Department of Plant Sciences

Urea, ammonium and nitrate are the most important nitrogen forms employed in agricultural plant production. Although nitrate has been shown to act as a signal for metabolism and plant development in physiological studies, so far no use is made of the signalling effect of different N forms in cereal plant production.

To investigate the effect of different N forms on shoot development, we performed nutrient solution experiments with spring barley and observed that shoot biomass production and in particular tillering decreased with an increased amount of nitrogen being supplied in the form of urea. We determined cytokinin translocation rates in the xylem under varied nitrogen nutrition or after supply of exogenous cytokinins in the presence of different nitrogen forms and found that different nitrogen forms strongly affected cytokinin translocation from roots to shoots.

To reproduce this nitrogen form-dependent effect in field trials, winter wheat was fertilised with stabilised N forms in the starter dressing. In fact, the supply of different nitrogen forms allowed to reproduce the effects observed in hydroponic culture. In dependence of seasonal variations this change in plant architecture also affected grain yield. Our results show that the signalling effect of stabilized nitrogen forms can be used to influence tiller number and yield components in wheat and barley.