathways on redox stabilization mechanism. Arabidopsis thaliana seeds, a model organism for plant research, were grown in flasks containing nitrate as the nitrogen source for 15 days. On the 9th day of the incubation period, they were nitrogen starved for 26 hours, then grown in two sets of flasks containing concentrated ammonium and nitrate respectively. After starving for 26 hours and growth in the concentrated nitrogen source, the plants were harvested on 1st, 3rd, and 5th days (thus the total 15 days); amount of protein, antioxidant enzyme activities, lipid peroxidation, changes in H2O2 levels, GS, GOGAT, and GDH enzyme activities were investigated. Both ammonium and nitrate decreased the amount of protein and GS activity, increased SOD, GR and AP activities; additionally, both affected CAT activity in the same way; however, H2O2 level and GOGAT activity were affected differently. Both the amount of MDA compounds and GDH activity were reversely affected by ammonium and nitrate.