Abstract
Optimization of nitrogen (N) use by grasses is a central issue of the current work. The effects of different N concentrations (0, 0.25, 0.5, 1.0, 2.5, and 5.0 mM NH4NO3) on growth of Brachypodium distachyon were assessed on controlled hydroponic culture. Maximal growth (132% of control) was obtained at 0.5 mM NH4NO3, critical N level, and was maintained at higher N concentrations. The highest N level (5.0 mM) has a similar effect on growth as 0.5 mM NH4NO3. It has no significant effects on water status, and total and reduced N contents in shoots while, increased those in roots, compared to plants receiving 0.5 mM NH4NO3. The high N availability, however, increased nitrate contents in shoots and roots by 3- and 20-folds, respectively, compared to those of plant receiving 0.5 mM NH4NO3. In addition, high N availability reduced the nitrogen use efficiency (NUE) by 18% compared to that of plant receiving only 0.5 NH4NO3. In view of B. distachyon productivity and environmental concerns, it is concluded that the critical level of N application should be 0.5 mM NH4NO3 and the excess fertilization led to a high nitrate accumulation.